Micromorphology of the Cactus Hill Site (44SX202),

Sussex County, Virginia

A thesis presented by

J. Taylor Perron

to the Departments of Anthropology and Earth and Planetary Sciences

in partial fulfillment of the requirements for the degree with honors

of Bachelor of Arts

Harvard University Cambridge, Massachusetts

March 1999

Contents

List of Figures III

List of Tables IV

Acknowledgements V

1. Introduction 1

2. The First Americans: A Review 4

3. Overview of the Cactus Hill Site 14

4. Methods 28

5. Results 34

6. Interpretations and Discussion 82

References 92

Appendix: Numerical Image Analysis Data

11

Figures

3.1 Topographic map showing location of the Cactus Hill Site 15 3.2 Topographic profile of the Cactus Hill Site 18 3.3 Hypothesized origin of major sedimentary units at Cactus Hill 19 3.4 Site map showing major excavation areas 21 3.5 Lithics recovered from Area A, Square 24, Level 14 23 4.1 Plan of Area A showing locations of micromorphology samples 29 5.1 Stratigraphic column for Area A 35 5.2 Thin section 1a 37 5.3 Thin section 1 b 39 5.4 Thin section 2a 41 5.5 Thin section 2b 43 5.6 Thin section 3a 45 5.7 Thin section 3b 47 5.8 Thin section 4a 49 5.9 Thin section 4b 51 5.10 Thin section Sa 53 5.11 Thin section 5b 55 5.12 Thin section 5c 57 5.13 Photomicrograph of Zone II sand 60 5.14 Photomicrographs of lamellar sand 62 5.15 Photomicrograph of Zone IV sand 63 5.16 Photomicrograph of Zone V sandy clay loam 65 5.17 Photomicrograph of Zone VI sandy clay 66 5.18 Image analysis data for thin section 1a 68 5.19 Image analysis data for thin section 1b 69 5.20 Image analysis data for thin section 2a 70 5.21 Image analysis data for thin section 2b 71 5.22 Image analysis data for thin section 3a 72 5.23 Image analysis data for thin section 3b 73 5.24 Image analysis data for thin section 4a 74 5.25 Image analysis data for thin section 4b 75 5.26 Image analysis data for thin section Sa 76 5.27 Image analysis data for thin section 5b 77 5.28 Image analysis data for thin section 5c 78

111

Tables

4.1 Locations and depth ranges of micromorphology core samples 30 4.2 Depth ranges of thin sections 31 4.3 Definitions of textural parameters used in image analysis 33 5.1 Description of thin section 1a 38 5.2 Description of thin section 1 b 40 5.3 Description of thin section 2a 42 5.4 Description of thin section 2b 44 5.5 Description of thin section 3a 46 5.6 Description of thin section 3b 48 5.7 Description of thin section 4a 50 5.8 Description of thin section 4b 52 5.9 Description of thin section 5a 54 5.10 Description of thin section 5b 56 5.11 Description of thin section 5c 58 5.12 Definitions of terms used in thin section descriptions 59

IV

Acknowledgements

This study would have been impossible without the help of a number of

individuals. I thank C.A.S. Mandryk for tireless guidance and encouragement at

every stage of this project; M.F. Johnson for granting access to the Cactus Hill

Site; P. Goldberg for his thoughts on the micromorphological evidence and for

granting access to the Micromorphology Laboratory, Department of Archaeology,

Boston University; O. Bar-Yosef and S. Yamada for granting access to the

facilities of the Stone Age Laboratory, Department of Anthropology, Harvard

University; T. Arpin for assistance in sample preparation ; P.T. Walsh for

assistance in the preparation of figures and for technical support; and J.H. Shaw

for granting access to the Structural Geology and Earth Resources computer

facility, Department of Earth and Planetary Sciences, Harvard University. This

research was supported by grants from the Departments of Anthropology and

Earth and Planetary Sciences, Harvard University, and the Harvard College

Dean's Summer Research Award.

v

1. Introduction

The fluted point tradition is the earliest archaeological horizon recognizable on a

large scale in the New World: fluted projectile points are found from northern

Alaska to Tierra del Fuego and from the Pacific Coast to the Atlantic Seaboard.

The most well-known fluted point complex in the Americas , defined by the

assemblage at the Blackwater Draw Site near Clovis, New Mexico, is bracketed

by radiocarbon age estimates of 11,200 and 10,900 years before present (Taylor et

al. 1996). Although Clovis , in the strict sense, is confined to the American

Southwest and Great Plains, a number of similar fluted point traditions in other

regions are considered part of the same archaeological horizon. Since Clovis is

the first widely recognizable cultural stratum in North America, many

archaeologists believe that Clovis peoples were the original colonists of the

continent. Consequently, most models that attempt to describe the peopling of the

Americas center around' the dispersion of a single wave of immigrants . A few

researchers, however, claim to have found sites with lithic assemblages and

radiocarbon dates that suggest a "pre-Clovis" occupation. Archaeological data

from pre-Clovis sites would have major implications for the reconstruction of

New World migration patterns. However, few of these sites have met the

rigorous criteria applied to pre-Clovis candidates . Thus far , only the Monte Verde

Site in southwestern Chile, dating to c. 12,500 B.P., contains cultural strata that

have been accepted by the archaeological community as pre-Clovis (Dillehay

1997; Meltzer et al. 1997).

1

This study focuses on the Cactus Hill Site (44SX202) in southeastern

Virginia, a recent addition to the list of pre-Clovis candidates. Archaeological

investigations conducted independently in separate areas of the site by J.M.

McAvoy (McAvoy and McAvoy 1997) and M.P. Johnson (1997) have revealed a

nearly continuous cultural sequence from Paleoindian to Late Woodland. During

the 1993 field season, McAvoy recovered ten quartzite artifacts and a scatter of

charcoal from a level 8 cm beneath a scatter of fluted point fragments dated to c.

10,900 B.P. The charcoal later yielded a radiocarbon date of c. 15,000 B.P. More

recent excavations have revealed additional material at this level, including a date

of c. 16,700 B.P. on charcoal samples recovered by flotation. In 1996 Johnson

excavated seven quartzite artifacts at a depth 23 cm below the deepest Paleoindian

level. These findings have led some archaeologists to identify Cactus Hill as a

potential pre-Clovis site (Beardsley 1998, Petit 1998). Three elements that must

be demonstrated at any site that purports to predate Clovis are 1) evidence of

human agency, 2) secure geochronology, and 3) undisturbed stratigraphic context.

The remains at Cactus Hill clearly fulfill the first requirement, and the existing

radiocarbon chronology and ongoing thermoluminescence (TL) dating may help

resolve the second issue. The work described here addresses the issue of

stratigraphic integrity.

The archaeological remains at Cactus Hill have been excavated from the

upper half of a sandy surficial deposit that is believed to be of eolian origin. The

upper portion of the dune sand shows no signs of stratification. Deeper sand is

marked by a series of wavy, roughly parallel , reddish brown textural bands, or

lamellae. Lamellae are more cohesi ve, finer textured and darker in color than the

interlamellar sand. The possible pre-Clovis artifacts were recovered from this

lamellar zone.

Artifacts in sandy sites are particularly susceptible to post-depositional

disturbance, highlighting the need for cautious archaeological interpretations at

Cactus Hill. Past studies of lamellae indicate that such features can form as a

result of several different geogenic and pedogenic processes. If the lamellae are

primary sedimentary features- or secondary features that developed as a result of

2

some stratigraphic characteristic of the dune sand-they may be evidence of

intact stratigraphy. If they are of purely pedogenic origin, they cannot be used as

an argument against post-depositional disturbance. This study describes the

character and origin of the sediments at Cactus Hill as a means of evaluating the

stratigraphic integrity of the archaeological deposits . This is accomplished

through the application of micromorphology, the analysis of soils and sediments

in thin section.

Chapter 2 reviews the principal arguments and evidence in the Clovis-pre­

Clovis debate . Chapter 3 introduces the Cactus Hill Site and gives an overview of

the previous geological and archaeological work at the site. The methodology

used in this study, including the collection , preparation and analysis of

micromorphological samples, is detailed in Chapter 4 . Chapter 5 presents the

results of field observations and thin section analyses. The final chapter interprets

these results, describing the depositional and post-depositional history of the

sediments at Cactus Hill and discussing the archaeological implications of these

findings .

The advantages of a geological approach to archaeological problems have

become increasingly evident in recent decades. Techniques from the earth

sciences can provide a wealth of information on the origin, formation , and

modification of the sediments at an archaeological site. This in turn can

illuminate the environmental history of an area, anthropogenic processes that

affected the formation of the site , and the post-depositional history of

archaeological remains. Earth science techniques are particularly useful in North

America, where the complexity of the postglacial sedimentary record can make

archaeological interpretations difficult. The results of this investigation

demonstrate the importance of a geologically informed perspective on

archaeological site formation processes.

3

--------------------------------------------------------------------------------------

2. The First Americans: A Review

The stakes

Why are archaeologists concerned with reconstructing the colonization of the

Americas? The interest is more than just academic: the peopling of the New

World is a case study in human colonization and development. As David Meltzer

(1997:755) puts it, the American case is "one of the few instances in which fully

modern humans radiated into a previously uninhabited continent." This has given

anthropologists the opportunity to document several features of colonizing

populations. One such feature is dispersal patterns: how do pioneer populations

move across a landmass? Do they radiate in waves through the continental

interior (Anthony 1990), or do they follow coastlines, infiltrating the interior via

river systems (Faught and Anderson 1996)? Another feature is the effect of

environmental factors on human adaptations: to what extent did novel

environmental constraints shape the subsistence strategies, technology, and social

structure of the first Americans? Third, even the most approximate

archaeological reconstruction of early Native American ancestry would help to

calibrate rates of genetic and linguistic evolution (Meltzer 1995), as well as

furthering our understanding of the similarities and differences among subsequent

Native American populations. Finally, tracing the arrival of the first Americans

would shed light on patterns and rates of cultural change, such as the rise of social

inequality and complexity.

4

The peopling of the Americas is a umque experiment m human

demographics and culture change in which the control has been provided for us.

Ironically, it is very poorly understood-more so, perhaps, than any other aspect

of North American prehistory. Even after a century of research, archaeologists

cannot agree on such basic points as the identity of the first Americans, the timing

of their arrival, the route of their migration, or the features of their lifestyle. The

development and application of new analytical techniques and the excavation of

countless sites have brought us closer to the answers, but a great deal of

uncertainty remains. Recent developments in New World archaeology have

forced archaeologists to reconsider long-standing assumptions about the earliest

inhabitants of this continent. An appreciation of the history of archaeological

thought on the peopling of the New World and an understanding of the current

evidence are essential if one hopes to evaluate the significance of the research at

the Cactus Hill Site. This chapter is not an attempt to resolve the many complex

issues tied to the peopling of the Americas; it aims only to introduce the reader to

the context in which Cactus Hill must be interpreted.

Archaeologists and Paleoindians: the last century

The history of thought on the peopling of the Americas began with a period of

speculation. European explorers, missionaries and colonists identified N ati ve

Americans as the descendants of Carthaginian exiles , Scythians or the Lost Tribes

of Israel , to name just a few theories (Fagan 1995). By the late 19th century,

many scholars suspected that humans had inhabited the continent during the

Pleistocene, but the antiquity of the first Americans could not be reliably

demonstrated (Lepper and Meltzer 1991). Many artifacts were isolated surface

finds , and New World archaeologists used them to construct a lithic chronology

by analogy to European sequences of the Paleolithic: "crude" attempts at stone

tool manufacture were assigned greater ages, whereas more "refined" specimens

were considered younger (Lepper and Meltzer 1991). However, other scholars

5

were quick to point out that the "crude" relics could represent the work of more

inexperienced flintknappers or "false starts" that were discarded. Artifacts found

in stratigraphic contexts were of little more use. As radiocarbon dating would not

be invented until the mid-20th century, there was no way to assign absolute ages

to most of these finds , and the small number of stratified sites made seriation

difficult.

The discovery in 1927 of fluted projectile points lodged in the ribs of an

extinct species of bison at Folsom, New Mexico, along with several other

purported kill sites found in the High Plains and the Southwest during the 1920s

and '30s, ended the debate over the Pleistocene antiquity of North American

Indians. These finds triggered the identification of a "fluted point horizon" that

spanned the continent, including a tradition that appeared to precede Folsom-type

points in some stratigraphic sequences. Named for the type-site of Blackwater

Draw near Clovis, New Mexico, the Clovis tradition quickly gained a reputation

as the earliest widely recognizable archaeological horizon in the New World. By

the 1950s thousands of fluted points had been discovered throughout North

America. Based on local geochronologies and typological similarities to Western

finds, archaeologists concluded that fluted points throughout North America must

be approximately the same age. The development of radiocarbon dating in 1959

put any remaining doubts to rest. Clovis sites in the west consistently dated to c.

11,500 to 10,500 B.P., and eastern sites were usually a few centuries younger

(Haynes 1964; Dincauze 1993). Recently acquired AMS dates have bracketed the

southwestern Clovis complex with age estimates of c. 11,200 and 10,900 B.P.

(Haynes et al. 1984; Taylor et al. 1996).

A great deal of research has been directed at the question of Clovis

origins. Though the exact migration route is the subject of intense debate, it is

generally agreed that the first North Americans crossed from Northeast Asia to

the New World via the Beringian landmass, a link between present-day Siberia

and Alaska exposed during the last glacial period. There is little agreement

beyond this basic assumption. Despite a considerable body of archaeological

6

work in Eastern Siberia and Alaska, the origin of fluted point peoples remains

unclear.

Several types of non-archaeological evidence have also been invoked in

the search for the first Americans . Based on a comparative analysis of native

North American languages and assumed divergence rates, Greenberg (1987;

Greenberg et al. 1986; Greenberg and Ruhlen 1992) has argued that the New

World was colonized by three distinct waves of immigrants. The Amerind group

is believed to have diverged from Old World populations before 11,000 B.P. The

Na-Dene and Eskimo-Aleut groups appear to be descended from migrants that

arrived in the New World around 10,000 and 4,500 B.P., respectively.

(Greenberg et al. 1986; Greenberg 1987). Turner (1985 , 1986) has used a

statistical analysis of dental traits in ancient and modern individuals from around

the globe to support this tripartite division of migratory populations. A number of

researchers, including Williams and colleagues (1985) and Szathmary (1996)

have presented arguments based on genetic evidence, but at present these data are

largely equivocal (Meltzer 1989).

To archaeologists , this body of ancillary evidence is intriguing ,

particularly when compared with the sparse material record of migrations to the

New World. The work in linguistics , human biology and the archaeology of

fluted point cultures is impressive, but it has produced a rather unfortunate result:

faced with the arguments for three discrete migrations to North America- two of

them younger than Clovis- and the apparent explosion of Clovis sites around

11,000 B.P., many archaeologists dogmatically accept the idea that Clovis peoples

were the first Americans (Haynes 1988; Meltzer 1989).

In reality, there is insufficient evidence to support this assumption. It is

conceivable that the Clovis explosion represents not a colonization, but rather the

spread of a highly visible lithic industry across an existing population. There is

also the possibility of early, unsuccessful migrations that left no genetic or

linguistic traces . The material remains of earlier peoples may be less visible

archaeologically for a number of reasons, including low population density or a

technology based mainly on perishable materials (Adovasio 1993) . Sites

7

subjected to erosional and depositional effects associated with the Pleistocene­

Holocene transition are less likely to have been preserved than younger sites. It

may be that we simply have not looked for early sites in the right places. The

evidence of pre-Clovis occupations is likely to be deeply buried, and there is no

guarantee that it is overlain by the archaeological remains of later peoples:

climatic, ecological and geomorphological changes since the late Pleistocene have

altered the Americas considerably (Graham 1990), and the places that pre-Clovis

peoples found attractive may not have been ideal for human habitation several

thousand years later. Finally, Meltzer (1989) suggests that the three hypothesized

migrations may have been prolonged "dribbles" rather than discrete events;

perhaps the arrival of fluted point makers was a large pulse within a continuous

stream of migrants. The Clovis-first hypothesis clearly is not the only possible

explanation for the observed patterns of archaeological, linguistic, and biological

evidence.

Was Clovis first?

Over the years , a number of sites in North and South America have been pushed

to the forefront of the debate because of their failure to fit into the Clovis-first

model of the peopling of the Americas . These sites typically attract attention

because of their unusual antiquity. Despite the popularity of the Clovis-first

paradigm, some scholars are willing to entertain the idea of an archaeological

culture that somehow slipped through the cracks, a truly aboriginal American

population that has evaded detection until now. Though we do not know what

pre-Clovis sites should look like, the general criteria for acceptance, summarized

by Meltzer (1995:32) are straightforward: "[The] remains should be undeniably of

human origin, either artifacts or bones ; they should be in undisturbed geological

contexts; and their age should be determined by indisputable radiometric dates."

One pre-Clovis candidate after another has failed to live up to these criteria under

scrutiny.

8

Two famous sites, long considered strong candidates for pre-Clovis

occupations, have recently fallen out of favor. Charcoal associated with fractured

quartzite cobbles at the Brazilian rockshelter of Pedra Furada has yielded

radiocarbon dates of c. 14,300 to 48,000 B.P. (Guidon and Delibras 1986).

However, it has been demonstrated that these "cobble tools" are probably geofacts

produced by the erosion of a conglomerate unit 100 meters above the rockshelter,

a sufficient height to produce fractures upon impact (Haynes 1988; Meltzer et al.

1994).

With radiocarbon dates as early as c. 19,600 B.P. (Adovasio et al. 1990),

the Meadowcroft rockshelter in southwestern Pennsylvania has been the subject

of debate for more than two decades. Although the radiocarbon dates are

stratigraphically coherent and appear to be consistent with the later cultural

sequence of the site (Adovasio et al. 1990), inconsistencies in the floral and

faunal records and the proximity of coal beds to the rockshelter have led many

scholars to believe that the lower strata have been contaminated by 14C-depleted

matter (Haynes 1980; Mead 1980; Kelly 1987; Tankersley and Munson 1992).

Dozens of lesser-known candidates have emerged, but problems with

dates, associations , or the nature of the allegedly pre-Clovis cultural material have

been exposed before these sites could cause much of a sensation. Of 50 pre­

Clovis candidates in 1964, nearly all had been ruled out by the end of the 1980s,

leading Meltzer (1995:22) to comment that "the shelf life of pre-Clovis claims

seems little more than a decade. " Archaeologists , deeply entrenched in the

Clovis-first paradigm, became distrustful of any pre-Clovis claims (Lynch 1991).

When the dust settled, all that remained was Meltzer ' s assertion that "the first site

to break the Clovis barrier will have to be utterly unimpeachable in all respects"

(1995 :33). It now appears that there is such a site, and it is currently reshaping

New World archaeology.

The Monte Verde Site, excavated between 1977 and 1985 by Tom

Dillehay (1989, 1997), is located on the banks of Chinchihuapi creek in southern

Chile. The site contains two archaeological levels (MVI and MVII) separated and

sealed by culturally sterile deposits. Dillehay believes that the MVII deposits,

9

which appear to represent a single living surface, are the result of a relatively brief

occupation, perhaps no more than a year. Soon after the inhabitants of MVII

abandoned the site, a thick layer of peat capped the sandy riverbed deposits. The

resulting anoxic conditions prevented the decay of many organic remains,

including mastodon bone and flesh; dozens of species of plants (some of them

burned or chewed); wooden and bone tools; wooden planks, posts and hides that

formed part of ten rectangular structures; hundreds of lithic artifacts and even a

human footprint. Almost 30 radiocarbon dates have been obtained for charcoal,

wood and ivory from the MVII surface and from overlying and underlying strata.

These dates place the MVII occupation of Monte Verde at c. 12,500 B.P., fully

1,300 years before the appearance of Clovis in North America.

Needless to say, Monte Verde has been subject to the same skepticism as

other pre-Clovis candidates. It has endured for two reasons: the first is Dillehay's

extraordinarily thorough documentation and analysis of the archaeological data.

The publication of the second monumental volume on Monte Verde (Dillehay

1997) marks the end of more than two decades of work on the site. The second is

the scrutiny of the site by scholars who were not directly involved in the

excavations (Meltzer 1997; Meltzer et ai. 1997). On Dillehay ' s request, a group

of Paleoindian specialists traveled to Chile in January 1997 to examine the site

and its collections. By the time they boarded the plane to return to the United

States, even the most dedicated skeptics in the group were convinced of the pre­

Clovis antiquity of Monte Verde (Meltzer et al. 1997).

Implications of the Monte Verde Site

The Monte Verde Site breaks the debate over the first Americans wide open.

Although the MVII occupation predates the Clovis culture by little more than a

millennium, the location of the site has monumental implications: if humans had

reached the southernmost tip of the South America by 12,500 B.P., their ancestors

must have migrated to the New World much earlier. Prior to the acceptance of

10

Monte Verde, archaeologists willing to entertain the possibility of pre-Clovis

occupations in the New World could only argue that there was insufficient

evidence to support the Clovis-first model; now they have sufficient evidence to

refute it. The findings at Monte Verde have also provided new ammunition in the

debate over the timing and route of the earliest migration(s) to the Americas.

By the late 1930s it was widely believed that the first Americans had

reached the New World via the Beringian landmass that was exposed during

glacial maxima. Since many of the earliest fluted point sites in North America are

located in the Great Plains, it is not surprising that archaeologists readily

embraced W. A. Johnston's (1933) idea of a deglaciation corridor running

through the Yukon Valley and the Mackenzie watershed, between the Laurentide

and Cordilleran ice sheets and along the eastern edge of the Rocky Mountains

(Mandryk et ai., in press). Until very recently, some geologists argued that the

two ice masses were separated by a narrow passage even during the Late

Wisconsinan glacial maximum. However, it now appears that the ice-free

corridor was more complex and transient than archaeologists had previously

thought. Geologic data indicate that the northern portion of the corridor was

blocked by ice and flooding from 30,000 to 11,500 B.P. (Jackson and Duk­

Rodkin 1996; Szeicz et al. 1995). The central portion was closed when

Laurentide and Cordilleran ice sheets coalesced between 21,000 and 18,000 B.P.

(Mandryk 1992, Jackson and Duk-Rodkin 1996).

Even where exposed land made the passage a physical reality, it appears to

have been ecologically inhospitable. By constructing a vegetational and

environmental record of the region and comparing it with the minimum biological

and social requirements 'of hunter-gatherers, Mandryk (1990, 1992) has shown

that the ice-free corridor could not have supported a viable population of hunter­

gatherers until after 12,000 B.P. Migrants to the New World could not have

followed an inland route from Eastern Beringia to areas south of the ice sheets

until after 11,500 B.P.

Since the Clovis "explosion" does not begin until c. 11 ,200 B.P., and

gIven the statistical noise associated with radiocarbon dates, Paleoindian

11

specialists have taken these geological and paleoecological revelations in stride.

The idea of an ice-free corridor is thoroughly entrenched in archaeological

thought (Easton 1992), and because the data on the corridor do not rule out the

possibility that the ancestors of Clovis peoples used such a route, Americanists

have been reluctant to consider other possibilities. However, the demonstrated

existence of pre-Clovis peoples south of the ice has spawned a reevaluation of

alternative hypotheses. Chief among these is the coastal route, first conceived by

Heusser in 1960. Over the years, a number of scholars (Fladmark 1978, 1979,

1983; Easton 1992; Rogers et al. 1992; Gruhn 1994) have argued that migrants to

the New World could have followed the Pacific coastline across Beringia and

down the Northwest Coast of North America. Proponents have traditionally

pointed to the milder climatic conditions found in coastal areas, the considerable

linguistic diversity among Northwest Coast populations (Greenberg 1987), and

the lack of archaeological sites in the region of the ice-free corridor. Skeptics

counter that early coastal sites would have been submerged by rising Holocene

seas, rendering the model untestable. Many also deny that the Northwest Coast

could have afforded a viable habitat for humans during the critical period when

migrations would have occurred.

Recent evidence, however, supports the existence of coastal refugia that

were suitable for human habitation even during the Late Wisconsinan glacial

maximum. The research, which spans paleoclimatology, sea level change, glacial

coverage and isostatic effects, sea-floor morphology and faunal and vegetational

records, describes a biologically and geomorphologic ally diverse tundra zone

along an outer coastline virtually uninterrupted by ice by 14,000 to 13,000 B.P.

(Mandryk et al. , in press). These data provide the necessary geographical,

ecological and temporal window for the arrival of pre-Clovis populations south of

the ice. Using a marine adaptation, the ancestors of the Monte Verdeans could

have traveled from Eastern Beringia to lower North America up to two millennia

before the ice-free corridor became a viable migration route.

The demonstration of a pre-Clovis presence in the New World has forced

archaeologists to reevaluate time-honored b'eliefs about the migratory movements

12

of the first Americans and about Paleoindians in general. The acceptance of

Monte Verde is unfortunate in a single respect: while the realm of possibilities

surrounding the peopling of the Americas has expanded considerably, only one

archaeological data point has been added. Regardless of the issue at hand, the

relevant information on the earliest inhabitants of the New World is minimal; we

know as little about the lifeways of the first Americans as we do about their

antiquity or their migratory route. Until a significant number of pre-Clovis sites

have been excavated, the gaps in the archaeological record will continue to be

filled by speculation.

The Cactus Hill Site must be viewed in the context of this debate. In the

field of pre-Clovis archaeology, each new site represents a 100% increase in the

size of the data set. The location, age and content of any site of demonstrated pre­

Clovis antiquity would have enormous bearing on the spatial and chronological

reconstruction of migration routes and on our understanding of the first

Americans themselves. Such a discovery would also help to guide the search for

sites of comparable antiquity. With the stakes so high, it is imperative that there

be no doubts as to the validity of any new information. The fact that one site has

been identified does not warrant relaxation of the standards by which new sites

are judged. Pre-Clovis candidates should be scrutinized as thoroughly as they

have been in the past, and the Cactus Hill Site is no exception.

