Embed Size (px)
Citation preview
The Excavation of Rood Block, Mountaineer Site, Gunnison, Colorado
By
Mark Stiger, PhD Department of Natural and Environmental Sciences
Western Colorado University Gunnison, Colorado 81231
June 15, 2019
Report of Activities
Western Colorado University Archaeological Field School--2016-2018 and SHF Project 2017-02-012
Colorado State Permits 2016-99; 2016-100; 2017-106; 74386
2
Table of Contents Table of Figures ...................................................................................................................... 3
List of Tables .......................................................................................................................... 4
Acknowledgements ................................................................................................................. 4
The Upper Gunnison Basin Region ..................................................................................... 7
Cultural History of the Upper Gunnison Basin .................................................................... 8
The Mountaineer Site ........................................................................................................ 11
Research Goals.................................................................................................................. 14
Field Methods ................................................................................................................... 14
Surface survey ............................................................................................................... 14
Excavation .................................................................................................................... 15
Lab Methods ..................................................................................................................... 16
History of Investigations ................................................................................................... 16
Field School 2016 ......................................................................................................... 18
Field School 2017 ......................................................................................................... 25
Field School 2018 ......................................................................................................... 27
Results .............................................................................................................................. 28
Surface Collection ......................................................................................................... 29
Archaeological Features ................................................................................................ 31
Archaeological Artifacts ................................................................................................ 34
Points. ....................................................................................................................... 34
Flake Tools. ............................................................................................................... 37
Debitage. ................................................................................................................... 37
Welded Tuff Flakes ............................................................................................... 40
Caliche coating...................................................................................................... 40
Bone. ......................................................................................................................... 40
Dating. ...................................................................................................................... 41
Conclusions....................................................................................................................... 43
References Cited ............................................................................................................... 44
Appendix A. Site Formation Processes ................................................................................ 46
Minor Post-Occupation Formation Processes ................................................................. 47
Downslope Movement ............................................................................................... 47
Wind ......................................................................................................................... 47
3
Insects and Rodents ................................................................................................... 48
Vegetation, Fires, and Caliche ................................................................................... 49
Major Natural Post-Occupation Formation Processes .................................................... 50
Expansion/Contraction of Sediment from Frost heave/Heat/Saturation ...................... 50
Modern Construction Activities ................................................................................. 56
Appendix B. Recognizing the effect of spatial processes .................................................. 57
Table of Figures Figure 1. The location of the Mountaineer Site. ........................................................................... 6 Figure 2. Radiocarbon dated sequence of floral and faunal remains and cultural features in the Upper Gunnison Basin. ............................................................................................................. 10 Figure 3. Radiocarbon dated feature recovered from excavations in the Upper Gunnison Basin. 11 Figure 4. Map of the surface collection of the Mountaineer Site. Green dots are debitage; other colors are tools. ......................................................................................................................... 13 Figure 5. The distribution of artifacts recovered by Alpine in 1994 and WCU in 1995. North is to top. ........................................................................................................................................... 18 Figure 6. Distribution of all surface artifacts collected from near Rood Block as of 2018. Black dots are debitage; red dots are tools. .......................................................................................... 19 Figure 7. Distribution of all artifacts recovered by Alpine in 1994, WCU in 1995, and WCU in 2016. North is to the top. ........................................................................................................... 20 Figure 8. Distribution of all artifacts in Rood Block with 1000N/1000E adjusted. North is to the top. ........................................................................................................................................... 21 Figure 9. Distribution of artifacts weighing more than 10 gm. North is to the top. ..................... 22 Figure 10. Photograph looking down at re-excavated Rood Block in 2016. Figures stand along the south side of the excavation block. Behind them can be seen the edge of modern bladed road. The provenience of the southwest corner of excavation block (the lower right .......................... 23 Figure 11. Excavations on east end of Rood Block showing soil surface above broken bedrock. North is to the top. .................................................................................................................... 26 Figure 12. Rood Block after the excavations in 2017. North is to the top. .................................. 26 Figure 13. The surface collection at the end of 2018. Tools are shown as red dots. .................... 30 Figure 14. Rood Block excavations at the end of the 2018 field season. Blue triangles are surface artifacts; green contour shows debitage; red contours shows bone fragments............................. 32 Figure 15.The projectile points from Rood Block and nearby concentration. A is a Folsom point base found in the southern concentration. B is a broken GBS projectile point found within the Rood excavation block. ............................................................................................................. 34 Figure 16. Bifaces from Rood Block and nearby concentrations. Three far left specimens came from Feature 1. The two artifacts at the top on the right side of photo are from the surface collection near Rood Block. The bottom four artifacts on the right are from Rood Block. ......... 35 Figure 17. Biface cores from Rood Block.................................................................................. 36
4
Figure 18. A large retouched flake from Rood Block. ............................................................... 37 Figure 19. Flake Tools from Rood Block and vicinity. Top row- graver; retouched edge; retouched edge. Bottom row-end scraper. .................................................................................. 38 Figure 20. Refit blade technology from Rood Block. Platforms are to top and left. .................... 39
List of Tables Table 1. Excavated area on Rood Block……………………………………………………..28 Table 2. Debitage frequencies over time at Rood Block…………………………………….37 Table 3. Bone fragments recovered by field school…………………………………………40
Acknowledgements The State Historic Fund of History Colorado supported the 2017 field season of this project. Katie Arntzen of the SHF provided advice and feedback on all questions that arose and helped our project find its way to completion.
The field school students, Chad, Jared, Suzanne, Rachel, David, and Meredith, provided labor and the joy of teaching interested learners. Suzanne Crown helped in the field, in the museum with curation, and with multiple tours. Dr. Lynn Sikkink conducted tours with sixth graders for which I am so grateful.
5
The Mountaineer Site (5GN2477) (Figure 1) was initially recorded in 1994 as a sparse
lithic scatter of unknown age, function, and affiliation during “pre-construction” reconnaissance
by a private cultural resource management firm. It was not until 2000, when a more intensive and
extensive survey was done by Western Colorado University (WCU) faculty and students, that a
temporally diagnostic artifact, a Folsom point, was found. Folsom points are considered to be
diagnostic artifacts of the period radiocarbon-dated to between 10,200 and 10,900 years ago.
This period is also known as the Younger Dryas, a period immediately following megafaunal
extinctions during which global warming suddenly reversed. Because of the unique data from an
interesting time it offered, Mountaineer became a focus of archaeological field research in 2001
by students and faculty of WCU, with the assistance of a State Historic Fund grant.
Undergraduate field schools were conducted on areas of the site in archaeological areas that had
been disturbed by modern activities. From 2001 to 2018, Western undergraduate field schools
worked on the following areas of Mountaineer:
Block A north, a winter Folsom lithic workshop1 Block A south, a residence containing Folsom and Great Basin Stemmed material Block B, a winter residence containing Folsom material Block C, a winter residence containing Folsom material Block F, a winter residence containing Folsom material Block G, a residence containing Folsom and Great Basin Stemmed material Block H, a residence containing Great Basin Stemmed material Rood Block, a residence containing Great Basin Stemmed material
During 2016-2018 WCU conducted undergraduate archaeological field schools on Rood Block
where the first subsurface test pit was dug.
1 Blocks A, north and south, B, C, D, F are detailed in The Mountaineer Site, edited by Andrews, Meltzer, and Stiger in press at University Press of Colorado.
6
Figure 1. The location of the Mountaineer Site.
7
Students were trained in excavation and intensive-survey techniques that have been used
on the Mountaineer site for 19 years. The main purpose of the field schools was to teach select
undergraduate archaeology students field and laboratory techniques and to professionally gather
significant archaeological information from the site. These activities on property owned by the
State of Colorado were conducted under Colorado State Archaeological Permits # 16-99 and 16-
100, 2017-106; 74386. This report describes the site and its setting in space and time, the
archaeological work conducted on this area of the site, the findings, and the interpretation of
these findings.
The Upper Gunnison Basin Region
The Upper Gunnison Basin (UGB) encompasses an 11,000 km2 area in southwestern
Colorado within the southern Rocky Mountains and on the eastern edge of the Colorado Plateau.
It has an elevation range of 2200-4300 m and no outlet lower than 2650 m except through the
narrow gorge of the Black Canyon of the Gunnison to the west. This canyon, which includes a
20 km section that is over 700 m deep and only 400 m across at its narrowest point, acts as a
filter for the movement of species in and out of the Basin. The UGB is probably the most
ecologically isolated of the five high-mountain basins in Colorado (North Park, Middle Park,
South Park, San Luis, and UGB). No other large, montane basin in Colorado is enclosed by such
extreme geographic barriers, and it is this feature that probably has caused the development of
the unusual climate, communities, and biogeographic patterns now present in the Basin.
Ecologically, the flora and fauna in the UGB appears to be depauperate in taxa that
should occur here, but do not, and the region has been recognized for its unique biogeographic
characteristics for plants and animals (Woodbury et al. 1962; Barrell 1969; Armstrong 1972).
