French Et Al Fire Geoarchaeology

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Holocene riprian landscape change around Quadalupe Ruin in the middleRio Puerco basin of New Mexico

Journal: Geoarchaeology

Manuscript ID: GEO-07-054

Wiley - Manuscript type: Research Article

Date Submitted by theAuthor:

01-Oct-2007

Complete List of Authors: French, Charles; University of Cambridge, ArchaeologyPeriman, Ricahrd; USDA Forest Service, Regional Social ScienceScott Cummings, Linda; Paleo InstituteHall, Stephen; Red Rock Geological ServicesGoodman-Elgar, Melissa; Washington State University,AnthropologyBoreham, Julie; University of Cambridge, Archaeology

Keywords: Rio Puerco, alluvium, incipient soil, fire, maize

John Wiley & Sons

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Holocene riparian landscape change around Quadalupe Ruin in the middle

Rio Puerco basin of New Mexico

Charles French (1), Richard Periman (2), Linda Scott Cummings (3), Stephen Hall (4),Melissa Goodman-Elgar (5) and Julie Boreham (1)

1: Department of Archaeology, University of Cambridge, Cambridge, CB2 3DZ, UK; 2: USDA Forest Service,

Albuquerque, New Mexico 87102-3497, USA; 3: Paleo Institute, 2675 Youngfield Street, Golden, Colarado

80401USA; 4: Red Rock Geological Services, Santa Fe, New Mexico 87508-9172, USA; 5: Department of

Anthropology, Washington State University, Pullman, Washington 99164-4910, USA

ABSTRACT

Geoarchaeological survey with associated pollen, charcoal, micromorphological andradiocarbon analyses of a 5 km stretch of the Rio Puerco channel and its associated

tributaries centered on the Guadalupe Ruin of northern New Mexico revealed an 11 meterthick alluvial sequence which had aggraded over the last 6000 years. There were five major

periods of instability which occurred at some point in the earlier Holocene and briefly

between 5750 and 5640 B.C., for a lengthy period between ca. 2300 Cal. yr B.C. and A.D.370, for a time in the first few centuries of the 1

stmillennium A.D., and since the late 19

th

century A.D. This valley fill sequence was interrupted by four major periods of relativestability and associated incipient soil development for a period prior to ca. 5700 B.C.,

between 2570 to 2280 Cal. yr B.C. and A.D. 370 and 540, and in the Puebloan period (ca.

A.D. 900-1400). Each palaeosol is a cumulic soil formed in a floodplain edge situation.

Multiple signatures of possible grassland and forest fires, in situ and in the catchment, wereobserved in the lower parts of the sequence prior to A.D. 370-540. These fires may havehelped enhance food resources for game animals by encouraging grass/shrub growth and/or

to increase the growth of cultigens like maize and other wild plants. Most importantly, ditchsystems were associated with the ca. 2570-2280 Cal. yr B.C. phase of soil development

which were possibly indicative of floodplain management and associated maize cultivation.

INTRODUCTION

The large watershed of the Rio Puerco has been of long interest to range managers,

geomorphologists and archaeologists alike because of the noticeable deterioration of therangelands since the 1880s through severe erosion (Scholl and Aldon, 1988; Nials, 2003;Phippen and Wohl, 2003), and the abundant evidence of human occupation of Archaic and

Pueblon times (Irwin Williams and Pippin, 1979; Baker and Durand, 2003).

The study area (Figure 1) is located on the southeastern margin of the Colorado

Plateau between Mesa Prieta and Mesa Chivato in north-central New Mexico. Its geology

consists of Mesozoic sandstones and sandy shales with tertiary basalts on the two Mesas

(Nials, 1972). Episodic erosion is reflected by multiple terrace and pediment surfaces, withPleistocene terraces capped by basalt dominate gravels (Crumpler 1982). Severe modern

erosion has drastically bisected the Holocene, alluvially infilled valley bottom (Figure 2), and

arroyos dissect the major tributary streams. Modern precipitation averages 20-25mm per year,most of which occurs as intense convectional thunderstorms in the summer months (Folks and

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Stone 1968). But it is not the lack of rain but the very brief residency of water in the drainage

system that is the problem, with the fast run-off through the deeply cut arroyos exacerbating

the effects of floods and run-off.

AIMS AND METHODS

This project aimed to build on the earlier geomorphological studies of the lower

Puerco basin by Love et al. (1982), by Nials (in Baker and Durrand, 2003) who concentrated

on the Arroyo Cuervo to Guadalupe drainage for the middle Puerco reach, and by Shepherd(1978) in the Tapia Canyon. Our fieldwork overlapped within the northernmost sector of

Nials (2003) study and concentrated on a ca. 5 km reach of the Rio Puerco centred on the

Guadalupe Ruin, a pueblo of the late 10 th to 12th centuries A.D. associated with Chaco

Canyon (Baker and Durand, 2003). Initially, the project set out to investigate the palaeo-environmental circumstances of the effects of fire on Holocene riparian landscapes in the Rio

Puerco basin. During the course of fieldwork, the remit of the project became focused on the

geomorphological contextualisation of the observed fire signals contained within the

sedimentary sequences of the Puerco basin and its tributary valleys. What were the sequencesof stability/instability, incision and infilling in this reach of the Rio Puerco, what relationships

did these events have to broader regional environmental signatures and occupation histories,and what were the implications of the observed burning events in terms of the nature of the

burns and their scale and impact on the landscape?

The geoarchaeological survey involved the sedimentary description of continuous

exposed sections of the Rio Puerco to north and south of Guadalupe Ruin and the lower

reaches of four associated tributaries, the Arroyos Tapia, Salado, Guadalupe and No Name

(Figures 1-6; Tables 1-4). This study specifically focused on palaeosol/alluvial contacts andfire reddened and charcoal-rich lenses in different parts of the alluvial valley fill sequence. We

conducted descriptive studies of the stratigraphy of the floodplain and valley fill depositscombined with targeted sampling for micromorphological, palynological and charcoalanalyses and radiocarbon assay, and prospection for buried archaeological features in the

alluvial floodplain. This combination of new data should begin to enhance our understanding

of the factors which may have lead to stability and instability in this landscape as well as theperiods of increased fire incidence. It may even be possible to relate these events to those in

the wider region and possibly suggest ways of sustaining these landscapes in the face of the

continuing and combined threat of desertification through low rainfall and the destruction byfire (cf. Chambers and Miller, 2004). Ultimately this may contribute to the broader decision-

making debate about riparian restoration efforts and future fire management and in the

southwestern United States.

THE GEOARCHAEOLOGICAL SURVEY

This paper reports on three field seasons of geoarchaeological survey and the pollen,charcoal and soil micromorphological data in combination with radiocarbon dating of three

main sedimentary/soil sequences in the Rio Puerco (Figure 1, profile A), Arroyo Tapia (Figure

1, profile B) and Arroyo Guadalupe (Figure 1, profile C) (French, 2002, 2003; ScottCummings, 2004; Hall, 2004).

The ca. 10-11m high section walls of the present day courses of the Rio Puerco and thefour canyons or arroyos exhibit a generally similar stratigraphic sequence (Figures 3-6; Tables

I-III). The arroyo walls expose a complex sequence of fine sand, silt and clay floodplain

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deposits with numerous minor and some major channel fills (Figures 3-6). While challenging,

it is possible to map and correlate these alluvial units (cf. Love et al., 1982).

The Rio Puerco Sequence

A single inset fill terrace characterizes the present day Puerco and defines about 4 mabove the present riverbed (Figures 2, profile A, 3 and 4). The Rio Puerco arroyo fill includes

both point bar sands and oxbow infills of silty clays deposited in slowly moving to still water.

The deposition of an inner fill terrace occurred in all the tributary arroyos as well and mayhave been deposited at the same time. Although radiocarbon dating can often be of limited

usefulness in trying to establish a chronology for the post-1890 sedimentation of the inner fill

deposits because of recycled charcoal from older sediments often resulting in a spurious old

age, this survey obtained two dates for the Puerco inset terrace bench of Cal. yr A.D. 1650-1890 and 1910-50. In addition, tree drilling for ring-counts of the cottonwood tree trunks

growing on this inset terrace opposite section A by Richard Periman indicated that the trees

were ca. 70+ years of age. This suggests that this terrace is at most about a century old.