13

3. Overview of the Cactus Hill Site

Regional Setting and Geology

Site location

The Cactus Hill Site (Figure 3.1) is located in southeastern Virginia's Coastal

Plain region, 7 km to the northeast of the town of Stony Creek and 21 km east of

the Fall Line, a Cretaceous beachhead that separates the Coastal Plain from the

Piedmont physiographic province. Cactus Hill is one of several Paleoindian sites

identified along the Nottoway River, a tributary of the Chowan River that

meanders through Sussex County . The site is located on the east bank of the

Nottoway approximately 130 km from its source, with a local drainage area of

2500 square km. With a crest at 22 m AMSL, the buried sand dunes that form the

site represent a local high in elevation. The river shoal and swamps that bound

the site are 14 to 18 m in elevation. Before it was channeled and drained in 1967

for agricultural purposes, a small depression immediately to the south probably

served as a drainage basin for the southern and western portions of the dune.

Paleoenvironment

During the Late Wisconsinan glacial maximum (23,000 to 16,500 B.P.), the mean

annual temperature in the Southeast was between 21 and 27°F lower than today.

The climate was drier and less seasonal than the present, with dominant westerly

winds (Whitehead 1973; Barry 1983). Sea level ranged from 300 to 390 feet

below the present level. Until the end of the Pleistocene, the northern half of the

14

.\ ·1 ;

* MN 1

J IaN II,

~ dl

Ii

1000 0 1000 '000 ' 000 F3 H H

Ei-a=::O,*"==<=3:=E3=::OE3,*"='~~~~==~==~"'+3",,,,,1 KllOMETtR

CO NTOUR INTERVAL 10 FEET DOTTED l!NES REP RESENT S·Foor CONTOUR.S

Figure 3.1. Topographic map showing the location of the Cactus Hill site. From Sussex, Virginia 7.5 minute quadrangle. The transect A-A' is shown in Figure 2.2. (From Jones and Johnson 1997.)

15

Coastal Plain was dominated by jack pine-spruce boreal forest (Delcourt and

Delcourt 1981, 1985).

By the latest Pleistocene and early Holocene (12,500 to 8,500 B.P.), the

vegetation had changed to a mixed deciduous and evergreen forest of oak, pine,

hemlock and hickory (Delcourt and Delcourt 1981, 1985). Displacement of the

cold Labrador Current by the northward-moving Gulf Stream brought warmer

temperatures and increased seasonality to the Coastal Plain by 10,500 B .P.

(Delcourt and Delcourt 1986). Rapid sea level rise decreased river gradients and

drowned coastal forests and wetlands (Bense 1994).

The period between 8,500 and 4,000 B.P., commonly referred to as the

Altithermal, brought even warmer and drier conditions to the Southeast. Pine

came to dominate much of the Coastal Plain during this period, though the

reasons for the invasion are not clear (Bense 1994). The mid-Holocene marks a

changeover from higher energy flu vial environments and near-shore

sedimentation to more stabilized channel environments and frequent alluvial

sedimentation (Schuldenrein 1996).

The late Holocene (3 ,000 B.P. to present) witnessed the establishment of

present-day environmental conditions in the Southeast. The average annual

temperature in the northern portion of the Coastal Plain is near 60°F, and although

the Atlantic Ocean (only 160 km to the east) moderates the climate significantly,

the temperature can reach seasonal extremes of -15 to 11 OaF. Vegetation of the

Coastal Plain is divided between southern pine along the coast and oak-hickory­

southern pine forests in the interior (Delcourt and Delcourt 1981). Cactus Hill

lies in the latter region. The proportion of deciduous trees relative to evergreens

at the site is quite high, due in part to the generous water supply provided by the

Nottoway River.

Geology

Late Pleistocene and Holocene sand dunes have been identified throughout the

Southeastern Coastal Plain, particularly on the eastern banks of rivers. Regional

studies of dune axis orientations suggest that most of the deposits were formed by

16

westerly winds (Jones 1996). At least eight dunes containing cultural material

have been identified along the Nottoway River (McAvoy and McAvoy 1997).

Jones (1996) and Jones and Johnson (1997) describe the geology of the

Cactus Hill Site. The first major terrace above the Nottoway River, on which the

site is located, is characterized by east-west trending ridge and swale topography

with an average relief of 1.5 m (Figure 3.2). The terrace terminates to the south in

the east-west striking Lee Hall Scarp, a feature visible at the eastern end of the

site. Auger samples have revealed three main sedimentary units at the site. A

surficial mantle of well-sorted, medium to fine eolian sand is underlain by poorly

sorted fluvial sand and gravel deposits in the northwestern part of the site; to the

southeast it is underlain by a silty clay unit capped with a possible paleosol.

Jones and Johnson hypothesize that the Lee Hall scarp was created by

fluvial downcutting into the basal clay deposit. The sand and gravel unit was then

laid down, filling the river valley. Northwest winds deflated this deposit,

transporting the sand-sized particles a few kilometers to the southeast, where they

accumulated against the exposed scarp. As the deflation of the fluvial unit

progressed, the growing dune eventually buried the scarp in the vicinity of Cactus

Hill (Figure 3.3). The upper portion of this eolian deposit is relatively featureless.

Deeper sand is marked by a series of wavy, roughly parallel, reddish-brown

textural bands, or lamellae. A modern soil has developed on the dune surface,

although it has been homogenized significantly by agricultural activity. Since the

1960s, the land surrounding the site has been used as a hardwood tree farm

(McAvoy and McAvoy 1997). A more detailed description of the site's

stratigraphy is presented in the Results section.

Archaeological Investigations

Cactus Hill lies on land owned by the Union Camp Corporation, a concern that

has mined sand and gravel from a pit adjacent to the site since 1978. According

17

(m) 25

10

(ft.) 80

70

A (north)

60 Nottoway River

40

° I ·

I I

° 1,000

A' (south)

Lee Hall Scarp

Caclus Hill

Ridge and swale topography

500 1,000 1,500 meters I I

I I I . I

2,000 3,000 4,000 5,000 feet

Figure 3.2. Topographic profile along transect A-A' (see Figure 3.1) showing the Nottoway River, river terrace, Cactus Hill and the Lee Hall Scarp. (From Jones and Johnson 1997.)

18

30

IS

!~'t.

Older formations

0 a. Valley cut into older formations

JO

IS

Older formations

o~----------------------------~ c. Valley cut into clay and older formations

30 .

1 5

Older formations

O~------------------------~ e. Deflation of sand and gravel and

accretion of aeolian sand to south

(ft) ioo

50

0

(ft) 100

50

o

(ft) 100

50

Older formations

b. Deposition of fluvial-estuarine clay unit

Older formations

(m) 30

15

0

(m) 30

IS

~--------------------------~O d. Deposition of sand and gravel

Older formations

(m) 30

15

o 0 f. Continued deflation during the Holocene and

aeolian sand spilling onto clayey upland

Figure 3.3. Hypothesized origin of major sedimentary units at Cactus Hill. (From Jones and Johnson 1997).

19

to McAvoy and McAvoy (1997), the site was first reported to the Virginia

Department of Historic Resources by a Richmond resident in 1985, but it was not

until a local farmer traced sand and artifacts deposited as roadfill back to the site

in 1988 that it garnered any attention from archaeologists. For the next five years,

members of the locally-based Nottoway River Survey (NRS) conducted several

small test and salvage excavations, revealing what appeared to be a cultural

sequence stretching back to the Early Archaic period, possibly earlier. In 1993,

local artifact collectors showed NRS crews and Michael F. Johnson of the

Archaeological Survey of Virginia fluted projectile points looted from pits near

the gravel mine. These discoveries convinced Johnson and Joseph M. McAvoy of

the NRS that a full-scale excavation should be conducted to save the site from

further looting and erosion. Once the excavation was announced, the Union

Camp Corporation halted timber harvesting and gravel mining in the vicinity of

the site and restricted access to the property.

Independent excavations conducted In separate areas of the site by

Johnson and McAvoy began in the fall of 1993 and have continued intermittently

to the present. Area A, investigated by Johnson, lies at the southern edge of the

gravel pit, on the east-west striking ridge that forms the crest of the dune. Area B,

the main area investigated by McAvoy, lies 75 m to the west on the same ridge.

Area C consists of salvage pits located on the western fringe of the gravel pit.

Area D lies at the edge of the pit opposite Area A (Figure 3.4). Both

investigations have revealed a nearly continuous cultural sequence from

Paleoindian (Clovis) to Late Woodland in the upper meter of deposits.

Radiocarbon dates, most of them on carbonized wood, are stratigraphically

coherent and are generally in close agreement with age estimates based on lithic

typologies (McAvoy and McAvoy 1997). For an in-depth treatment of the results

of both investigations, the reader is referred to McAvoy's and McAvoy's (1997)

and Johnson's (1997) reports on their excavations at Cactus Hill.

A striking discovery came during the 1993 field season. Excavating

within the lamellar zone of Area B, McAvoy encountered a cluster of fluted point

fragments and related debitage associated with a scatter of carbonized southern

20

n ' +

CLAY-BOTTOM WETLAND

\ \

/ I

\

/

/ !

CACTUS HILL SITE 44SX202 SUSSEX CO., VA

o 10 20 30 40 m '-........ _ ....... --'--'

Figure 3.4. Site map showing major excavation areas. (Modified from McAvoy

and McAvoy 1997.)

21

pme. This charcoal subsequently yielded a Beta date of 1O,920±250 B.P. Nearly

8 cm directly below this cluster, McAvoy unearthed a few fragments of

carbonized white pine associated with seven quartzite flakes and three quartzite

core blades. These charcoal fragments produced a Beta date of 15,070±70 B.P.

Additional excavations were undertaken by McAvoy in spring 1996 to investigate

the possibility of a pre-Clovis component at Cactus Hill. In several locations,

clusters containing blades and blade cores were again encountered below "Clovis­

like" artifacts . One flotation sample of fine charcoal particles associated with a

blade cluster yielded a radiocarbon date of 16,670±730 B.P. Due to the paucity of

charcoal in. this area of the excavation, no dates were obtained for the apparent

Clovis horizon.

Encouraged by McAvoy 's results, Johnson resumed his investigation of

Area A in 1996, focusing his efforts on the squares in which a Paleoindian

component had been identified during the previous field season . Excavating in

the lamellar zone at a level comparable to that of McAvoy's finds, 23 cm below

the deepest Paleoindian horizon, Johnson uncovered a linear scatter of quartzite

artifacts, including seven blades and two fragments of the same unfluted

lanceolate projectile point (Figure 3.5). A cluster of charcoal recovered from the

same square and level as the blades was submitted for radiocarbon dating, but the

results of these analyses were inconclusive (Johnson, personal communication) .

No other artifacts have been recovered beneath the Paleoindian horizon in Area

A.

The recent findings at Cactus Hill have attracted the attention of the

archaeological community. A number of Paleoindian specialists visited the site

during McAvoy's 1996 excavations, including Dennis Stanford of the

Smithsonian Institution and C. Vance Haynes of the University of Arizona.

Despite the limited body of literature on the site, several archaeologists have

identified Cactus Hill as a potential pre-Clovis site (Beardsley 1998; Hall 1998;

Petit 1998). Johnson's and McAvoy's results are compelling for a number of

reasons. In each case, the artifacts and dated material appear to have been

recovered from the same stratigraphic level, with less than 3 cm of variation in the

22

Quartzite 24-14-1

" " . " .

'0 . ".' ....

Quartzite 24-14-3

Metamorphosed quartzite?

24-14-5

24-14-4

I (

4cm

, ~ .

Quartzite 24-14-2

Quartzite 24-14-6

Quartzite 24-14-14

Figure 3.5. Lithics recovered from Area A, Square 24, Level 14. (From Johnson 1997.)

23

vertical provenience of either McA Yoy' s 1993 find or the scatter uncovered by

Johnson. Second, Johnson has identified two fragments of a projectile point with

the same vertical provenience. Third, these artifacts have been recovered below a

Paleoindian level with a radiocarbon date of 10,920±250 B.P. Fourth, McAvoy's

two radiocarbon dates on the lowest cultural strata in Area B, while much earlier

than any others yielded by the site, are of comparable antiquity. Finally, the

presence of textural lamellae in the zones ' from which these artifacts were

recovered in Areas A and B may be an indicator of undisturbed stratigraphy.

However, Johnson ' s and McAvoy's results do not constitute unequivocal

evidence of a pre-Clovis presence at the site. There are a number of reasons for

caution in assessing the significance of the finds at Cactus Hill .

The question of stratigraphic integrity

Three elements must be present at any site that purports to predate Clovis . First,

there must be clear evidence of human agency. Second, a secure geochronologic

sequence must be established. Third, the evidence of pre-Clovis human activity

must have been recovered from an undisturbed stratigraphic context. The artifacts

excavated by Johnson and McAvoy clearly fulfill the first requirement, and the

combined application of radiocarbon techniques and luminescence dating may

help resolve the second issue (Johnson, personal communication). The question

of stratigraphic integrity, however, has not been given sufficient attention. Both

Johnson and McAvoy report that, while the overall cultural stratigraphic sequence

is quite coherent, vertical translocation of artifacts and organics appears to have

occurred to varying degrees throughout the site.

Cultural materials in sandy sites are particularly susceptible to post­

depositional disturbance . Thorns (1998) emphasizes the potential for

disarticulation and downslope or down-profile movement of occupation surfaces

at sandy upland sites, noting that homogenization of sandy sites can occur within

a few millennia. Thoms is also careful to point out that what appears to be well-

24

preserved cultural stratigraphy at a sandy site may actually be reconstituted

stratigraphy generated by biological activity or pedoturbation. Peacock and Fant

(1998) discuss the potential effects of bioturbation, in particular the burial and

translocation of artifacts, in silty and sandy contexts. They also outline the

competing roles of progressive, or stabilizing, and regressive, or homogenizing,

pedogenic processes on sandy sediments. Waters (1996) gives an in-depth

treatment of archaeological site-formation processes in eolian environments,

highlighting the different geologic mechanisms that can influence the distribution

of archaeological remains in wind-deposited sediments. Prior to burial, artifacts

can move along the surface of a dune with or against the prevailing wind or be

shifted by small-scale deformation features, including folds, faults and slumps.

Even if burial occurs rapidly enough to preserve the systemic context of a surface,

a dune that is not stabilized by vegetation or changing climatic conditions can

migrate or deflate, reworking the existing stratigraphy and even redepositing an

entire cultural sequence on a common surface. The potential for geogenic,

biogenic and pedogenic disturbance in sandy sites highlights the need for

conservative archaeological interpretations based on an understanding of site

formation processes.

A second cautionary note concerns the use of textural lamellae as an

argument for stratigraphic integrity. Past studies of lamellae indicate that such

features can form as a result of several different geogenic and pedogenic

pathways. A few authors (Wurman et al. 1959; Robinson and Rich 1960; Hannah

and Zahner 1970) describe textural bands apparently deposited as fluvial

sediments. A number of researchers have reported on lamellae formed solely

through pedogenic processes, such as the rhythmic precipitation of illuvial clay

(clay translocated by percolating water) or the flocculation of clay by free iron

oxides or carbonates (Folks and Riecken 1956; Dijkerman et al. 1967; Gray et al.

1974; Schaetzl 1992). Others (Wurman et al. 1959; Gile 1979; Cable 1996;

Rawling 1997) describe lamellae formed as textural discontinuities between

sedimentary strata triggered the redeposition of suspended clay. If the lamellae

are primary features-or secondary features that developed as a result of some

25

textural characteristic of the dune sand-they may be evidence of intact

stratigraphy. If they are of purely pedogenic origin, lamellae cannot be used as an

argument against post-depositional disturbance.

Objectives

In light of the potential for syndepositional and post-depositional disturbance in

sandy sites and the problem of equifinality in lamellar formation , it is clear that a

better understanding of the character and genesis of the sedimentary features at

Cactus Hill is necessary. This study seeks to answer two major questions: First,

what are the textural, compositional and genetic characteristics of the

macroscopically distinct units at Cactus Hill? Special emphasis will be placed on

the microstratigraphic character of the surficial sand deposits and lamellae in an

attempt to identify evidence of stratification, textural changes or disturbance that

is not visible in the field. Second, what sequence of geogenic, pedogenic and

biogenic processes produced the sedimentary configuration observed at the site?

The techniques most commonly employed in studies of site stratigraphy

are visual observations of the stratigraphic column and bulk chemical and

physical analyses. But whereas field observations and bulk analyses are valuable

for their efficiency, they are of limited value when the archaeologist is concerned

with subtle relationships between humans and their sedimentary environment, the

sequence of events that generated a given deposit, or stratigraphic details invisible

to the naked eye (Goldberg 1992). Micromorphology-the microscopic

examination of soils and sediments in three dimensions or in thin section-is a

valuable technique that can be used to complement more traditional methods of

sedimentological analysis.

The technical advantages of micromorphology over other techniques are

numerous. The high resolution afforded by microscopes is clearly advantageous,

as it permits the observation of features that are all but -invisible to the unaided

eye. Also obvious is the fact that bulk sampling homogenizes sediments,

26

destroying the original structure of the material , whereas both block samples and

thin sections preserve the integrity of samples. As Holliday and Stein (1989) have

demonstrated, the fact that micromorphology is based on non-digestive techniques

also eliminates a significant source of experimental error.

These technical advantages give the micromorphologist access to various

types of geological and archaeological information, all of which are discussed in

detail by Courty and colleagues (1989) and FitzPatrick (1993). Perhaps the most

obvious task that can be approached through micromorphology is the

characterization of the general sedimentology of a site, including the composition

of strata, the nature of boundaries and discontinuities between layers , and the

identification of vertical and horizontal patterns within the stratigraphic column.

Micromorphologists can also address the problem of geomorphology, an area of

study that includes chronological changes in the landforms, sedimentary

environments and erosional processes of a site or region. Paleopedology , the

study of ancient soils and soil-formation processes, is a related topic on which

micromorphology can generate a wealth of data. Micromorphological data can be

used to make paleoecological and paleoclimatic reconstructions, since the

characteristics of sediments and soils and the processes that produce them are

largely dependent on local and regional environmental conditions.

Perhaps the most powerful aspect of micromorphology is its ability to

identify the sequence of events that generated a sedimentary assemblage

(Goldberg 1980, 1992). Determining the life history of a sample demands an

intimate understanding of all the processes-sedimentary, anthropogenic and

post-deposition aI-that have shaped a deposit. In this sense, micromorphology is

particularly well suited to archaeology 's goal of unraveling stories. Although it

has been applied less frequently than other techniques , micromorphology is a

powerful analytical tool that can be used to address a wide range of

geoarchaeological questions. A micromorphological investigation of the deposits

at Cactus Hill should provide valuable information on the stratigraphic integrity

of the site.

27

4. Methods

Field methods

This study is based on fieldwork conducted in Area A of the Cactus Hill Site in

June 1998 in cooperation with Michael F. Johnson of the Archaeological Survey

of Virginia. Initial fieldwork consisted of participation in excavations to gain an

appreciation of the nature of the sediments to be studied. The exposed walls of

excavated squares were examined in the interest of selecting appropriate sites for

the collection of micromorphology samples. Changes in color and texture were

used to identify different stratigraphic units, and the depths of the boundaries

between these units were noted. Sample locations were selected such that the

resulting sequence of samples would span most of the visible stratigraphy of the

site , including obvious boundaries between units and the levels from which the

possible pre-Clovis materials were recovered. Although the stratigraphy was

quite uniform throughout Area A, an effort was made to collect the samples as

close as possible to the square from which the seven quartzite artifacts were

excavated. Figure 4.1 shows the locations of these lithics and the five

micromorphology samples collected in Area A. Table 4.1 gives the exact location

and depth range of each sample.

28

f;~ t'/. ,j

22 I 23 m Ml

21 14

~'If\ \" 1 L _ ";

r'u:" 1 .

u ~6

24

15

~ I' ~ --5 t"" , I

; \ l.)

I 1 I 2 I

25

26

Figure 4.1. Partial plan of Area A showing locations of micromorphology samples and lithics recovered from Square 24, Level 14. Artifacts and samples are not to scale.

1) 0_0

• 0\

'" m.n

3-10

Table 4.1. Locations and depth ranges of micromorphology samples.

Coordinates from NW Depth (cm)

Sample Square corner of square (cm) East South Top of core Bottom of core

1 2S 30 287 86.4 111.8 2 2S 42 287 109.2 132.1 3 22 296 171 143.5 163 .8 4 22 296 17l 163.8 184.2 5 22 120 168 118.1 143.5

Each sample was collected by driving a 25 cm section of 2" by 3"

galvanized gutter pipe down into the sediment approximately 5 cm from the

exposed stratigraphic face . The sampling area was saturated with water to ease

penetration and minimize the possibility of sediment collapse. After the location

and depth range of the core were recorded, the surrounding sediment was

excavated and the core was removed. Orientation markings were placed on the

pipe, and its ends were sealed with tissue paper and packing tape. The cores were

then transported to the laboratory and refrigerated at 5°C until processing.

Laboratory methods

Sample impregnation was performed at the Micromorphology Laboratory,

Department of Archaeology, Boston University. Tape and tissue paper wrappings

were removed from each core, and the samples were dried in an oven for one

week at 70°C. The galvanized pipe encasing each sample was perforated on each

side with a 1/8" nail to allow air and resin to pass through. Each sample was laid

in an aluminum pan and impregnated with a polyester/polystyrene resin. Resin

was added incrementally over a period of two weeks so as not to trap air in the

voids within samples. Once impregnation was complete, samples were dried in

an oven for one week at 65°C.

Cutting was performed in the Thin Section Laboratory, Department of

Earth and Planetary Sciences, Harvard University. Cores were cut longitudinally

30

into slabs 1 cm thick, producing east-west cross-sections of the sediments

sampled. Two (or three, in ·the case of sample number 5) 5.1 by 7.6 cm blocks

were cut from the best slab such that all representative features and boundaries

between units were contained within individual blocks. Thin sections were

prepared from these blocks by Spectrum Petrographics, Inc., Eugene, Oregon.

Table 4.2 gives the depth range covered by each thin section. These ranges, along

with the vertical provenience of the possible pre-Clovis materials, are shown on a

generalized stratigraphic column for Area A in Figure 5.1.

Table 4.2. Depth ranges of thin sections.

Section

Depth Ia Ib 2a 2b 3a 3b 4a 4b Sa Sb Sc (cm)

Top 96.5 104.1 111.8 119.5 145.8 153.4 165.1 172.7 119.9 127.5 135.1

. Bottom 104.1 111.8 119.5 127.2 153.4 161.0 172.7 180.3 127.5 135.1 142.7

Thin section analysis

Thin sections were initially examined at low magnification in a microfiche reader

to identify and demarcate areas of textural and compositional homogeneity.

Using a petrographic microscope, each area was examined at various

magnifications in plane polarized, cross polarized and circularly polarized light.

Qualitative descriptions of thin sections were made using the concepts and

terminology presented in Bullock and colleagues' Handbookfor Soil Thin Section

Description (1985) . Within each area, the microstructure, voids, basic mineral

and organic components, and pedofeatures were described qualitatively.

Semiquantitative estimates of void space, mineral abundances, particle size

distributions and pedofeature densities were made by comparison with frequency

charts.

To obtain a quantitative measure of textural variations within the deposits

at Cactus Hill, image analysis techniques were applied to the thin sections. Using

31

a solid state video camera attached to a petrographic microscope, a series of

digital images were taken at a magnification of 40X along a 72 mm vertical

transect 17 mm from the left edge of each slide. In sections 3b, 5a and 5b, the

transect was taken 17 mm from the right edge to avoid gaps in lamellae. A

graduated stage was used to advance the slide in increments of 2 mm. Each of 36

2 by 2.6 mm frames was imaged in plane polarized and circularly polarized light.

Each image was saved as a TIFF file and analyzed using Image Pro Plus®, an

image analysis tool developed by Media Cybernetics, Inc. Since clay appears as

the only dark object in plane polarized light, these images were used to calculate

the percentage of each frame's area occupied by clay. Sand-sized mineral grains

appear as the only bright objects in circularly polarized light, and so these images

were used to measure several textural parameters of the coarse fraction, including

the area, perimeter, intermediate diameter, roundness, and orientation of each

grain. The results of these measurements were used to calculate additional

parameters for each frame, including original void space, grain size distribution,

mean roundness, and mean orientation. The definitions of these parameters are

listed in Table 4.3. For each thin section, grain size distribution, original void

space, clay content, mean roundness and mean orientation were plotted against

depth to test for vertical trends and differences between units.

32

Table 4.3. Definitions of quantitative textural parameters used in image analysis.

Parameter Definition Area Area of a grain in square microns Perimeter Distance around the outer edge of agrain Intermediate Shorter dimension of the smallest rectangle that can be circumscribed about diameterl a grain

Roundness Square of the ratio between an object's perimeter and the circumference of a circle with the same average radius.

Orientation Angle between the long axis of a grain and vertical; measured in the clockwise sense

Clay content Percentage of the total frame area occupied by clay-sized particles Original void

Percentage of the total frame area not occupied by mineral grains space

Modal abundance of various size classes of mineral grains. Grain size For a given size range, modal abundance is calculated by dividing the total distribution2 area occupied by grains of that size range by the total area occupied by all

grains. Mean roundness Mean roundness of all grains in a given frame or size range Mean orientation Mean orientation of all grains in a given frame or size range

lThe intermediate diameter was used as a measure of grain size to approximate as closely as possible the results of a sieve analysis. 2The following size classes were used for grain size analyses: very fine sand (intermediate diameter of SO - 100 /-lm); fine sand (1 00 - 200 /-lm) ; medium sand (200 - sao /-lm); coarse sand (SaO - 1000 /-lm); very coarse sand (1000 - 2000 /-lm).