For example, piñon trees (Pinus edulis) are notably absent throughout the basin, though juniper
8
occurs in numerous areas. Colorado vertebrates that occupy the same elevational ranges and
habitats as those within the Basin, but are absent here, include (but are not limited to)
woodhouse’s toad (Bufo woodhousei), short-horned lizard (Phrynosoma douglassii), collared
lizard (Crotaphytus collaris), western rattlesnake (Crotalus viridis), sagebrush vole (Lemmiscus
curtatus), and thirteen-lined ground squirrel (Spermophilus tridecemlineatus) (Hammerson 1986;
Fitzgerald et al. 1994). The fossil evidence indicates that many of these species existed in the
Gunnison region during the late Pleistocene, along with several extinct mammals (e.g., Acinonyx
trumani, Equus sp., Bootherium bombifrons, Euceratherium sp. [Emslie 1986; Nash 1987]).
Mesas were formed by the ancestral Gunnison River and its tributaries eroding through a
level expanse of welded tuff deposited by a nearby mega-volcanic event approximately 25 mya.
The Mountaineer Site is found on top of one such tuff mesa, “Tenderfoot Mountain,” 2.5 km
south of Gunnison, Colorado. The sediment across the site is a thin and variable mixture of
aeolian dust and eroded bedrock. The topography is such that with the exception of windblown
material, all deposits on the mesa top are derived from in-place bedrock or brought in by humans
or animals. Almost all modern and ancient artifacts are found in the top 10 cm of the sediment
unless an excavation has cut into the loess.
The Gunnison River, a major tributary of the Colorado, flows a mile northwest of the site
through the town of Gunnison, Colorado, 277 m (900 ft) lower than the site. The ancestral
Gunnison River and Tomichi Creek deposited cobbles of a wide variety of material around the
base of the mesa; numerous tested quartzite cobbles of various colors are found there. Other
highly eroded ancestral creek deposits, bearing differing varieties and qualities of quartzite
cobbles depending on paleo-drainage, are found in isolated spots around the Basin.
Cultural History of the Upper Gunnison Basin
9
Besides unusual ecological communities (Armstrong 1972; Barrell 1969; Stiger 1980),
the UGB also has a rich archaeological record spanning the Holocene. Over 3000 archaeological
sites have been recorded in the Basin ranging from Paleoindian to historic in age. Archaic lithic
scatters are common at lower elevations and several have been excavated at least on a limited
scale (e.g., Elk Creek Village, Checkers Site, Van Tyle Village [Euler and Stiger 1978; Stiger
1993; Rood 1996]).
The Tenderfoot Site (elev. 2350 m), located 2.5 km southeast of Gunnison, was
excavated more thoroughly as part of a summer field school at WCU from 1991 to 2000 (Stiger
2001) and is one component of a long-term research program at the University. The relatively
shallow sediments (most < 20 cm) at the Tenderfoot Site have allowed large-scale horizontal
excavations, providing considerable data from multiple occupations and associated houses,
features, and artifact assemblages. Although only 0.3% of the site was excavated, two block
excavations totaled over 500 m2. Moreover, over 80 features have been located. Sixty
radiocarbon dates from charcoal have revealed a detailed chronology and occupation history of
the site. Most of these dates span the period 8000 RYBP2-3000 RYBP and add to the total
number of radiocarbon dates (>170) now known from archaeological sites and features in the
UGB. This total chronology of all dated features from numerous archaeological sites in the
Basin indicates some striking patterns, with marked intervals for certain types of food processing
pits, hearths, structures, and game drives. These patterns probably reflect changes in food-
processing and environmental exploitation that may be correlated with episodes of climate
change and a shifting emphasis in lithic technology from bifacial tools to flake tools (Stiger
2001).
2 RYBP – Radiocarbon Years Before Present
10
From 8000 RYBP to about 3000 RYBP the cultural-environmental sequence of the UGB
is well-dated and dynamic. On the Tenderfoot Site excavations uncovered six complete Early
Archaic structures and associated outside areas that document changes in features, in flora and
fauna, and in stone technology through time (Figures 2 and 3). For more detail on the
chronology see Stiger 2017.
Figure 2. Radiocarbon dated sequence of floral and faunal remains and cultural features in the Upper Gunnison Basin.
11
The Mountaineer Site
The Mountaineer Site is located on an isolated mesa top at 2620m asl in the center of a
high mountain valley. The first Folsom points discovered on the surface of the site indicated that
at least part of the site was ancient. All radiocarbon-dated Folsom sites yield dates between
10,200 and 10,900 radiocarbon years ago during a time of climate change called the “Younger
Dryas.” Although a period of important environmental and cultural evolution, only a few
Folsom-age sites have been found and studied in Colorado. Additional intensive surface surveys
of the surface on Mountaineer have located well over one hundred artifact clusters (Figure 4).
Seventeen of these clusters have produced diagnostic Folsom materials spread across an area 300
meters by 400 meters on the mesa top that measures 1200 meters by 400 meters. More Folsom
clusters may be identifiable with more intensive field work, as we see on Rood Block. On
Mountaineer, the only temporally diagnostic artifacts directly associated with clusters of debris
are Folsom Points and Great Basin Stemmed (GBS) points and one Middle Archaic camp with
Figure 3. Radiocarbon dated feature recovered from excavations in the Upper Gunnison Basin.
12
large side-notched points (Mallory) located over 100 m from the areas that yielded Folsom
material.
WCU has conducted a field school each summer from 2001 to 2018 utilizing parts of the
site which had been damaged by modern activity. In 2002, we invited Dr. David J. Meltzer of
Southern Methodist University (SMU) to visit and evaluate the site and collections. From 2002
to 2011, SMU conducted excavations in two excavation blocks, Block C and Block D. Beyond
“digging” on the site, field school students participated in numerous detailed multiple-year
studies of natural formation processes on site, including freeze-thaw, forest fires, lightning,
grazing animals, human trampling, wind, rain, and thermal expansion of soils. For a detailed
history of excavations and formation processes on Mountaineer see Andrews et al. 2019.
13
Figure 4. Map of the surface collection of the Mountaineer Site. Green dots are debitage; other colors are tools.
14
On Mountaineer, the WCU field schools and SMU have fully excavated four large
Folsom pit structures well-dated to 10,400 RYBP. Three of these large structures (Blocks B, C,
and F) were used as residences, and one (Block A north) served a more specialized function of
biface and projectile point manufacture. Additionally, three smaller shallow structures (Blocks
A south, G, and H) have been excavated and have produced a lithic assemblage including
Folsom and Great Basin Stemmed (GBS) points. This report describes an additional small
shallow structure in Rood Block that has produced a GBS projectile point.
Research Goals
The 2016-2018 WCU field schools re-examined the area of the first archaeological test
excavations that were conducted on Mountaineer when it was initially recorded in 1994. Alpine
Archaeological Consultants in 1994 and WCU in 1995 both tested the area, but the results of that
field work did not show much understandable patterning of artifacts. We went back in part to
this first excavation, now named “Rood Block,” to clarify what archaeological remains were
present because cell-phone companies have proposed new enhancements to their facilities and
their access roads. The results of this work are given in this report.
Field Methods
Surface survey At the start of each field season from 2016-2018 the students and the PI conducted an
intensive survey across the area around Rood Block. The surveyors systematically crawled on
their hands and knees, placing pin flags at every artifact observed. Then students mapped the
artifacts with a total station or a sub-centimeter GPS, then collected and labeled them. All
surface-collected artifacts were then integrated into the excavated-artifact assemblage to be
analyzed, reported in the Results section of this report, and curated.
15
Surveyors found four temporally diagnostic artifacts across this area: a GBS projectile
point fragment, a Folsom point, and two channel flakes. Surveyors also located several small (1-
2 cm) fragments of Opal CT, a distinctive yellow to red mineral. The geological source of Opal
CT is not known. It fractures into blocky chunks completely unusable for chipped stone.
Recovered from other excavation blocks on Mountaineer were two small pieces of Opal CT that
exhibited ground faces. They may have been used for pigment or for adding friction to lithic
platforms similar to the chalking of a cue. Opal CT has been recovered from six structures,
including Rood Block, on the Mountaineer site with lithic assemblages including Folsom points
and/or GBS projectile points. I am aware of no other reports of Opal CT on archaeological sites
in the UGB or beyond. Finally, surveyors recovered a large flake tool fragment that conjoins to
another piece found over 400 m away on another GBS occupation on Mountaineer.
Excavation Excavation grids were set up with a total station on a permanent site grid system. We
began excavation by removing the loose top sediment (5-10 cm), which covered a compact fine
sediment containing tiny calcareous pebbles. In the upper loose sediment were numerous
bedrock welded tuff fragments up to a softball in size. If rocks were loose, they were removed.
If rocks were embedded in the compact sediment below, they were left in place.