Although the base of the Puerco sequence was often obscured by section fall deposits,

the aggrading sequence begins with the repeated dark brown lenses of organic silty clay whichexhibits a columnar blocky ped structure (unit F; 1050-1100 cm) (Figures 3 and 4). By

comparison with better dated Arroyo Tapia sequence (see below), it is suggested that this

material accumulated from at least ca. 6000 to 2570 Cal. yr B.C. (Table III).

Unit E (625-1050 cm) above is comprised of a substantial thickness of laminated silty

clays interrupted by the repeated deposition of fine sands and silts over a depth of ca. 4 m

(Figures 3 and 4). This unit was associated with wide channels infilled with laminated sandsdefining at this level both upstream and downstream. Subsequently, there are two-three

superimposed horizons of organic silty clay over a depth of ca. 1.3m, each about 30-35cmthick (unit D; 500-625 cm), which exhibited a columnar blocky ped structure, and wereinterrupted by thin lenses of silt and clay (Figures 3 and 4). The radiocarbon dates for the base

of this unit indicate that this occurred over a relatively short time of about 100-300 years,

between ca. 2570 and 2280 Cal. yr B.C., and a similar range of radiocarbon dates for thissame unit were forthcoming from the Arroyo Tapia (see below) (Table III).

Defining at the base of unit D are open U-shaped cut features or ditches that wererecorded in at least three locations in the Rio Puerco and in two instances in the Arroyo Tapia

(Figures 3, 4 & 6). These ditches are up to ca. 1.2 m in width and 1 m in depth, and apparently

aligned at a right-angle to the floodplain and current channel. Importantly, the primary fill of

the recut ditch at the base of unit D contained pollen data that indicated two major types ofpalaeo-vegetation were present at this time. First there was widespread moist grassland in this

alluvial floodplain and second there was a minor signature of maize pollen also present

(Figure 9; Table VI).

The next unit C (140-500 cm) consisted of ca. 3.6 m of bedded fine sands and silts

which intermittently exhibited thin lenses of included fine charcoal (Figures 3 and 4). In oneinstance about 1 km south of Guadalupe Ruin, a small ditch defined at the ca. 200 cm level.

Further downstream, this phase of floodplain aggradation is associated with a relatively small

and shallow (


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first fine sands and silts, and then fine sand and silty clay above, the surface of which is the

present day valley floor. This ground surface is associated with numerous Puebloan period

sites (cf. Baker and Durand, 2003), and so is believed to date to between about A.D. 950 and1300.

The Tributary Sequences

Owing to the complexity of the palaeo-floodplain stratigraphy as exposed in the arroyo

walls along the Rio Puerco, coupled with the difficulty of closely inspecting the 11 meter highexposures, the alluvial geomorphology of the tributary arroyos, the Tapia, Salado, Guadalupe

and No Name (Figure 2) were also investigated. It was reasoned that the alluvial

stratigraphy of the tributaries should be graded to and in synchronicity with fluvial deposition

and erosion of the adjacent master Puerco stream (Hall, 2004). Indeed the alluvial sequenceand chronology of the tributary arroyos appears to match the major events observed in the

same reach of the Rio Puerco, with the exception of the Arroyo Salado which was dominated

by numerous inter-cutting channel deposits of all periods. According the composite sequence

from the Arroyos Tapia (Figure 1, profile B) and Quadalupe (Figure 1, profile C) sections isdescribed below (Figures 5 and 6; Table II).

Six alluvial units were observed in the Arroyos Tapia and No Name and eight units

in Arroyo Guadalupe, the base of each marked by an erosional unconformity (after Hall 2004).

Typically, these valley fills comprised a series of finely to coarsely bedded fine sands/coarsesilts interrupted by occasional thin units of silty clay. The silty clays generally exhibit thin

bedding and thin clay drapes that can be traced for one meter or more laterally. The clay beds

also include occasional lenses of fine sand less than 10 cm thick. In particular, above and

below unit D (at 475-760 cm), there frequently occurred thin (


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stable surface of unit D. Upon the infilling of the D/C channel, sandy sediments were once

again deposited on the floodplain, burying the A horizon soil and unit D.

The overlying unit B (100-180 cm) is a brown, hard clay with some structural ped

development at its upper surface. A charcoal lens at 150cm gave two radiocarbon dates

centred on about Cal. yr A.D. 450 (Table III). Finally unit A (0-100 cm) is a gravelly sandthat is coincident with the last arroyo fill sediments subsequent to the filling of a deep channel

with axial basalt gravels.

Lenses of either strongly reddened sediment over a depth of 2-5 cm (Figure 7) and/or

thin lenses (


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shallow, standing water containing eroded fine soil/sediment material and phases of drying-

out in the base of the ditch.

The transition zone between the final infilling of the ditches and the base of the

associated palaeosol is composed of non-laminated silty clay with a minor very fine quartz

sand component exhibiting a well developed sub-angular blocky ped structure. This fabricrepresents fines deposited in still water conditions that subsequently became stabilised and

sufficiently well drained for long enough for soil mixing processes to occur, some organic

accumulation, and good structural organisation to develop, thus beginning to create a soil.The upper part of this incipient palaeosol is a very fine to fine quartz sand with successive

illuvial infillings of micro-laminated, dark brown or highly amorphous organic-rich, silty clay

infillings of the void space. This suggests repeated depositions of silt, clay and bioturbated

amorphous organic matter, with much included fine charcoal from fires in the catchment alsopresent. This soil is increasingly being affected by alternative wetting and drying episodes and

fines deposition in still water conditions, probably reflecting a combination of the seasonal

rise and fall of groundwater in an active floodplain of the day and run-off water containing

eroded fine soil/sediment.

To conclude, this palaeosol is a cumulic alluvial soil that is essentially associated witha period of greater landscape stability. It may represent a series of superimposed incipient soil

horizons characterised by organic accumulation, soil mixing processes and structural

formation within the context of a very slowly aggrading, seasonal, flood meadow type ofenvironment. It is suggested that each major phase of stability in the valley infilling sequence

exhibits similar characteristics.

The Arroyo Tapia

Although both reddened and fine charcoal-rich units were observed throughout thisreach of the Rio Puerco drainage in all units of the valley fill sequences except for theuppermost unit A, examples were only sampled from the Arroyo Tapia (Figure 1, profile B).

In each case, the alluvially derived fine sands to silty clay deposits in units D-F contained

included greater or lesser amounts of fine charcoal (


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General Features

It is apparent that there are a number of repeated but similar soil/sediment typesoccurring within the Rio Puerco drainage around Guadalupe Ruin. These include well sorted,

very fine to fine quartz sands, inorganic and amorphous organic silty clays, and very fine

quartz sandy clay loams. The less common, unoriented, irregular aggregates of sandy/siltyclay loam may represent eroded soil material derived from slope wash processes, whereas the

alluvial facies are finely bedded versions of fine to very fine sands, silts and silty clays, with

the thicknesses of the laminations varying from


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Rio Puerco

The pollen data from the horizon associated with the recut ditch at about 625 cmwithin Unit D was well preserved and is suggestive of continuing but more variable, sparse

pinyon-juniper woods, with small frequencies of oak (Figures 3, 4 and 9; Table VI). The

recovery of small quantities of fir and pine pollen represent long distance wind transport ofpollen from these trees growing at higher elevations. There was also willow and mesquite (at

its extreme northern range) growing along the river, with sedges and saltbush in the

floodplain. Importantly, there was also evidence for maize and charcoal, possibly associatedwith anthropogenic activities. Charcoal frequencies were variable but the recut ditch at the

base of unit D yielded the largest frequency of minute (


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portion of the record is dominated by Chenopodium-amaranth pollen, with smaller quantities

of Artemisia, high-spine Asteraceae, and Poaceae pollen noted as the major elements

representing local saltbush and related plants, sagebrush, various members of the sunflowerfamily, and grasses. Toxicodendron-type pollen is noted in the upper two samples, suggesting

the presence of poison ivy. Other pollen types noted in small quantities includeArceuthobium,

low-spine Asteraceae, Liguliflorae, Brassicaceae, Sarcobatus, Corylaceae, Cyperaceae,Ephedra, Eriogonum, Fabaceae, Petalostemon, Liliaceae, Onagraceae, Opuntia, Polygonumsawatchense-type, Toxicodendron, Rosaceae, Cercocarpus, Saxifraga-type, Shepherdia-type

and Sphaeralcea. Recovery ofArceuthobium pollen represents dwarf mistletoe growing onsome of the local trees.