33

5. Results

Field observations

Observations of the stratigraphy in Area A of the Cactus Hill Site revealed six

distinct stratigraphic zones. These zones, along with the depth range of each thin

section and the vertical provenience of the possible pre-Clovis artifacts, are shown

on a generalized stratigraphic column for Area A in Figure 5.l. Each zone is

described below.

Zone I (0 to 20 cm). The upper 20 cm of the deposits at Cactus Hill consist of a

very dark grayish brown (10YR3/2) sandy A horizon disturbed by historic

agricultural activity and modem tree farming. Tree roots, root fragments and

wood debris comprise a significant fraction of Zone 1.

Zone II (20 to 100-120 cm). Underlying the A horizon is a zone of yellowish

brown (10YR5/4) medium to fine sand. The thickness of this unit ranges from 80

to 100 cm depending on the upper limit of the underlying lamellar zone. There is

little variation in the color or texture of the sand. The abrupt boundary between

Zones I and II is defined by the lower limit of the plow zone.

Zone III (100-120 to 167 cm). Below the zone of featureless sand is a horizon

marked by a series of parallel, dark brown (10YR3/3) textural lamellae. The

lamellae, typically 0.5 to l.5 cm thick, are separated by 2 to 5 cm of yellowish

34

40

60

80

100

.. . ' . · , '.' . . . :

, ' , , . . ' , ' . '. . . · . '" .

. . ' . . . ' .. .. . . ' ., ..

. .

. . ..

. . . ' . , .

. ' '. . . . . '

. .' ..... . :

.. "

'. . . . . ', ..

. .

. .

. . . . . ' .. .

.. . . . . " . . . . . . ' ..

. . . . . . . ' . . .....

"-- i .... .... ....<., .• :: ................•......

. ' . 3a

1.,,;'..;,,' ___ ~"". ............ __ ~ 3b . . . . 160 ' ., . . . . . ' '. · . " ...

180

Zone

I

II

III

IV

V

VI

Figure 5.1. Stratigraphic column for Area A showing depth ranges of thin sections and vertical provenience of lithics recovered from Square 24, Level 14. Artifacts are not to scale.

35

-------- -------------------------------------------------------------------------------~

brown (10YRS/4) medium to fine sand very similar to Zone II sand. Lamellae are

finer textured, darker in color and more cohesive than interlamellae. In cross

section, they appear as wavy, broken bands that parallel both the modem surface

and the contact between Zones I and II. Viewed from above, they are patchy and

discontinuous. The uppermost lamellae in Zone III are thinner and more

discontinuous than deeper lamellae. As its upper limit varies between 100 and

120 cm below the surface, the lamellar zone ranges from 47 to 67 cm in thickness.

The boundary between Zones II and III is defined by the appearance of lamellae.

Zone IV (167 to 171 cm). A thin zone of yellowish brown (lOYRS/6) loamy sand

delineates the lower limit of the lamellar zone. The boundary between Zones III

and IV is diffuse and indistinct.

Zone V (171 to 176 cm). A ·unit of dark yellowish brown (10YR4/6) sandy clay

loam underlies zone IV. The boundary between Zones IV and V is mottled and

irregular.

Zone VI (176 cm to ?). A dark yellowish brown (10YR4/4) sandy clay is the

lowermost unit exposed in Area A. The boundary between Zones V and VI is

wavy and diffuse.

Thin section descriptions

Thin sections and subsections are shown in Figures S.2 through S .12. Detailed

descriptions of the microstructure, voids, basic mineral and organic components

and pedofeatures visible in each thin section are presented in Tables S .1-S .11.

These results have been combined into an overview of the microscopic character

of Zones II through VI. Numbers in parentheses refer to the corresponding thin

sections and subsections. Table S.12 provides definitions of terms used in thin

section descriptions.

36

, "

.' .. .~

..... .

" , -". "..:. ~~ , ~~

.., ~ '; , I •

'i , .. >.

-. -<. " ,

""

. .. ,:

I'

' .. " t .... , ... '

.. '

,

. .' . f'

.' .'

,. 1-.

1a

..

.; ....

.. ; .. t­. :' -;'i. . . .:,. . . '~

;:-. "

..... . { ."

Figure 5.2. Thin section 1a. See Table 5.1 for description.

J

. t

I

The rectangle shows the location of the image analysis transect.

37

Table 5.1. Description of thin section la

Sub- Micro-Voids Bas ic mineral and organic components Pedofeatures

section structure N/A Pellicu lar 40% of section area 60% of section area 3% of section area

grain Type % Descri ptio n Type %

Size di stribution Mineralogy Descri ption Type % Description

structure (mode %)1 (mode %)2

Simple 100 Subangu lar, Sand 100 C 60%, M 35%, f Q 85, Plag Moderately to well-sorted Typ ic 100 Reddish to yellow ish Chitonic packing weakly 5%, VF 5% 10, Ksp 5, slibangllliar grains with coati ngs brown, non-lami nated, related spherical voids M+W moderate to hi gh weakly oriented , distribu- L 00-400~lm in +HM<I sphericity. Very few speckled , impure clay tion diameter. fe ldspar grains show coatings 1O- 50~ll1l

complex. or cross-linear thick. alteration to clay.

IC=coarse, M=medium, F=fine, VF=very fine 2Q=quartz, P=plagioclase feldspar, Ksp=alkali feldspar, M=muscovite and biotite, W=carbon ized wood, HM=heavy minera ls, including epidote, hornblende, and augite.

00 (f)

'.

I' , ~ . ....

, " . . -'. '.,

, . . ~-,,': •• "f. :. .r ,.

,. '- ~ .,

" . . . -~ .. , . .

;-

"

.... .......

'. ' . .... =\- .. "J'

'f;

1b Figure 5.3. Thin section 1 b. See Table 5.2 for description. The rectangle shows the location of the image analysis transect.

39

Table 5.2. Description of thin section 1 b

Sub- Micro-Voids Basic lIlineral and organic components Pedofeatures section structure

i Pellicular 40% of subsection area 60% of subsection area 5% of subsection area grain

Type % Description Type % Size distribution Mineralogy

Description Type % Description structure (mode %)1 (mode %)2 Simple 100 Subangular, Sand 100 C 60%, M 35%, F Q 90, Plag Moderately to well-sorted Typ ic 100 Reddis h to

Chitonic packing weakly 5%, VF 5% 8, Ksp 2, subanglu lar grains with coatings yellowish brown, related spherical voids M+W+ moderate to high non -lami nated, distribu- 100-400/lm in HM<I sphericity. Very few weakly oriented, tion diameter. feldspar grains show speckled, dusty

complex or cross-linear clay coatings 10-alteration to clay. 50~ll11 thick.

II Pellicular 20% of subsection area 60% of subsection area 20% of subsection area to

Type % Description Type % Size distribution Mineralogy

Description % Description bridged (mode %)1 (mode %)2 Type

grain Si mple 100 Subrounded, Sand 100 C 50%, M 45%, F Q 90, Plag Moderately to well-sorted Typic 70 Yellowish brown structure packing weakly 5%, VF X% 8, Ksp 2, subanglular grains with coatings to brown, non-

spherical voids M+W+ moderate to hi gh laminated , weakly Chitonic- 50-400~lm in HM<l sphericity. Very few oriented, speckled, gefuric diameter. feldspar grains show dusty clay coatings related complex or cross- linear 20- 1 OO~lm thick. distribu- alteration to clay. Form bridges tion between grains.

Crescent 30 Yellowish brown coatings to brown, weakly

microlalllinated, strongly oriented, limpid to dusty clay coatings 50-100~lm thick. Fill bottoms of voids, narrow intergranular spaces.

lC=coarse, M=medium, F=fine, VF=very fine 2Q=quartz, P=plagioclase fe ldspar, Ksp=alkali feldspar, M=muscovite and biotite, W=carbonized wood, HM=heavy minerals, including epidote, hornblende, and augite

o "'i"

.' .: _" J. ,f .'.

[ I 11 Ii ,.

Figure 5.4. Thin section 2a. See Table 5.3 for description. The rectangle shows the location of the image analysis transect.

41

Table 5.3. Description of thin section 2a

Sub- Micro-Voids Basic mineral and orga ni c components Pedofeatures section structure

N/A Pellicular 50% of section area 45% of section area 5% of section area grain

Type % Descri ptiol1 Type % Size di stribution Mineralogy

Description Type % Description (mode %)1 (mode %)2 structure

Simple 100 Subanglilar, Sand 100 C 20%, M 70%, F Q 85, P lag Moderate ly to well -sorted Typic 95 Reddi sh to Chitonic packing weakly 10%, VF X% 10, Ksp 5, subang lular to subrollndcd coatings yellowish brown, related spherical voids M+W+ grain s with moderate to non-Iami nated, distribu- lOO-500~m in HM<I high sphericit y. Very few weakly ori ented, tion diameter. feld spar grains sho w speckled, du sty

complex or cross- linear clay coatings lO-a Ite ration to cl ay. 50~llll thick.

C hi tonic related distribution.

Crescent 5 Yellowish brown coatings to brown, weakly

mi cro lami nated, strongly oriented, limpid to dusty clay coatings 50-I OO~ll11 thick. Chitonic re lated di stribution . Fill bottoms of voids, narrow intergranular spaces.

IC=coarse, M=medium, F=fine, VF=very fine

2Q=quartz, P=plagioclase feldspar, Ksp=alkali feldspar, M=muscovite and biotite, W=carbonized wood, HM=heavy minerals, including epidote, hornblende, and augite

I I

C'l -.:t

2b Figure 5.5. Thin section 2b. Roman numerals refer to subsections described in Table 5.4. The rectangle shows location of the image analysis transect.

43

Table 5.4. Description of thin section 2b

Sub- Mi cro-Voids Basic mineral and organi c components Pedofcaturcs section structure

i Pellicular 40% of subsection area 55% of subsection area 5% o f subsection area grain

Type % Description Type % S ize d istributi on Mineralogy

Description Type % Descripti on structure (mode %)' (mode %)~ Simple 100 Subangul ar, Sand 100 C 20 %, M 70%, F Q 85, Pl ag Moderately to well -sorted Typic 100 Reddish to yell owish

C hitonic packing weakly spheri ca l 10%. VF 5% 10, Ksp 5, subanglll iar to subl'O unded coatings brown , non-related vo ids 100-500f,lm M+W+ grains with moderate to high laminatcd, weakly di stribu- in diameter. HM < I spheri city. Very few feldspar oriented, speckled, tion grains show complex or cross- dusty clay coatings

lincar altcration to c lay. I 0-5 Of,l III thick. ii ,iii Pellicular 25% of subsection area 50% of subsection area 25% of subsection area

to bridged Type % Description Type %

Si ze di stribution Mineralogy Description Type % Descripti on grain (mode %)' (mode %)2

structure Simple 100 Subangul ar, Sand 100 C 5%, M 50%, F Q 85, Pl ag Moderate ly to well -sorted Typ ic 20 Yellowish to reddish packing weakl y spheri cal 45%, VF X% 10, Ksp 5, subanglula r to subrounded coa tings brown, non-

Chitonic- vo ids 50-300f,lm M+W+ grains with moderate to high laminated, weakly gefuric in diameter. HM <I spheri city. Very few feldspar ori ented, speckled, re lated grains show compl ex or cross- dusty cl ay coatings di stribu- linear alteratio n to clay. 1O- 100f,l1Tl thic k. ti on Form bridges

between grains. Crescent 20 Yellowish to reddi sh coatings brown,

microl aminated, strongly ori ented, ~ limpid to dusty c lay coatings 100-200JJm thick. Fill bottoms o f vo ids, narrow intergranu lar spaces.

Dense 60 Yellowish to redd ish incom- brown, non-plete laminated to weakly infilling microl aminated,

weakly ori ented, speck led, dusty in fillin gs 50-300JJm in diameter.

'C=coarse, M=medium, F=fine, VF=very fine 2Q=qualtz, P=pJagiocIase feld spar, Ksp=alkali feldspar, M= ll1uscovite and biotite, W=carbon ized wood , HM=heavy minerals, including epidote, hornblende, and augite

I' .. ~ . ~ '.

~. ·1 ~

.,'- . . , ' ': .

, "'1' " .-: p ~ . ' . , "

of ... ;-r ....

::: . .t ' . :' \ ; =~1, ~ ~~~ . ..

'I

Figure 5,6. Thin section 3a. Roman numerals refer to subsections described in Table 5.5. The rectangle shows the location of the image analysis transect.

45

Table 5.5. Description of thin section 3a

Sub­section

I ,lll ,V

1I ,lv,vi

Micro­structure

Pellicular to single grain structure

Chitoni c related distribu­tion

Pellicular to bridged gra in structure

Gefuric related distribu­tion

Voids

50% of subsection area

Type

Simple packing

%

100

Description

Subangu lar, weakly spherical voids 100-500~m in diameter.

25% of subsection area

Type

Simple packing

%

100

Description

Subangular to subrounded, moderate ly spherical voids 50-200~m in diameter.

'C=coarse, M=medium, F=fin e, VF=very fine

Basic mineral and o rga ni c components

50% of subsection area

Type %

Sand 100

Size dist ribution (mode %)'

C 30%, M 40%, F 30%, VF X%

50% of subsection area

Type I %

Sand I 100

Size distribution (mode %) '

C 5%, M 50%, F 45 %, VF X%

M in eralogy (mode %)2

Q 90, Plag 8, Ksp 2, M+W+ 11 M < I

Mineralogy (mode %)2

Q 90, Plag 8, Ksp 2, M+W+ HM < I

Description

Moderately to we 1.l -sorted subangllli ar grai ns with moderate to high spheri city. Very few fcldspar grai ns show compl ex or cross­linear a lteration to clay.

Description

Moderate ly to we ll -sorted subanglul ar grains with moderate to hi gh sphericity. Very few feld spar gra ins show complex or cross­linear aiterat ion to clay.

Pedo reatures

I % of subsection area

Type % Description

Typic 100 Reddi sh to coatings ye ll owish brown,

non-laminated, weak lyoricnted, speck led, dusty clay coatings I 0-50~m thick.

25% of subsection area

Type % Descri pt ion

Typic 20 Yellow ish to coatings reddish brown, non-

laminated, weakly oriented, speckled , dusty clay coatin gs I 0-50~111 thick. Form bridges between gra ins.

Crescent

1

60 Yellowish to coatings reddi sh brown,

microlam i nated, strongly oriented, limpi d to dusty clay coati ngs I 00-300~lm th ick. Fi II bottoms of voids, narrow

_ __ intergranular sQaces. De nse 20 I Ydlowi,,, 10 incom- redd ish brown , non-pl ete lam inated to weak ly infillin g mi cro lam in ated,

moderately oriented, speck led, dusty infillings 50-200~m

in diameter.

2Q=quartz, P=plagioclase feldspar , Ksp=alkali feldspar, M=muscovite and biot ite, W=carboni zed wood, HM =heavy min erals, including epidote , hornbl ende, and augite

\0 -.::t

... ' . I · \

.. y ....

" '

I I "

1- . , :

3b Figure 5:7: Thin section 3b: Roman numerals refer to subsections described in Table 5:6: The rectangle shows the location of the image analysis transect

47

Table 5.6 . Description of thin section 3b

Sub- Micro-Voids Bas ic min eral and organic components Pedofeatures section structure

i,iv,vj Single 50% of subsection area 50% of subsection area I % of subsection area grain

Type % Description Type % Size distribution Mineralogy

Description Type % Description structure (mode %)' (mode %)2 Simple 100 Subangular, Sand 100 C 40%, M 40%, F Q 90, P lag 8, Moderately to well -sorted Typic 100 Reddi sh brown,

Chitonic packing weakly spherica l 20%, VFX% Ksp 2, suban glular gra in s w ith coatin gs non -laminated, related voids 100- M+W+ moderate to hi gh spheric ity. weakly oriented, distribu- SOOf..lm in 11M < 1 Very few fe ldspar g rai ns speckl ed, elusty clay tion diameter. show complex or cross- coatin gs I 0-50~lm

linear alteration to cl ay. thick. ii,iii ,v Bridged 30% of subsection area 50% of subsection area 20% of subsection area

grain Type % Description Type %

Size di stribution Mineralogy Description Type % Description structure (mode %)' (mode %)2

Simple 100 Subrounded to Sand 100 C 40%, M 40%, F Q 90, PI;Jg 8, Moderately to well-sorted Typic 20 Yellowish to Gefuric packing rounded, 20 %, VF X% Ksp 2, subanglular grains w ith coatings reddish brown, non-related moderately M+W+ moderate to hi gh sphericity. lamin ated, weakly di stribu- spherical voids HM<I Very few fe ldspar g rains oriented, speckled, tion 50-300f..lm in show compl ex or c ross- dusty clay coatings

diameter. linear alteration to c lay. 1O-50f..lm thick. Form bridges between grains.

C rescent 60 Yellowish to coatin gs reddish brown,

l11icrolal11 i n ated, stron gly oriented, I impid to dusty cl ay coati ngs 1 00-400~lm thi ck. Fill bottoms of voids, narrow intergranular spaces.

Dense 20 Yellowish to incom- reddish brown, non-plete laminated to weakly infilling l11icrol aminated,

moderate ly oriented, speck led, dusty infi ll ings 50-300f..l111 in diameter.

'C=coarse, M=l11ediul11, F=fine, VF=very fine

2Q=quartz, P=plagiocl ase feldspar, Ksp=alkal i fe ld spar, M=muscov ite and biotite, W=carboni zed wood, HM=heavy minerals , including epidote, hornbl ende, and augite

00 -.::t

: .

4a Figure 5.8. Thin section 4a. Roman numerals refer to subsections described in Table 5.7. The rectangle shows the location of the image analysis transect.

49

TabJe 5.7. Descripti on of thin section 4a

Sub- Micro-Voids Bas ic mi nera l and organi c components

section structure i S ingle 50% of subsecti on area 45% of subsection area

grain Type % Description Type %

Size distribution Minera logy Descri ption

structure (mode %) ' (mode %)'

Simple 100 Subangular, Sand 95 C 30%, M 50%, F Q 90, !'Iag 8, Moderately to we ll -sorted Chi tonic packing weak ly spherical 20%, VFX% Ksp 2, subanglular gra ins with related voids I 00·400~lm M+W+ moderate to high sphericity . distribu- in diameter. HM < I Very few I"cldspar grains show tion; locall y complex or cross- linear gefur ic alteration to clay.

S ilty 5 Dense, gray to brown, speckled , clay unori ented infi llings within

groups of gra ins. Often isotropic.

ii Pellicul ar 45% of subsection area 50% of subsection area to bridged

Type % Description Type % S ize distri bution Minera logy

Description grain (mode %) ' (mode %)' structure Simpl e 100 Subangular, Sand 90 C 30%, M 50%, F Q 90, Plag 8, Moderately to well -sorted

pack ing weak ly spheri ca l 20%, VF X% Ksp 2, subanglular grai ns with Chi toni c- voids I 00-400~lm M+W+ moderate to high spheri city. gefuric in diameter. 11 M < I Very few feldspar gra ins show related complex or cross- linear di stribu- alteration to clay. ti on Sil ty 10 Dense, gray to brown, speckled ,

clay unoriented infi llings withi n groups of gra ins. Often iso tropic.

iii Bridged 10% of subsecti on area 80% o f subsecti on area grain

Type % Description Type % Si ze distribution Mineralogy

Descri pti on structure (mode %)' (mode %)'

S imple 100 Subangu lar, Sand 70 C 30%, M 35 %, F Q 90, Plag 8, Moderately sorted angular to Close pack ing weak ly spherical 25 %, VF X% Ksp 2, suba ngul ar grains wit h moderate porphyric voids 50-200~lIn in M+ 'vV+ sphericity. Very few feldspa r related dia meter. HM < I grains show complex or cross-distribu- li near al teratio n to clay. ti on Clay 30 Dense, brown, speckled ,

and unorien ted infi ll ings. Often sil t isotropic.

'C=coarse, M=medium, F=fin e, VF=very fin e 'Q=quartz, P=plagioclase feldspar. Ksp=alka li feldspar, M=l1l useovite and biotite, W=carbonized wood, HM=heavy mi neral s, including epido te. hornblende, and augite

!'cdo l"ca tllres

5% of subsecti on area

Type 9f, Descri pt ion

Ty pi c 100 Ye llowish brown to coatings brown, non-laminated ,

weak ly oriented. speckled. dusty clay coat ings I 0-75~lI ll

th ick on 25% o f grai ns.

5% of subsecti on area

Type % Description

Typic 100 Yellowish brown to coatings brown, non-laminated ,

wea kl y orient ed, speckled, dusty clay coatings I 0-75~lm

thi ck on 25 % of grains.

10% of subsecti on area

Type % Descri ption

Typic 95 Yellowish brown to coa tj ngs brown, non-laminated,

weakly ori ent ed, speckled. dusty clay coatings I 0-75~lm thi ck on 25% of gra ins.

Crescent 5 Redd ish brown, coa tings microlaminated,

strongly oriented, limpid to dusty clay coati ngs I 00-200~1 111

thick . Fi ll botto ms of voids, nalTOW intergranular spaces.

, ,

I I

, ,

o If)

Figure 5.9. Thin section 4b. Roman numerals refer to subsections described in Table 5.8. The rectangle shows the location of the image analysis transect.

51

Table 5.8 . Description of thin section 4b

Sub- Micro-Voids Basic mineral and organi c components Pcdofeatures section structure

i Bridged 10% of subsection area 80% of subsect ion area 10% of subsect ion area grai n

Type % Description Type % Size di str ibution Mi nera logy

Dcscription Type % Description structure (mode %)' (mode %)' Simple 100 Subangu lar, Sand 70 C 30%, M 35%, F Q 90, Plag 8, Moderate ly sorted angu lar to Typic 95 Ye ll owish brown to

C lose packi ng weakly spher ical 25%, VF X% Ksp 2, subangular grains with coatings brown, non-porphyric vo ids 50-40011m M+W+ moderate sphericity. Very few laminated, weak ly related in diameter. HM < I feldspar grains show comp lex oriented , speckled, dislribu- or cross-li near ~ lt c ra t i on to dusty clay coatings lion clay. 10-75J.!1ll thick on

25% of grai ns. Crescent 5 Reddish brown,

Clay 30 Dense, brown, speckled, coatings microlaminated, and unoriented infi ll ings. Often strongly oriented, si lt isotropic. limpid to dusty clay

coatings 100-2OOI1Ill thick. Fill bottoms of voids, narrow in tergranu lar spaces.

ii Bridged 10% of subsection area 85% of subsection area 5% of subsection area grain

Type % Descript ion Type % Size distribution Mineralogy

Description Type % Description structure (mode %)' (mode %)' Simple 100 Subangul ar, Sand 70 C 35%, M 35%, F Q 90, Plag 8, Moderale ly sorted subanglular Crescent 100 Yel lowish brown,

Close packing weak ly spherical 20%, VF X% Ksp2, grains wilh moderate coatings microlami nated, porphyric vo ids 50-2OOl1m M+W+ sphericity . Very few feldspar strongly oriented, re lated in diameter. HM < I grai ns show complex or cross- dusty clay coatings distribu- li near alteration to c lay. I 00-200llln thick. tion Clay 30 Dense, dark brown, speckled, Fill bottoms of voids,

and unori ented infi llings . Often narrow intergranu lar silt isotropic. spaces .

III Bridged 8% of subsection area 90% of subsection area 2% of subsection area grain

Type % Description Type % Size distribut ion Mineralogy

Description Type % Description structure (mode %)' (mode %)' Simple 100 Subangular, Sand 50 C 30%, M 25%, F Q 90, Plag 8, Moderately sorted angu lar to Crescent 5 Redd ish brow n,

Close packing weakly spherical 25%, VF X% Ksp 2, subangular grains with coati ngs microlaminated, porphyric voids 50-200J.!m M+W+ moderate sphericity. Very few strongly oriented, related in diameter. HM<I feld spar grains show cOlllplex limp id to dusty clay d istribu- or cross-linear alteration to coatings 100-200J.!m tion clay. thick. Fill bottoms of

C lay 50 Dense, dark brown, speckled, voids , narrow and unoriented infill ings. Often intergranular spaces. silt isotropic.

'C=coarse, M=medium, F=fine, VF=very fine 'Q=quartz, P=plagioclase feldspar, Ksp=alka li feldspar, M=muscovite and biotite, W=carboni zed wood, HM=heavy minera ls, including epidote, hornblende, and augite

N If)

r •.• ,: .~ r

) .

\ - ;)

./ ..:. . ~ ... . . , : "' 4 ... . " ~.'. \ , " . .': ,{ ,

:).l./ .. ,, -:;. 4l-' • I

Figure 5.10. Thin section Sa. Roman numerals refer to subsections described in Table 5.9. The rectangle shows the location of the image analysis transect.

53

Table S.9 . Description of thin section Sa

Sub- Micro-Voids Basic min cra l and org;nli c C0111pon cnts Pcdofcat llrCS

section structure i,iii,v Single 50% of subsection area 50% of subsection area I % of subsection area

grain Type % Description Type %

Size distribution Mincra logy Dcscription Type % Description

structure (mode %)1 (mode %)2

Simple 100 Subangu lar, Sand 100 C 40%, M 40%, F Q 90, Plag 8, Moderately to well -sorted Typic 100 Reddi sh brown, Chitonic pack in g weakly spherical 20%, VF X% Ksp 2, suban glul ar grain s with coati ngs non-laminated, related void s 100- M+W+ moderate to hi gh spheri c ity. weakly o riented, di stribu- 500l-1m in HM < I Very few feld spar grains speckled , dusty clay tion diameter. show complex or cross- coatin gs 10-50~lm

linear alterat ion to clay. thick.

ii ,iv,vi Bridged 30% of subsection area 50% of subsection area 20% of subsection area grain

Type % Descript ion Type % Size di stribution Mineralogy

Description Type % Description structure (mode %) 1 (mode %)2

Simple 100 Subrounded to Sand 100 C 40%, M 40 %, F Q 90, Plag 8, Moderately to well -sorted Typic 20 Yellowish brown to Gefurie packing rounded, 20%, VF X% Ksp 2, subanglular grain s with coatin gs brown, non-related moderately M+W+ moderate to hi gh spheri city. laminated, weak ly distribu- spherical voids HM <1 Very few feld spar grains oriented, speckl ed, tion 50-400l-1m in show complex or cross- dusty clay coatings

diameter. lin ear alterati on to clay. 10-50l-1m thick . Form bridges between grains.