Sediment was removed in 50 cm X 50 cm quads, in natural levels depending on location
(for more information on natural site stratigraphy see Stafford 2005). Trowels, brushes, and
buckets were used to remove all sediment to shaker screens lined with window screen for
preliminary sifting. The material caught by the window screen was then bagged, labeled, and
taken to the archaeological wet lab on campus for processing. After water-screening through
window screen, the remaining sediment was air dried, rescreened dry through 1/8 inch hardware
16
cloth and then hand sorted to remove all cultural and important natural material. Each kind of
material was bagged, labeled, and set aside for analysis.
Lab Methods
The laboratory analysis of recovered materials was done in a fashion consistent with that
of earlier archaeological investigations on Mountaineer. Stone artifacts were separated into
debitage and stone tools. Debitage was further broken down by raw material and technological
indicators. Special kinds of debitage, such as channel flakes, scraper sharpening flakes, blades,
and overshot flakes, were given further attention. Stone tools were measured and described more
fully. All tools were examined for use wear.
The faunal specimens recovered from the field school excavations consisted almost
entirely of bone fragments that are less than 0.5 cm. The bone assemblage was examined by
Ronald J. Rood (2018) who concluded the bones had been processed prehistorically, and
although unidentifiable were likely from large mammals.
History of Investigations In 1994, Alpine Archaeological Consultants of Montrose, Colorado was contracted by
two cell-phone companies to survey and inventory archaeological resources that had been
impacted by the companies’ previously completed construction of powerlines, roads, and
tower/shack pads on WCU property on Tenderfoot Mountain (Pope and Gruebel 1994). Field
inspection by Alpine of the powerline consisted of one archaeologist walking “pedestrian
transects spaced 15 m apart to a distance 15 m on either side of the trench” (Pope and Greubel
1994:7). The field archaeologist found and recorded a sparse lithic scatter of rhyolite and
quartzite as 5GN2477, and excavated one 1 m x 1 m test pit in three 5-cm levels.
17
Alpine’s test pit was put in an area of sparse lithic artifact scatter damaged by
powerline construction. One quartzite flake and one quartzite biface fragment were found on the
modern ground surface of the test pit and two more quartzite flakes were found via screening
through ¼” mesh. After excavation, the pit was backfilled. Alpine’s report recommended
eligibility of the site for nomination to the National Register and for mitigation, avoidance, and
monitoring.
After Alpine’s report was received, State Archaeologist Dr. Collins requested more
information on the site from the cell companies. The cell company, Cell One, then contracted
with WCU to further evaluate the site with 20 test pits.
PI Ronald J. Rood (Rood et al. 1995), then with WCU, and students excavated those
20 test pits in 1995. Rood resurveyed, remapped, and recollected the surface distributions of
artifacts in the immediate area around the test pit. Five isolated test pits, plus a 4-m-x-4-m block
placed over Alpine’s test pit were excavated in 1 m x 1 m squares and nominally 10-cm levels,
but as is pointed out in Rood et al. (1995:6), “…bedrock was usually reached between five and
eight centimeters below the modern surface.” Sediment was screened through 1/8” mesh and no
backfilling was done. An additional 104 flakes and four more bifaces were found in the
surrounding squares (Figure 5). After excavations were completed, the back dirt of the original
test pit stood pedestaled.
All of the work done in 1995, including surface collection and test excavations, was
given provenience from the southwest corner of the original Alpine test pit, designated 1000
North/1000 East. In 2000, a single archaeological survey grid system was organized for the
entire mesa and all surface artifact collections and excavations were given provenience in this
new system. For reporting Rood Block, we continue to use the grid system used by Rood et al
18
(1995) and Pope and Gruebel (1994) for excavation in Rood Block. Since both grid systems are
aligned to the same north, conversion and graphic overlays between the two grids is
arithmetically simple.
Figure 5. The distribution of artifacts recovered by Alpine in 1994 and WCU in 1995. North is to top.
Field School 2016 After our initial intensive surface survey (Figure 6), the 2016 excavations on Rood
Block consisted of three activities. First, we removed and processed the backfill from the
original 1994 test pit, still pedestaled as left in 1995; this had been originally screened with ¼”
mesh. Our 2016 processing recovered over 100 lithic artifacts, including a large quartzite biface
fragment that refit with a piece recovered in 1994. Second, we re-excavated the remaining
squares of the 1995 4 m x 4 m test excavation. In many grid squares, some sediment had been
left on bedrock. We removed and processed this sediment in 50-cm-x-50-cm quads. The third
and final field school activity was opening six new one-m-square test pits in 50-cm-x-50-cm
quads on the north and east end of Rood Block. These grid squares were excavated to exclude
19
the possibility of another artifact cluster intersecting from the north, and to better understand the
formation of the feature on the east side of Rood Block.
Figure 6. Distribution of all surface artifacts collected from near Rood Block as of 2018. Black dots are debitage; red dots are tools.
20
Artifacts from the three excavations have been combined in the following manner.
Artifacts from Alpine’s work (a biface fragment and three flakes3), from rescreened back dirt
from grid square 1000N/1000E (115 artifacts) and from WCU’s first excavation (104 artifacts)
of the 4-m-x-4-m grid square, all have horizontal provenience by only 1 m x 1 m grid square. A
few large flakes were given point provenience by the 1995 WCU excavators, but the other
artifacts found in a given grid square were first assigned quad provenience in as nearly-equal
numbers as possible to all four quads of a grid square. Hence, a contour map describing this
distribution of artifacts in Rood Block (Figure 7) shows contours through Alpine’s original test
pit at 1000N/1000E as appearing to be stretched, almost looking like a tee-shirt being pulled
from opposite sides. The 119 artifacts from the original test pit composed the highest total count
of artifacts in the original 4-m-x-4-m excavation block. The artifact counts in the grid squares
neighboring 1000N/1000E are higher in the squares to the north side of 1000N/1000E than in
those to the south side. Rather than assuming that the artifacts were evenly distributed by quad
in the original test pit, the quad counts are adjusted to reflect the artifact distribution in adjoining
squares by moving ten artifacts each from the two south two quads and adding them to the two
north quads4.
Figure 7. Distribution of all artifacts recovered by Alpine in 1994, WCU in 1995, and WCU in 2016. North is to the top.
3 These artifacts have been returned to the CT Hurst Museum. 4 119 artifacts evenly divided counts—30, 30, 29, 30 and adjusted counts—40, 40, 19, 20
21
The adjusted distribution of lithic artifacts in Rood Block (Figure 8) clearly shows that
there are two major concentrations of artifacts, a smaller west aggregation and a larger east
aggregation. Mapping only the statistically significant aggregations5 shows the western to be
small and shaped like a fat crescent, while the excavated portion of the eastern aggregation
appears round.
Figure 8. Distribution of all artifacts in Rood Block with 1000N/1000E adjusted. North is to the top.
5 See Appendix Recognizing Spatial Processes
22
Numerous large (over 10 gm) quartzite flakes were found across the western group of
artifacts (Figures 9 and 10). Many of them refit, including a single flake from the 1995 surface
collection. The remains of five large bifaces were recovered, some of which refit to debitage or
other biface fragments. The refitting is extremely time-consuming and ongoing but it does very
clearly demonstrate that bifacial-reduction and blade-reduction techniques that were used. The
western concentration of artifacts represent the debris from the activity of a single individual at a
time, sitting or kneeling outside, manufacturing several large quartzite bifaces. There is no
evidence of a nearby fire. Large lithic debris was tossed to the northwest. Smaller material
tended to be dropped. The lithic assemblage in the western half of Rood Block is almost entirely
quartzite.
Figure 9. Distribution of artifacts weighing more than 10 gm. North is to the top.
23
Figure 10. Photograph looking down at re-excavated Rood Block in 2016. Figures stand along the south side of the excavation block. Behind them can be seen the edge of modern bladed road. The provenience of the southwest corner of excavation block (the lower right
At the end of the 1995 fieldwork, Rood (1995 field notes) suspected that a prehistoric
structure was present immediately adjacent to the eastern edge of his 4-m-x-4-m test-excavation
block because his subsurface test grazed it. At the end of the 2016 field school, this feature was
only partly excavated but it appeared to be round, at least three meters in diameter, and to
contain a different artifact assemblage than that found in the western area. A distinctive brown
chert material and numerous bone fragments in addition to quartzite artifacts were recovered
from this feature. As we excavated this eastern side of the block, we became increasingly
confident that here were the remains of an ancient structure. At the end of the 2016 field season
we did not have time to completely excavate the structure properly, so we finished levels in those
24
grid squares but we did not complete excavation to a floor or sterile deposit. We planned to
complete the excavation of the structure the following summer in 2017.
We had hoped to recover enough bone for dating samples from the 2016 excavation,
but did not even though more bone was recovered from the structure in the last days of the field
season. While it was far from certain, the presence of a structure, an artifact assemblage of
almost several thousand pieces (Figure 8), and the absence of any ground-stone artifacts very
strongly suggested this occupation dated to the Paleoindian period.