A single pollen sample was also examined from an organic duff layer within the inset

terrace bench that formed within the past century. Quantities ofJuniperus and Pinus pollenare increased compared with most of the prehistoric samples examined from this arroyo.

Recovery of a small quantity ofQuercus pollen indicates that oak grew as part of the local

pinyon/juniper woodland. The presence of a small quantity ofArceuthobium pollen indicates

that dwarf mistletoe parasitized local trees. Quantities ofArtemisia, High-spine Asteraceae,Chenopodium-amaranth, and Poaceae pollen are relatively small in this sample, representing

local sagebrush, members of the sunflower family, chenopods and grasses. Other non-arborealpollen types recorded include Low-spine Asteraceae, Brassicaceae, Ephedra, Eriogonum,

Plantago, Rosaceae, Saxifraga-type, and Sphaeralcea, indicating the presence of various

members of the sunflower and mustard families, ephedra, wild buckwheat, plantain, membersof the rose family, saxifrage, and globemallow.

THE RIO PUERCO LANDSCAPE SEQUENCE

The present day Rio Puerco channel and the associated arroyos in the Guadalupe Ruinreach have made deep incisions of up to ca. 11 m through the middle and later Holocene

sediment record of this landscape (Table VII). This major valley-wide process of severeincision has occurred since the late 18 th/19th centuries. In places in the main Puerco channel

floor there has been some infilling and the creation of terrace benches that define about 4 m

above the rivers base. This inset terrace is probably no more than 75-100 years old. Indeed,

nearly all arroyos in the southwest include one, and in some cases two, inset terraces ofhistoric age (Hall, 2004). In the last few years, incision and the cutting of new gullies through

the Pueblo period valley base is continuing (Figure 2), and this is undoubtedly associated with

the very sparse modern vegetation, thunderstorm events and current decade-long drought inthis area.

The whole Puerco sequence is characterised by alternating periods of episodic alluvialsediment accumulation interrupted by periods of relative stability associated with incipient

soil formation over at least the last 6000 years (Table VII). The five major periods of

instability represented by the aggradation of eroded sediments and major periods of riverchannel incision occurred at some point in the earlier Holocene (unit H in the Arroyo

Quadalupe only), and briefly between 5750 and 5640 B.C. (unit E), for a lengthy period

between ca. 2600-2300 B.C. and A.D. 370-540 (unit C), for a time in the second half of the 1st

millennium AD (base of unit A), and in the last one to two hundred years. Certainly, theupper 300 cm of clayey oxbow sediment of the most recent inset terrace in the Rio Puerco has

been dated to post-1954 using radiometric isotopes cesium-137 (Popp et al., 1988). In each of

these periods of alluvial accumulation, there was associated down-cutting of the contemporarymain and tributary river channels as well as channel avulsion across the valley floor. Major



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periods of incision certainly occurred around A.D. 1000, which was also observed elsewhere

in the middle reaches of the Rio Puerco (Nials, 2003), but by far the most drastic channel

incision has occurred in post-Puebloan times and with the present channel beginning after1885-90 (Bryan, 1925, 1928; Hall, 2004).

The sediments infilling the Puerco and tributaries alluvial floodplain range from veryfine to fine sand, silt and silty clay, deposited in repeated fine laminae of less than a few

centimetres in thickness. It has been suggested by Hall (2004) that overbank silt and clay

probably represent about 60% of the vertical sequence in these arroyos and are derived fromupstream areas of the Rio Puerco watershed. In contrast the fine sands and silts are largely

derived from the local tributaries. Hall (ibid.) has also speculated that the slowly accumulating

overbank clays also represent about 90% of the time preserved in these deposits with the

remainder marked by channel incision and the deposition of faster water-transportedsediments. They have probably been deposited by run-off and sheet erosion processes, and are

suggestive of similar open, poorly vegetated and semi-arid conditions as pertain at present.

The four major periods of stability in this reach occurred for a period prior to ca. 5700B.C. (unit F in the Puerco and unit G in the tributary valleys), and between 2570 to 2280 B.C.

(unit D), A.D. 370 and 540 (unit B), and in the Puebloan period (ca. A.D. 900-1400).These phases are characterised by the formation of a series of superimposed (or cumulic),

incipient soils. In each case, the textural, structural and organic features suggest that the

aggradational dynamic had slowed remarkably, allowing the deposition of fine alluvialsediments in the valley system with associated stability and vegetational development

sufficient to add a significant organic component to the alluvial sediments and lead to

incipient soil development. These phases of soil formation also signify a more moist climatic

regime. This is best exemplified in unit D (ca. 2600-2300 Cal. yr B.C.), where there are atleast two/three major episodes of weak soil formation in this unit interrupted by more minor

phases of renewed sand/silt alluvial deposition that are consistently evident in this drainagesystem. Thus these phases of weak soil development alternated with the deposition of silts andclays aggrading in shallow, standing water conditions.

Defining in unit D in both the Rio Puerco and Arroyo Tapia and to a lesser extent inunit C, some ditch features were observed (Figures 3-6). These features are undoubtedly man-

made as they are symmetrical and have distinct edge contacts with the alluvial subsoil

deposits and cumulic soils, and were sometimes re-cut and deepened on the same alignment,and are located at right angles to the contemporary river. The ditches may have been dug to

help drain a persistently slightly wetter zone in the seasonal floodplain of the day, and/or to

retain run-off water and effectively act as an irrigation ditch. Certainly the occurrence of these

ditches at several locations in the study area suggests that they are indicative of a widerarchaeological phenomenon and represent some degree of land management from about 4200

years ago, or within the Late Archaic period.

Thus the pollen data in unit D and in the base of the recut ditch at profile A in the

Puerco sequence (Figures 3 and 9; Table VI) indicates that this alluvial floodplain was

supporting riparian vegetation of moist grassland against a background of sparse pinyon-pine,juniper and oak woodland with a diverse non-arboreal flora. But importantly, there are strong

hints from theZea mays or maize pollen and the fine burnt grass charcoal present in the ditch

system and associated soil that this floodplain edge zone was also deliberately used for maizeagriculture.

THE EVIDENCE FOR FIRE



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Particularly during the aggradation of alluvial sediments in units H, F, E and C in the

Arroyos Tapia and Quadalupe, there are numerous signatures of fires. This evidence for fireoccurs in two main forms, either as in situ burns leading to the reddening of the upper few

centimetres of the clay-rich alluvial sediment and as lenses of fine to very fine charcoal

associated with laminar fine sand/silt alluvial sediments, presumably washed-in with run-offfrom fires in the immediate catchment.

What do these fire signatures represent - lightning strike and/or deliberately set fires?Certainly in Late Archaic times (unit D) a wide variety of non-arboreal pollen was present

which was indicative of grasses, sedges, saltbush, sagebrush, the occasional legume and also

maize as well as sparse pinyon pine and juniper trees (Figures 9 and 10). There is also a mix

of micro-charcoal and larger pieces of charcoal reflecting both widespread burning ofgrassland and more localised fires, which may imply both natural and deliberately set fires.

One strong possibility is that fire was used to encourage grass and shrubby plant growth to

enhance the food resources available for a variety of game animals, and/or there was

deliberate burning of specific plant communities to increase the production of cultigens (suchas maize) and other wild seed and fruit bearing plants? Other possibilities are that these burnt

layers may have resulted from burning of fields in order to increase soil fertility as occurred inPuebloan times (E. Karlstrom, 1983), to kill weeds as in Hopi legends, or even for warming

nearby crops (Courlander, 1974). They may also represent brief human occupation and/or

phases of vegetation re-growth and the in situ burning of grassland, shrubs, trees or fallenlogs.

The consideration of some other fire studies in the Southwest suggests possibilities for

the inter-relationships of fire severity, climatic regime, erosion processes and the potentialtime periods of erosion activity. For example, a study of alluvial fans of the last millennia in

central Idaho (Pierce et al., 2004) has suggested warmer climatic periods with severe droughtsled to stand replacing fires which triggered large debris-flow events, whereas cooler periodswere associated with low severity fires which served to maintain more open stands of trees.