C rescent 70 Yellowish brown to coatings brown ,

microlamin ated, strongly or iented, limpid to dusty clay coatin gs I 00-300~lm

th ick. Fi II bottoms of voids, narrow intergranul ar spaces.

Dense 10 Yellowish brown to incom- brown , non-

plete laminated to weakly infilling microlaminated,

moderately oriented, speckled, dusty infill ings 50-400[..lIll in diameter.

lC=coarse, M=mediulll, F=fine, VF=very fine 2Q=quartz, P=pl agiocl ase fe ldspar, Ksp=alkal i fe ldspar, M=mu scovite and biotite, W=carboni zed wood, HM=heavy minerals, includ ing epidote, horn blende, and augite

I

!

1

I

-.:::t tn

5b Figure 5.11. Thin section 5b. Roman numerals refer to subsections described in Table 5.10. The rectangle shows the location of the image analysis transect.

55

Table 5.10. Description of thin section 5b

Sub- Micro-Voids Basic mi ll eral a ll d organ ic compone nts Pedoreatures section structure

i,iv Single 50% of subsection area 50% of subsection area I % of subsection area grain

Type % Descr.iption Type % Size distribution M inera logy

Descript ion Type % Description structure (mode %)1 (mode %)2 Simple 100 Subangular, Sand 100 C 40%, M 40%, F Q 90, Plag 8, Moderate ly to well-sorted Typic 100 Redd ish brown,

Chitonic packing weakly spheIical 20%, VFX% Ksp 2, subanglular grains with coatings non-lam inated, related voids 100- M+W+ moderate to high sphericity. weakly oriented , distribu- 500]1m in HM < I Very few fe ldspar grains speckled, dusty clay tion diameter. show complex or cross- coatings I 0-50~lm

linear alteration to clay. thick. ii,iii,v Bridged 30% of subsection area 50% of subsection area 20% of subsection area

grain Type % Description Type %

Size distribution Min era logy Description Type % Description structure (mode %)1 (mode %?

Simple 100 Subrounded to Sand 100 C 40%, M 40%, F Q 90, Plag 8, Moderately to well -sorted Typic 20 Yellowish to Gefuric packing rounded, 20%, VF X% Ksp 2, subanglular grains with coatings reddish brown, non-related moderatel y M+W+ moderate to high sphericity. laminated, weakly distribu- spherical voids HM<I Very few feldspar grains oriented, speckled, tion 50-400]1m in show complex or cross- dusty clay coatings

d iameter. line;:lr alterat ion to clay. I 0-50]1m thick. Form bridges between grains.

Crescent 40 Yellowish to coatings redd ish brown ,

m icrolam inated , strongly oriented, limpid to dusty clay coatings 100-300]1m thick. Fill bottoms of voids, narrow intergranu lar spaces.

Dense 40 Yell owish to lIlCO[1l- reddish brown, non-plete laminated to weakly infilling microlami nated,

moderately oriented , speckled, dusty infi ll ings 50-400]1m in diameter.

IC=coarse, M=medium, F=fine, VF=very fine

2Q=quartz, P= plagioclase feldspar, Ksp=alkali fe ldspar, M=muscovite and biot ite, W=carbonized wood, HM=heavy minerals , includi ng epidote, hornblende, and augite

I I

\0 If)

- I ";" . ,..'!

• • • III ,"

" -

:'

\ ,

/ )- , .. " , , ',>: ':,V" . ~ ' ." • 1 ":' 1, f . • • ,",

, , . .. ~. . : . " ~ ~

, \' , \. \:'

, ,'

-,

" " 0 '

. ~

~ ... ,

" I'

" ',' : .~

' '':''!' .••

"

.!.

, . 'y ,

-': / "" " ..,

, 'I " ,, " .... ..

" : t ~

,!-"

" J i ,

j

j

I ' ,l t

I

•

- ,

I '

-"

Figure 5.12. Thin section 5c, Roman numerals refer to subsections described in Table 5.11 . The rectangle shows the location of the image analysis transect.

57

Table 5. 11 . Description of thin section Sc

Sub- Micro-Voids Basic mineral and orga ni c components Pedo rcatures section structure

i,iii,v Single 50% of subsection area 50% of subsecti on area I % o f subsection area grain

Type % Description Type % Size d is tri bution M ineralogy

Descri ption Type % Description structure (mode %)1 (mode %)2 Simple 100 Subangul ar, Sand 100 C 40%, M 40%, F Q 90, Plag 8, Moderately to well -sorted Typic 100 Reddi sh brown,

Chitonic packin g weakl y spheri cal 20%, VFX % Ksp 2, subanglul ar gra in s with coat in gs non-lamin ated. related vo ids 100- M +W+ moderate to hi gh sphericity. weak ly oriented, di stribu- 500llm in llM < I Very few feldspar grain s speck led, dus ty clay tion di ameter. show compl ex or cross- coat ings I 0-2511 III

linear alteration to clay . thick . ii,iv ,vi Bridged 25 % of subsection area 50% of subsection area 25% of subsection area

grain Type % Description Type %

Size distribution Mineralogy Descri ption Type % Description structure (mode %) 1 (mode %)2

S impl e 100 Subangul ar to Sand 100 C 30 %, M 40 %, F Q 90, Plag 8, Moderately to well-sorted Typic 10 Ye llow ish brown to Gefuric packing subrounded, 30%, VF X% Ksp 2, subang lular grain s with coatings brown, non-related moderately M + W+ moderate to hi gh spheri ci ty . lamin ated, weakly distribu- sph erical voids HM< I Very few fe ldspar gra in s oriented , speck led , tion 50-20011111 in show com plex or cross- dusty cl ay coatings

di ameter. lin ear alterati on to clay. 1 0-50~lm thick. Form bri dges between grains.

C rescent 70 Ye llow ish brow n to coatin gs brown,

microlaminated, s trongly oriented, limpid to dusty clay coatin gs 100-400~lm thick. Fill bottoms o f voids, narrow

intergranul ar spaces. Dense 20 Yellowish brown to incom- brown, non-pl ete laminated to weakl y infill ing microlamin ated,

moderately oriented, speckled, dusty in fillin gs 50-2OOllm in di ameter.

lC=coarse, M=medium, F=fine, VF=very fin e

2Q=quartz, P=pl agioclase feldspar, Ksp=alkali feldspar, M=l11uscov ite and bi oti te, W=carboni zed wood, HM=heavy minerals, including epidote, hornbl ende, and augite

,

00 tr)

Table 5.1. Definitions of terms used in thin section descriptions.

Term Definition Bridged grain

Almost entirely sand-sized grains bridged by fine material, usually clay. structure Chi tonic related

Coarser units are surrounded by a cover of smaller units. distribution Close porphyric

Coarse fabric units occur in a dense groundmass of smaller units. Many related distribution

coarse units do not touch other coarse units.

Crescentic An elongate, crescent-shaped pedofeature coating a grain, void or aggregate.

coatings Dusty clay Composed of clay containing microparticles up to 3f.lm in diameter.

Gefuric related Coarser units are linked by braces of finer material.

distribution

Infilling Soil material filling more than 90% of a void. Incomplete infillings have some voids; dense infillings leave no void space.

Limpid clay Uniform clay without inclusions of micro-particles. Microlaminations Alternating thin (<30f.lm) laminae of limpid and speckled clay.

Degree of preferential orientation of particles below the reso lution of a

Orientation petrographic microscope. Strongly oriented clay particles are usually parallel to a given surface; weakly oriented clay consists of unaligned particles.

Packing voids Equant to elongate interconnected voids occurring between single grains.

Pedofeatures Discrete fabric units present in soil materials recognizable from adjacent material by a difference in concentration in one or more components.

Pellicular grain Almost entirely sand-sized grains with most grains coated by fine material.

structure Roundness and

Description of the relative sharpness of particle corners . angularity Sorting Expression of the degree of variation in particle size. Speckled clay Clay containing small (2f.lm) opaque particles. Sphericity Overall form of the particle regardless of the sharpness of edges or corners. Tvpic coating Pedofeature of uniform thickness coating a grain, void or aggregate

Source: Bullock et al. (1985)

Zone II (la; Ib; 2a) . The unit directly beneath the modern soil consists of a well

sorted medium to fine sand composed of subangular, moderately to highly

spherical grains arranged in a pellicular grain structure (Figure 5.13). The

mineralogical composition of the sand is 85 to 90% quartz, 8 to 10% plagioclase,

and 2 to 5% K-feldspar. Muscovite and biotite, heavy minerals and carbonized

wood make up less than 1 % of the coarse fraction. Very few feldspar grains are

partially altered to clay. Between 40 and 50% of each section is occupied by

subangular, weakly spherical packing voids 100 to 400 /-Lm in diameter. Typic

coatings of speckled, reddish to yellowish brown, non-laminated, weakly oriented

59

Figure ~ .. 13. Zone II ~.nd (scdlon 1(1). WldUI of frame is 2.6 mm at ...ox. PPL.

60

clay on sand grains comprise 3 to S% of each section. These coatings, typically

10 to SO !lm thick, are distributed chi tonically relative to the coarse fraction.

Zone III (2b ; 3a; 3b; 4ai; Sa; Sb; Sc) . Interlamellae (2bi; 3ai,iii , v; 3bi,iv,vi; 4ai;

Sai ,iii,v; Sbi ,iv; Sci ,iii,v) are composed of a medium to fine sand that is texturally,

structurally and mineralogically very similar to Zone II sand. Lamellae (2bii,iii;

3aii,iv,vi; 3bii,iii ,v; Saii ,iv,vi; Sbii,iii ,v; Scii,iv,vi) have a bridged grain structure

and are distinguished from interlamellae by a high proportion of pedofeatures (20

to 2S%) with a gefuric related distribution (Figure S.14). Roughly 10 to 20% of

these pedofeatures are typic coatings up to SO!lm thicker than those observed in

Zone II. Many of these coatings form bridges between grains. Between 40 and

70% of lamellar pedofeatures are microlaminated crescentic coatings of yellowish

to reddish brown, strongly oriented, limpid to dusty clay. These coatings, which

range from 100 to 400 !lm in thickness, have formed at the bottoms of voids and

in narrow intergranular spaces. Dense incomplete infillings of non-laminated to

weakly microlaminated, moderately oriented, yellowish to reddish brown dusty

clay make up the remaining 10 to 40% of intergranular pedofeatur~s. The

discontinuous appearance of lamellae is due to variations in the abundance of

such pedofeatures. Texturally and mineralogically, the lamellar coarse fraction is

very similar to interlamellar sand. Due to the high concentration of clay, lamellae

have only 2S to 30% void space, significantly less than interlamellae.

Zone IV (4aii) . Texturally and mineralogically, the sandy fraction and

pedofeatures of Zone IV are very similar to Zone II sand and the interlamellae of

Zone III. Zone IV is set apart by the presence of small clusters of sand grains

cemented together by dense , unoriented infillings of gray to brown silty clay

(Figure S.lS) . These clusters are typically 1000 to 1S00 !lm in diameter.

Zone V (4aiii; 4bi) . Although it is mineralogically similar to overlying zones ,

Zone V is texturally and structurally distinct. Subangular, weakly spherical

packing voids comprise only 10% of the zone, while basic mineral and organic

61

Figurc 3.14. (a) Lamt'llar ~'lnd (scction In). Width of fr aml' i~ 2.6 mm a t 4OX. (b) Cfl'sct'nUc coaUngs in lanlt'llar Y()id~ (s~ction Ja). Width ur frame is 1 mm at .lOOX. PPL

62

Figure .5.15. Z91le IV &and, ~howlng clu~tlT or grains cemcnt.l'd bJ clay and silt. 'Width of f'rame I~ 2.6 mm at 4OX. PPL.

63

components occupy roughly 80% of each subsection. The high proportion of silt

and dense , brown, unoriented clay relative to sand is the most noticeable feature

of Zone V. The clay and silt provide the infrastructure of the sediment, creating a

close porphyric related distribution (Figure 5.16). Also notable are the reduced

roundness and sphericity of grains , the absence of coarse sand and the abundance

of very fine sand. Pedofeatures similar to those in overlying zones occupy

approximately 10% of Zone V. Roughly 95% of these are typic coatings on

grains, and 5% are relatively thin (100-200 /lm) crescentic coatings at the bottoms

of voids and in narrow intergranular spaces.

Zone VI (4bii). The moderately to poorly sorted basic mineral components of

Zone VI, which comprise 90% of the sediment, stand in marked contrast to those

of overlying zones. The sand and clay/silt fractions occur in equal proportions

and exhibit a close porphyric related distribution (Figure 5.17). Sand grains are

mineralogically similar to those of Zones II through V, but are more angular and

less spherical. The presence of coarse sand and the reduced abundance of simple

packing voids also distinguish this unit from Zone V. Pedofeatures, which consist

entirely of crescentic coatings similar to those in overlying zones, occupy only

2% of the sediment.

One element observed in thin section was omitted from the preceding

descriptions. It is evident from Figures 5.2-5 .12 that the sections are dotted with

large voids several hundred microns in diameter. They are particularly abundant

in areas of high clay and silt concentration, including Zone III lamellae and Zones

V and VI. Microscopic observations of these voids revealed that they are not

filled with polyester resin, nor are they coated with clay. Furthermore, no resin­

filled or clay-coated voids of comparable size were observed in any of the thin

sections. Based on these observations, it was concluded that these "pseudovughs"

are artifacts created by incomplete impregnation of the samples and subsequent

loss of material during the thin sectioning process. It is hypothesized that these

artifacts are concentrated in areas of high clay and silt content due to the inability

64

Figure ~.l6. Zone V ~andJ clay loam (~t.'dlon 4b). Width of frame is 2.6 mm at 4OX. PPL

65

Figure ~.J7. Zone VI sandy clay (St'Ction 4b). \Vidlh of frame Is 2.6 mm at 4OX. PPL

66

of the polyester resm to pass through intergranular spaces filled with fine

material. Voids of this type were ignored in formulating the above descriptions.

Image analysis

Image analysis data are presented graphically in Figures 5.18 through 5.28 .

Numerical data can be found in the appendix. Image analysis data served to

verify, amend, or refine qualitative and semiquantitative estimates of several

textural parameters, including the particle size distribution and mean roundness of

the coarse fraction and the clay content of each subsection. Image analysis

techniques also permitted the measurement of parameters that are difficult to

evaluate using qualitative methods, such as original void space and mean grain

orientation.

Clay content

Several trends are apparent in clay content, the fraction of each image occupied

by clay-sized particles. Zone III interlamellae have a slightly higher

concentration of clay (15 to 25%) than Zone II sand (10 to 15%). Lamellae

appear as spikes in clay content reaching 30 to 40%. Figures 5.24 and 5.25 show

a steady increase in clay content from Zone III to 20 to 30% in Zone IV, 25 to

40% in Zone V and 35 to 45% in Zone VI.

Original void space

Original void space, defined as the fraction of an image not occupied by mineral

grains , gives a proxy of void space in the absence of pedofeatures. The most

conspicuous feature of the original void space data is an apparent increase in

original void space where clay content is high. However, reexamination of thin

sections confirmed that these apparent increases in original void space reflect the

loss of material due to incomplete sample impregnation, a phenomenon discussed

above. Note that in the instances in which lamellar frames were not affected by

67

. " ' . ,

y~ , , ;': ' ; ,':::: • :' ~J ..... ~--=-, - '- " ~: .. --- _._-. . - . " ,;:

~, / , . . .., '-----,- MI. __ r - ·_ .... -,- . !--~ ... -. 100 ,

10 20 30 40 50 60 gO

8 I

7

« W 80

a:: « 5

~ 0

4

3

1 0

1 ~ 0 ~ 0

W 90 0 0

80 6 0

500

."] z 70 0 0 200. 500

f= 80 · . 10 0,200 ::) ro . 50 ,100 a: 50 '

f-5!2 4

0 W N U5 z « a:: CJ

0

1 70

leO

1 50

fii 1 40

UJ 1 30 UJ a: 120

CJ UJ e. z 0

~ 70

6

UJ 50

CC 40

0 30

20

10

2

3

(j) r--\ (j) w Z 4

0 . 500·1000~ Z ::) 0 2 00. 500 0 5 _

a:: . 100,2 00

. 50·1 00 6

7

0 10 20 30 40 50 60 70

Figure 5,18, Image analysis data for thin section 1 a, Up direction is to the left.

68

.. " ,~ ."

.'

. ~. '." ... ~

, r .. 0, r '-0 ' . ' . . ,." .I :.

... -, l . ~. ~ . ". . ~, , . ! - ;\~ , I ~ '~O l "'::': --'--- - r- . ;'~ - ........ -~- ----- ··- -1 --- ~~ , " ~ .. ~-.~ I ~-~f -;--~--' - i:

90--i _ ___ ~___ 20 ____ ~_ 40 _ __ ~___ '" j >~l-- --~ ___ h____ -- --- --- - - ;

~ 60; _ -- ------- ---- - ---- - -- I

~ 501------ ------------ -- ---------- ----- -----------I-ClaYconte;:;t-~~ 40-1------------------------------- ----- __ ----- _ ------- ------------_1_ _ Original v~ id space

~ 0

W 0 0 ~ Z 0 i= ~ CD Ci I-en 0 w N U5 Z <i: CC CJ

en W W CC CJ w e. z 0

~ I-Z W Ci 0

en en w z o z ~

~

:o+----------------~==~=-~~==-=~-~=:~=-~~-~=~---------~=-l

8

70

80

3

, ,

, , ' 0

9

8

7

6

5

4

3

2

4~-------------

51--------------

I

10 -----;~ O

. 500· 1000 1-1 !

0 2 00.500

il 100· 2 00

. 50- 100

-~,-------.------------~

Distance along t ran ect (mm) ---~do~-----4~1 0'-----~5~0-----~6Mo-------,}0

Figure 5.19, Image analysis data fo r th in section 1 b. Up directio n is to the left.

69

." -"r:r ~ .. ~'.... " . , ":!:~

~t~ "~ ~_ It ~ . . :-;: !r~ - ~;-. --~' .. 1o''i;1 : -: ':.:" .:~ ; J. - :. ~io do ._- ' - -' 4'0 50 610 :',: r 90 +--------- -.-~ 80 1 --------- _________________ I

70 ~----- •. ~ 4 L5 80~~ -- - - __ u _______ --' _______________________ I

a:: ______ I ;; 50 --------- -------------- -------- --------- - - ---I Clay content rI (f:: 40 t-------------------------- ----------- ----~ ori: al void spa~I_----!:

:: ----------- -- --------------- --------.. ---------=~-~~==~-----------=l 1 0

0

;g-O g O W 0

0 eo

6 Z 7 0

0

i= eo ::l CO ~ 5 0

f0-CI)

0 40

W N 30

U5 Z 20

~ a:: (!J 1 0

0

l e o 150

1 4 0 en 130 W W 1 20

a:: 1 1 0 (!J

W 100 e- gO Z 0

e o

~ 70

eo Z 50 W ~ 4 0

0 30

20

1 0

2

CI) Cl) 3 W Z 0 4 Z ::l 0 5 a::

6

~

1- - - 4 ----1---; --- 1----------------------1---- 100-200 200- 500

r-----------~--------------------j--500 - 1000 r--~

~-----------1-------------------------~--- Total sand I---~

r---------\-i'- ---\---------------------------- ------1

Distance along transect (mm) 7 _L - I 1 1 I 1 I 50 ------6~AO-----~70 0 10 20 30 40

Figure 5.20 . Image analysis data fo r thin section 2a. Up di rection is to the left.

70

;,g o 40

30

20

10

0

~ 90

W 0 0

80

~ Z

70

0

i= 80

=> a:l a: 50

f0-CI)

40 0 W N 30

U5 Z 20

«

..; . ... • , ------r--~-----i

50 60

----L-- Clay content

Original void space ~----------------------------- ----C==-=:.:=:~~':::...:..::.:.::..2'...::.::.:::_J-------1

f------------------------------- ---------------. - ______________________ ~.L----------

. 500-1000iJ

0200-500

Ii 1 00-200

. 50-100

a: 10 -(!J

0

1 7 0

160

150

(j) 140

W 130 W a: 120

(!J 110 W B 100

Z 90

0 80

~ 70

60 Z W 50

a: 40

0 30

20

10

2

CI) Cl)3 W Z 04 Z => 05 a:

7 .L- I Distance along transect (mm) I

---~~----~2~10----- 3~I O--~---4~IO~~-~-~~~0-----~6~0----~70 0 10

Figure 5.21 . Image analysis data for thin section 2b. Up direction is to the left .

71

·.--- ---'''-'-~~-' T-:-_

I: . A ~_ ' . ', ~ . '

1 00 r ·----~;O -

90 I ----------~ ~---- -I

30

. . . .- - -....-~-

4 . • .....

h f --=-~ 1----4 0 6'0

eo t ------- -----------------------« ::~~ !:: -_.---.. ..... . ...:~=== ___ --~--_== J . ~~:;o::~:,:',P". ~

! 30 t------------ -------- -~''''~---I ,

10

0

~ 0 90

W 0 0 eo

6- . 500- 1000J-l

Z 70

0 0200-500

i= eo . 100-2 00 ~ CO a: 50

I-C/)

40

0 W N 30

U5 Z 2 0

« a: 1 0 C!J

0

170

1 60

150

U)1 40 ~-----------------------------------------------~ tlj 1 30 ~ _____________________________________________ ~

a: 1 20 +-_______________________________________________ ~

C!J 11 0 f-------------- -------------- ------f'..----- - -------------1 W

~ 1 00 ~~~~~~---~--~-- ;::~~~::::::~::~~~::~~~~~~~:I~~;;~~:J~~~~~ Z 90

0 eo

i= 70 ;:: 6 0

Z 5 0 W

a: 40

0 30

2 0

10

2

C/) C/) 3

W Z 0 4 Z ~ 0 5 a:

6

Distance along transect (mm) 7 _LI _ ___ _ I

10 __ ~,L-------~,~-----~,~----~I

o 20 30 4 0 50 60 7 0

Figure 5.22. Image analysis data for thin section 3a. Up di rection is to the left .

72

" . _r '

:

-~-- -100 20 30

1>0 t-----

. ,f " ."

- - ; 60

80 +-________________ ________________________________________ -------~

70 t--~~--~~-~~~~~~=_-----~~~~~----~~--------------_J

~ 80 _~~--------~~----------~,--~----------

W

~ 50 +-- ------------- ----------------------- -- --- ----- -------r.==~~~~~~;_-~-----! ~ - Clay content

~ 40 t - ----------- - -- ------ --- ------- - ------ --------- ---- - ______ _______ ~_~o~~r~ig~in~a~l _v~Oi~d~s~p~a~ce~II--_l

30 -~---------------------------------,-, ----------------------~

10 +----------------------------~~--------------------------------~'---~------~

o

~ 90

W o o 80

6 z 70 o i= 80 ::::> III a: 50

~ £5 40

W N 30 en z 20

< ~ 10 (.!)

o

.500-1000~

0200-500

170 +---------------------------------------------~

180 +-------------------------------------------~

150 +----------------------------.~----------------~

OJ 1 4 0 +--~--------------------------~~L--------------~ tl1 130 +-~--------------------------~---------------~ ~ 120 t---------------------------~----------------~

m 11 0 t-------------­B100 -j~--

z o

~ z w a: o

I> 0 ?"~;;;;;.:~--~I'.!lII!~r"_:7'_\.___-~~~;"'~lio;..:: --'11'--\' '- -\---~.--'- -I--~,,~-----, __ -=_.,."'" ..... ~ ---.::'~c-

8 0 +---'''''-..... ~ f -

70 t---T--r ----~~-·or--------~\---V~'L----I---------~------~~--~

60 +----\-f-----------------~-----~~-----IF==~~~~~---~ 50 t----------------------------f------~

40 --100-200

30 200-500 20 +---- ------------------- -----------1 __ 500-1000

10 Total sand I----~

2

~3 W Z 04 Z ::::> 05 ~

6

7 o

Distance along transect (mm) I I

10 20 30 40 50 60

Figure 5.23. Image analysis data for thin section 3b . Up direction is to the left.

73

70

, ~J " 1

10 ~-~------i- - ...... . ~

90 1

I

20

:: J=~-~-~-=== ..•. ~-:"=~==----=-=-----------i « 60

W a: 50 « ~ o 4 0

30

20

1 0

0

~ 90

W 0

0 80

6 z 70

0

i= 6 0

::::> CO a: 5 0

I-00 4 0 0 W N 3 0

U5 Z 20

« a: 1 0 (!J

0

1 7 0

1 6 0

15 0

(j) W

1 40

W 130

a: (!J

1 20

W 110

B 1 00

Z 90

0 60

~ 7 0

Z 60

W 5 0 a: 4 0 0

30

20

1 0

0

2

00 00 3

W Z 0 4 Z ::::> 05 a:

6

7

1 ________ _ - - ------- - ----------------------j

I L ______ _ - ---------------------------L- - Clay conte nt

-------------------------------------!:======='---~

i----------- - ------------- ----------- -- -------- --------

• 500- 1 OOO~ I 1 i ' 0200- 500 '

. 100-2 00

. 50-100

+------______________ _ _ ______ _ ____ 1 ___ 50- 1 00~

+-------------------------------~--- 100-2 00

200 -500 +------------------------------~ ___ 500-1000

,--

0

Total sand

Distance along transect (mm) 1 1

10 20 -----~-----~------3~10~----~4~0------f50~----~6~, O~----~)O

Figure 5.24. Image analysis data for thin section 4a. Up direction is to the left.