The west-side biface reduction area was probably associated with the occupants of the
structure. It has the size and shape of a drop zone model consistent with a seated or kneeling
activity. If so, it would argue against a deep winter occupation because outside activities likely
would have been limited. On the other side of the mesa, the debris from Folsom primary biface
manufacture in a suspected winter occupation did not appear as small concentrations outside or
in, but was found scattered outside both a residence (Block F) and the community structure
(Block A north) (Stiger 2017). These differing spatial distributions of early-stage biface
manufacturing debris point to an important difference in activity organization. In winter context,
the spatial distribution of debris from percussion biface reduction was found outside in a pattern
consistent with a standing knapper or a seated or kneeling knapper working on a on a hide or mat
(either inside or out), that at the conclusion of knapping was taken outside and shaken or
dumped. However, the debris pattern found at the western feature of Rood Block is consistent
with the debris pattern of a single actor seated or kneeling outside, likely a warm season outside
activity.
Two findings at this time pointed to the similarities between the other Paleoindian
occupations on site and Rood Block. First, the initial lithic technology and biface manufacture is
25
similar. Both occupations produced large prismatic blades resulting from reduction of large
quartzite cobbles into large bifaces. Also, both occupations yield Opal CT which was imported
from a presently unknown source for a presently unknown use. No other reports of Opal CT are
known from other sites in or out of the UGB.
A noteworthy field observation is that the densest surface artifact distribution on Rood
Block was not found above the densest sub-surface artifact distribution, which is also the case on
all Folsom and GBS blocks on Mountaineer. This occurrence shows that high-density surface
artifacts are not always the best key to subsurface features.
Field School 2017 In May 2017, we resumed excavation of what we were confident was a structure in Rood
Block. First, we expanded a row of grid squares across the northern side of the western half of
Rood Block to make sure the outside lithic reduction area did not continue to the north.
Excavation revealed only a few artifacts in this area.
We then completed excavation of the small structure across the east side of Rood Block.
As always, we began excavation by removing the loose top sediment. In this sediment were
numerous bedrock fragments up to 25 cm (Figure 9 and 10). If rocks were loose they were
removed. If rocks were embedded in the compact sediment, they were left in place. Figure 11
illustrates this compact soil after removal of the loose top sediment. As is shown, numerous
rocks embedded in the compact surface show on the surface around the perimeter of the
structure. More research is needed on the formation of the compact surface but it appears to be
soil development.
26
Figure 11. Excavations on east end of Rood Block showing soil surface above broken bedrock. North is to the top.
While stone tools were not found inside the structure (Figure 12), a large number of small
debitage pieces was recovered. Most of this debitage is made of quartzite similar to the material
making up the debitage found outside; however, a few low-density concentrations of brown-
chert debitage were present. A broken Great-Basin Stemmed point was recovered just outside the
structure.
Figure 12. Rood Block after the excavations in 2017. North is to the top.
27
A considerable quantity of bone fragments was recovered just outside and south of the
structure. None of these bones is identifiable to genus or species and none contained enough
collagen for a radiocarbon date.
Given the outside activities, it is likely this structure was used during the warmer months
of the year. It appears that a trash dump and toss zone are located south of the structure. This is
a common spatial pattern seen in the ethnographic record. At the end of the 2017 field season,
we planned excavations the following summer to include investigations of additional trash
deposits and evaluations of the small concentration of surface artifacts in the area northeast of
the block.
Field School 2018 The first task accomplished during the field school was an intensive surface survey of the
area spatially associated with Rood Block. Students and faculty crawled across the site to evenly
cover the entire area and home in on productive locations. Once again, intensive survey and re-
collection show persistent patterns of concentrations.
One of the important questions our research had for the work done on Rood Block was,
how long ago was it occupied? In 2017, we had obtained some bone in which the collagen was
poorly preserved so more bone was needed. In May 2018, the WCU archaeological field school
resumed work on Rood Block hoping to obtain additional faunal material. Specifically, we
wanted to systematically remove the remaining trash deposits on the south side of the structure
between the excavation block and the modern bladed road. We salvaged these deposits which
28
likely would have been destroyed by erosion of the road cut within the next few years.
Unfortunately, analysis proved that even with the additional fragments we recovered, the sample
still did not yield an analyzable amount of collagen for AMS radiocarbon dating.
However, surface collection of Rood Block and other nearby artifact concentrations did
provide datable artifact evidence of Rood and two other nearby artifact concentrations. A broken
GBS point was found on the surface of Rood Block, the “find spot” was just outside the structure
in a possible trash area. A Folsom point base and a channel flake were found in the southern-
most of the surface concentrations. A second channel flake was recovered from the southeastern
surface artifact concentration. These artifacts are consistent with our suggested date of
occupation during the Younger Dryas.
Field school students conducting an intensive surface survey in 2017 had noticed a small
surface concentration of small pieces of debitage located a meter or two northeast of the
excavation block. We had intensively surveyed and surface collected this area years before, yet it
was surprising how many artifacts were present. Foot traffic, both from archaeologists and
visitors to the site, was enough to disturb the sediment and expose archaeological artifacts. The
students had considered excavation of this area a priority for future work and in response we
excavated a small 4-m-x-5-m test block during 2018.
Results Western’s archaeological field school spent three field seasons (2016-2018) excavating
and conducting an intensive surface survey on a small portion of the Mountaineer Site
(5GN2477). The initial subsurface testing in 1995 had showed lithic blade technology similar to
what was found years later in a Folsom structure in Block A, Mountaineer Site. The
29
technological similarity suggested to us that we to reexamine this excavation block and the
immediate surrounding area.
Table 1. Excavated area on Rood Block.
Year Area Excavated m2 Area Re-excavated m2 Total Area Excavated m2
1994 1 - 1
1995 15 1 16
2016 6 16 22
2017 28 - 50
2018 28 - 78
Surface Collection After the 2018 field season, the surface collection showed at least ten distinct artifact
clusters in the area around and likely associated with Rood Block. The artifacts found on the
surface of Rood Block make-up two such clusters and we might reasonably surmise that the
other surface clusters could be signaling similar subsurface remains. A plot of the tools
recovered from surface collection also shows that most of the tools are associated with debitage
concentrations (Figure 13).
Excavation of the aligned surface artifact concentrations in Blocks A, B, C, and F and
those aligned in Blocks A south, G, and H on Mountaineer, showed that aligned surface clusters
may indicate multiple contemporaneously occupied structures within a community. Material
recovered from aligned clusters yield similar radiocarbon results, projectile point styles, and
lithic raw-material. Although having identical radiocarbon, points, or lithic sources does not
30
guarantee contemporaneity among structures, Rood Block and the other clusters in its alignment
are likely the remains of yet another community of Folsom-age people.
Figure 13. The surface collection at the end of 2018. Tools are shown as red dots.
31
Archaeological Features The final distribution of surface artifacts is illustrated in Figure 12. At least 10 small
debitage concentrations appear across the area. It is unknown how many of these concentrations
are the remains of structures occupied during this early time period. Some of the concentrations
may not be the remains of structures at all, as a warm-season camp would be expected to produce
a variety of outside activities. Three of the concentrations have produced Paleoindian
diagnostics: Folsom and GBS points, channel flakes, and Opal CT. The alignment of the
concentrations indicates they were located relative to each other, which argues for their
contemporaneity.
Figure 14 shows the excavation block at the end of 2018. Three features were located
during excavation. At Feature 1 the remains of biface manufacture were found outside and west
of Feature 2, a small structure. To the northeast, Feature 3 was a chipping station marked by tiny
pieces of debitage.
Feature 1 is a biface manufacturing locus centered on 1000N/1000E, the first test square
excavated in 1994. Numerous biface fragments were recovered around this debitage
concentration. The debitage in this western feature is entirely quartzite and several biface
manufacturing sequences can be partially refit. The refit sequences show that the quartzite
selected for knapping came from cobbles similar to those found locally in natural deposits. The
reduction sequences look very similar to biface manufacturing in a Folsom community structure
in Block A located across the mesa to the west. Blades or prismatic flakes were removed from
cores, then thinned and shaped as bifaces. Some of the blades were retouched or used for heavy
cutting. Only a couple of small bone fragments were recovered from the excavations in the
western half of Rood Block.
32
Figure 14. Rood Block excavations at the end of the 2018 field season. Blue triangles are surface artifacts; green contour shows debitage; red contours shows bone fragments.
Feature 2 is a bloated triangle-shaped structure with its 3.5 m base to the southeast and
the apex 4 m to the northwest. The floor of the structure was constructed by removing the top 10
cm of surface sediment and bedrock fragments that protruded. A door is not apparent but the
bone and debitage deposit outside indicates a southeast entry. The densest debitage and bone
distributions in the excavation block were found inside Feature 2. The debitage was in three
33
concentrations and the bone was in four. While no tools came from inside the structure, a GBS
point and a flake tool were recovered from just outside to the south, as was the majority of the
almost 600 bone fragments recovered. Construction of the modern road removed the cultural
deposits located more than a meter south of the structure. Four small bone concentrations were
found inside the structure. A small piece of Opal CT was found in the bone fragment
concentration. Several pieces of burned daub were found inside the structure.