Moderate annual to multi-annual droughts produced frequent fires. After severe burns, there

was reduced infiltration and smooth soil surfaces which led to increased run-off, withsediment entrained through slope wash, rilling and gullying. After smaller event, low severity

burns, there were discontinuous run-off sediment yields, but a few years later after tree death,

the consequent loss of root strength promoted shallow landslides. A longer-term study inYellowstone suggested that episodes of fire-induced sedimentation occurred at intervals of

about 300-450 years during the last 3.5 millennia, indicating a regime of occasional but high

severity fires (Meyer and Pierce, 2003). Another study (Legleiter et al., 2003) after the 1988

Yellowstone National Park fires indicated that high run-off events and even moderate flowsprovided sufficient energy to evacuate the finer grained material delivered from the burned

hillsides to the channel network over a period of 5-10 years, and then induced channel

incision. Observation of a severe rainstorm in 1994 on the recently burned hillslopes of StormKing Mountain, Colorado (Cannon et al., 2001), witnessed a surface run-off dominated

process of progressive sediment entrainment, rather than infiltration triggered failure of

discrete soil slips, but did not imply significant channel erosion. A simulation study based ofrecent burns in the Oregon Coast Range (Roering and Gerber, 2005) suggested that post-fire

erosion rates exceeded long-term erosion rates by a factor of six with local topography

reacting differently in terms of rapid post-fire erosion, and fire-related processes may havecaused up to 50% of the temporally averaged sediment production on steep slopes.



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Consequently, it is suggested that the fire signatures in the pre-Puebloan Puerco

sequence are much more likely to be related to more frequent, light surface fires in a more

open environment than stand-replacing fires that may have lead to large debris flow events.Today the Rio Puerco carries very high sediment loads, delivering 78% of the total suspended

sediment load of the Rio Grande even though it only drains 26% of the Rio Grande basin

(Aby et al., 2004). Consequently, any hope of restoring an area like this one in the CibolaForest to a more stable wooded landscape may be almost impossible as the trend to a warmer

future promotes the likelihood of severe fires and associated run-off erosion and gully

incision.

RELATING THE RIO PUERCO SEQUENCE TO THE WIDER REGION

There are many suggestions as to the causes of arroyo cutting (Cooke and Reeves1976; Cooke et al., 1993: 157-160) with explanations ranging from either past and present

human land-use changes, or random environmental changes or climate changes. Some authors

believe that arroyos are cut during periods of increased available moisture (Dutton, 1882;

Hall, pers. comm.), whereas others would posit that they are a consequence of dry intervalswith decreased vegetative cover and increased run-off and discharge (Bryan, 1925; Antevs,

1952; Haynes, 1968; Euler et al., 1979; T. Karlstrom, 1988), and others argue for a non-climatic model of episodic erosion related to floodplain variability (Schumm, 1977).

Moreover when fire is involved, post-fire erosion rates tend to be more rapid with less

infiltration and greater run-off, especially after severe, stand-replacing burns (Pierce et al.,2004; Roering and Gerber, 2005). To tackle this problem adequately one really requires a

whole variety of data ranging from settlement history to dendrochronological, palynological,

charcoal and faunal records to rainfall patterns and geomorphological process data (Rose,

1979; Rose et al., 1981; Nials and Durand, 2003).

Certainly in our study area, there are now some quite well dated alluvial, incipientpalaeosol and palaeo-channel sequences. These can be related to some wider events in thearchaeological and erosional records, but only rarely directly to climatic records. Of course,

detrimental climatic factors as such need not be the sole cause of this phenomenon, but may

have also been related to devegetation associated with mis-management of this marginallandscape by both over-intensive grazing (cf. Wildeman and Brock, 2000). In an early

assessment of gullying history and search for the origin and cause of the erosion, Bryan (1928:

280) observed that the destructive arroyo cutting occurred between 1885 and 1890,immediately after the area was fully stocked with cattle. This pattern similarly applied

throughout much of the Southwest (Bryan, 1925; Scholl and Aldon, 1988; Phippen and Wohl,

2003). These authors concluded that overgrazing had led directly to decreases in vegetative

cover that in turn led to increased run-off and the increased erosive power of streams. Incontrast, Karlstrom (1983, 2005: 9) has observed in Red Peak Valley and Yellow Water

Washes on Black Mesa, Arizona, that where present day lowered water tables reflected a local

response to regional drought, this resulted in dramatic arroyo down-cutting.

It is also possible to compare our results to the model of landscape development put

forward by Nials and Durand (2003) for the adjacent reach of the middle Puerco. Followingon Nials (1972) earlier work in the middle Puerco which suggested that a series of palaeo-

arroyos were cut within the period ca. A.D. 900-1350 and especially between A.D. 1175 and

1200, Nials and Durand (2003: 43-53) created a Precipitation Effectiveness Index modelbased on dendrchronological and archaeological survey data. This model suggested that there

were two periods of more effective precipitation in the 10 th and 12th centuries A.D. and two

periods of ineffective rainfall in the 11th and 13th centuries A.D. Periods of more effective



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precipitation led to increased frequencies of settlements clustered in valley bottoms along the

sandy floodplain near the confluences of the tributaries and main river, whereas these same

areas were affected by progressive arroyo cutting leading to less available and suitable landfor agriculture and made settlement more dispersed over a wider area. Increased intensity of

summer rainfall and associated run-off is postulated as the factor in arroyo formation, but this

same process would also make the areas at the base of slope and floodplain edge moresuccessful for farming, and with some water management potentially even more favourable.

This equation of increased surface run-off from sparsely vegetated to dry, barren slopes which

results in progressive sediment entrainment and its redeposition in the valley floor andassociated channel incision would appear to be the best possible explanation for the periods of

instability observed in our survey. Although our survey mainly detected possible features of

water management in the floodplain in unit D, some 3500 years earlier than the period

modeled, this must be indicative of relative stability in the floodplain associated with less run-off and therefore a necessity to capture/retain water in some manner if the floodplain was to

sustain either maize agriculture and/or to enhance grass and shrub growth to encourage game.

There are other well dated alluvial sequences from the southwest region forcomparison, particularly from Chaco Canyon and the McElmo Canyon drainages in the Four

Corners (Force, 2004) and in the Rio del Oso, New Mexico (Periman, 2005), as well as BlackMesa (E. Karlstrom, 2005) and middle Gila River to its confluence with the Salt River

(Huckleberry, 1995; Waters and Ravesloot, 2001) in Arizona for example. In the Rio del Oso

study, a quite similar landscape of sparse juniper and grassland dominated landscape with oakand pine at higher elevations existed in the Archaic period (ca. 5500 B.C.-A.D. 600) was

associated with common fires and alluvial sedimentation which was interrupted by seven

phases of cumulic soil development (Periman, 2005). The sandy alluvial sedimentation nearly

doubled during the Puebloan occupation of the valley, and more than doubled subsequentlybetween A.D. 1400 and 1765 (ibid.).

In Forces (2004) study of the Chaco Wash and the McElmo Canyon drainages, heuses archaeological, and especially ceramic, records to determine temporal and spatial

patterns of erosion and alluviation. In the McElmo drainage it is suggested that in the single

terrace there is evidence of two major units (ca. A.D. 500-700 and A.D. 900-1300) separatedby an unconformity that represents arroyo entrenchment which migrated ca. 5 km upstream in

about 200 years, and alluvial aggradation. Moreover, there was probably also aggradation in

the side canyons and consequently migration of these also. The Chaco sequence, modifiedfrom earlier work (Bryan, 1954; Hall, 1977; Loves 1980; Love et al., 1982), includes

floodplain deposition in the valley floor during the period ca. A.D. 1-900, an entrenched

meandering (Bonito) channel which appears to have cut through a ca. 9-14 km reach of these

older deposits from ca. A.D. 900-1025, which then began to simultaneously infill between ca.A.D. 1025 and 1100. Even though the Puebloans built check-dams and continued to use the

valley floor for agricultural land, their activities must have been part of the cause in the

initiation of entrenchment. Indeed there may well be a widespread phenomenon of channelentrenchment beginning around A.D. 1000 across the Southwest region as Hall (1977) has

previously observed and exemplified by a number of authors in many different watersheds

(Hall, 1990; Miller and Kochel, 1999; Waters and Haynes, 2001; Nials, 2003; E. Karlstrom2005; Waters and Ravensloot, 2001).

Apart from this there appears to be a wide range of potential variability across theregion in terms of particular reach histories as determined by individual reach characteristics.