74

80

70

« eo

W a: 50 « ~ o 40

30

20

1 0

0

~ 0 90

w 0

0 80

6-Z

70

0

i= 80 ::) CD a: 50

l-(/)

40 is w N 30

U5 Z 20

« a: 10 (!)

0

1 70

1eo

1 5 0

if) 140 W

130 W a: 120

ill "0

a 1 00

Z 90

0 8 0

~ 70

Z eo

W 50

a: 40

0 30

20

10

2

(/) (/)3 W Z 0 4 I z

I ::) 0 5 a:

e ~ I

7 0

------

--_._--

Clay content ------

-------

. 500 - 10 00 ~ I 0200-50 0 : • "o.,tj . 50- 10 0

~

100-200

2 00-5 00 __ 500- 10 00

-~

Distance along transect (mm) I I I I I I

10 20 30 40 50 60

Figure 5.25. Image analys is data fo r thin section 4b. Up direction is to the left.

75

I

I

I

I 70

20

10

0

~ 0 QO

W 0

0 80

~ Z

70

0

f= 80 ::) CO a: 50

f-(/)

40 (5 W N 30

U5 Z 20

~ a: 10 (!)

0

170

160

150

(j) 140 W

130 W a: 120 (!) W 110

e.,00 Z QO ·

0 8 0

~ 70

f- 60 Z W 50

a: 40

0 30

20

10

2

(/) (/)3 W Z 04 Z ::) 05 a:

6

7 J 0

/; -.

,------ -----'---, 30 40

.. , .. . . ~

Clay content

______ r-- Original void space

--- -_._----------- -- -------j

Distance along transect (mm) ----- ~"C"0--------=2'::l o----~0 40 I

50

• 500-1 OOO~

0200-500

I 60

Figure 5.26. Image analysis data for thin section 5a. Up direction is to the left.

76

I 70

'00

gO

80

70

~ 80

UJ a: 50 ~ ~ o 40

30

20

'0

0

~ gO UJ 0 0 80

6-z 70

0 f= 80 ::l CD a: 50

f-(J)

40 is UJ N 30

Ci5 Z 20

<i: a:

'0 ~

0

'70

'60

'50 (j)

'40 UJ UJ '30 a: '20 ~ UJ "0 0 _ 100

Z 0

~ Z UJ a: 0

gO

80

70

80

50

40

30

20

'0

2

(J) (J) 3

UJ Z 04 Z ::l 05 a:

Clay content

Original void space

. 500- 1000 11

0200-500

Ii 1 00-200

t-------------------------------------t1-------------~--- 50-10011

+-------------------------------------~+--------------4--- 100-200

200-500 500 -1 000 (-------------(

Total sand

Distance along transect (mm) 7 o~1 ----------~1 10~--------~2~lo----------~30~--------~4~lo----------~5 O~--------~6~I O~--------~~O

Figure 5.27. Image analysis data for thin section 5b . Up direction is to the left.

77

-~ 20

« 60

W a:: 50 « ;,g o 40

30

-r"':-30

I " . .. ,. - ~ ~

i 50

'-

' . i -·- ~-

60

------- --- ------------------ ------ - - - ----1

20 - ----=- ------- -------- -----------

'0

0

;g 0 9 0 W 0

0 80

6-z 70

0

i= 60

:J ell a: 50

I-(J) 40 0 W N 30

en Z 20

« a:: '0 (!J

0

'70

'60

'50

en ' 40 W '30 W a:: ' 20 (!J

, ' 0 w e. ' 00

z 90

0 ao

~ 70

I- 60 Z W 50

a: 40

0 30

20

' 0

2

(J) (J) 3 W Z 0 4 Z :J 05 a::

6

7

. 500 - 1 000~ 0200-5 00 j . 100 -2 00

.50- 100 - ----

~

r--------\--------------------------------------------------4 ___ 100-200

2 00- 500 +--------\--------------------------------------------------4 ___ 500-1 0 00

1 j

I 0

t I 10

Distance along transect (mm) :-- ----"'20:-- - - - - 3'0- 4

10 1

50

Total sand

1

60

Figure 5.28. Image analysis data for thin section 5c . Up direction is to the left.

78

I 70

this problem, there is no increase in original void space (2biii, 5aii). Aside from

this artifact of the impregnation process, only one trend is evident: whereas the

values for the upper two sections from Zone II (la and 1b) fluctuate about 60%,

values in the lower part of Zone II and Zone III fluctuate about 65 to 70%. This

trend is supported by qualitative observations. Since the matrix of clay and silt in

sections 4a and 4b could not be distinguished from clay pedofeatures based on

color, original void space was not measured for Zones IV through VI.

Grain size distribution

The image analysis data confirm that the coarse fraction of Zones II and III

consists of 5 to 15% coarse sand, 55 to 65% medium sand, 20 to 30% fine sand,

and 5 to 10% very fine sand. However, the data reveal one phenomenon that

could not be resolved through qualitative observation , a subtle fining trend

between the lower part of Zone II and Zone III. This trend appears as a slight

decrease in the proportion of coarse sand from 10 to 15% in Zone II to roughly

5% in Zone III. There are no perceptible differences in grain size distribution

between lamellae and interlamellae. Finally, the grain size data confirm that the

sand-sized fraction becomes finer textured in Zones V (50-60% medium sand, 25-

35 % fine sand, 10-20% very fine sand) and VI (5-10% coarse sand, 40-55%

medium sand, 25-35% fine sand, 10-20% very fine sand), including the absence

of coarse sand from Zone V.

Grain orientation

Grain orientation is defined as the angle between the long axis of a grain and

vertical. Mean orientation measures the average orientation for a given sample of

grains. It is important to note that this parameter reflects not the degree of

variation in the orientation of the grains within each frame, but the angle of

preferential orientation. For instance, a collection of grains with random

orientations between 80 and 100° will have the same mean orientation as a

collection of grains with random orientations between 60 and 120°, but a

collection of grains with random orientations between 50 and 110° will have a

79

mean orientation that differs from the other two groups. Mean grain orientation

for the sand-sized fraction in each section generally varies between 80 and 100°,

with the individual size fractions displaying slightly higher ranges of variability.

Both observations indicate that there is no preferential angle of grain orientation

other than horizontal in any of the stratigraphic zones. In addition, there are no

observable differences in the mean orientation values of lamellae and

interlamellae.

Roundness

Roundness IS defined as the ratio between a grain's perimeter and the

circumference of a circle with the same average radius. A perfect circle has a

roundness of one, while more angular objects have higher values. For Zones II

through IV, roundness values for individual size fractions range from 2 to 4, while

the values for the total sand fraction typically vary between 2.5 and 3.5, indicating

subangular to subrounded grains. There are no significant differences in mean

roundness between lamellae and interlamellae. The observed increase in

angularity in Zones V and VI is most apparent in the lower roundness values of

the medium sand fraction.

Summary of results

A combination of field observations, qualitative thin section descriptions and

quantitative image analysis data has permitted a detailed assessment of the subsoil

stratigraphy atCactus Hill. Zones II and III consist primarily of a well sorted,

medium to fine quartz sand with typic clay coatings on most grains. There are no

significant depth-related variations in mean orientation or mean roundness of the

sand-sized fraction. There are some subtle textural trends in this sand, however:

Zone III is marginally finer textured than the lower part of Zone II, with a higher

clay content and slightly more original void space. The dark color and finer

80

texture of the lamellae in Zone III result from a high proportion of clay

pedofeatures, including typic coatings, crescent coatings and dense infillings.

Other than this defining feature, the thin section analyses indicate no textural

differences between lamellae and interlamellae.

The coarse fraction and pedofeatures of Zone IV are very similar to those

of Zones II and III . However, this thin band of sediment contains clusters of

grains cemented together by infillings of dense, silty clay similar to that observed

in Zones V and VI.

The mottled, irregular boundary between Zones IV and V marks a

dramatic change in the sediment. Zone V is considerably finer textured than

overlying units, a sandy clay loam with little void space and a high proportion of

clay and silt. Zone VI is a sandy clay with slightly less void space and a higher

proportion of clay and silt than Zone V. The coarse and fine fractions of both

horizons are distributed in a close porphyric pattern, and the sand-sized grains are

significantly more angular than those in overlying strata.

81

6. Interpretations and Discussion

Origin of subsoil stratigraphic zones

The results of field observations and thin section analyses presented in Chapter 5

permit a more detailed and complete understanding of the genesis of sedimentary

strata at Cactus Hill.. Despite the absence of characteristic dune features such as

cross-bedding or slipfaces, the high degree of sorting, paucity of fragile minerals,

and relatively constant particle size distribution and mineralogy of the Zone II and

III sand support Jones' and Johnson's (1997) conclusion that the sand is eolian

(Courty et al. 1989; Waters 1996). These lines of evidence also indicate a

relatively invariable parent material and constant transport energy. The

observation that most dunes in the Southeastern Coastal Plain were created by

dominant west winds (Jones and Johnson 1997) suggests that the source of the

dune sand lies in the fluvial sand and gravel deposits to the northwest. The slight

differences in grain size distribution and original void space of Zones II and III

may indicate subtle changes in wind energy, as affected by meteorological

phenomena and changes in local geomorphology and vegetation, or textural

variations in the fluvial deposits being deflated. Alternatively, these apparent

differences may simply be the result of intrasite variations in the eolian sand that

are not correlated with depth.

Typic coatings on sand grains in Zones II and III are composed of dusty,

non-laminated, weakly oriented clay distributed evenly over the grain surface.

These characteristics suggest that the coatings were not formed by gravitational

settling of suspended clay, since this process usually produces thicker coatings on

the upper surfaces of grains (Dijkerman et al. 1967). Two possibilities remain.

82

First, coatings may have been present in the fluvial parent material and been

preserved over the short transport distance between the fluvial deposits and

Cactus Hill. Courty and colleagues (1989) note that this phenomenon is not

uncommon ·in eolian sands. Alternatively, the coatings may have formed through

wetting and drying cycles , a process known from laboratory experiments to

produce coatings with similar properties (Dijkerman et al. 1967). Variation in the

thickness of typic clay coatings through the stratigraphic column, particularly the

difference between coatings observed in lamellae and interlamellae, suggests that

coatings are partially if not entirely illuvial in origin, a result that favors the

wetting-drying cycle hypothesis. Thus the most likely explanation for the

generally thicker clay coatings and higher overall clay content of Zone III is the

dissolution of Zone II coatings by percolating water and subsequent redeposition

of the clay in Zone III when the basal clay unit slowed the wetting front, allowing

it to evaporate.

The question of lamellar genesis is of considerable importance at Cactus

Hill. The work of a number of researchers indicates that lamellae can form as a

result of geogenic processes , a combination of geogenic and pedogenic

phenomena, or pedogenic processes alone. A few authors (Wurman et al. 1959 ;

Robinson and Rich 1960; Hannah and Zahner 1970) describe textural bands of

sedimentary origin. A larger number of workers have reported on lamellae

formed solely through pedogenic processes, such as the rhythmic precipitation of

illuvial clay or the flocculation of clay by free iron oxides or carbonates (Folks

and Riecken 1956; Dijkerman et al. 1967; Gray et al. 1974; Schaetzl 1992).

Others (Wurman et al. 1959; Gile 1979; Cable 1996; Rawling 1997) describe

lamellae that appear to have formed due to textural discontinuities between

sedimentary strata.

Several features of the Cactus Hill lamellae indicate that they are of

illuvial rather than sedimentary origin. The lamellar coarse fraction is virtually

indistinguishable from the rest of the eolian deposits : the only major difference

between lamellae and interlamellae is the abundance of clay pedofeatures that

have formed in intergranular spaces, including bridges between grains, crescentic

83

coatings and dense infillings. The strong orientation and microlaminations

evident in many of these pedofeatures suggest they are composed of illuvial clay

(Torrent et al. 1980; Courty et al. 1989; FitzPatrick 1993). All these features are

frequently observed in natural lamellae of probable illuvial origin (Dijkerman et

al. 1967) and have been replicated in laboratory experiments by percolation of

clay solutions through columns of sand (Bond 1986).

The primary source of this clay is likely Zone I, the A horizon that caps

the eolian sand. This interpretation is supported by the observation that lamellae

parallel the modern surface (Dijkerman et al. 1967; Gile 1979). Typic clay

coatings on mineral grains in Zones II and III are another potential source of

illuvial clay. As noted above, the thicker coatings and higher overall clay content

of Zone III may signify the net translocation of clay from Zone II to Zone III,

including the dissolution and reprecipitation of typic coatings.

The lack of differences in particle size distribution, original void space,

orientation and roundness between lamellar and interlamellar sand indicates that

the Cactus Hill lamellae did not form because of textural discontinuities in the

eolian deposits . These lamellae can only have been produced by a physical or

chemical leaching mechanism unrelated to the textural properties of the sand.

Wurman and colleagues (1959) suggested that lamellae of purely pedogenic

origin could be produced by evapotranspiration at the forward margin of a wetting

front. This mechanism seems unlikely, given the even spacing and relatively

uniform development of the Cactus Hill lamellae. The only remaining possibility

is a rhythmic chemical precipitation phenomenon.

One such mechanism, described by Bond (1986), involves the rhythmic

precipitation of clay from a supersaturated solution or suspension. Hallsworth

(1963) verified in laboratory experiments that dissolved or suspended clay

precipitates spontaneously once it reaches a threshold concentration. In this

scenario, dissolved clay from Zone I would be carried down through the profile

by percolating water. The concentration of clay in the solution would increase as

typic coatings in Zone II were partially dissolved. At a certain depth , the

percolating water would become supersaturated, and clay would precipitate out

84

until it was in equilibrium with the solution. The wetting front would continue to

advance, dissolving clay coatings and precipitating the clay once the suspension

again became supersaturated. Even a faint rhythmic precipitation of clay could

initiate a feedback loop in which coflocculation and mechanical sieving of clay

particles caused incipient lamellae to become more developed (Dijkerman et al.

1967). Such a process could produce a series of regularly spaced, parallel textural

lamellae in an otherwise uniform sand.

Folks and Riecken (1956) and Wurman and colleagues (1959) have

suggested a similar phenomenon of rhythmic precipitation involving the

dissolution and reprecipitation of free iron carried by organic chelating agents.

The flocculation of suspended clay by bands of iron radicals would then initiate

the development of textural lamellae. The reddish to yellowish brown color of

f!lost of the lamellar pedofeatures observed at Cactus Hill indicates the

coflocculation of clay and iron, but as Rawling (1997) notes, it is very difficult to

determine which was emplaced first. The observation that lamellae and the

thicker typic coatings of Zone III have a similar upper limit suggests that the

mechanism proposed by Bond is a more likely explanation for the formation of

lamellae at Cactus Hill. The thicker coatings of Zone III may have caused

percolating clay suspensions to become supersaturated, triggering the rhythmic

precipitation of lamellar clay. Thus the observed distribution of illuvial clay in

the eolian sand may be the product of two superimposed processes: the net

translocation of clay from Zone II to Zone III by wetting and drying cycles ,

followed by lamellar formation in the zone of higher clay concentration. The

variable upper limit of the lamellar zone, a feature commonly observed in

lamellar soils (Robinson and Rich 1960), probably reflects intrasite variation in

the depth of the transition from lower to higher overall clay content. The weaker

development of shallow lamellae, such as those observed in section 2b, reflects

the gradual transition from lower overall clay content in Zone II to higher content

in Zone III.

Two unique features of the Cactus Hill lamellae also provide information

about the processes responsible for their formation . First, capping and link

85

capping of sand grains, illuvial pedofeatures frequently observed in the field and

in laboratory experiments, are absent from the lamellae at Cactus Hill. Secondly,

concave-up crescentic coatings in voids and narrow intergranular spaces dominate

the lamellar pedofeatures. These features suggest that percolation rates in the

eolian sand are too rapid to allow suspended clay to settle gravitationally on the

upper surfaces of individual grains. Instead, clay settles gravitationally when

percolating water becomes trapped within voids that are partially sealed off by

narrow intergranular spaces or clay bridges between grains. Thus the formation

of crescentic coatings, which make up the bulk of lamellar pedofeatures, probably

did not occur until typic coatings, bridges between grains and infillings were

developed enough to slow percolating water.

There is no simple way to determine the age of textural lamellae of illuvial

origin. Experimental evidence indicates that incipient lamella formation can

occur very rapidly in well-drained sediments, perhaps within a period of months

or years (Bond 1986). The likelihood that Zone I is a major source of illuvial clay

implies that the lamellae at Cactus Hill postdate the formation of the modern soil,

a feature that may be no more than a few centuries old and certainly postdates the

Middle Woodland Period.

Zones V and VI define the upper limit of the basal clay unit recognized by

Jones and Johnson (1997). The continuous gradation between clay, silt and sand

fractions and the lack of laminations or orientation in the clay suggest that the

clay and silt in this unit are of primary, rather than illuvial, origin. The close

porphyric related distribution of the coarse and fine fractions implies that they

were deposited simultaneously rather than by the emplacement of clay and silt

into an existing sand deposit. The finer texture of the sand fraction, the

abundance of clay and silt and the poor sorting of mineral components suggest

that Zones V and VI are high-energy overbank deposits of the Nottoway River

(Courty et al. 1989; Waters 1996).

Jones and Johnson (1997) and McAvoy (McAvoy and McAvoy 1997)

have interpreted Zone V as a possible paleosol that formed on the basal clay unit.

Micromorphological observations do not support this interpretation, for no signs

86

of pedogenesis, such as the loss of fine material, accumulation of organic matter,

deposition of translocated clay and silt, or extensive weathering of silicate

minerals (especially feldspars and mica) are observed in Zones V or VI.

However, it is important to recognize that diagenetic alteration of sediments or

truncation of the soil profile by erosional processes can obscure such

characteristic features of pedogenesis (Courty et al. 1989). Alternatively, both

zones may represent part of a paleosol whose contact with the basal clay unit is

not exposed in Area A.

Zone IV represents the onset of eolian deposition at Cactus Hill.

Microscopically, the presence of small clusters of material similar to Zone V

material is the only feature that distinguishes Zone IV from Zones II and III.

This , along with the mottled, irregular boundary between Zones IV and V,

suggests that the two units have been partially homogenized by some physical

mechanism. Possibilities include syndepositional disturbance during the earliest

stage of eolian deposition or a post-depositional process , such as bioturbation,

whose effects are underscored by the textural difference between the two zones.

Sequence of depositional and post-depositional events

One advantage of microscopic analyses of soils and sediments is the ability to

reconstruct the sequence of events that generated a deposit. This is particularly

valuable in archaeology, where site formation processes are of utmost importance.

Micromorphological observations are generally consistent with the mechanism

proposed by Jones and Johnson (1997) for the origin of the major sedimentary

units at Cactus Hill , but they also allow more detailed inferences about

depositional and post-depositional processes. Overbank deposits of sandy clay

were laid down by the Nottoway River to form the basal unit. Fluvial

downcutting created a north-facing scarp in this clay deposit, and the river cut was

partially filled in by sand and gravel bed load deposits. Further downcutting

transformed these fluvial deposits into subaerially exposed terraces. Dominant

87

northwest winds deflated the sandy terraces, transporting coated or uncoated

mineral grains several hundred meters to the southeast, where they began to

accrete against the exposed scarp, eventually burying the scarp. A soil may have

formed on the clay deposits sometime between the deposition of the clay and the

onset of eolian sedimentation. Biotic activity or some other disturbance

mechanism produced an irregular, partially homogenized contact between the clay

unit and the eolian sand.

Human occupation of the dune began partway through the period of eolian

deposition, after the sand had overtopped the clay scarp, and continued virtually

uninterrupted until Middle Woodland times. Eolian deposition ceased sometime

during the Late Holocene. The presence of a generally coherent cultural sequence

and radiocarbon chronology indicates that the dune was stabilized by the

formation of a soil before significant deflation or migration of the eolian sand

could occur.

The translocation of clay from this soil and from partially dissolved clay

coatings on sand grains to the lower part of the eolian sand resulted in the

formation of a zone of textural lamellae either through rhythmic precipitation of

suspended clay or the flocculation of suspended clay by rhythmically precipitated

iron oxides . Subsequent coflocculation of clay and mechanical sieving led to

further lamellar development. Lamellae may have formed at any time since the

genesis of the soil. Although they do not appear to have been significantly

disturbed since their formation , the purely pedogenic , potentially recent origin of

.lamellae suggest that they bear little relevance to the stratigraphic integrity of the

eolian deposits.

Archaeological implications

Although this study was conducted in Area A and the results are not directly

applicable to Area B , the proximity of the two excavation areas and the

similarities between their stratigraphic sequences suggest that the conclusions

88

presented here are an apt description of the stratigraphic evolution of the entire

southern portion of the site, particularly in terms of the origin and character of

major sedimentary units and lamellar genesis. The archaeological deposits at

Cactus Hill show no textural or compositional signs of primary stratification.

Textural lamellae are chemically precipitated illuvial features thickened by the

coflocculation of clay and mechanical sieving of suspended particles. They are

probably derived primarily from clay leached from the modem soil that caps the

dune, and are potentially of recent origin. As stated in Chapter 3, lamellae formed

by sedimentary processes or by precipitation of clay in response to textural

properties of the parent material are indicators of stratigraphic integrity. Lamellae

that are entirely pedogenic in origin, like those at Cactus Hill, cannot be used as

an argument against post-depositional disturbance.

Despite the unstratified character of the eolian deposits, the results of

Johnson and McAvoy remain compelling for the same reasons outlined in Chapter

3. Furthermore, it should be stressed that the uniform textural and mineralogical

character of the eolian sand does not necessarily indicate homogenization of the

sediment; more likely, it is the result of a homogeneous parent material.

However, the sedimentology of the site provides no evidence that artifacts and

charcoal recovered below the Clovis horizon have not been affected by post­

depositional disturbance. Although the presence of a coherent cultural sequence

and radiocarbon chronology capped by a soil indicates that no large-scale post­

depositional disturbance processes have affected the eolian sand, it is possible that

the sand has been affected by smaller-scale processes such as bioturbation,

cryoturbation, or folding, faulting and slumping associated with changes in dune

morphology (Waters 1996).

Colin Renfrew (1976:2) has remarked that "every archaeological problem

starts as a problem in geoarchaeology." This is particularly true in the realm of

Paleoindian studies. At present, potential pre-Clovis sites are subject to the same

test as the mammoth kill sites of the 1930s: a viable candidate must provide clear

evidence of human agency, a reliable geochronologic sequence, and undisturbed

stratigraphy. Until a significant number of early sites have been documented in

89

nonisolated stratigraphic contexts, each new candidate should be, and will be,

subject to the same unrelenting geoarchaeological scrutiny.

The Cactus Hill Site, and the possibility of a pre-Clovis presence on the

eastern coast of North America, hangs in this balance. While there is abundant

evidence of a Paleoindian presence at Cactus Hill, the geological evidence is as

yet incomplete. This investigation detected no unequivocal microscopic or

macroscopic evidence that the Paleoindian artifacts at Cactus Hill were excavated

from an undisturbed stratigraphic context. However, this does not imply that the

eolian deposits are significantly disturbed: the site should not be abandoned as a

pre-Clovis candidate until all potential avenues of geoarchaeological investigation

have been explored.

The results of this study do not constitute evidence against an early

Paleoindian presence at Cactus Hill. Instead, they should serve to direct future

research by limiting the types of evidence that must be examined. At this writing,

the only information on post-depositional disturbance at Cactus Hill comes from

discrepancies in the cultural sequence, such as overlaps in the vertical

distributions of artifacts from well-known assemblages, similar inconsistencies

between radiocarbon dates, and obvious evidence of bioturbation, including root

tubes and rodent burrows. In the future, geoarchaeological work at the site should

focus on other methods that can be used to gauge the degree of post-depositional

disturbance in the eolian sand. Two promising avenues for research are discussed

here.

It has been demonstrated that the magnetic susceptibility of surfaces is

enhanced by natural or anthropogenic burning processes (LeBorgne 1955).

Variations in the magnetic susceptibility values of archaeological sediments have

been used to detect stable surfaces and anthropogenic features (Ellwood et al.

1995 ; Sternberg and Lass 1998 ; Dalan and Banerjee 1998). Magnetic

susceptibility readings of the stratigraphic column in Area A of the Cactus Hill

Site were collected by the author and c.A.S. Mandryk in June 1998. These data

will be analyzed for site-wide depth-related trends that may indicate intact

stratigraphy.

90

Thermoluminescence (TL) or optically stimulated luminescence (OSL)

dates are perhaps the most promising avenue for future research at Cactus Hill.

M. F. Johnson has collected TL samples in Area A in an effort to determine the

burial age of mineral grains (Johnson, personal communication). The results of

such an analysis would serve two important functions . First, since they provide

an estimate of the depositional age of the matrix itself rather than of scattered

organic matter, luminescence dates would help to establish a more secure

geochronology at the site. Secondly, if luminescence dates corroborate the

cultural and radiocarbon chronologies, they would present a strong argument for

post-depositional stability of the eolian deposits.

Conclusions

The eolian sand that forms the Cactus Hill Site shows no macroscopIc or

microscopic signs of textural or compositional stratification. Textural lamellae

are chemically precipitated illuvial features thickened by the coflocculation of

clay and mechanical sieving of suspended particles. They are probably derived

primarily from clay leached from the modern soil that caps the dune, and are

potentially of recent origin.

A combination of field observations and micromorphological analyses

detected no indicators of stratigraphic integrity in the deposits at Cactus Hill.

Because of the fundamental character of the archaeological sediments at the site,

it may be extremely difficult to meet the rigorous criteria to which pre-Clovis

candidates are subjected. Nonetheless , the Cactus Hill Site should not be

abandoned as a pre-Clovis candidate until all potential avenues of

geoarchaeological research have been explored.