Feature 3, northeast of the structure, is a small two-lobed concentration of small
fragments of quartzite debitage. The two lobes of the concentration indicate two different
chipping positions used by one or more knappers.
34
Archaeological Artifacts Points. One projectile point (Figure 15-B) was recovered from the surface of the excavated area
of Rood Block. A brown chert midsection shows edge grinding above the lower break. The
Figure 15.The projectile points from Rood Block and nearby concentration. A is a Folsom point base found in the southern concentration. B is a broken GBS projectile point found within the Rood excavation block.
midsection expands above the stem. A second projectile point (Figure 15-A) is a gray quartzite
Folsom base found on the surface of the southernmost surface concentration. Both sides of the
point are fluted and both edges are ground.
Bifaces.
All bifaces and biface fragments found are made of quartzite (Figure 16). No biface
fragments were recovered from inside the structure. Most of the excavated biface fragments
came from around Feature 1 (Figure 13) as did several large biface/cores (Figure 17).
35
Figure 16. Bifaces from Rood Block and nearby concentrations. Three far left specimens came from Feature 1. The two artifacts at the top on the right side of photo are from the surface collection near Rood Block. The bottom four artifacts on the right are from Rood Block.
36
Figure 17. Biface cores from Rood Block.
37
Figure 18. A large retouched flake from Rood Block.
Flake Tools. Several flake tools or retouched flakes were recovered from the excavations and intensive
surface collections (Figure 13). Most of these flake tools are cutting or slicing tools (Figure 19).
One large, thick, red-chert end scraper (Figure 19, bottom) was recovered a dozen meters
northeast of the excavations. Most of the end scrapers found in all time periods in the UGB are
made of chert.
Debitage. Debitage was the most common artifact type found on Rood Block, as it is on most sites
in the area. Over the various field schools almost 5000 pieces of debitage were recovered from
38
Rood Block. Blade technology is represented in the Block (Figure 20). Blade technology has also
been found in Block A, a Folsom lithic workshop, even though it is usually associated with
Clovis.
Figure 19. Flake Tools from Rood Block and vicinity. Top row- graver; retouched edge; retouched edge. Bottom row-end scraper.
Table 2. Debitage frequencies over time at Rood Block.
Year Quartzite Chert Total
1994/1995 108 - 108
2016 1293 33 1326
2017 1988 106 2094
2018 1353 51 1404
Total 4742 190 4932
39
Figure 20. Refit blade technology from Rood Block. Platforms are to top and left.
The vast majority (96.15%) of the debitage recovered from Rood Block was quartzite.
The debitage from other Younger Dryas aged occupations on Mountaineer have been much
lower. This ratio is thought to be important in understanding the occupants’ settlement patterns
because there are many available quartzite sources nearby. Chert on the other hand, comes from
a greater distance away, more on the margins of the Basin. The Rood Block quartzite-to-chert
ratio is much closer to what is found on Archaic-aged occupations. It is probable that the high
percentage of quartzite is related to the season of occupation and whence the occupants moved
prior to occupying Rood.
40
Welded Tuff Flakes.
In the original site recording in 1994, field archaeologists were impressed with the
welded tuff outcrops on Mountaineer that might have been used as a prehistoric lithic material
source. On the original site form, it is stated that the surface artifacts consist mainly of welded
tuff. However, Rood (et al. 1995) concluded that the welded tuff was not obviously worked by
knappers and most locations that have a lot of exposed broken welded tuff are also locations of
modern heavy equipment use. Since then a few undoubted artifacts of welded-tuff have been
found. Further study has concluded that welded tuff could be used for some purposes, but overall
there is little evidence of intentional use and no evidence of systematic use.
Caliche coating Numerous artifacts recovered from the excavation on Rood Block have a caliche coating.
This coating is found on artifacts from all the other early occupations on Mountaineer. The
caliche also formed on the nearby Tenderfoot Site where it coated the lower half of rock slabs
used in Archaic firepits sometime after their last use at 6300 RYBP. Again this is consistent
with our suggested period of use in the Younger Dryas.
Bone. Faunal remains from the site were examined by Ronald J. Rood. No bone was
identifiable to genus or element. The 482 bone fragments recovered appear to be remains from
heavy processing of bones from large mammals; they were concentrated on the south side of the
structure with several small concentrations found inside the structure.
41
Table 2. Bone fragments recovered by field school.
Year Bone fragment count
1994, 1995 -
2016 144
2017 263
2018 175
Total 482
Dating. A high priority of our work was to obtain datable material to indicate when Rood Block
was occupied. We had anticipated that we would use radiocarbon dating to analyze bone
collagen. From Block A, we obtained very precise dates using ribs and a bison tibia. According
to Dr. Thomas Stafford, who processed those samples, the collagen was extremely well-
preserved. Since those samples were run, we have submitted several bone samples from different
excavation blocks to several labs for dating and none have yielded the necessary collagen. We
have discussed the possible reasons for the recent failure of our samples to return collagen with
scientists at several radiocarbon labs, who most commonly suggested that an agent of collagen
destruction was heat, probably from cooking.
The first bone samples that yielded dates came from a lithic workshop in Block A. One
sample came from one of several large-mammal rib fragments that was approximately 7 cm
long. These rib fragments were found near a stone anvil and chopper. Binford (1978:152)
describes how the Nunamiut break fresh uncooked caribou ribs into short segments in
preparation for “rib sucking.” Frozen or dried ribs reportedly acquired an unpleasant sour taste.
42
The second dating sample from Block A came from a large bison tibia fragment that was
against the back wall of the lithic workshop in an area with several small lithic flake tools, such
as a drill and graver. When found, the tibia was abutting a bison phalanx. The other bones found
in this area are probably post-depositional splinters from the tibia. The tibia and the phalanx are
not cooked food remains; they are technological remains. Dr. Phil R. Geib (personal
communication) indicated he uses similar bones in flint knapping.
By luck apparently, the first bone radiocarbon samples we submitted happened to have
the best collagen preservation. Most of the faunal remains we found are highly processed large
mammal bone. Future sampling for bone should look to dumps, butchering locations, and craft
locations. Even though our most recent bone radiocarbon results are disappointing, we did learn
something about the formation processes at the site. And while not as secure or accurate as
radiocarbon dating, we now have found artifacts that place some of the occupation between
10,900 and 10,200 RYBP.
The finding of Folsom points and GBS points in what appears to be contemporaneous
occupations on Rood Block is consistent with earlier findings on Mountaineer of fluted points
and GBS points from a single structure (Block G). Within the desert west, the temporal
placement of GBS projectile points is complicated by a lack of artifacts from securely dated
contexts and a lack of consistency in defining terminology. The GBS points without any context
from Mountaineer could be classified individually with any number of names, such as, “Jay”,
“Bajada”, “Rio Grande”, “Windust”, and perhaps “Hell Gap(ish).”
Finding the temporal placement of this distinctive style will rely on more and better-dated
samples from tight contexts such as the interior of structures. Although it is currently without
radiocarbon support, Rood Block has produced and will produce artifact assemblages important
43
to better understanding of Colorado prehistory specifically, as well as to the temporal placement
and social relationship between GBS-point and fluted-point makers in the Great Basin and the
Southwest.
Conclusions Rood Block represents prehistoric occupation during the Younger Dryas. The
structure was used as a residence for a small group, perhaps a nuclear family. The structure
sheltered some lithic reduction, and food preparation/consumption of large mammals with nearly
complete processing of the bone. While some minor technological manufacturing and
maintenance remains were found inside the structure, early stages of lithic biface tool
manufacturing and maintenance took place outside, one to two meters from the structure. The
presence of several outside activity areas indicates that the weather during occupation was not
inclement but was conducive to outside activities.
The plan view of the excavated structure in Rood Block compares closely with numerous
Arctic ethnographic (Reinhardt and Reinhardt 2003) and !Kung ethnoarchaeological (Yellen
1978) examples. Furthermore, the distribution patterns within the outside activity areas are quite
close to patterns produced in an important experimental archaeological example (Bowers et al
1978).
44
References Cited Andrews, B., D.J. Meltzer, and M Stiger, Editors 2019 Mountaineer Volume in progress. University Press of Colorado: Boulder. Armstrong, D. M. 1972. Distribution of Mammals in Colorado. Monograph University of Kansas Museum of Natural History 3: 1-415. Barrell, J. 1969. Flora of the Gunnison Basin. Natural Land Institute, Rockford, Illinois. Binford, LR 1978 Nunimiut Ethnoarchaeology. Academic Press:New York. Binford, LR 1983 In Pursuit of the Past. Thames and Hudson: London. Crown, S 2016 Excavation of Block H, the Mountaineer site. Report on file with Colorado State Archaeologist’s Office. Diggle, PJ 1983 Statistical Analysis of Spatial Patterns. Academic Press: New York. --- 2014 Statistical Analysis of Spatial and Spatio-Temporal Patterns. Third Edition. CRC Press: Lancaster. Emslie, S. D. 1986. Late Pleistocene vertebrates from Gunnison County, Colorado. Journal of Paleontology 60 (1): 170-176. Euler, R. R. and M. Stiger. 1978. Test excavations at five archaeological sites in Curecanti National Recreational Area, Intermountain Colorado. Report on file, National Park Service, Midwest Archaeological Center, Lincoln. Feller, W 1971 An Introduction to Probability Theory and its Applications. Volume 1. John Wiley and Sons: New York. Huffman, S 2015 Excavation of Block H, the Mountaineer site. Report on file with Colorado State Archaeologist’s Office. Nash, D. T. 1987. Archaeological investigations at Haystack Cave, central Colorado. Current Research in the Pleistocene 4: 114-116.