For example, E. Karlstroms (2005) study of two drainages on Black Mesa in Arizona has

observed that entrenched arroyos began to aggrade at about >24,260, 11,070, 9660, 8800,



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CONCLUSIONS

The depositional history of the Rio Puerrco basin study area around Quadalupe Ruinexhibits a consistent sequence throughout the last ca. 6000 years. It also offers both contrasts

and corroboration with broader regional and sub-regional trends and sequences. Our work has

developed and refined the earlier research of many others in this watershed (Bryan, 1928;Love et al., 1982; Nials, 2003; Shepherd, 1978). Two major sets of environmental parameters

seem to pertain and alternate. First, there are phases of instability marked by greater run-off

and the deposition of fine sands/silts in an aggrading floodplain, often associated with channelincision, all of which are associated with repeated fire signatures which are probably surface

light rather than stand-replacing fires, both on the floodplain edge and elsewhere in the

catchment. Second, these phases alternate with periods of relative stability associated with

slower and finer run-off and overbank sedimentation, a more moist climatic and soil regimeassociated with incipient soil formation on the floodplain with only occasional fire signatures.

There is a wide measure of agreement with respect to the two most recent periods of channel

incision in the few centuries after A.D. 1000 and in the late 19th

century, with at least two

earlier periods of entrenchment observed prior to Cal. yr A.D. 370-540 and 5750-5640 Cal. yrB.C. Moreover, as early as about 4200-4000 years ago there appear to be good indications of

some land management and an effort made to capture run-off water within the floodplain, tomaintain groundwater tables and possibly deliberately enhance both wild and cultivated plant

growth.

Acknowledgements

This project was funded through two Research Joint Venture Agreements between the United StatesDepartment of Agriculture Forest Service, Rocky Mountain Research Station, Cultural Heritage

Research - Work Unit 4853 and the Department of Archaeology, University of Cambridge, and the

Paleo Research Institute in Golden, Colorado. We would also like to thank Beta-Analytic Inc. forproviding the comprehensive suite of radiocarbon dates, and Julie Boreham of the Department of

Archaeology, University of Cambridge, for making the thin sections, as well as assistance in the field.Matt Brudenell, Steve Hall, Ann-Maria Hart, Ivy Owens and Richard Periman all provided

illustrations. Susan Smith of the Laboratory of Paleoecology, Northern Arizona University, Flagstaff,is much thanked for doing the pollen and charcoal counts. Thanks also to the critical and constructive

comments of the anonymous referees.

REFERENCES

Aby, S., Gellis, A., & Pavich, M. (2004). The Rio Puerco arroyo cycle and the history of

landscape changes. U.S. Department of the Interior, U.S. Geological Survey.(http://geochange.er.usgs.gov/sw/impacts/geology/puerco1/).

Antevs, E. (1952). Arroyo cutting an infilling. Journal of Geology, 60, 375-385.

Antevs, E. (1955). Geologic-climatic dating of the West. American Antiquity, 20, 317-335.Baker, L. L., & Durand, S. R. (Eds.) (2003). Prehistory of the Middle Rio Puerco Valley,

Sandoval County, New Mexico. Portales: Archaeological Society of New Mexico

Special Publication No. 3.Bryan, K. (1925). Date of channel trenching (arroyo cutting) in the arid Southwest. Science,

62, 338-344.

Bryan, K. (1928). Historic evidence on changes in the channel of the Rio Puerco, a tributary

of the Rio Grande in New Mexico. Journal of Geology, 36, 265-282.Bryan, K. (1954). The geology of Chaco Canyon, New Mexico, in relation to the life and

remains of the prehistoric peoples of Pueblo Bonito. Smithsonian Miscellaneous

Collections 122, no. 7.

http://geochange.er.usgs.gov/sw/impacts/geology/puerco1/http://geochange.er.usgs.gov/sw/impacts/geology/puerco1/


17/40

ForPeer

Review

Bullock, P., Fedoroff, N., Jongerius, A., Stoops, G., & Tursina, T. (1985). A Handbook of

Soil Thin Section Description. Wolverhampton: Waine Research.

Cannon, S. H., Kirkham, R. M., & Parise, M. (2001). Wildfire-related debris-flow initiationprocesses, Storm King Mountain, Colorado. Geomorphology, 39, 171-188.

Canti, M. G., & Linford, N. (2000). The effects of fire on archaeological soils and sediments:

Temperature and colour relationships. Proceedings of the Prehistoric Society, 66, 385-395.

Chambers, J. C., & Miller, J. R. (2004). Great Basin Riparian Ecosystems: Ecology,

Management and Restoration. Society for Ecological Restoration International.Washington: Island Press.

Clark, J.S., & Royall, P.D. (1996). Particle-size evidence for source areas of charcoal

accumulation in late Holocene sediments of eastern North American lakes. Quaternary

Research, 43, 80-89.Cooke, R.U., & Reeves, R.V. (1976). Arroyos and environmental change in the American

Southwest. New York: Oxford University Press.

Cooke, R., Warren, A., & Goudie, A. (1993). Desert Geomorphology. London: UCL Press

Ltd.Courlander, H. (1974). The Fourth World of Hopis: The epic story of the Hopi Indians as

preserved in their legends and traditions. Albuquerque, NM: University of NewMexico Press.

Crumpler, L. S. (1982). Volcanism in the Mount Taylor Region. In J.A. Gambling &

S.G.Wells (Eds.), Albuquerque Country II, Guidebook of the New Mexico GeologicalSociety Thirty-third Annual Field Conference (pp. 291-298). Socorro: New Mexico

Geological Society.

Damp, J. E., Hall, S. A., & Smith, S. J. (2002). Early irrigation on the Colorado Plateau near

Zuni Pueblo, New Mexico. American Antiquity, 67, 665-676.Delcourt, H.R., & Delcourt, P.A. (1997). Pre-ColumbianNative American use of fire on

southern Appalachian landscapes. Conservation Biology, 11, 1010-1014.Dutton, C.E. (1882). Tertiary history of the Grand Canyon district. U.S.G.S. Monograph 2.

Washington, DC: U.S. Geological Survey.

Euler, R.C., Gumerman, G.J., Karlstrom, T.N.V., Dean, J.S., & Hevly, R.H. (1979). The

Colorado Plateaus: Cultural dynamics and paleoenvironment. Science, 205, 1089-1101.

Folks, J.J., & Stone, W.B. (1968). Soil Survey, Cabezon Area, New Mexico. U.S. Department

of Agriculture, Soil Conservations Service and U.S. Department of Interior, Bureau ofLand Management, Washington, DC.

Force, E. R. (2004). Late Holocene behaviour of Chaco and McElmo Canyon drainages

(Southwest U.S.): A comparison based on archaeologic age controls. Geoarchaeology,

19, 583-609.Force, E.R., Vivian, R.G., Windes, T.C. & Dean, J. (2002). Relation of Bonito Paleo-

Channels and Base-Level Variations in Anasazi Occupation, Chaco Canyon, New

Mexico. Arizona State Museum Archaeological series 194. Tuscon: University ofArizona.

French, C. (2002). Long-term landscape and fire history of riparian areas of northern New

Mexico and western Montana; Interim Report 2: Field assessment of the Rio Puercoand Arroyo Tapia, New Mexico. Unpublished report (11/7/2002), U.S.D.A. Forest

Service Rocky Mountain Research Work Unit 4853.

French, C. (2003). Long-term landscape and fire history of riparian areas of northern NewMexico and western Montana. Interim report 4: Second field assessment and sampling

of stratigraphic sequences in the Arroyo Tapia and Rio Puerco, New Mexico.



18/40

ForPeer

Review

Unpublished report (10/7/2003), U.S.D.A. Forest Service Rocky Mountain Research

Work Unit 4853.

Hall, S. A. (1977). Late Quaternary sedimentation and paleoecologic history of ChacoCanyon, New Mexico. Geological Society of America Bulletin, 88, 1593-1618.

Hall, S. A. (1990). Channel trenching and climate change in the southern U. S. Great Plains.

Geology, 18, 342-345.Hall, S. A. (2004). Fluvial and riparian environments of the Middle Rio Puerco, New

Mexico: a review of Holocene sedimentation history. Unpublished report

(11/10/2004), U.S.D.A. Forest Service.Huckleberry, G.A. (1995). Archaeological implications of Late Holocene Channel Changes

on the Middle Gila River, Arizona. Geoarchaeology, 10, 159-182.