91

Adovasio, J.M. 1993

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98

Appendix: Numerical Image Analysis Data

Image analys is data for thin section 1 a

Distance along Clay content Original void space Grain size di stribution mode % Mean orientation (O from vertica l) Mean roundness lra nsecl (mm) (% area) (% a rea) 50-100um 100-200um 200-500um 500- 1000um 50- 100um 100-200 m 200 - 500~m 500-1000 1m Total sand 50-100um 100-200um 200-500um 500- 1000 lm Total sand

0 11. 20 53 .23 7 .25 20 .96 71. 78 0 .00 86 .81 80 .63 88 .92 85 .51 2 .64 2 .32 3 .4 2 2 .78 2 12 .38 55 .77 5.46 18 .44 76 . 10 0 .00 85 . 18 111 16 91 .99 94 .67 2 .62 2 .32 3 .60 2 .89 4 9 .09 5225 5 .53 2 1.50 72 .97 0 .00 85 .74 89 .07 106 .44 93 .82 2.44 3.05 2 .6 7 2 .72 6 11 .35 58 .88 7 .05 26 .89 66 .0 6 0 .00 80 .28 90.16 85 .31 8 5 . 18 2 .34 2 .50 3 .0 6 2 .60 8 11.36 58 .84 5.32 18 .65 55 .92 20 . 11 83 .5 0 80 .55 96.7 5 161 .94 88 .87 2 .30 2 .65 3 . 15 3 .61 2 .70 10 11 .46 64 .69 7 .33 14.71 63 .25 14 .70 77 .44 117 .78 94 .85 61 .9 5 92 .57 2 .36 3.48 3.43 4 .83 3 .02 12 9 .89 59.45 5 .55 25 .99 68 .46 0 .00 87 .99 105 .72 113 .29 102 .63 2 .14 2 .28 2 .67 2 .35 14 8.69 57.40 5 .2 1 23.42 71.36 0 .00 98 .39 103 .77 9 1. 41 98.4 7 2 .00 2 .88 3 .31 2 .71 16 10 .8 1 56 .65 5 .53 25 . 10 56 .33 13 .0 3 107 .93 100.92 79 .00 112 .57 97.4 7 2 .47 2 .65 2.74 2 .98 2 .62 1 8 12 .06 63 .56 6 .24 2 1.04 72.72 0 .00 67 . 16 88 .85 105.98 86 .7 1 2 . 10 2 .72 3 .65 2 .80 20 13 . 17 66 .42 7 .99 39 .30 52 .71 0 .00 95 . 14 99 .98 91.47 96 .58 2 .43 2.75 3.46 2.74 22 12 .05 66 .17 9 . 11 29 .31 49.19 12 .40 80.46 82 .21 88 .29 153.89 83 .9 1 2 .33 2 .70 3 .0 5 1.95 2 .61 24 12 .21 60 .86 7 .34 17 .94 74 .71 0 .00 73 .55 81 .64 99 .53 84 .66 2 . 11 2 .54 2 .86 2 .49 26 11 .22 64 . 13 8 .97 25 .91 65 . 12 0 .00 105 .42 106.41 95 .67 103 .29 2 .37 2 .73 3 .77 2 .85 28 9 .54 56 .61 3 .61 19.44 65.08 11 .87 82 .52 10 4.74 89 .33 65.7 2 93 .54 2 .9 1 2.32 2.70 2 .86 2 .60 30 12 .14 52.65 4 .62 17 .72 59 .09 18 .58 87 .49 80.41 78 .02 75 .6 1 81 .99 2 . 17 2.31 2 .37 5 .6 1 2 .39 32 10.44 56 .26 7 .30 25 . 19 43 .6 5 23 .87 87.41 98 .94 91.8 7 153 .77 94 .07 2 .34 2.71 2 . 14 2 .74 2.43 34 9 .81 63 .21 4 .40 27 .63 67.96 0 .00 73 .27 80 .07 84 .00 79 .07 2 .68 3 . 12 2.73 2 .88 36 10.78 6 1.34 6 .0 1 19 .24 66 .14 8.62 76 85 120 .89 79 .45 172 .2 2 94 .33 2 .28 2 .81 2 .53 6 .08 2 .6 1 38 10 .90 58 .55 4.13 23 .77 62 .75 9 .35 85 .04 93 .50 105.77 17 2 .63 96.46 2.78 2 .30 2.47 1.48 2 .47 40 10.46 56 .87 4 .50 2 1.91 65 .67 7 .92 110.52 92 .53 89 . 17 144 .3 4 96 .91 2 .13 2 .48 2 .9 3 1.94 2 .54 42 7.49 59 .38 5 .12 17 .43 77.46 0 .00 97 .12 94 .62 86 .82 92 .35 2 .82 3. 18 2 .80 2 .89 44 8.43 63 .07 5 .50 24 .08 70.4 1 0 .00 88.45 90 . 12 91 .60 89 .93 2 .62 2.69 3 .30 2 .84 46 8 .97 60 .95 4 .93 28 .53 66 .54 0 .00 70 .86 89 .77 101 .30 87 .66 2. 14 2 .58 2 .30 2 .37 48 9 .08 62 .20 5 . 15 27 .24 56 .62 10 .99 96 . 18 94 .52 107 .77 82 .39 97 .91 2 .33 2 .34 3 .37 3 .89 2 .61 50 10 .51 69 .8 1 8 .80 26.46 46 .34 18.40 109 .66 76 .95 118.94 52 .54 98 .82 3. 17 2 .76 3 .66 5.2 2 3 .17 52 10 .59 60.08 7 .72 26 .27 66 .01 0 .00 81.54 91.82 74 .41 83 .52 3 .04 3 .55 3 .12 3.25 54 10.75 62 .16 7.47 21.15 71.38 0 .00 106 .43 93 .70 9 1.01 98 .2 4 2 .45 2 .87 2 .72 2 .65 56 11.85 65 .48 7 .60 29.43 62 .97 0 .00 85 .44 83. 98 110.60 92 .0 9 3 .03 2.52 2 .45 2 .66 58 12 .54 61.8 1 4.69 31.32 63 .98 0 .00 60 .87 89 . 10 81.79 79 .35 2 25 2 .94 3 .68 2 .96 60 12 .25 58.46 7 .22 20.57 62 .27 9 .95 84 .65 93.49 95 .88 12 .9 1 89.35 2 .58 3 .03 2 .55 3 .56 2 .72 62 13 .29 57 .15 6 .10 17 .75 65 .47 10 .68 86 .08 95 .7 1 95.72 17 .85 91 .04 2 .56 2 .24 2 .90 2 .02 2 .55 64 11 .80 66 .56 11. 39 26 .83 61.78 0 .00 86 .82 91.48 106.32 93 . 14 2 .39 2 .74 3 .88 2 .87 66 11 .93 64 .02 7 .33 33.46 59 .21 0 .00 88 . 19 98 .28 111.41 97 .89 2 .42 2 .69 2 .61 2 .56 68 12 .09 66.69 6 .00 24.11 69 .89 . 0 .00 81 .65 75 . 15 86 .03 80.30 2 .3 1 2 .78 3 .12 2.73 70 12 .77 63 .20 7 .09 23.04 51.35 18 .52 103.39 95 .63 73 .34 144 . 15 93 .83 2 .79 3.37 2 .68 34 .62 3 .43

Image analysis data for thin section 1 b

Dista nce along Clay conten t Ori ginal void space Grain size distri bution mode "10 Mean or i en t a ti on~ fr om vertica l) Mean roundness tra nsect (mm) (% .r •• ) (% .rea) 50- 100.m 100-200 m 200-500.m 500- 1000.m 50- 100.m 100- 200 tm 200-500 1m 500-1000 m Total sand 50-100.m 100-200.m 200-500 1m 500- 1000 1m Total sand

0 11. 72 64 .83 8.32 25 .05 53 .43 13 .20 94.76 8 7.9 1 99 .46 63 .96 93 .26 2.52 2 .37 3 .45 2 .6 3 2.70 2 9 .78 57 .98 5 .22 21.49 73.29 0 .00 78 .52 97 .38 93.78 90 . 12 2 .40 2 .48 3 . 10 2.68 4 11 .25 62 .28 7 .08 16 .80 76 . 12 0 .00 87 .77 61.33 94.4 7 84 .04 2 .29 2 .70 2.58 2 .49 6 11.01 63 .58 9.70 23 .23 67 .07 0 .00 91.36 99 .40 83 . 15 9 1. 20 2 .55 2 .95 3 .69 3 .0 1 8 13 .04 67.25 5 .08 20 .77 60 .56 13 .58 76 .72 102.43 79 .26 38.2 1 85 .06 2 .24 3 . 19 2.93 2 .32 2 .77 10 1 1.09 65 . 17 7 .38 3 1.17 38 .27 23 . 18 77.33 83 . 14 6 1.89 92.8 1 77 .97 2 .05 2 .52 2 .46 3 .07 2.34 12 8.50 70 .03 13.46 33.73 52 .81 0.00 74 .63 84 .48 102.28 83 .00 2 .60 2.58 2 .55 2 .58 14 8 .2 0 68 .86 6 .37 23.31 63 .54 6.78 94.72 98 .66 7 1.31 106.20 88 .36 2 24 3.75 2 .88 11. 93 3 . 10 16 15. 01 67 .20 6 .3 0 22 .88 70 .82 0.00 105 .13 89 .49 75 .50 90 .0 1 2 .68 2 .39 3 .67 2 .88 18 9.28 62 .27 6 .59 13 .50 79.9 1 0 .00 72.74 77 .83 95 .30 82 .99 2 .23 3 .58 2 .93 2 .85 20 11 .70 63 .2 1 6·.79 26 .26 66 .95 0 .00 84 .85 95 .66 96 . 17 92 .2 1 2 .39 2 .61 2 .6 1 2 .54 22 9 .37 60 .65 4.48 22.3 1 61 .53 11 .69 11 7 .58 84 .84 64.46 10 1.47 87 .53 2 .3 1 2 .36 3 . 19 1.4 8 2.6 1 24 16.05 62.34 3 .64 3 1.74 64 .62 0 .0 0 95 .09 11 3 .21 94 .40 103 .06 2.52 2.60 3 .25 2 .78 26 12 .34 48 .59 2 . 14 15 .66 26.29 55 .9 1 74 .24 92.86 78 .94 91.23 84 .22 2.20 3 .49 3 .01 4.33 3 .09 28 10 .69 58.95 5 .54 17.49 76.98 0.00 73.58 88.09 104.21 88.94 2 .65 2.66 2 .73 2 .68 3 0 10.66 62.50 4 .25 27 .90 67 .85 0 .00 83 .02 88 .23 98 .56 90.48 2 .18 3 .41 2 .93 2 .93 32 14 . 1 1 59.85 7 .58 26 .48 58.72 7 .22 1 17 .61 9 1.87 90 68 1 14 .6 1 101. 16 2.76 2 .53 3 . 16 2. 4 1 2 .78 34 13 .28 65 .3 7 11 14 39 .64 49 .22 0 .00 103.17 79 .72 86 .08 90 .32 2 .2 1 2 .58 2 .83 2.49 36 12.25 53.7 1 3 .29 21.60 57 .23 17.88 78 .57 96 .9 5 58.70 81 .78 79 .39 2 .10 2.58 2 .67 3.08 2 .5 1 38 11.37 63 .82 6 .18 30.93 47 00 15 .89 71.44 79 .5 2 59 .32 51 .29 7 1. 1 1 2 .65 2 .37 2 .9 1 4 .24 2 .64 40 9 .88 64 .89 8 .56 23.24 56 .83 1 1.37 82 .99 85 .8 1 109.33 0 .98 89.48 2 .3 1 3 .11 3 .33 6.73 2 .87 42 12.05 6 1.33 7 .38 34.54 58 .08 0 .00 95 .34 79 .52 105 .90 9 1.92 2.49 2 .87 2.78 2.7 0 44 1 1. 42 57 .93 5 .03 23 .7 1 48 .93 22.32 73 .39 88 .82 103.20 29 .32 86.42 2 .25 2 .53 3.40 4 .29 2 .70 46 9.50 65 .07 9 .53 25 .80 64 .67 0 .00 99.42 104 .24 12 1.72 106 .8 1 2 .5 1 2 .99 2.96 2 .77 48 15.40 76 .64 8 .75 43.79 47.46 0 .00 82 .44 94 .4 1 92.34 89 .33 2 .48 2 .50 3 .72 2 .7 1, 50 13 .64 6 1.77 4.16 14 .87 69.25 11 .7 1 104.26 68 .5 4 94 .08 68 .86 88 .56 2 .43 2.89 4 . 14 6 .50 3.25 52 11. 73 70 .98 7 .90 34.98 57 . 13 0.00 77 .59 66 .52 117 .43 80 .39 2.48 2 .45 3 . 15 2 .59 54 12 .65 66 .67 7.90 26 .37 65 .73 0 .00 77.75 99.66 87.64 88.4 1 2 .32 3 .32 3 .43 2 .99 56 11.66 6 1.42 5 .55 16.82 66 .0 1 1 1.62 62 .83 82 .59 104 .4 1 63.4 2 81 .85 2 .53 2 .35 4 .13 2 .99 3 .00 5 8 11. 1 1 64 .00 7.69 29 .28 63 .03 0 .00 93.77 97.78 11 8.06 100.88 2 .45 2 .49 2 .99 2 .59 60 9.65 75 .30 6 .95 39.29 53.76 0.00 107 .80 84 .7 1 11 1.75 98 .27 2 .39 2 .75 3 .79 2 .82 62 12.38 73 .28 11. 07 28 . 19 60.73 0 .00 83.73 100 .39 85 .85 90.35 2 .32 3 .63 3 .8 1 3 .12 64 12 .65 82 .88 15.33 34 .97 49.70 0.00 64 . 11 79 .88 88 .65 73 .44 2 .22 3 .64 3 .35 2 .86 66 11. 26 67 .56 4.75 32 .35 62 .89 0 .00 108 .67 74 . 18 61.55 81 .49 2 .55 2 .99 2 .65 2.77 68 9 . 19 60 .42 4.81 19 .56 67 .02 8 .61 102 .72 86 .84 99 .28 166.69 97 .9 1 2 . 17 3 .76 2 .89 2.94 2 .89 70 7.98 74 .62 4.45 27 .8 7 47 .91 19.78 81.17 95 .65 78 .27 170.06 88 .26 2.49 2.88 2 .96 1. 64 2 .76 - ---

Image analysis data for thin section 2a

Di stance along Clay content Original .... old space Grain size di stribution mode % Mean orlen t atlon~" from vertical Mean roundness transect (mm) (% area) (0,. area) 50-100um 100·200 tm 200-500,m 500-1 000um 50- 100um 100-200um 200-500 ,m 500-1000 ,m Total sand 50-100 ,m 100-200um 200-500,m 500 - 1000 ,m Total sand

0 13 .91 60 .67 5 .65 28 . 17 66 . 18 0 .00 79 .58 90 .86 77 .26 83 .20 2.62 3 .34 2 .61 2 .89 2 12 . 18 55.25 5 .56 21 .39 30 .78 42 .26 93 .03 104 .48 8 1.14 128 .0 I 96 72 2 .48 2 .59 3 .26 2 .65 2 .70 4 13 .98 6 1.34 5 . 11 29 .53 53 .5 1 11. 85 77 .05 104 .45 8 1 17 101.76 90 .88 2 .01 2 .75 2 .76 2.78 2 .54 6 14.80 57 .66 5.36 30 .82 43 .58 20 .25 84 .94 100 .24 104 .51 32 .8 1 95.46 2.95 3 .33 3 .71 2 .0 1 3.27 8 13. 15 63 . 16 10 .25 27 .36 62 .40 0 .00 92 .04 100. 13 100 .31 96 .46 2 .34 2 .93 3 .07 2 .69 10 8 .8 1 61 .56 5 . 15 13 .48 66 .72 14 .65 110 .04 76 .45 8 1.64 33 .2 5 90 .45 2 .43 3 .78 3 .67 1.98 3 . 19 12 14.08 62 .03 6 .92 28 .26 41 .85 22 .96 83 .96 67 .69 79 .89 117.99 77 .52 2 .32 2.20 3 .31 5 .59 2 .57 14 12 .2 1 63 .44 6 .21 24 .9 5 56 .9 5 11.89 94.78 83 .49 60 .37 33 .79 80 .4 1 2 .29 2 .96 3 .35 2 .86 2 .83 1 6 14 .06 7 1 .96 8.41 32.68 58 .92 0 .00 108 .82 10 3 .39 87 .60 102 .5 1 1.94 3 .23 2 .71 2 .61 18 11.01 73 .38 7 .00 21 .93 57 .52 13 .56 88 .00 88 .46 114.55 4 .49 92 .83 2 .62 2 .89 2 .8 5 2 .38 2 .77 20 13 .77 68 .06 5 .88 31 .44 46 .25 16 .43 89 .50 72 .65 92 .99 157 .56 83 .90 1.83 2 .87 2 .77 6 .51 2 .6 1 22 15.46 71.85 9 .51 30 .74 59 .75 0 .00 70 .40 87 .8 1 94 .32 81.71 2.47 3 .57 2 .53 2 .87 24 13 .04 73 .03 7.79 44 .58 47 .63 0 .00 69 .80 100.26 74 .80 84 . 13 2 .44 3 .28 3 .87 3 . 12 26 17 .20 7 1.43 10 .81 27.04 43 .89 18 .26 85.71 80.73 108.87 105 .85 88 .08 2 .49 2 75 4 .38 3 . 1 1 2 .9 1 28 13 .45 68.62 3 .92 29.44 54 .37 12 .26 68.42 80 .47 94 .23 61.49 80 . 10 2 .47 2 .48 4 .03 2 .31 2 .8 1 30 12.89 75 .26 7 .21 35.24 57 .55 0 .00 93.49 84 .9 1 99 .34 91.35 2 .69 3 .07 2 .95 2 .92 32 16.57 67 . 17 7 .15 37 .82 55 .03 0 .00 84 .03 83 .72 97 .93 87 .62 2 44 3 .25 3 .32 3 .00 34 18 .29 66 .71 7.68 3 1.07 61 .25 0 .00 78.74 102 .85 112.73 95 .25 2 .47 2.89 2 .89 2.72 36 14.30 74 .22 8 .93 3 1.50 44 .63 14 .94 82 .46 . 95.75 91. 18 62 .53 89 .23 3 .56 2 .89 3.68 2 .45 3 .28 38 9 .01 70 .95 5.46 16 .22 58.85 19 .46 91.71 109 .90 103 .68 90 .72 100 .80 2 .26 2 .52 3 .42 4 . 12 2 .75 40 14.66 76 .62 10.96 26 .79 62.25 0 .00 90 .33 101.06 99 .39 95 .66 2 .50 3 .04 4 .29 3 . 11 42 12 . 10 70.23 5 .97 20 .85 42 .39 30 .78 82 .29 94 .03 101.48 130 . 17 92 .39 2 .77 2 .66 3 .2 1 3 .79 2 .87 44 16 .08 77 .63 9.61 44.38 46.0 I 0 .00 71.18 97 .6 7 68 .03 82 .46 2 .22 2 .69 4 .56 2 .87 46 9.31 73 .26 8 .55 31.66 59 .79 0 .00 68 .59 107 . 11 58 .60 79 .85 2.79 3.22 3 .65 3 . 16 48 15 .72 74 .67 9 .78 35 .22 55 .0 I 0 .00 83 . 14 91 . 16 97 . I 8 88 .69 2 .66 3 .34 3 .28 3 .03 50 17 .42 73 .0 1 9 .04 32 .90 42 .09 15 .97 80 .57 84 .67 83 .49 75.66 82.77 2. 29 3 . 13 6 .05 5 .70 3 .43 52 15 .39 75 .98 7 .92 35 .53 56 .55 0 .00 69 .39 91.19 11 9 16 88 .77 2 .88 3.49 3 .94 3 .36 54 14 .91 66 .03 6 .35 21.89 50 .63 21.14 72 .99 86 . 15 60 .85 44 . 13 74 .87 2.47 2 .98 5 .00 3 .45 3 .29 56 14 .80 76 .20 11 .62 36 .08 52 .29 0 .00 75 .00 71. 13 88 .7 2 76 .18 2 .4 7 2 .84 3 .33 2 .76 58 16.76 74 .82 12 .24 40 .54 47 .22 0 .00 90 .68 90 . 11 78 .73 88 .72 2 .62 3 .44 5 .58 3 .38 60 14 .31 76 . 11 12 .89 33 .96 53 .15 0 .00 81.36 88 .76 84.72 84 .64 2 .32 3 .21 4 .4 1 3 .04 62 11 .04 74 .81 8 .27 19 .43 57 .09 15 .22 9 ·1.09 94 .83 102 .87 117 .87 95 .20 2 .68 3 .66 3 .55 3 .67 3 . 16 64 16 .58 76 .66 10 .08 26 .75 63.18 0 .00 90 .81 97 .06 106.47 96 .82 2 . 13 4 . 16 3.75 3 . 13 66 15.2 1 79 .21 11. 53 41.28 47 .20 0 .00 99.99 82 .77 96 .87 92 .53 2 .00 2 .95 3 .88 2.72 68 14 .44 73 . 19 5 .31 27 .08 67 .61 0 .00 80 .24 83 .56 87 .74 83.57 2 . 17 3.57 3 .59 3.05 70 14.55 72.20 5.85 32.14 62.00 0 .00 87.47 104 .93 78.71 93 .08 2 .76 2.72 _4.-45 3 . 16

Image analysis data for thin section 2b

Di s tance 810"g Clay content Original void space Grain size di stribution mode % Mean orie ntation (O from vertical Mean roundness transect (mm) 1% area) 1% area) 50- 100u m 100-200u m 200-500u m 500-1000um 50-100um 100-200um 200-500 1m 500- 1000u m Tota l sand 50- 100u m 100-2001m 200-500 m 500-1000um Total sand

0 14 .54 65 .53 12 .57 23 .87 63 .55 0 .00 87 .44 80 .52 92 .56 86 .5 1 2 .7 6 3.27 3 .58 3 . 10 2 2 4 .0 4 6 1 10 6.73 28 .06 55.35 9 .86 9 1.7 1 79 .27 10 1.3 1 99.76 89 .33 3 .04 3 .32 4 .35 6 .62 3 .5 1 4 23 .46 71 .59 9 .6 0 2 1. 83 55 .2·4 13 .34 85 .63 72. 0 4 8 1. 42 86 .99 80 .96 2.98 3.90 3 .23 3.7 1 3 .30 6 27 .6 1 7 1. 99 10 .67 28 .64 60 .69 0 .00 70 .91 95 .64 11 3.88 89 .60 2 .48 3.26 3 .52 3 .0 1 8 2 1. 83 67 .97 8 . 18 24 .80 67 .02 0 .00 73 . 11 82 .65 94 . 14 82.47 3 . 12 2 .93 5 .03 3 .66 10 21.05 7 1.96 7 .20 43 .2 1 49 .60 0 .00 68 .48 89 .91 68 .77 78 .78 2 .49 2 .59 3 .54 2 .73 12 20 .29 66.73 6 .02 21.32 60 .20 12 .46 109.57 1 13 .05 87 .50 166.04 104 .86 2.4 5 2 .85 3 .36 1.92 2 .84 14 24 . 13 74 .06 10 . 10 37 .30 52 .60 0 .00 9 1. 76 80 .52 87 .97 86 .48 2 .58 3 .38 3 .68 3.15 16 22 .32 73 .09 10 .73 33 . 19 56 .08 0 .00 83 .10 78.73 49 .02 75 .50 2 .80 4 .16 3 .46 3 .44 18 22 .14 74 .67 8 .66 38 .43 52. 91 0 .00 90 .50 99 .38 98 .32 95 .9 2 2 .95 3 .73 5 .27 3 .71 2 0 24 .27 73.82 13 .4 3 3 1.5 4 55 .0 3 0 .00 8 5 .08 92 .0 2 94 .90 88 .92 2.75 3.4 1 4 .16 3. 18 22 20 .91 69.74 12.4 4 24 .89 49 .58 13 .09 77 .05 87 .88 98 .83 5 1.7 9 83 .35 2 .71 4.52 3 .69 8 .03 3 .5 1 2 4 23 .67 72 .79 5 .52 32 .06 62.42 0 .00 6 3 .05 97 .24 83 .9 7 8 1.48 2 .6 1 3 .03 3 .7 1 3 .06 26 22 .27 75 .34 9 .96 36 .49 53 .54 0 .00 89 .75 8 1.06 87 .44 85 .66 2 .45 2.79 4 . 10 2 .9 1 28 23 .0 0 69 .60 6 .69 35 .45 57 .87 0 .00 65 .09 97 .68 83 .23 84 .2 4 2 .00 3 .0 7 2 .85 2.70 3 0 2 4 .72 73 .59 7.43 26 .99 65 .59 0 .00 69 .64 73 .74 79 .25 73 .44 2 .35 2 .57 3 . 12 2 .62 32 22 .24 67 .33 7 .63 29 .98 62 38 0 .00 96 .2 1 85 .0 1 10 5 .47 93 .98 2 .59 3 . 12 2 .82 2 .84 34 24 .6 3 71.86 8 .85 27 .09 64 .06 0 .0 0 80.29 98 .80 86 .2 1 87 .43 2 .72 2 .75 3 .36 2 .87 36 2 2 .90 76.60 13. 15 38 . 16 48 .70 0 .00 93 .65 93 .27 85 .96 92 .54 2 .10 3 .38 2 .95 2 .70 3 8 22 .0 7 70 .59 13 .6 8 34 .69 5 1. 63 0 .00 79 .18 8 1.1 6 75 .87 79 .27 2 .49 3 .24 3.43 2 .9 2 4 0 18 .47 60 .92 5 .07 22 .67 72 .26 0 .00 82.38 96 .05 69 .73 82 .9 1 2 .97 3 .26 3 .80 3 .33 42 18 .10 66 .67 7 .73 27 . 13 65 . 13 0 .00 69 .80 97 .85 77 . 15 81.92 2 .69 2.72 2 .55 2 .66 44 16 .7 4 70 .00 8 .12 19 .59 72 .28 0 .00 98.79 82 .07 11 7 .92 99 .84 2 .63 2 .47 3 .46 2 .85 46 18.79 64 .29 5 .67 30 .39 63 .95 0 .00 85 .84 67 . 18 9 5 .43 81 .02 2 .84 3 .6 1 3 .64 3 .33 48 14 .99 64 .5 1 5 .05 14 .9 1 80 .04 0 .00 1 17 .62 95 .86 84 .2 4 99 .91 20 1 3 .03 2 .99 2 .63 50 27 .06 68 .38 6 . 16 29 .7 5 64 .09 0 .00 97.18 93 .77 8 8 .22 93 .66 2 .27 2.78 2 .69 2 .57 52 16 .59 66 .52 4 .07 3 1.0 1 64 .9 1 0 .00 11 0 .3 1 98 .82 95 .2 0 10 1 13 2 .27 2 .82 3 . 1 1 2.74 5 4 18. 44 64.3 1 8 .8 6 11 .27 70 .13 9 .75 9 7 .92 60 .70 68 .32 16 2 .62 82 .52 2.50 2 .5 7 2 .90 5 .18 2 .68 5 6 19 .98 63 .15 7 .14 24 .23 68.63 0.00 82 .42 9 1. 11 96 .92 90 .0 5 2 .60 3 .01 3 .50 3 .0 3 5 8 14 .04 67.06 6 .57 43 .22 23.53 26 .69 10 1. 88 78 .23 98 . 18 18 .73 87 .95 2 .77 2 .88 3 .03 3 .70 2 .88 60 14 .25 69 .84 9 .26 27 . 19 63 .55 0 .00 9 1 18 92 .57 90.46 9 1. 54 2 .83 2 .52 2 .84 2.72 6 2 18 .02 63 .23 3 .80 26 .30 69 .90 0 .00 106. 1 1 117 .14 11 0 .02 111.99 2 .66 2 .61 4 . 13 3 . 10 64 20 .8 0 70 .03 7 .25 23 .58 57 .70 11.48 103.24 83 .60 84 . 16 20 .44 90 .33 2 .70 2.74 3 .09 2.54 2 .8 1 66 17.4 1 68 .10 6 .99 29.72 63 .29 0 .00 94 .94 102 .96 94 .22 97 .52 2 .32 2 .57 2 .58 2 .47 6 8 16.24 65 .85 10 . 12 3 1.69 58 .20 0 .00 77 .00 101.77 74.40 84 .7 9 2 .67 3 .6 1 2 .63 2 .98 70 19.4 7 69 .26 5 .30 29 .52 6 5 .18 0 .00 82.87 100 .53 73.94 8 7 .68 2.74 3 .2 9 3.02 3. 0 5