45
Pope, MC and RA Greubel 1994 Cultural Resource Inventory of the Cellular One Utility Line and Archaeological Monitoring of the Cellular One Cellular Site on Tenderfoot Mountain, Gunnison, Colorado. Alpine Archaeological Consultants. Rood, R. J. 1996. Archaeological excavations at 5GN2478, Elk Creek Village, Curecanti National Recreation Area, Gunnison County, Colorado. Report on file, Dept. of Anthropology, Western Colorado University, Gunnison, Colorado.
Rood, RJ, D Callihan, CD Dukeman, and M Stiger 1995 Archaeological testing at 5GN2477: Gunnison County, Colorado. Report on file Department of Anthropology Western Colorado University, Gunnison, Colorado. Schiffer, M 1987 Formation Processes of the Archaeological Record. University of New Mexico Press: Albuquerque. Stiger, M. 1980. Altithermal adaptations in Curecanti National Recreation Area, Colorado. In Proceedings of the Conference on Scientific Research in the National Parks , edited by National Park Service, pp. 316-323. National Park Service, Washington, DC. --- 1993. Archaeological investigations at the Tenderfoot Site. Western Colorado University, Gunnison, Colorado. --- 2001. Hunter-Gatherer Archaeology of the Colorado High Country. University Press of Colorado, Boulder. --- 2005. The Excavation of Block B, Summer 2002. The Mountaineer Site 5GN2477. Report to Colorado State Historic Fund. --- 1986 Technological Organization and Spatial Structure in the Archaeological Record. Unpublished dissertation. Department of Anthropology, University of New Mexico: Albuquerque. --- 2018 Block F. MS for volume on Mountaineer. Edited by Brian Andrews. --- 2018 Block A. MS for volume on Mountaineer. Edited by Brian Andrews. --- 2018 Early Prehistory in the Southern Rocky Mountains. Chapter 10 in Archaic Prehistory of the Southwest. Edited by Brad Vierra. University of Utah Press: Salt Lake. Vandenbusche, D 1980 The Gunnison Country. B&B Printers:Gunnison. Woodbury, A. M. et al. 1962. Ecological studies of the flora and fauna of the Curecanti Reservoir Basins, western Colorado. Univ. of Utah Anthropological Papers No. 59: 1-285.
46
Appendix A. Site Formation Processes
Spatial analysis was conducted in order to understand the cultural and natural formation
processes on site. The prehistoric human activities of interest across the Mountaineer site formed
archaeological deposits on two different living surfaces, the ground surface at the time of the
activity and a cultural surface (or floor of a structure) excavated into that ground surface. We
expect that archaeological deposits on the Mountaineer site have been subjected to numerous
natural post-occupation formation processes such as, downslope movement; wind; insects;
rodents; vegetation; fire; and caliche formation with minor impact on the artifacts and
distributions. However, frost heave and modern construction on the site have contributed much
more post-occupational disturbance to the spatial patterning of artifacts.
A combination of natural formation processes might move artifacts deposited on the
natural prehistoric ground surface differently than those same processes move artifacts deposited
on an artificial, culturally constructed surface, such as the floor of a pit structure excavated into
sterile deposits (Eckerle et al. 2011). The mode of floor construction, in part, will determine
artifact deposition inside the structure. Floors that are hard-packed earth, loose sediment,
vegetation, snow, or hides will each be cleaned differently and leave behind different spatial
patterns of archaeological remains.
Floors of snow permitted the occupants of ethnoarchaeological Inuit winter structures to
purposefully dispose of trash into and through the floor and for small trash items to incidentally
work their way down into the snow. This “vertical trash disposal” was used in place of a trash
dump (Savelle 1984). Informants reported periodically adding a new layer of snow above the
old to provide a clean floor. As a result Savelle (1984:521) notes, these ethnographic Inuit
winter houses show a much greater concentration of trash inside structures than outside. Floors
of loose sediment or vegetation would also allow or result in “vertical trash disposal.”
Human activities during occupation may trample artifacts into a floor or surface
depending on the different kinds of floor or surface (Eckerle et al. 2011). Furthermore, across a
large site like Mountaineer, structures and hearths have focused prehistoric human activities both
inside and outside to create bound and unbound trample zones. Trample zones might also be
created by activities that are focused in space but not bound to a hearth [an unbound, unbounded,
trample zone]. On soft floors of loose sediment or vegetation, bounded trample zones, or activity
areas inside structures, create thicker floor deposits due to longer and more intense use.
47
Unbounded trample zones, or outside activity areas, may be horizontally more extensive than an
entire structure, but they may also be as small as the space it takes for one person to do a task.
Occupational trampling (Eckerle et al. 2011) can help preserve evidence of activity areas
but trampling across sites and reoccupation of sites as described by Ascher (1968) for the Seri,
can damage the spatial association of earlier materials. It is prudent to suspect some mixing of
artifacts from different levels on lithic scatters; however, the Mountaineer site surface artifact
distribution suggests that inter-occupation mixing is relatively less compared to other studied
lithic scatters.
On Mountaineer, the pace and pattern of occupation and reoccupation is slow and large
compared to that of the nearby Tenderfoot site (Stiger 2001). Surface collections made on both
sites with similar methods show two very different artifact distributions. On Mountaineer
numerous isolated small aggregations of artifacts, about 10 m-15 m in diameter were found
while on Tenderfoot surface collections showed the site was a large complex spatial aggregation
of artifacts with many small high-density areas. Comparable block excavations on both sites
show a high number of differently-dated, yet adjacent-structures on Tenderfoot, while on
Mountaineer structures are horizontally much farther apart yet likely contemporaneously
occupied. There is no evidence of re-occupation of structures (multiple floors or remodeling) or
superimposed structures on either site, but occupations marked by surface artifact aggregations
on the Mountaineer site are likely to be relatively untrammeled by post-occupation human foot
traffic from later prehistoric residential use of the site (Ascher 1968).
Minor Post-Occupation Formation Processes
Downslope Movement
Downslope artifact movement is documented on artifact scatters located on surfaces
sloped between 44◦ and 10◦ (Rick 1976). The Mountaineer site does have some sloping areas but
the excavation blocks are all on very level terrain that have less than 5% slope. Still there
probably has been some relatively insignificant downslope movement of surface artifacts.
Wind
At two meters above the ground, the wind can blow across the site at 60 mph. At ground
level the wind velocity is considerable less. The upper 5-10 cm of sediment is loose and
unconsolidated silt and welded-tuff bedrock fragment mulch with a thin mantle of low, sparse
48
vegetation. Small artifacts (<1 cm) can easily disappear if dropped on the modern ground
surface thus be sheltered from movement by the wind. Larger artifacts resist movement by the
wind. “It is very rare for any particles bigger than sand size (2 mm) to be moved by wind across
a rough surface. Particles between 2 mm and 0.05 mm generally move by saltation, while
particles less than 0.05 mm travel in suspension…” (Paton 1978:66-67). To mitigate against the
effect of wind-created artifact aggregations in eddies downwind of structures on Mountaineer, all
excavated fill was water-screened through 1/8” mesh catching artifacts approximately 3 mm and
larger and allowing smaller artifacts which are most likely to have been moved by the wind, to
pass through. Assemblages excavated with these methods are also more comparable to the
material to the Early Archaic archaeological collections from the Tenderfoot site (Stiger 2001).
Dial (1994) found size-sorted lithic artifacts on a lithic scatter site in Curecanti National
Recreation Area, 30 km west of Mountaineer. After exhaustive research she argues that this
sorted assemblage was produced by the combination of three natural post-occupational
processes, slope, wind, and runoff from precipitation. In this specific example, any one single
process might not have been sufficient to move artifacts. However, each process adds its effect
to the effect of the other processes and produces a sorted non-random distribution.
Insects and Rodents
The remains of insects and rodents have been discovered in the excavations on
Mountaineer. Ants still occupy the site. Some varieties of ants can move very small artifacts
and aggregate them at their nests (Schoville et al. 2009). Examination and incidental excavation
of several such nests on Mountaineer has shown no concentration of artifacts. Thousands of the
exoskeletons of the Uinta strawberry root weevil were found in the fill of Folsom structures on
the site. The weevil no longer lives in the UGB but it does persist 100 km west, where it migrates
each fall into cellars and basements. The weevils’ presence in considerable numbers on
Mountaineer may show that even post-occupation, the structures were still subterranean enough
to be attractive to these overwintering insects. The carapace of the insect is brittle and many of
them are intact suggesting little post-occupation trampling and crushing at least since the insects’
occupation of the structures.