Irwin-Williams, C., and Pippin, L.C. (1979). Archaeological and paleoecological

investigations of Guadalupe Pueblo, Sandoval County, New Mexico: A preliminaryreport (pp. 309-330). In P.H. Oehser & J.S. Lea (Eds.), National Geographic Society

Research Reports: 1970. Washington, DC: National Geographic Society.

Haynes, C.V. Jr. (1968). Geochronology of late Quaternary alluvium. In R.M. Morrison and

H.M. Wright, Jr. (Eds.), Means of correlation of Quaternary successions (pp. 591-631). Proceedings VII INQUA. Salt lake City, UT: University of Utah Press.

Karlstrom, E.T. (1983). Soils and geomorphology of Black Mesa. In F.E. Smiley, D.L.Nichols, & P.P. Andrews (Eds.), Excavations on Black Mesa, 1981: A descriptive

report (pp. 315-342). Research Paper 36. Carbondale, IL: Southern Illinois University

of Carbondale Center for Archaeological Investigations.Karlstrom, E.T. (1986). Stratigraphic and pedologic evidence for a relatively moist early

Holocene on Black Mesa, northeastern Arizona. Current Research in the Pleistocene,

3, 81-83.

Karlstrom, E.T. (2005). Late Quaternary landscape history and geoarchaeology of twodrainages on Black Mesa, Northeastern Arizona, USA. Geoarchaeology 20, 1, 1-29.

Karlstrom, T.N.V. (1988). Alluvial chronology and hydrologic change of Black Mesa andnearby regions. In G.E. Gunnerman (Ed.), The Anasazi in a changing environment (pp.45-91). Cambridge: Cambridge University Press.

Legleiter, C. J., Lawrence, R. L., Fonstad, M. A., Marcus, W. A., & Aspinall, R. (2003).

Fluvial response a decade after wildfire in the northern Yellowstone ecosystem: Aspatially explicit analysis. Geomorphology, 54, 119-136.

Love, D. W. (1980). Quaternary Geology of Chaco Canyon, Northwestern New Mexico.

Unpublished PhD, University of New Mexico, Albuquerque.Love, D. W., Hawley, J. W., & Young, J. D. (1982). Preliminary report on the geomorphic

history of the lower Rio Puerco in relation to archaeological sites and cultural

resources of the lower Hidden Mountain Dam site. In P. L. Eidenbach (Ed.), Inventory

Survey of the Lower Hidden Mountain Floodpool, Lower Rio Puerco Drainage,Central New Mexico (pp. 21-65). Tularosa: Human Systems Research Inc.

Marion, G.M., Schlesinger, W.H. & Fonteyn, P.J. (1985). CALDEP: a regional model for

soil CaCO3 (caliche) deposition in southwestern deserts. Soil Science, 139, 468-481.Marshall, A. (1988). Visualising burnt areas: patterns of magnetic susceptibility at Guiting

round barrow (Glos., UK). Archaeological Prospection, 5, 59-177.

Matson, R. G. (1991). The Origins of Southwestern Agriculture. Tuscon: University ofArizona Press.

Meyer, G. A., & Pierce, J. L. (2003). Climatic controls on fire-induces sediment pulses in

Yellowstone National Park and Central Idaho: A long-term perspective. ForestEcology and Management, 178, 89-104.

Miller, J.R., & Kochel, R.C. (1999). Review of Holocene hillslope, piedmont, and arroyo



19/40

ForPeer

Review

system evolution in Southwestern United States: Implications to climate-induced

landscape modifications in southern California. In M.R. Rose & P.E. Wigand (Eds.),

Trends and extremes of the past 2000 years (pp. 139-192). Proceedings of theSouthern California Climate Symposium, October 25, 1991, Technical Report No. 11.

Los Angeles: Natural History Museum of Los Angeles County.

Minnis, P.E. (1985). Social Adaptation to Food Stress: A Prehistoric Southwestern Example.Chicago: University of Chicago Press.

Murphy, C. P. (1986). Thin section preparation of soils and sediments. Berkhamsted: AB

Academic.Nials, F. L. (1972). Geology. In C. Irwin-Williams (Ed.), The Structure of Chacoan Society in

the Northern Southwest (pp. 131-144). Contributions in Anthropology, 4, 3. Portales:

Eastern New Mexico University Press.

Nials, F. L. (2003). Geology and geomorphology of the middle Rio Puerco valley. In L.L.Baker & S.R. Durand (Eds.), Prehistory of the Middle Rio Puerco Valley, Sandoval

County, New Mexico (pp. 21-34). Archaeological Survey of New Mexico, Special

Publication No. 3.

Nials, F.L., & Durand, S. R. (2003). Environmental change in the middle Rio Puerco valley.In L.L. Baker & S.R. Durand (Eds.), Prehistory of the Middle Rio Puerco Valley,

Sandoval County, New Mexico (pp. 35-53). Archaeological Survey of New Mexico,Special Publication No. 3.

Nials, F.L., Gregory, D.A. & Graybill, D.A. (1989). Salt River streamflow and Hohokam

irrigation systems. In D.G. Graybill, D.A. Gregory, F.L. Nials, S.K. Fish, C.H.Miksicek, R.E.Gasser & C.R.Szuter (Eds.), The 1982-1984 Excavations at Las

Collinas: Environmenet and Subsistence (pp. 59-76). Archaeological Series 162,

(Volume 5). Tuscon: Arizona State Museum, University of Arizona.

Periman, R. (2005). Modeling landscapes and past vegetation patterns of New Mexicos RioDel Oso Valley. Geoarchaeology, 20, 193-210.

Phippen, S. J., & Wohl, E. (2003). An assessment of land use and other factors affectingsediment loads in the Rio Puerco watershed, New Mexico. Geomorphology, 52, 269-287.

Pierce, J. L., Meyer, G. A., & Jull, A. J. T. (2004). Fire-induced erosion and millennial-scale

climate change in northern ponderosa forests. Nature, 432, 87-90.Popp, C. J., Hawley, J. W., Love, D. W., & Dehn, M. (1988). Use of radiometric (Cs-137,

Pb-210), geomorphic and stratigraphic techniques to date recent oxbow sediments in

the Rio Puerco drainage Grants uranium region, New Mexico. Environmental Geologyand Water Science 11, 253-69.

Roering, J. J., & Gerber, M. (2005). Fire and the evolution of steep, soil-mantled landscapes.

Geology, 33, 349-52.

Rose, M. R. (1979). Preliminary annual and seasonal dendroclimatic reconstruction for theNorthwest Plateau, southwest Colorado, Southwest Mountains, and Northern

Mountain regions, A.D. 900-1969. Unpublished manuscript, Portales: Department of

Anthropology, Eastern New Mexico University.Rose, M. R., Dean, J.S., & Robinson, W.J. (1981). The Past Climate of Arroyo Hondo, New

Mexico, Reconstructed from Tree Rings. Arroyo Hondo Archaeological Series,

(Volume 4). Sante Fe: School of American Research.Scholl, D. G., & Aldon, E. F. (1988). Runoff and sediment yield from two semiarid sites in

New Mexicos Rio Puerco watershed. Research Note RM-488. U.S.D.A. Forest

Service, Rocky Mountain Forest and Range Experiment Station.Schumm, S.A. (1977). The fluvial system. New York: Wiley.

Scott Cummings, L. (2004). Pollen and charcoal analysis of stratigraphic samples from Tapia



20/40

ForPeer

Review

Arroyo and Rio Puerco, New Mexico. Paleo Research Institute Technical Report 02-

08.

Shepherd, R. G. (1978). Distinction of aggradational and degradational fluvial regimes invalley-fill alluvium, Tapia Canyon, New Mexico. In A. D. Miall (Ed.), Fluvial

Sedimentology: Canadian Society of Petroleum Geologists, Memoir 5, 277-286.

Stoops, G. (2003). Guidelines for the Analysis and Description of Soil and Regolith ThinSections. Madison: Soil Science Society of America.

Stuiver, M., & van der Plicht, H. (1998). Editorial comment. Radiocarbon 40, 3, xii-xiii.

Stuiver, M., Reimer, P. J., Bard, E., Beck, J. W., Burr, G. S., Hughen, K. A., Kromer, B.,McCormac, G., van der Plicht, J., & Spurk, M. (1998). INTCAL98 Radiocarbon Age

Calibration 24,000-0 cal BP. Radiocarbon 40, 3, 1041-83.