Image analysis data for thin section 3a

Di stance along Clay conte nt Original void space Grai n size distribution (mode % ) Mea n orientation-.f' from vertical Mea n roundness tra n sect (mm) (% oreo) % oreill 50- 100rm 100-200 um 200-500um 500- 1000um 50-100rm 100-200.m 2 00-500rm 500- 1000 m Total sand 50 -1 00 1m 100-200.m 200-500rm 500 -1 000um Total sand

0 15 .87 62.47 8 .29 23 .65 48 . 15 19 .91 9 1.59 99.0 1 70 .95 33.51 89 .47 2 .49 2 .63 2 .49 2 .0 4 2 .54 2 19 .28 67 .9 1 6.88 41.39 51. 73 0 .00 98 . 12 94 .31 107 .23 98 .57 2.64 2 .3 6 3 .36 2 .69 4 11 .77 62 .69 4 .51 28.35 67 . 14 0.00 8 1.1 8 9 1.48 102 .25 9 1.80 2 .66 2.96 250 2 .73 6 11. 33 72 .22 5 .95 43 .98 50 .07 0 .00 100.5 1 92 .66 10 1.02 96.62 2 .20 2 .37 2 .64 2 .37 8 11 .53 66 .64 8 .50 29 .73 6 1. 77 0 .00 103. 13 92 .89 80 .42 93.53 2 .23 2 .69 2 .89 2 .57 10 13 .72 63.84 8 .92 25 .52 65.56 0 .00 79 .90 82 .20 98.04 85 .63 2 .4 1 2 .35 3 .00 2 .56 12 13 .39 65 .98 9 .63 29 . 14 6 1.24 0 .00 78 .6 1 77 .82 92 .63 8 1.27 2.22 2.7 2 2 .40 2 .44 1 4 17 .85 64 . 18 6 .52 24.7 5 57 . 17 11 .56 102 .54 83 .34 63 . 19 33.64 84 .09 2 .6 1 2 .7 1 2 .8 1 3 .82 2.72 1 7 32.66 66. 11 8 .43 28.82 62.75 0 .00 7 1.89 82 .96 90 . 10 80 .99 2.5 1 2 .99 2 .93 2 .80 1 9 26. 71 75 .36 8.7 1 29 .61 6 1 .68 0 .00 97 . 14 82 .47 93 .56 9 1.34 3 .09 2 .6 1 3 .36 3 .00 2 1 16.83 72.6 1 11 .36 27 .33 6 1. 31 0 .00 9 1 .05 86 .34 10 1.30 9 1 .50 2 .62 2 .98 2 .76 I

277 1 23 32.66 74.95 12 .75 42.74 44 .5 1 0 .00 90 .95 90 .33 74 .93 88 . 11 2 .55 2 .65 3 .67 2 .77 26 19 .07 59.73 7.17 36.16 56.6 7 0 .00 70 .29 85 . 18 97 .60 82.88 2 .49 3 .55 2 .3 1 2.93 28 19.80 62 .60 7 .4 1 29.93 62 .66 0 .00 88.14 85 .6 1 83 .53 85 .89 3 . 17 3 .25 2.79 3 .09 1 30 13 .63 58.88 12 .0 1 3 1 .41 32 .70 23 .89 88 .82 78 .59 67 .33 69.45 8 1.54 2 . 10 2 .83 2 .63 4 .05 2 .47 32 16. 2 1 62.27 12.77 29 .40 57 .84 0 .00 90 .35 69 .65 7 1 .03 79 .24 2 .42 2 .58 3 .73 2 .72 3 4 17 .68 6 8 .02 10 .77 29.5 1 59 .32 0 .00 83 .02 87 .84 94 .6 1 87 .59 2 .44 2.78 3 .2 1 2.74 36 18 .28 7 1. 83 9 . 10 41 .16 49.74 0 .00 77 .03 94 .68 99 .50 88 .50 1.78 2 .88 2.52 2 .36 3 8 18 .59 63 .49 8 .34 22. 10 69 .56 0 .00 74 .52 88 .63 8 7 .50 82 .73 2 .98 2 .92 3.75 3 . 19 40 13.90 64 .24 10 .35 38.90 50 .75 0 .00 88 .23 80 .02 69 . 12 80 .94 2 .44 2 .63 2 .83 2 .60 4 2 14.7 1 62.66 9 .76 32 .54 57.70 0 .00 94 .2 1 76 .33 85 . 19 85 .04 2 .92 2 .47 2 .22 2.59 44 17 .28 63 .4 1 6 .09 39 .83 54 .09 0 .00 82 .69 83 .05 75 .96 81.64 2 .27 2 .8 1 2 . 14 2 .5 1 46 17 .78 69 .90 5 .39 25. 11 69 .50 0.00 79.82 11 4.43 86 .64 94 . 14 2 .94 242 2 .57 2.64 48 24.5 0 73 .85 10 . 10 35.03 54.87 0 .00 93 .5 1 94 .43 97 .04 94 .53 2 .97 2.4 2 3.09 2.78 50 23 .32 67 .66 5 .95 32 .90 6 1. 14 0 .00 106 .24 87 .86 95 .9 1 95 .66 2 .90 3 .06 3 . 13 3 .0 2 5 2 15.02 65 . 17 10 .02 24 .32 56 .04 9 .63 75 .62 87 .54 77 .85 20.74 79 .25 2 .92 2.76 3 .63 6 .24 3 .07 54 18 .84 56 .36 4.42 22 .75 62 .92 9 .92 101.39 85 . 19 110.46 16 .82 96 .68 2 .23 2 .8 1 2 .95 1.57 2 .67 5 6 15 . 19 58 .4 1 6 .46 18 .56 67 . 10 7 .88 90 .52 82 .2 3 89.9 1 84 .05 87 .60 2 . 11 3 .2 1 2 .64 2.38 2 .62 5 8 16 . 13 57.8 1 5 .04 28 .3 1 66.65 0 .00 93 .22 95 . 19 85.49 9 1.80 2 .57 2 .2 7 2.65 2.47 6 0 14. 17 62.6 1 7. 12 29 .26 54 .78 8 .84 95 .27 92 .58 97.24 74.25 94 .45 2.48 2.4 1 2 .23 2 .23 2.39 6 2 12 .91 58.92 5.53 29 .4 1 65 .06 0 .00 88.84 85 .63 88 . 17 87.29 2 .47 2.70 2.57 2 .59 64 22.76 72 . 19 7 .55 34 .94 36 .36 2 1. 15 10 6 .45 90.45 97 .93 27 .35 97 .29 2 . 17 2 .88 2 .67 5 .77 2 .59 66 18.06 64 .47 6 .87 26 .0 1 67 . 12 0 .00 96 .87 86 .45 9 1. 84 9 1.48 2 .56 2 .70 2.20 2 .5 1 6 8 16.56 7 1 .28 17 .08 30 .29 52.63 0 .00 92 .36 84 . 11 89 .79 89 .37 2 .93 2 .8 1 2 .23 2 .77 7 0 15.94 60 .2 1 7 .68 34 .46 57 .87 0 .00 79.95 98 .52 8 7. 08 89 .02 2 .06 2 .09 2 .31 2. 14

Image analysis data for thin section 3b

Di stance along Clay content Original void space Grain size distribution mode % Mean orientation " from vertical Mean roundness tra nsect Imml 1% a real 1% .re& 50-10~m 100-200u m 200-500u m 500- 1000 m 50-100 m 100-200 m 200-50~m 500-1000um Total sand 50- 100u m 100-200um 200-500um 500- 1000 .m Total sand

0 12.35 59 .86 10 .63 33.12 56 .25 0 .00 103.85 84 .87 92 .5 1 94 .43 2.27 2 .38 3 . 11 2.46 2 12 .17 62 .05 5.23 39 . 18 42.98 12 .62 87.98 86 .55 90 .33 13 1.9 1 8827 2 .40 2 .4 1 2.59 4 .78 2.47 4 14.48 63.72 8 .67 37 .36 4 1.56 12.41 94 .61 77 .64 94 .22 141.36 87 .70 2 .34 2 . 10 3 .96 2.49 2 .52 6 16 .31 69 .90 6.55 25 . 11 68.33 0 .00 90 .46 53 .20 104 .05 77 .92 2 .49 2.76 3.32 2 .81 8 14 .60 70 .38 11.05 45.33 43.62 0 .00 88.64 86.90 67 .35 84 .9 1 2 .66 2 .36 3.32 2.62 10 19 .69 6793 9.94 30.29 59.77 0 .00 88.46 90.93 96 .79 91.10 2 .80 2.72 3. 11 2 .84 12 17.83 59 .27 6.43 38.07 55.49 0 .00 100.26 81.99 107 .25 92 .8 1 2 .39 2.54 2 .52 2.49 14 20.70 70 .05 8 .31 43 .24 48.45 0 .00 102.29 98.59 75 .93 94.79 2 .77 2. 0 9 2.79 2.46 16 24.95 71. 95 9 .07 2 1. 76 69 .17 0 .00 98.36 71 .28 77.02 83 .9 1 2 .39 2.69 2 .54 2.52 18 18.42 68 .57 8 . 11 32.59 59.30 0 .00 96 .88 81 .09 10 4 .82 93 .54 2.82 2 .68 2.7 1 2.75 20 22 .21 67.00 6 . 12 34 .50 59 .38 0 .00 65.40 7 1 .44 114 .4 1 79.88 3 .24 2 .83 4 .06 3 .28 22 24.92 68 .04 7 .57 21.55 70.88 0 .00 90.07 92.47 77.9 1 87 .10 2 .82 3.2 1 2 .90 2.95 24 15 .58 65. 19 11.30 38 .66 39.56 10.48 79.4 7 78 .97 115.56 97 . 17 85.49 2.81 2 .73 3.3 1 2 .05 2.85 26 10 .59 59 .10 9 .49 33 .96 56.55 0 .00 83 .6 1 102 .16 69 .43 88 .91 2 .3 1 2.77 2 .63 2.58 28 12 .35 6 1. 68 7 .97 41.86 36 .40 13 .76 78 . 12 95 .49 80. 12 175 .98 87 .62 2 .99 3 . 18 2 .32 4.62 3.00 30 14 .01 64 .19 5.92 23 .87 70.20 0.00 85 .0 1 76 .64 94 .83 85 .2 4 3 .39 2.37 3 .86 3 .18 32 18 .08 65 .51 7 .5 1 24 .94 54.77 12.79 81.64 73 .69 74 .53 102 .30 77.35 2 .63 2 .86 4 .92 2.33 3. 19 34 19 .80 64 .20 10.09 32 .26 44.5 1 13 . 14 104.62 95.24 106.41 59 .53 101 15 2.61 3 .69 2 .74 2.7 1 3.02 36 33 .33 68 .61 10 .53 48 .04 41.44 0 .00 67.66 104 .64 91.2 1 88 .23 2 .39 2 .76 2 .42 2.56 38 23 .0 8 71. 77 9 .77 35 .92 54.3 1 0 .00 84.84 70 .00 83 .56 78.53 3.25 2.65 2 .37 2 .83 40 22.78 64 .22 6.26 43.09 50 .65 0.00 76 .01 91 .87 90 .61 86.46 2 .69 2.67 3.7 1 2.88 42 14 .27 57 .69 8 .07 20 .45 58 .05 13.43 100.41 111.21 87.26 24.43 99 .68 2 .55 2 .29 3 .02 2.2 1 2 .58 44 13.74 60.75 6 .32 24.72 59 .33 9 .63 107.4 1 95 .53 108.54 148 .89 103 .60 3 .09 2 .65 2 .66 3.85 2.82 46 12.48 68 . 10 12 .60 37 .68 40 .22 9 .49 102 .73 100.97 107 .77 140 .56 103 .38 2 .86 3.77 6.06 5.27 3.69 48 14.85 64 .26 10 .28 37.05 52 .66 0 .00 86 .02 92 .66 105.82 9 1.93 2 .88 2 .95 3 .07 2.94 5 0 13 .24 62.8 1 6.35 25 .06 68.59 0 .00 83 .04 79 .5 9 8438 82.04 2.78 3 .77 2 .62 3 . 13 52 13 .25 64. 12 11. 58 32.75 55 .67 0 .00 72 .28 76 .79 7 1.57 73 .63 2.42 2 .87 3 .65 2.8 1 54 14.43 59 .57 8 .46 32.44 59 .0 9 0 .00 87 .8 1 88 .63 9 1.74 89 .08 2 .51 2.73 3.27 2.78 56 15 .74 59. 14 8 .28 29.94 61 .77 0 .00 88 .4 1 77.72 85 .61 83 .94 1.93 2 .35 2.73 2 .30 58 9.07 60.63 7.51 33 .35 59 .14 0 .00 80 .29 97 .28 97 .22 91.27 2 .62 2 .57 3 .37 2.82 60 9.33 62 .02 8 .65 24.06 42 .71 24 .57 100.35 73.41 94 .63 106 .5 1 90 .77 2.65 2 .84 2 .77 3.78 2.76 62 12 . 15 62 . 19 5 .83 26.8 1 67.36 0 .00 75.67 93.83 90 .28 86 .90 2.35 2 .23 2.40 2.31 64 14 .26 62 .47 7.46 38 .29 54 .25 0 .00 71.05 94.4 1 74 .41 82 .25 2.00 2 .42 2.82 2 .35 66 15 .28 58.78 8 .2 3 32 .29 47 .06 12.43 77.4 1 90.39 109.93 96 .54 89 .86 2 .33 2.71 2 .05 1.73 2.42 68 12.36 62.61 11. 72 31.87 56.41 0 .00 84 .93 75 .72 82 .01 81 16 2.73 2.28 2.50 2.52 70 25.03 65.60 6.18 28 .53 65 .29 0 .00 104.59 101. 76 89.24 99.43 2.35 3.34 2.87 2.90

Image analysis data for thin section 4a

Distance a long Clay conten t Grain size distribution mode % Mean orientation <> from vertical Mean roundness transect lmm) 1% orea l 50- 100"m 100-200um 2 00-500um 500- 1000um 50-100um 100-200 "m 200-500um 500- 1000um Total sand 50- 100u m 100-200um 200-500um 500-1 000um Total sand

0 9.10 8. 18 28 52 63.30 0.00 94 .36 78 .02 9 1. 42 87 .76 2.49 2 .09 2 .54 2 .36 2 7 .28 6.97 27 .00 66 .03 0 .00 108 73 81.4 1 99 .92 94 .63 2.72 2 .83 3 .07 2 .87 4 9 .8 7 9 .09 28. 0 6 34.79 28.06 96 .06 97 .36 99.46 20 .7 5 95 .15 2 .10 2 .98 3 .0 8 4.7 1 2 .65 6 15.09 6 .82 30 .84 62 .34 0 .00 93 .48 93 .90 1 17 .30 99 .37 2 .27 2.42 2 .36 2 .35 8 20 .63 5.45 3 1 .13 46 .90 16 .53 80 .70 93 .09 89.36 57 .7 5 87 .28 2.1 1 3 .00 3 .54 2 .66 2.76 10 14.48 11.93 27 .76 60 .3 1 0 .00 93.23 73 .95 86.85 86 .07 2 .60 2 .62 3 .85 2 .87 12 13.38 9 .34 22 . 13 34 . 16 34 .37 85 .93 64 .76 82.52 106 .83 78.48 2 .65 2 .87 2 .66 3 .26 2.76 1 4 8 .92 8 .06 20 .94 59.44 11 .57 94 .92 94 . 14 80.60 172 .6 1 92. 30 2 . 19 2 .65 4 .59 5 .59 2.94 16 11 .60 4.4 1 3 1 .10 39.45 25 .04 70 .94 75 .68 61.28 72 .08 71 .29 2.40 3 .17 2 .54 5 .0 8 2 .88 1 8 9 .87 11.93 32 .23 55 .84 0 .00 9 1.1 0 74 .33 112.22 88 .93 2.47 2 .55 3 .27 2 .65 2 0 9 .77 10 .56 32 .0 7 57 .38 0 .00 9 1 .28 76.41 83 .38 83 .93 2 .88 3 .62 3 .2 1 3 .23 22 12 .59 8.28 3 1.20 38 .25 22 .27 76 . 10 92.95 61.15 52.47 79 .08 2 .35 2 .7 5 3 . 15 3 .08 2.67 24 14.96 9 .6 1 28 .85 6 1.55 0.00 88 .62 109.79 96 .66 98 . 12 2 .26 3 .29 2. 99 2 .8 1 26 14 .12 10. 16 29 .57 60 .28 0.00 78.47 83.56 75 .33 79 .53 2 .8 1 3 .42 3 .69 3 .22 28 17 .6 7 12.04 30 .34 57.62 0 .00 8 1.23 71 .83 91.36 79 .72 3 .09 3 . 10 4 .53 3 .32 30 16 .77 12 .35 31.20 42.40 14.05 70 .58 67 .61 82 .63 119.83 7 1. 82 2.38 2 .27 3 .92 4.78 2 .61 32 22.47 7 .13 28 .66 64 .2 1 0 .00 88 .58 90.65 84 .24 88 .57 2 .99 2.57 4 .28 3 .07 34 2 1. 6 7 12 . 10 30 .53 4 1. 35 16.02 83.48 11 0 .32 75 .67 13.40 90 .79 2 .56 2 .61 3 .32 2 .69 2 .68 36 24 .51 7 .8 1 47 .04 45 . 16 0.00 93 .06 91.44 102. 12 94 .03 2 .09 2.4 1 3 .62 2 .52 38 27 .89 14.25 5 1 .98 33 .77 0 .00 80 .38 80 .65 64.76 79 .05 2 .22 3.18 3 .89 2 .82 40 20 .13 8 .28 37 .99 43.3 1 10.43 93 .16 70.01 100. 19 6 1. 40 84 .6 3 2 . 15 2 .66 2 .80 1.98 2 .49 42 2 1. 4 8 6 .58 30 .3 1 63 . 11 0 .00 85 . 15 107 .53 120.26 103 .44 1.9 1 2 .15 3.15 2 .34 44 26 .38 15.47 34.06 50 .48 0 .00 76 .87 10 1. 6 1 9 1. 32 87 .08 2 .2 1 2 .67 3 .20 2 .51 46 24. 0 4 9 . 11 38 .68 52.21 0 .00 10 1.16 91.57 118.26 100.08 1 .87 2 .44 2 .43 2 .20 48 22 .34 12.47 37 .22 50 .3 1 0 .00 92 .29 92 .73 95.55 93.02 1.86 2 .52 2.76 2.28 50 25.70 12 . 18 33 .77 54 .05 0 .00 89 .22 96.45 82 . 11 90 .91 1.9 1 2 .36 2 .63 2 . 19 52 22 .56 10.63 32 .78 56 .58 0 .00 109 .38 74 . 12 74.78 90.4 5 2 .37 2 .87 3 .66 2 .82 54 22.3 1 7 .66 34.84 57 .50 0 .00 89 .68 89 .06 61.07 84 .9 1 1.89 2 .69 4 . 1 1 2 .63 56 23 .47 20.44 44.53 35 .03 0 .00 84 .58 96.70 9 1.05 89 .30 2 .24 2 .36 3 .55 2 .4 1 58 25 .39 14.05 4 1.44 44 .5 1 0 .00 84 .08 9 1.01 87 .87 87.40 2 .69 3 .33 4 .06 3 . 17 60 25 .53 8.06 25.94 66 .00 0 .00 84 . 11 10 5 .65 85.49 92 .05 2 .50 3 .53 2.48 2 .86 62 22 .6 1 13.09 47.5 1 39.40 0 .00 67 .28 82 .74 100 .87 77 .30 2.44 3 .04 3 .38 2.79 64 32.6 1 19 . 14 35.20 45.66 0 .00 85.76 73 . 16 72 .99 80 .52 2 .04 2 .77 3 .45 2.42 66 35. 9 3 17 .80 30 .81 5 1 .39 0 .00 91.33 90.47 76 .17 89 .2 1 2. 19 2 .58 2 .53 2 .35 68 26.8 1 12 .02 42.09 45 .89 0.00 93.72 80 .02 85 .77 87.42 1.8 2 3 .05 3 .85 2.54 70 36.0 1 19.27 45.29 35.44 0 .00 101.50 97 .92 11 9 .87 102 . 13 2.15 2.46 3 .34 2 .38

Image analysis data for thin section 4b

Distance along Clay content Grein size di stribution mode %1 Mean orientation (0 from vertical) Mea n roundness transect Imm\ (% .rea) 50 -100u m 100-200u m 200-500u m 500-1 000 m 50-1 00um 100-200um 200-500um 500- 10001m Total sand 50 -100u m 100-200um 200-500um 500· ' 000 1m Total sand