Rodent skeletal remains were encountered in the Mountaineer excavations. Most are
likely post-occupational and likely show that the structures, once abandoned by people, provided
homes to rodents. During excavation, if complete rodent skeletons were encountered they were
49
considered borrow deaths and recorded in notes. Rodent burrows were mapped when observed.
During sorting of washed sediment samples only rodent skulls and long-bones were removed
once it appeared a nearly complete rodent had been present. Most rodent remains were not
identified, but modern species on site include ground squirrels and microtines or voles. While
the ground squirrels do destructive borrowing in archaeological deposits, voles are relatively
benign and do not construct large and deep burrows that squirrels are wont to do.
Vegetation, Fires, and Caliche
A burned tree stump were observed and mapped during excavations of Rood Block. This
natural feature was distinguished from cultural post holes by having an irregular outline and
profile and by having a large out-of-place rock on its margin. A caliche coating on the side and
top surface but not the bottom surface of the rock showed that the rock had been moved since
caliche formation. Caliche formed naturally on the bottom of rocks embedded in the ground
surface of Mountaineer and other sites in the UGB. On the Tenderfoot site, located 2.5 km from
Mountaineer, what appears to be the same caliche formation was found coating the lower half of
in situ slabs used to build Early Archaic fire pits radiocarbon dated to ~6000 RYBP (Stiger
2001). These observations argue that the rocks on Mountaineer were first embedded in the
ground prior to caliche formation. At some time after 6000 RYBP caliche formed on the
underside of rocks. After caliche formation, trees grew on site and as they grew they reoriented
the stones near the expanding trunk. Upturned caliche-covered bottoms of stones showed the
disturbance. The trees burned at a later time which is confirmed by radiocarbon dating, the
burned tree stumps, and by the spatially associated burned-caliche-coated Folsom artifacts and
rock.
The Mid-Holocene burning of later intrusive trees that grew inside structures also acted
to dry and further preserve daub that was buried nearby in the fill. Similar to what is found on
much later Southwestern Ancestral Pueblo structures, post-occupation burning of intrusive
vegetation can help preserve archaeological daub and mud plaster, if the fire does not burn too
hot vitrifying the daub.
The burning of the post-occupation vegetation contributed charcoal and ash to rotted
vegetation in the structure fill. This organic material appears to have contributed humic acid to
the sediment which contaminated the collagen of the Folsom-aged faunal material. All four
AMS radiocarbon samples for which the collagen gelatin was filtered with XRD resin yielded
50
ages that were consistent with other known Folsom dates. Three of the four specimens that were
not treated were 500 to 1000 years too young.
Major Natural Post-Occupation Formation Processes
Expansion/Contraction of Sediment from Frost heave/Heat/Saturation
Archaeologists working in the Southern Rocky Mountains have been acutely aware of the
effect of frost processes on archaeological material since the publication of the landmark
research on high-elevation archaeological sites south of Rocky Mountain National Park
(Benedict and Olson 1978) and at the summit of Vail Pass (Gooding 1981). Both of these
reports carefully document the effect of the location, high in the Colorado mountains, on the
natural erosion and deposition after occupation. In particular, a striking plot of the vertical
distribution of artifacts on the Hungry Whistler site (Benedict 1978:43, Figure 36) showed that
the majority of tools were found on the modern ground surface. This graphic (see Figure A-1)
became well-known as it was used in the influential and reprinted chapter on formation processes
by Wood and Johnson (1978:342) and in the textbook, Principles of Geoarchaeology (Waters
1992:297). All these discussions recognize the potential for natural processes to alter the vertical
distributions of artifacts on sites susceptible to frost heave. However, even this textbook
example of frost heave, on what Benedict called “probably the most frost-disturbed site in the
world” (p.c. cited in Johnson et al. 1977:146), greatly overemphasizes the resulting disturbance.
Figure A-1. The distribution of artifacts by level on the Hungry Whistler Site (after Benedict and Olson 1978:43).
51
Benedict’s Figure 36 is a bar graph of the percentage frequencies of four different artifact
types6 by nine levels (eight 2.5 cm excavation levels and the surface) on the Hungry Whistler
site. It shows that 64.4% of the large butchering tools and 68.2% of the grinding tool fragments
were found on the modern surface and the rest were found in a low normal curve centered about
10 to 15 cm depth. He notes the two largest artifact types are nearly absent in the upper
excavation levels down to about 5 cm below modern ground surface. While most of the small
flakes and projectile points were found spread across the eight excavated levels, 13.7% and
28.6% were found on the ground surface. Benedict (1978:42-44) acknowledges problems with
the data for the graph but nevertheless interprets the patterning as representing frost heave
preferentially affecting larger items. Recognizing the top sediment levels are subject to more
diurnal and rapid changes in temperature and moisture, he attributes the absence of large artifacts
in the upper excavation levels to artifacts entering from deeper burial by frost heave and “the rate
of upfreezing rapidly accelerates dramatically, leading to rapid ejection at the ground surface.”
Clearly, Benedict (1978:44) is aware of “the fact that a larger sector of the terrace was
surface-collected than was excavated overemphasizes the ejection of artifacts at the ground
surface.” The assemblage descriptions (Benedict 1978:47-70) and the distribution maps
(Benedict 1978:20) indicate there were perhaps two pieces of ground stone and only one
butchering tool on the surface in the excavated area7. Considering only the surface artifacts
collected from the excavation area would revise the surface percentage of the butchering tools to
7.7% and of the grinding tool fragments to 5.5%. While the potential for frost-heave of artifacts
is undeniable on archaeological sites in temperate locales, Benedict’s data indicate that at 3500
m elevation in the Southern Rocky Mountains, a few artifacts only moved vertically 15-20 cm
maximum in over 5000 radiocarbon years. This seemingly minor amount would make
microstratigraphic analysis and the separation of multiple occupation levels difficult if not
impossible, had they been present8, but it would be an overstatement to suggest most artifacts in
6 Benedict’s four types, “flakes”, “projectile points”, “butchering tools”, and “grinding tool fragments”, sort in order from small to large as measured by mean weight, mean length, and mean thickness. 7 Benedict does not report the surface flake counts of excavated areas. All 49 projectile points for which levels are shown in Benedict 1978, figure 36 are shown on maps as coming from excavated areas. 8 While 40 of the 49 projectile points recovered at the site are considered Mt. Albion Corner-notched points, 14.3% (N=9) are considered to be one of four or five other styles (Benedict 1978:47-53) perhaps indicating multiple occupations on site. Radiocarbon dated features indicate multiple occupations are highly probable.
52
mountain archaeological assemblages have been rapidly ejected from the subsurface deposits to
lay on the ground surface.
Even without the augmented the tool counts, the vertical distribution of Hungry Whistler
artifacts still shows evidence of significant frost heave modification. Additionally, Olson
(1978:95) presents vertical distribution data on a second lithic scatter site (5BL70) located near
the Hungry Whistler site that also supports the hypothesis that frost heave moves artifacts
upward from buried living surfaces. Olson (1978:94-96) further asserts that evidence indicates
stone artifacts 6 cm or less in length and weighing less than 100 gm are more affected by frost
heave than larger artifacts.
Excavations elsewhere in the Southwest, showed that larger artifacts tend to be higher in
the deposit. Vertical size-sorting of artifacts in the fill of early single-occupation pit structures
has been reported before (Stiger 1986:263-264) and has been generally attributed to compression
and expansion of sediment at different water saturation and temperature. However, trash
disposal of larger items out the door of a pit structure could bias the vertical size distribution if it
was examined in only these two dimensions.
The plot of artifact counts by 5 cm level for all of Block A on Mountaineer show a few
artifacts on the surface, the highest count in level 1, and slowly declining counts until about level
8 where the counts decline quickly to just a trace. Seven-hundred refitting artifact pieces from
Block A were vertically distributed similar to the distribution of all artifacts by level except
considerably more refits were found on the surface of the Block. The explanation for the high
frequency of refits on the surface may be that larger artifacts, which are pushed to the surface by
frost heave, are also easier to refit; or perhaps large pieces of trash were thrown out the door of a
pit structure where they remained near the surface. Nevertheless, several of the refitting
sequences from the production of large bifaces are made from flakes found in different levels
from surface to 50 cm below. The wide vertical distribution of refitting flakes indicates
significant post-depositional vertical movement of artifacts in structure fill (Villa 1982).
Apparently the material that was on the floor of the structure at abandonment was vertically
displaced during infilling and afterwards by frost heave. As the fill accumulated from aeolian
and other minor processes, it was not as packed as the “native” sediment which might have
allowed more vertical movement by frost heave. On Mountaineer the stratigraphic position of
53
artifacts, including the modern ground surface, tells very little about relative age and justifies
analyses of artifact distributions after collapsing all levels into one.