Swetman, T. W. (1993). History and climate change in giant sequoia groves. Science, 262,

885-889.Talma, A. S., & Vogel, J. C. (1993). A simplified approach to calibrating C14 dates.

Radiocarbon 35, 2, 317-322.

Waters, M.R., & Haynes, C.V. (2001). Later Quaternary arroyo formation and climate change

in the American Southwest. Geology, 29, 399-402.Waters, M.R., & Ravesloot, J.C. (2001). Landscape change and cultural evolution of the

Hokokam along the middle Gila River and other river valleys in south-central Arizona.American Antiquity, 66, 2, 285-299.

Whitlock, C., & Larsen, C. P. S. (2001). Charcoal as a fire proxy. In J. P. Smol, H. J. B.

Birks, & W. M. Last (Eds.) Tracking Environmental Change Using Lake Sediments(Volume 3), Terrestrial, Algal and Siliceous Indicators (pp. 75-97). Dordrecht: Kluwer

Academic.

Wildeman, G., & Brock, J. H. (2000). Grazing in the Southwest: History of land use and

grazing since 1540. In R. Jemison and C. Raish (Eds.), Livestock management in theAmerican Southwest (pp. 1-25). Amsterdam: Elsevier.

Revised and re-submitted, September 25, 2007



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Figures

1. Location map of the study area in the Rio Puerco basin (Note: contours in feet; A is the Rio

Puerco profile as in Table 1; B: is the Arroyo Tapia profile as in Table 2) (M. Brudenell,based on 1:100,000 1999 BLM Edition of Chaco Mesa)

2. A view westwards across the Rio Puerco valley to the north of Guadalupe Ruin with the

modern incised channel and new gully formation evident (C. French)

3. Close-up of the main section (profile A) of the Rio Puerco near Guadalupe Ruin showing

Unit D with the incipient soils and the associated Archaic period re-cut ditches of ca. 2500-2200 cal. B.C. (R. Periman)

4. Schematic section of the main alluvial units and river channels in the Rio Puerco reach near

Guadalupe Ruin (A-M. Hart after C. French)

5. The Arroyo Tapia section at profile B (S. Hall)

6. Schematic section of the main alluvial units and river channels in the Arroyos Tapia and

Guadalupe (A-M. Hart after C. French)

7. A fire reddened zone (labeled A) as exposed in unit E of the Canon Tapia profile with an

inset photomicrograph of the in situ burnt surface horizon of fine sandy clay (frame width

4.25mm; cross polarised light) (C. French)



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8. Photomicrograph of a lens of fine sandy alluvial, valley infilling sediments with re-

deposited fine amorphous organic matter and micro-charcoal (labeled C) in unit F in the

Arroyo Tapia at profile B (frame width 4.25mm; plane polarised light) (C. French)

9. Pollen diagram of the Rio Puerco sequence with the associated charcoal frequencies and

concentrations (data supplied by Susan Smith, Laboratory of Paleoecology, Northern ArizonaUniversity, Flagstaff) (L.Scott-Cummings)

10. Pollen diagrams of the Arroyo Tapia sequence with the associated charcoal frequenciesand concentrations (data supplied by Susan Smith, Laboratory of Paleoecology, Northern

Arizona University, Flagstaff) (L.Scott-Cummings)

Tables

I. The stratigraphic sequence in the Rio Puerco basin at Guadalupe, located at Profile A

II. The stratigraphic sequence in the Arroyo Tapia based on profile B with two additional,

basal units added from Arroyo Quadalupe

III. Radiocarbon dates of the major units and burnt/reddened lenses in the Arroyo Tapia and

Rio Puerco drainages with calibrations given at 2 sigma or 95% probability (after Stuiver etal., 1998; Stuiver and van der Plicht, 1998; Talma and Vogel, 1993)

IV. Summary of the main features in the micromorphological analysis

V. Provenance of the pollen and charcoal samples taken from the Arroyo Tapia and Rio

Puerco profiles

VI. Summary pollen data with the relative frequencies of arboreal and non-arboreal pollen,

woodland, weeds, Poaceae andZea pollen, and the numbers ofZea aggregates in the Arroyo

Tapia and Rio Puerco profiles

VII. Interpretative sequence of incision, infilling and erosion, vegetation, and relative stability

and soil formation phases in the Rio Puerco basin around Guadalupe



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Unit Depth (cm) Description

A 0-30 fine sand and silty clay alluvium acting as modern soil profile and present dayvalley floor with Pueblo period remains; deep, sand/gravel infilled channels cutfrom this level to the base of the present Rio Puerco

30-100 fine sand/silt alluvium

B 100-140 dark brown, organic, silty clay with columnar blocky ped structure; incipientsoil

development

C 140-500 bedded fine sands and silts, with occasional thin lenses of fine charcoal; ditch definesca. 200 cm

D 500-625 2/3 superimposed horizons of brown, organic, silty clay with columnarblocky ped

structure; cumulic, incipient soil development; recut ditches define at base of this unit;with pollen indicative of localised pinyon-juniper woods with some oak, willow &mesquite & diverse non-arboreal pollen; grasses & sedges common with moist areas;

maize present; local fires

upper surface inset terrace bench on south side of modern channel with large, 70+ year old,at ca. 600 cottonwood trees

E 625-1050 bedded fine sands/silts/silty clay alluvial deposits; with wide, large channels definingat this level upstream and downstream; reddened lenses at 1040 cm; local fires

F 1050-1100 brown organic silty clays with columnar blocky ped structure developed on bedrock;cumulic incipient soil development

1100+ base of incised modern channel

Table I. The stratigraphic sequence in the Rio Puerco basin at Guadalupe, located at profile A



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Unit Depth (cm) Description

A 0-30 fine sand/silt alluvium acting as the present day valley floor with Pueblo periodremains; deep (11 m), sand/gravel infilled channel incision from this surface to base ofarroyo wall

30-100 bedded fine quartz sand, with some thin (3 cm) cay beds in the lower part of the unitwith secondary carbonates throughout; basal contact is an erosional unconformity thatmay correspond to a channel with axial basalt gravels exposed downstream; thischannel also cut into unit B below

B 100-180 brown silty clays exhibiting a columnar blocky structure and weak A horizondevelopment at the top of the unit; cumulic incipient soil development;

interruptedby two lenses of fine sand; charcoal lens at ca. 150 cm; in situ lens of reddened

sediment at 165-170 cm

C 180-215 bedded fine sand215-235 bedded fine sand and sandy silts235-245 finely bedded silty clay245-247 in situ burnt silt/very fine sand; with a hearth defining at this level247-310 bedded silty clays and fine sands310-425 bedded fine sand/silt with occasional silty clay lens425-425.5 thin (


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H 1050-1100 in situ burnt lenses in bedded yellowish brown alluvial silty clay

1100+ modern channel bed

Table II. The stratigraphic sequence in the Arroyo Tapia based on profile B with two

additional basal units added from Arroyo Quadalupe

Context Unit Depth

(cm)

Laboratory

number

Conventional

radiocarbon age(yr B.P.)

Calibrated date

(2 sigma)

Arroyo Tapia:

Charcoal lenstowards base ofunit

B 150 Beta-186730;Beta-186731

1620+/-40;1610 +/- 40

Cal. yr A.D. 370-540;Cal. yr A.D. 380-540

Middle soildevelopmenthorizon (of three)

D 655 Beta-186733 3900+/-40 2480-2280 Cal. yr B.C.

Charcoal lensnear top of unit

E 785 Beta-186742 4280+/-40 2920-2870 Cal. yr B.C.


E 870 Beta-186735 4410+/-40 3310-3230 &3310-2910 Cal. yr B.C.

Charcoal lens atbase of unit

E 890 Beta-186738 4950+/-40 3790-3650 Cal. yr B.C.

Charcoal lenstowards top ofunit

F 910 Beta-186739 5280+/-50 4240-3980 Cal. yr B.C.

Charcoal lens inmiddle of unit F 930 Beta-186744 5310+/-40 4240-4030 &4020-4000 Cal. yr B.C.

Charcoal inmiddle of unit

F 930 Beta-186740 6180+/-40 5270-5010 Cal. yr B.C.

Charcoal lens inmiddle of unit

F 932 Beta-186745 6550+/-40 5550-5470 Cal. yr B.C.