0 35 .68 17 .22 32.2 1 50 .57 0 .00 98 . 18 98.71 104.00 99 .25 2 .09 2 .69 2 .37 2.33 2 22 . 13 13.39 27.7 1 58 .90 0 .00 83 .43 73 .08 112 .25 84 .96 2 .06 2 .93 2 .82 2 .47 4 28 .82 11 . 11 43 .27 45 .63 0 .00 106 .56 104 .54 81.69 101 .9 3 2 . 18 2 .29 2 .87 2.33 6 38.33 22 .74 34 .25 43.00 0 .00 93 .86 82 .34 6 1. 68 87 . 14 2 .Q7 2 .32 2 .85 2 .2 2 8 37 .94 19 .88 51.54 28.58 0 .00 7 1.57 77 .52 89 .38 75 .70 2 .23 2 .29 4 .35 2 .48 1 0 28 .47 19 .44 30 .63 49.93 0 .00 99 . 13 78 .36 64.45 88 .52 2 .03 2 .34 2 .88 2 .24 12 34.42 12.09 36 . 11 5 1 .8 1 0 .00 80 .54 10 1.02 90 .07 89 .09 2 . 14 2 .68 2 .53 2 .39 1 4 34 . 18 12.30 33 .68 54 .02 0 .00 86.29 80.69 98 .26 86 .84 2 . 11 2 .2 5 3 .20 2 .37 16 37 .0 1 13.88 48.60 37 .52 0 .00 98 .69 89 .95 104.39 95 .79 1 .75 2 .44 3 .89 2 .32 1 8 37.80 15 . 10 28 .39 56 .5 1 0.00 75 .07 77 .94 86.84 77 .8 1 2. 15 2 .37 2 .88 2 .33 2 0 31.30 13 .33 42 . 19 44.48 0 .00 90 .94 96 .20 68 .89 89 .94 2 .20 2.70 2 .75 2 .48 22 25 .20 15 .6 1 41.47 26 .67 16 .25 84 .94 89 . 12 107 .74 33 .50 87 .48 2 .46 2 .22 2 .68 2 .37 2 .38 24 26.79 13 .58 18 .89 48 . 14 19 .39 86 .67 82 .04 86 .95 6 .76 84.58 2 .05 2 .55 2 .57 4 .07 2 .30 26 30 .66 13.74 27.14 39 .48 19 .64 109 .35 97 .65 104.38 76 .48 104 .60 2 .25 2 .91 2.76 1 .9 1 2 .53 28 30.6 1 8.78 25 .32 65.91 0 .00 71. 17 80 .08 88 .95 78 .46 2 .38 2 .75 2 .93 2.64 30 30.7 1 13.33 35 . 10 5 1.57 0 .00 92 .29 92 .41 90.21 9 1.93 2.76 2 .51 3 .56 2 .83 32 27 .99 9.79 2 1. 23 68 .97 0 .00 7 1.4 1 96.78 75 .75 79 .3 2 2 .09 2 .8 3 2 .24 2 .33 34 36 .66 17 .98 4 1.05 40 .97 0.00 93 .60 93 .02 94.98 93 .53 2 .06 2 .38 2.32 2.2 1 36 32 .59 15 .25 39 .88 44 .86 0 .00 88 .98 72 .9 5 108 .23 85 .70 2 . 1 1 2 .2 2 2 .37 2 . 18 38 28 .25 17 .88 52 .03 30 .09 0 .00 80 .99 97 .96 47 .84 84 .52 2 .22 2 .54 3 .51 2 .44 40 28 .95 12 .25 35 .66 3 1.73 20 .36 80 .59 99 .43 92 .28 76 .47 88 .6 3 2.07 2 .8 7 3 . 19 1.7 1 2 .49 42 37.66 15.44 36 . 14 48.4 2 0.00 98 .33 77 .96 97 .86 9 1 .49 2 .04 2 .35 2.6 1 2 .2 1 44 40.38 13 .64 36 .23 27.40 22 .7 3 78 .60 94 .0 1 124.74 23 .59 87.11 2 .06 2 .30 3 .59 3 .48 2 .29 46 29.60 9 . 12 39 .85 5 1.03 0 .00 101. 62 98 . 14 100 .58 99 .98 2 .2 2 2 .92 3 .24 2 .66 48 38.89 11 .28 26.43 32 .08 30 .2 1 77 . 10 98 .45 92 .04 3 . 10 84 .43 2 .30 2 .20 3 .06 2 .87 2 .37 50 37 .23 14 .43 24.72 38 . 10 22.75 64 .86 85 .24 78 .07 135.9 2 72 .96 2 . 19 3 .20 3 .06 1 .97 2.57 5 2 37 .48 14 .97 27 .00 58 .03 0 .00 80 .58 80 .92 99 .52 83 .89 2 .22 3 .25 2.73 2.56 54 38. 12 22.49 33 .55 43 .96 0 .00 76 .49 76 .50 82.78 77 . 11 2 .08 2 .89 5 .39 2 .62 56 36 . 17 16 .6 1 27 .23 56 . 16 0 .00 11 7.24 94 .85 109.09 109 .50 1. 90 22 j 308 2 . 16 5 8 35.49 2 1. 05 24 .00 54 .95 0 .00 10 1.1 0 86 .98 90 .65 96 .0 3 2 .2 9 2 .58 3 .05 2.47 60 34.6 1 16.33 30.00 53 .67 0 .00 80.71 75 . 1 1 107.06 82 .53 2 . 17 3 . 14 2.52 2 .48 62 4 1.26 18 .48 4 1 .74 39 .78 0 .00 90 .27 92 . 16 89 .93 90 .92 2 . 1 3 2.92 2 . 18 2 .42 6 4 42.42 15 .59 33.89 50.5 1 0 .00 82 .57 86.23 78.70 83 .04 2.43 2 .63 3.22 2 .60 66 4 1 .82 14. 18 3 1 .06 54 .76 0 .00 94 .40 86 .25 107 .08 94 . 14 2 .3 6 2 .26 2 .81 2 .4 1 68 37 .35 13.80 3 1 . 15 55 .06 0 .00 83 .22 89 .08 94 .53 86 .56 2 .07 2 . 15 2 .64 2 . 17 70 43.76 19.48 39.88 29.79 10 .85 83 . 15 89 .84 81.64 124 .68 85 .70 1.96 2 . 14 2 .43 2 .95 2 .07

Image analysis data for thin section 5a

Di stance along Clay content Original void space Grain size distribution mode % Mean orientation --.t from vertical) Mean roundness transect (mm) (% .rea) (% .r •• ) 50-100 m 100-200nm 200-500"m 500- 1000"m 50- 100"m 100-200"m 200-500"m 500-1000"m Total sand 50 -100"m 100-200"m 200-500 1m 500-10001m Total sand

0 9.66 56 .36 4 .98 27 .89 59 . I 8 7 .95 90 .70 65 .3 7 97 .27 139 .68 83 .54 2 .2 2 2.57 3 . I 9 4 .08 2 .68 2 8 .62 59 .0 1 4 .86 23.00 72 . 14 0 .00 77 .97 75.44 103 .07 85.72 2 .76 2 .80 3 . 13 2 .90 4 4.51 54 . 16 4 .97 13.80 8 1.22 0 .00 8 1.92 77 . 17 81 .3 1 80 .2 7 2 .96 2 .44 ~.7 5 3 .09 6 8 . I 7 60 . 19 4.22 33 .7 1 62 .07 0 .00 71 .49 88 .70 68 .24 78 .54 2 .93 2 .2 I 2.51 2 .49 8 9 .87 60 .55 5 .24 19 .08 75 .67 0 .00 83 .64 95 .45 1 10 .26 96 .97 2 .39 3 .80 3 .02 3 .04 10 8 .63 53 .04 5 .57 16 .9 I 77 .51 0 .00 72 . I 0 96 .44 98 .7 9 88 .05 2 .6 3 2 .9 1 2 .37 2 .62 12 8.46 61 .0 1 3 .39 16 .03 80 .58 0 .00 91.00 1 I 8 . 19 106 .02 105.46 2 .82 2 .86 3 .86 3 .27 14 24 .33 66 .28 3 .89 25 .82 59 . 16 11.13 75 .98 79 .77 76 .32 166 .96 79.4 2 2 .40 2 .5 1 3 .60 4 .28 2 .84 16 28.68 58 .61 4 . I 5 19 . I 3 56 .75 19 .97 84 .96 84 .93 76 .41 78 .86 82.4 2 3 .2 2 3 .14 2 .85 2 . 12 3 .07 18 21.94 58 .4 1 2 .99 20 .55 76 .46 0 .00 69 .56 102 . I I 94 .44 91.16 2 .32 2 .9 1 3 .37 2 .93 20 8 .87 62 .39 6 . 10 34 .3 I 59 .59 0 .00 71.35 90 .50 94 .36 85 . 18 2 .48 2 .96 3 . 13 2 .84 22 4 .05 56 .52 4 .82 32 .26 54 .67 8 .25 82 .24 91 .3 2 98 .94 162 .01 91.90 2 .76 2.70 3 .43 2 .00 2 .89 24 8 .89 54 .95 5 .2 I 22 .03 72 .76 0 .00 94 .80 87 .81 100 .86 94 . I 2 2 .93 3 .32 2.73 3 .02 26 I 1 .79 65 .22 8 .34 35 .58 56 .08 0 .00 100.88 87 .00 84 .05 90 .60 2 .71 3 .34 2 .57 2 .95 28 6 . I 4 57.79 5.78 27 .07 60 .31 6 .85 76.06 78 .86 90 .97 I I 5 .68 81. 72 2 .24 3 .02 3 .20 1.89 2 .81 30 5.92 61.18 9.72 29.46 60 .82 0 .00 106 .94 87 .82 102 .9 1 99 .34 2 .76 3 .29 3 .54 3 . I I 32 7 . I 3 58 .73 4 .66 24 .65 70 .69 0 .00 75.09 89 .89 103.54 90 .4 I 1.79 3 . I 0 3.02 2 .71 34 5.48 56 .78 5.2 I 35 .55 59 .24 0 .00 80 .43 88 .53 90 .08 86 .58 2 .03 2.88 3 .30 2.73 36 5.23 56 .78 5 .88 26 .67 59 .23 8 .22 91 .79 100 .16 98 .0 1 174 .03 97 .64 2 .49 3.38 4 .06 5 .20 3 .3 I 38 5.93 62.39 8.30 26 .33 65 .38 0 .00 89.7 1 80 .05 88 .82 86 .23 3.04 3 .06 3.22 3 .09 40 11.1 9 7 1.26 I I .59 32 . 10 56 .31 0 .00 75 .91 77 .39 70 .90 75 .60 2 .85 2.70 3 .41 2 .89 42 28 .40 70 .23 10 .73 2 1.16 68 . 11 0 .00 93 . 15 92 .43 72 .97 87 .20 2 .56 2 .88 3 .09 2 .80 44 10 .71 69 .53 4.35 20 .0 1 75 .64 0 .00 85 .83 83 .32 77 .93 82 .28 2 .38 2 .99 3 .32 2.92 46 8.78 64 .27 3 .96 30 .51 50 .6 6 14 .87 103 .58 61. 73 91 .17 139.72 81.17 2 .83 2 .47 3 .60 5 .26 2 .88 48 11. I 5 63 .01 6 .48 25 .46 68 .06 0 .00 68 .64 99 .68 126 . 10 95 .38 2 .25 2 .97 3 .44 2 .83 50 7 .38 55 .50 8 .60 27.7 1 49 .94 13 .75 95 .68 108 .53 101.34 82 .59 101 .23 2 .44 2 .29 2 .87 4 .63 2 .53 52 7 .86 67 .27 8 .38 45 .29 46 .33 0 .00 64 .45 84 .7 6 84 .37 76 .80 2 .57 2 .75 3 .85 2 .85 54 6 .88 63 .31 6 .92 18 .31 74 .77 0 .00 87 .70 101.57 99 .30 95 . 12 2 .89 3 .49 3 .45 3 .23 56 7 .03 54.26 3 .96 20 .00 6 1. 18 14 .85 107 .32 108 .49 65 .08 70.07 94 .73 2 .34 3 .52 3 .25 4 .9 5 3 . 14 58 10 .45 58 .86 6 .93 2 1.25 7 1.82 0 .00 60 .75 100 . 15 87 .98 80 .68 2 .70 2 .59 3 . I 4 2 .81 60 7 . I I 52 . 1 I 2.55 18 .28 54 .32 24 .85 75.78 I I 1.32 92 .40 128.89 95 .89 2 .52 2 .34 2 .95 1.58 2 .6 1 62 6 .61 53 .96 4 .37 15 .97 55 .03 24 .63 86 .89 79 .28 93 .44 I I 7.79 87 .94 2 .43 2 .96 4 .56 3 .92 3 .27 64 6.88 53.43 5 .49 25 .84 62 .74 5 .93 90 .07 96 .52 87 .38 71. I 2 91.60 2 .95 2 .3 1 2 .61 5 .57 2 .65 66 8 .95 53 .96 3.44 19 .26 62.44 14 .86 90 . 12 98 .07 62 .8 1 24 .97 82 .81 2 .23 2 .96 2.70 6 .37 2.75 68 13 .65 68 .36 10.55 3 1.1 I 58 .34 0.00 87 .50 92 .07 84 .9 1 88.43 2 .59 2 .56 2.57 2.58 70 11.54 64.34 5.37 24 .93 69 .70 0.00 76.27 95 .70 103.53 9 1.31 2 .39 2.66 2.32 2. 47 - -- ----

Image analysis data for thin section 5b

Di stance along Clay content Original void space Grain size distribution mode 'Yo} Mean or ientation 0 from vertical Mean roundness transect lmml (% . r.al (% .rea) 50 -100pm 100-200 m 200-500um 500 -1000um 50-100um 100-200pm 200-50QJ1.m 500- 1000 m TOlal sand 50-100um 100-200 tm 200-500um 500- 1000u m Tolal sand

0 11 .92 54.84 4 .46 15 .62 59 .37 20.55 7 1. 62 102 . 14 103 .64 48 .53 92.43 2 .40 2 .63 3.02 2 .72 2.69 2 10 .42 57 .69 5 .36 18 .40 76 .23 0 .00 90 .66 81.54 77 .04 83 . 12 2 39 2 .48 3 .32 2.76 4 9.4 1 62.69 6.36 25 . 12 60 .30 8.21 105.28 81 .61 85 .32 107 .83 91. 72 2 .40 2 .33 2 .56 3 .03 2.43 6 7.43 66 .23 6 .08 28 .96 64 .96 0 .00 79 .42 97 .09 77 . 12 86 .22 3 . 12 2.96 3 .19 3.07 8 7 .68 58.30 5.14 16 .3 1 66.84 11 .70 99.7 1 111 17 98 .2 1 143 .63 103 .33 2 .22 2. 11 3 . 13 1.8 1 2.5 1 10 10.78 60 .69 8.35 29 . 12 5 1. 39 11.1 4 94 .68 98 .31 9 1.99 58.78 95.03 2 .90 2.76 3.23 5 .95 2.97 12 9 .67 64.33 7.45 33 .90 46 . 10 12 .55 9 1.85 69 .01 108 .25 56.25 84 .09 3 .18 3.08 2 .84 2 .61 3 .06 14 12. 10 60.20 6.26 26.19 58.00 9 .55 91 .00 82 .31 90 .96 9008 87 .57 3 .55 3.27 3.08 2.0 1 3.30 16 22 .56 6 1.1 3 5.94 26 .50 55.40 12 . 16 98.46 86 .86 90.79 96.10 91.83 2 .78 3.05 2.55 2 .39 2 .8 1 18 17 .22 65 .00 8.57 30.75 60 .68 0 .00 89.33 78.82 90.4 1 86 .27 2 .97 2 .96 3.32 3 .07 20 12 . 17 65 .85 6.54 27 .86 65.60 0 .00 10 3 .33 99 .24 103.93 10 2 .02 2 .33 3 .13 2 .94 2.80 22 10 .90 69 .33 7.76 43 .33 48 .9 1 0 .00 87 .96 86 .69 107 .67 9 1.37 2 .89 2 .80 3 .76 3 .02 24 14. 13 69.12 6 . 17 30.42 63.4 1 0 .00 81.66 101.56 79 .87 89 .08 2.7 2 2 .90 3 .61 2 .99 26 12.63 61.24 5 .0 1 22 . 15 72 .85 0.00 67 .35 78 . 10 7 1.0 2 72 .48 2 .90 2 .50 2.68 2 .68 28 15 .42 63.75 5 .58 17 .90 66 .40 10 . 12 64 .80 88.26 109 .25 84 .55 87.71 2 .28 2 .33 3 . 18 3 .43 2 .64 30 15 .04 65.12 8 .23 30 .29 61.48 0 .00 103. 10 87.7 1 97.46 96 .43 2.75 2 .9 1 2.75 2 .80 32 8.66 62 .71 8 .24 22 .42 47 .89 2 1.45 82 .66 90 .30 60 .64 177. 12 83 .28 2 .55 2 .56 3 .92 3 .39 2 .8 7 34 11. 98 60.37 6.42 21.1 0 64 .80 7 .68 10 5.61 60 .62 85 .22 12 .96 85 .20 2 .65 3 .35 3 .87 2.7 1 3.2 1 36 11. 94 66. 72 4 .58 36.29 45.97 13 .15 84 .30 77 .6 1 109.19 178.78 87 .53 2 .14 3 .24 3.86 2.23 3. 10 38 11.68 67.30 7 .09 25.90 67 .01 0 .00 93 .87 88 . 17 87 .98 90.25 2 .94 3 .94 3 .3 1 3.39 40 10 .80 6 1.8 2 6 . 15 23.35 70 .50 0 .00 90.63 92 .06 98.38 93 .87 2.38 2.87 3 .20 2.83 42 10 .65 58.83 7.5 1 34.51 57 .99 0 .00 109 .22 87 .98 83 .90 94 .57 2 .60 2.99 3 .2 1 2 .90 44 12.5 1 57 .31 7.14 22 .82 70.04 0 .00 87.24 104 . 12 109 .50 98 .99 2 .47 3.7 1 3 .01 3.07 46 10 .0 5 6 1.0 5 7.64 23.4 1 62.75 6 .20 77.77 92 .08 84 . 10 107.72 84.27 2.9 1 2 .79 3 .68 5.12 3 .08 48 14 .22 62 .1 3 6 .33 27.38 66 .30 0 .00 95 .09 92 .55 98.86 95 .27 3.08 3 .45 3 .27 3.27 50 13 .6 1 67 .03 8.90 26.75 64.35 0 .00 98.47 70 .39 71.25 82 .28 3 .02 3 .09 3 .00 3 .04 52 13.07 66. 16 9.82 20.48 69.70 0 .00 84 .57 77 .12 76 .80 80.40 2.72 3 .2 1 3.73 3 . 13 54 11.3 5 63 .64 11.89 14 .86 73.25 0 .00 77.22 90 .9 1 77. 18 79 .91 2 .66 2 .78 2.78 2.72 56 10.02 58.71 7 .02 34 .71 58.27 0 .00 81 .64 101 .51 11 3 .82 98.05 2 .50 3 .09 2 .66 2 .80 58 9 .29 54.28 5.5 1 26 . 14 58 .98 9.37 85 .24 72.47 73 .60 128.27 77.33 2 .88 2 .67 2 .47 6 .35 2.73 60 21.29 72 .90 11.1 5 45.03 43.83 0 .00 86.5 1 61.60 96 .32 77 .39 2 .72 2 .66 2.44 2.65 62 23.85 59.16 5 .80 15.70 59 .86 18 .64 77.12 99 .48 68.42 165.24 84 .67 2 .53 2.67 3.18 6.11 2.88 64 16.56 68 .67 5 .00 25.74 69.27 0.00 99.93 68 .52 91 .75 86 .02 2 .23 2 .30 2.98 246

1

66 14 .83 66.63 6.98 40 .94 43 .63 8.45 83.75 102 .99 37.32 97 .99 85 .94 2 . 15 3.40 2 .20 4 .63 2.79 68 9.03 65.76 9.72 40 .97 49.31 0 .00 101.83 95.82 65 .98 92.79 2 .87 3 .52 3.54 3 .27 7 0 21.19 71.43 12.62 36. 16 51.22 0 .00 81.49 85 .20 104 .90 86 .77 3. 19 4.00 5 .69 3 .92

Image analysis data for thin section 5c

Distancl!! along

tran sect (mm\ Clay content

1% are al Original void space

1-;;' area}

4 .28 6 .77

13 . 45

11 .68

59.27 1 5 . 44 1 23 .87 1 62 . 46 1 8 .23

1 0 12

1 4 16

1 8

20 22 24 26 28

30 32 34

36 3 8 40

42 44

46 48

50 52 5 4

5 6 58 60 62

64 66

68

7 0

8 . 93

9 .55 10 . 93

19 . 63

3 1. 98 27 .08

13.64

2 0 .64

24 .96

11 . 07

B.96

7. 17 7 .23

10.05 5 . 94

9. 7 9 17 . 56

19.45 1 2 . 54

9 .83 1 0 . 92

5 . 90 6 . 13

8 .39 10.89

7 .88

7 .60

8 .38 7.91 7 . 46

9 . 09

8 .57

55 . 83

60.25

6 1 .55

54 . 99 53 , 77

64 .09 65 .07

68 . 28 66 .39

6 8 . 16 6 5 . 73 58 . 64

60.73 6 1. 55

60 .52 56 .B2

59 .55 53 .82

56 .4 2 57 . 60

58 .29 55 . 73

63 .58 67 .65

57 . 62 57 .29

6 0 . 8 1

6 1.43

54.85 5 7.09

5 8.55 53 . 1 4

55 .50 48 . 84

5 7.68

4.83

5 .65 8 .38 4 .22 5 . 77 5 .89

8 .35

13 . 10

11 .27

7.6 1

6 .80 6 .46

8.74

6 .86 7. 6 8 7 .23

6 . 7 7

5 .85 7 . 8 1 3 .6 1

6 . 95 7 .05

10 .60

6 . 54

6 .30 5 . 08

6. 12

5 . 97

4 . 49

5 . 08 6 .80 3 .55 5 .29

6 . 03

6.50

23 . 76

22.72 33 .8 1

25 .85 23 .04 24 .2 6

24 . 63 36 .2 1

2 1. 32 3 1 .73 33 . 1 1

27 .30

23 .66 22 . 17

27 .50 30 .99 26 .75

23 .38 3 4 .87

30 .34

29 . 16

23 .56 43 . 54

25 . 40

23 .60 24 . 47

24 .52 35.00 24 .43 18 .85 28 .06 23 .0 1

10 .85

16 .80

1 8 . 09

64 . 55

7 1 . 62

49 . 74 57 . 92 71. 19

5 1.09

58 . 13

50 . 69 67 . 4 1

48 .78 60 . 10 66 . 24

67 . 60 70 . 97

55 .36 6 1. 78

66 . 48 70.77

5 7.32

66 . 05 63 .89 69 . 40

45 .86

68 . 07 58 .96 70 . 44

69 . 36

59 . 04

6 0 . 93

76 . 07

65 . 13

73 . 44

69 . 11 53 . 97

66 .89

6 .87

0 .00

8 .08

12 . 0 1

0 .00

18 .75

8 .88 0 .00

0 .00 11 .89

0 . 00 0 .00

0 .00

0 . 00 9 . 47

0 .00

0 .00 0 . 00

0 . 00 0 . 00 0 .00

0 .00 0 .00 0 .00

1 1 . 14

0 .00

0 .00

0 .00

10 . 15

0 . 00 0 . 00 0 . 00

1 4 .75

23 .20

8 .52

50-100um !

83 . 65 1 81.47 1 91.491 55 .57 82 . 92

62 . 65 8 1. 49

88.43

96.78

77 . 04

80 . 0 9

89 .59 83 .37 79 . 04

74 . 19

88.34

98 . 23

87 . 02

73 . 84

97 . 75

79 .32 102 . 94

89.28 83 . 90

86 .35 96 .86 8 1. 55

96 . 9 0

107 . 32

82 . 04

98 _90

85 . 12

89.86 79 .33 75 . 11

7 1 . 88

92 .86

86 . 76 65.49

84 .28

75 .82 9 1. 57

75 .66

90 . 2 3 88 . 73 80 . 5 9

76 .00 77 .4 t 87 .09

88 .67

93 .6 7 87 .43

98 .3 3

98 . 5 6 1 14 .75

79 .3 6

90 .62 75.20

107 . 57

107 .64

90 .33 90 . 56

84 . 98

9 1 . 92

83. 5 1

78 . 10

84.03

77 .26 76.57

99 .07

88 .37

90 .05

69 .05

85 . 16

8 1. 85

94 .03

80 . 6 1 70 .05

93 . 13

9 7. 6 9

9 2. 17

104 .76

8 1. 53 8 1. 64

96 .80 100 . 19

80 . 4 0

89 .57 89 . 9 1

111 .3 8

100 .86

77 . 17

88 .35 93 .87

103 . 50

9 1 . 46

95 . 99

64 . 84

92 . 15

92 .3 3

94 . 27

73 . 40

85 . 54

85 . 8 1 76 .03

7 1 . 66 92 . 52

82 . 6 1 85 .4 1

8S .0 4

t 50.0 1

11 .34

107 . 53

61. 17

72.7 4

70.4 6

26 . 72

19 .59

142 .61

143.36

80.09

Tolal sand

85 .2 0 83 27

78 .82 86 . 45

76 .75

9 3 .39

87 . 48

83 .28 8 8 .0 4

8 1 .22

82 . 66 86 . 06 93 .85

8 9 . 42

9 1 .87

86 .26 107 . 96

84 . 9 9

89 .7 8

83 . 02 98 . 25

99 .87

93 . 2 1

87 . 97

83 .87 96 .39

86 .02

90 . 49

8 1 . 82

82 . 99 80 .82 85 .07

78 .36 93 . 7 9

81 .21 78 .80

50· 100um

2 .6 1 2 . 77

2 . 5 1 2 . 28 2 . 17

2 .28 2 .56 2 .55

2 . 15

2 .82 2 .05 2.2 4

2 . 32 2 . 56 2 . 67

2 . 28 2 . 17

2 .83

3 .02 2.44 2 .75

2 .27

2 . 12 2 .55

2 .00

3 .55 2 .2 9 2 . 13

2 .49

2.86 2 . 51 3 . 03 3 . 17

2 8 5 2 . 47

2 . 09

Mean roundness

100-200u m 1 200 -500 u m !S<lO-1 000'"

2 .33 1 3.47 1 2 .05 2 .41

2 .4 6

2 .64

2 . 74

2 .65

2.73

2 .39 2 . 72

3 .80 2 . 93

3 . 37 3. 14

3 .39

2 . 49

2 . 64

2 . 06 2 .86

3 . 26

2 . 22 2 .38 2 .63

2 . 64

2.76

3 .59 2 . 78 2 . 74

3 . 04 2.97 2 .4 8

3.0 1

2.70

2 .79 2.30 3. 17

2. 5 7

2 .67

2 .75

3 . 46

3 .83 3 .04

2. 63 2 .60 3 . 12

3 . 24 2 .77

3 .56 3 .50 3 .87

4 . 15

3 . 65

2 .87

3. 89 2 . 66 3 . 4 5

3 .34

2 . 97

3 . 11

3. 05 3 . 49 2 . 76 2 . 15

2 .64

3 .62 2 .95 2 .83 2 . 95 3 . 40

3 .0 1

2 .88

3.0 1

4 .32

7.08

5 . 4 1

1 . 97

5 .60

6 .07

4 . 63

3 . 0 9

7 . 17

3 . 2 1

3.75

2.06

Tolal sand

2 . 8 1

2 . 63 2 . 5 9 2 . 73

2 . 90 2 . 64

2 . 63 2 .55

2 .55

3 .20 2 . 6 1 3 . 05

2 . 99 3 . 22 3 .07

2.68

2 .32 3 . 12

2 . 99 2.57

2 . 74 2 . 62 2.58 2 .73

3 .0 1

3 . 05 2.44 2 .59 2 .97 2 . 8 0

2.79 2.87 3 . 10

2 .83 2 .84

2 .55