F 966 Beta-186746 6720+/-40 5700-5600 & 5580-5560 Cal.yr B.C.

Charcoal frominset terrace

c. 800 Beta-186747 170+/-40 Cal. yr A.D. 1650-1890 &1910-1950

Rio Puerco:

Charcoal frominset terracebench in base ofmodern channel

c. 665 Beta-186747 170 Cal. yr A.D. 1650-1890 &1910-1950

Charcoal fromprimary fill ofditch in base ofunit

D 600 Beta-186732& 186734

3950+/-40 2570-2520 &2500-2330 Cal. yr B.C.

Charcoal fromburnt lens nearbase of unit

E 1040 Beta-186743 6820+/-40 5750-5640 Cal. yr B.C.



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Table III. Radiocarbon dates of the major units and burnt/reddened lenses in the Arroyo Tapia

and Rio Puerco drainages with calibrations given at 2 sigma or 95% probability (after Stuiveret al., 1998; Stuiver and van der Plicht, 1998; Talma and Vogel, 1993)

Unit/context Main matrix Features/inclusions Interpretation

Rio Puerco:

Unit D, base; basal ditchfills at 632-625 and 625-

614 cm

fining upwards sequenceof alternating lenses of

clay/silt and silt/fine sand

silty clay, amorphousorganic matter, fine

charcoal fragments &calcium carbonate

open ditch receiving infillof fines in slow/shallow to

still/shallow waterderived from run-off

Unit D, base; uppersecondary ditch fill at555-545 cm

non-laminated silty claywith minor fine quartzsand

sub-angular blocky pedstructure

fines deposition in stillwater in ditch withsubsequent incipient soildevelopment

Unit D, lower palaeosol;520-510 cm

fine to very fine quartzsand

successive void infillingsof micro-laminated,amorphous organic-rich,silty clay; includedcommon fine charcoal

repeated depositions offines and organic matterand fire derived finecharcoal representingaggradation and weak soil

development with a highgroundwater table,probably in a floodmeadow situation

Unit B; bedded sands,122-110 cm

alternating silty clay andsilt/fine quartz sandlaminae

abundant included fine tovery fine charcoal

run-off and overbankalluvial deposition onfloodplain with wash-outfrom fires

Arroyo Tapia:

Unit C, eg. of reddened

lens, 335-325 cm

1-2cm thick, silty clay;

overlain by fine sandyclay

amorphous iron

impregnated; withoverlying, intercalatedweakly striated dusty clay

temporary surface of

alluvial deposits with insitu burning; thenrenewed overbankalluvial deposition

Unit C, eg. of reddenedand charcoal-rich lens,310-300cm

1-3cm thick, alternatinglenses of sandy clay witha surface crust of orienteddusty clay and burntamorphous organic matterand micro-charcoal in avughy, fine sandy clay

included very finefragments of charcoal

alternating in situ burntalluvial surfaces andinwashings of micro-charcoal in fine, oncemore organic-rich,alluvial sediments

Unit B: eg. of charcoal-rich lens, 135-125 cm

1-2cm thick; irregularaggregates of very fine tofine quartz sand and very

charcoal fragments of


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fine sandy clay sesquioxides; gypsum inthe pores

formation indicative ofhigh temperatures andevaporation

Table IV. Summary of the main features in the micromorphological analysis

Site Sample

no.

Unit Depth

(cm)

Description

Arroyo Tapia: 1 B 150 charcoal lens in upper zone of slowly aggrading silty clays withcolumnar blocky structure

2 C 245-7 in situ burnt silt/very fine sand

3 D 505-15 burnt lens in the middle zone of slowly aggrading silty clays

with columnar blocky structure4 D 655 in situ burnt sand/silt with discontinuous charcoal

5 D 760 in situ burnt sand/silt with discontinuous charcoal

6 E 865 in situ burnt sand/silt

7 D 675-85 thick lens of charcoal and in situ burnt sand/silt

8 D 645-55 silty clay lens with charcoal on upper contact

9 D 690-7 silty clay lens with charcoal

10 D 575 discontinuous in situ burnt zone in bedded fine sands withcharcoal

11 D 590 discontinuous in situ burnt zone and charcoal in bedded finesands

12 D 690-1 charcoal and in situ burnt sand/silt

13 D 704 in situ burning and fine charcoal associated with discontinuous

clay lenses in bedded fine sands and a recut ditch14 D 708 in situ burning and fine charcoal associated with discontinuous

clay lenses in bedded fine sands and a recut ditch

15 D 741 in situ burning and fine charcoal associated with discontinuousclay lenses in bedded fine sands and a recut ditch

16 40 organic duff layer in inset terrace, likely deposited sometime inthe past 100 to 50 years

Rio Puerco: 17 B 105 upper zone of slowly aggrading silty clay with columnar blockyped structure

18 B 120 upper zone of slowly aggrading silty clay with columnar blockyped structure

19 B 135 upper zone of slowly aggrading silty clay with columnar blocky

ped structure20 D 500 top of the middle zone of three major horizons of slowly

aggrading silty clay with columnar blocky ped structure; recutditch defines within this zone

21 D 550 middle zone of the middle buried soil composed of slowlyaggrading silty clay with columnar blocky ped structure; recutditch defines within this zone

22 D 550 primary fill of smaller, earlier ditch defining at the base of themiddle buried soil horizon composed of slowly aggrading siltyclay with columnar blocky ped structure

23 D 570 basal fill of small, earlier ditch defining at the base of themiddle zone of middle buried soil horizon; composed of slowlyaggrading silty clay with columnar blocky ped structure

24 D 625 basal fill of large ditch defining at the base of the middle zoneof middle buried soil horizon; composed of slowly aggradingsilty clay with columnar blocky ped structure



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Table V. Provenance for the pollen and charcoal samples taken from the Arroyo Tapia andRio Puerco profiles

Sample: Sum

arborealpollen

Sum

non-arboreal

pollen

% Trees % Weeds %

Poaceae

% Zea No. of

Zea

aggregate

s

ArroyoTapia:1 192 317 38.2 25.9 9.4 - -

2 167 242 42.5 30.1 2.0 - -

3 163 267 38.4 38.4 6.0 - -

4 156 265 37.6 43.4 2.4 - 2

5 180 231 44.0 39.4 1.0 - -

6 151 295 34.9 34.7 5.6 - 2

7 88 317 21.7 67.7 1.5 - 4

8 227 237 48.9 30.4 1.5 - 19 159 295 35.1 43.6 3.3 - 2

10 293 375 44.8 32.3 3.0 - -

11 179 281 39.3 36.1 5.4 - -

12 40 307 13.5 48.2 3.7 - 2

13 40 366 11.2 51.9 5.4 - 2

14 41 379 9.7 56.2 7.1 - 2

15 29 339 8.2 81.8 0.8 - 2

16 192 238 44.9 33.3 6.7 - -

RioPuerrco:17 229 178 56.3 37.1 - 2.2 1

18 103 343 23.3 55.8 2.9 - -

19 80 337 21.1 50.8 2.9 0.5 -

20 103 357 22.8 52.2 7.2 - -

21 167 320 34.2 43.1 5.5 - -

22 121 267 31.5 42.0 10.6 - 1

23 172 340 33.6 41.0 2.9 - -

24 141 307 31.5 41.1 54.6 - -

Table VI. Summary pollen data with relative frequencies of arboreal and non-arboreal pollen,

woodland, weeds, Poaceae andZea pollen, and the numbers ofZea aggregates in the ArroyoTapia and Rio Puerco profiles



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Unit Interpretation Date

Terraceinset

Infilling of base of present day Puerco river channelSparse pinyon-pine, juniper, oak woodland with sagebrush, grasses,non-arboreal flora and little charcoal

20th century A.D.

ModernPuercochannelandtributaryarroyos

Severe river incision and extensive erosion of valley fill deposits from A.D. 1765;especially from A.D.1885-90

A Valley infilling and then stability represented by cumulic soildeveloped on fine sandy/silt alluvium as Puebloan to present day soilprofile; Puerco valley incised by very deep (ca. 11m) and wide riverchannel, and Arroyo Tapia incised by shallower (


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H Valley infilling with silty clay alluvium with localised fires in theArroyo Quadalupe

Table VII. Interpretative sequence of incision, infilling and erosion, vegetation, and relative

stability and soil formation phases in the Rio Puerco basin around Guadalupe



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