Basketmaker and early Pueblo pit structure excavations in southwest Colorado are
commonly conducted by removing structure fill in two vertical levels. The upper excavation
level begins at the ground surface and terminates 10 cm above the floor. The second level, often
termed “floor fill,” begins 10 cm above the floor and continues to the floor. Often the upper
level of sediment is removed with relatively expedient methods including forgoing screening and
using heavy equipment. The reasoning behind this strategy is that material recovered from the
upper level would be the remains of trash thrown or washed in at some post-occupational time
and hence, unimportant. Much more careful techniques are used on the material excavated from
the “floor fill” which is considered to be more relevant to the occupation of the structure. On
Mountaineer, there is no evidence of later materials in the fill of the structure and the refit
artifacts show vertical movement of up to 50 cm which may be a product of an additional 8,500
years of frost heave and possibly the product of the harder packed floors of Basketmaker and
Pueblo pit structures.
Frost heave complicates making inferences from the stratigraphic position of artifacts.
Likewise, several researchers have warned of the potential complication of frost-action on
surface artifact distributions (Bowers et al. 1978, Hilton 2003). These researchers working in
different parts of Alaska found apparent significant horizontal movement of replica lithic
artifacts placed on the ground after only three years of exposure to the elements. The importance
of these findings is that they show surface assemblages are not necessarily spatially static and
stable but they can be dynamic. These researchers urge extreme caution when interpreting
artifact spatial distributions in areas where freezing occurs, because the pattern of surface
artifacts at site abandonment may have been re-arranged by frost processes (Bowers et al.
1983:568; Hilton 2003:199). However, confounded variables and short-term observations of
these studies complicate any direct application of these warnings to Mountaineer. For example,
Hilton (2003) distributed his “artifacts” across an area with a slope of 12.5% which makes the
artifacts more susceptible to movement by wind and rain (Rick 1976:139), and frost heave. The
Mountaineer site is much more level with a slope of approximately 3%, hence artifacts on the
surface should be less susceptible to other movement processes.
54
Other things equal, movement from frost action is dependent on soil moisture and cold
temperatures. The environment of the Mountaineer site is very dry, receiving around 15 cm of
annual precipitation. In 2001, it was unclear how this might affect artifact movement from frost
processes, so 200 numbered aluminum tags were placed as “artifacts” on the Mountaineer site in
2001. These tags were mapped with a total station over a period of eight years to study natural
processes that move surface artifacts. The “artifacts” were round and identical except for a
stamped sequential number which obviated a couple of extraneous variables of earlier formation
studies. The shape and size of an artifact can influence how and when it is moved by freeze-
thaw, wind, or water. By eliminating variability in size and shape, the annual natural movement
of artifacts on the surface can be better described and the movement process itself defined.
Within the first two weeks of their placement, on average the tags moved very short (~2.5
cm) distances. By late summer to early fall, the tags had moved again. In the next year, the tags
moved several times. From then on, the tags moved annually the same mean distance which was
approximately (+/- 0.02 mm) the diameter of the tags. The consistency in the mean annual
distance moved, no matter what direction or when, shows some mechanical factor is at work.
The fact that the tags moved by increments or steps that equal their diameter is evidence that the
tags are moved by having one side lifted until the tag is vertical. From there tags sink into the
sediment and become buried or they eventually fall over, moving horizontally one diameter from
where they were. This model of surface artifact movement accounts for the Mountaineer data,
specifically the high frequency of upright and leaning tags and the mean annual movement equal
to the diameter of the tag. Hilton’s (2003) explanation of similar artifact movement data is that
needle ice lifts artifacts as it grows upward. At some point the ice collapses, dropping the tag to
the ground. Needle ice has been observed in the Mountaineer area. Perhaps it could lift rocks or
artifacts in some circumstances, but the collapse of an ice structure holding aloft a tag, resulting
in the tag coming to rest vertically is possible, but improbable as is the average annual movement
being equal to the artifacts’ diameter. No artifact or tag lifted by needle ice has been observed
on the Mountaineer site.
55
Table 3. The movement of tag "artifacts" on the Mountaineer site.
Date of Mapping
Days Since Last Tally
Average Movement
from Origin (meters)
Days Elapsed
Since Initial
Number of tags
missing
5/22/2001 0 0 0 0
6/5/2001 14 0.025654 14 6
6/19/2001 14 0.027012 28 6
9/22/2001 95 0.052827 123 19
6/5/2002 256 0.059133 379 17
7/12/2002 37 0.082401 416 17
10/2/2002 82 0.126933 498 25
7/3/2003 274 0.134559 772 27
6/27/2004 360 0.140695 1132 32
8/6/2005 405 0.152556 1537 40
9/17/2006 407 0.163037 1944 44
7/29/2007 315 0.160646 2259 45
7/19/2008 356 0.168569 2615 44
A second important observation from the Mountaineer tag study, is that some of the
“artifacts” began to move into the sediment within the first year with approximately 12
additional tags becoming partially buried each year thereafter. While most tags once buried
remained buried, a few tags disappeared for a few years only to reappear near where they had
earlier disappeared. One tag that had been completely buried by natural processes was excavated
2 cm horizontally and 3 cm vertically from where it had been placed on the surface years earlier.
This vertical movement of artifacts into and out of the sediment has been documented numerous
times, but perhaps the most relevant is the extensive surface collection analysis on the
Tenderfoot site located 2.5 km west of Mountaineer (Stiger 2001:117-128).
The nearby Tenderfoot site is a large lithic scatter that was completely surface collected
several times and excavated over 10 years. Within a short period after each complete surface
collection had mapped and removed all visible artifacts, more artifacts became exposed by
natural processes which favored the movement of some artifacts to the surface (Stiger 2001:123).
56
These studies concur with Bowers et al. (1978) and Hilton (2003) that the surface of the
ground and the artifacts that rest upon it can be mobile vertically and horizontally. It seems
doubtful that all the artifacts on the Mountaineer site have remained in place over 10,400
radiocarbon years, however, the evidence from the long-term on-site tag study shows that the
average horizontal movement of artifacts due to frost heave is much less than one might fear,
especially with the relatively fast burial of most tags. Vertical movement of artifacts is perhaps a
greater disturbance with which to reckon, but the apparent lack of reoccupation of the structure
allows for meaningful analysis of collapsed levels.
Modern Construction Activities
Without a doubt, modern construction activities have had a great adverse impact on the
archaeological deposits on Mountaineer. Two bladed roads were constructed through Rood
Block. Off-road vehicles have driven through the site in several places. Broken glass bottles
were removed from Rood Block during excavation. Plans to improve the road and expand
damage to the site herald more future problems.
57
Appendix B. Recognizing the effect of spatial processes In an ethnoarchaeological study of cultural spatial processes, Binford (1978) documented numerous ways cultural material becomes arranged as it enters the archaeological record, e.g., by being dropped, dumped, placed, and tossed. These depositional processes can produce artifact distributions that can be described on a continuous scale from aggregation to dispersion. For example, a seated-activity area used repeatedly may be represented by a concentration of debris at that location. Conversely, if large debris is messy or dangerous it might be tossed and archaeologically represented by dispersed large items away from the area where they were generated or used. Seated-activity drop zones and dump zones are created by activities that aggregate items on a site. Seated activities that generate debris can take place inside a structure or outside, but dumping and tossing debris was probably done outside.
Toss zones and extensive activity areas, such as large mammal butchering areas (Binford 1983:166-167) were formed by actions that tended to disperse items out and away from a central locus. Toss zones are often areas where larger items are selectively dispersed away from a seated-activity area. Extensive activity areas often are characterized by empty central regions encircled by rings of debris. These item-dispersing activities usually take place outdoors.
Aggregations of artifacts will be created in drop zones of activities that create artifacts such as knapping stone or breaking bones for marrow. These concentrations will likely be non-random clusters of artifacts within the total use area of an occupation on a site. Dispersing activities, such as cleaning up an aggregation of lithic debris or bone fragments and dumping it outside can leave artifacts across a broader area, having a randomizing effect on artifact distributions.
Similar to these cultural spatial processes, numerous natural processes also disperse artifacts into larger areas and act to randomize once aggregated distributions. Schiffer (1987) has pointed out the effect of many natural spatial processes in altering the location of archaeological material on sites and thus altering the potentially interpretable cultural spatial patterning. A few natural spatial processes, such as running water or wind, can create artifact aggregations from more dispersed artifact distributions. However, there is no evidence of either force playing a role in the distributions on Mountaineer.
In fact, most natural spatial processes act to diffuse artifact spatial distributions. For instance, undoubtedly freeze-thaw processes over millennia have moved Mountaineer artifacts. Yet, the artifact distributions in the blocks are highly aggregated as a population.
Understanding the causes of distributional patterning is obviously important to most archaeological spatial analyses. And the first step in a formal spatial analysis is usually a comparison of an observed distribution to a random distribution (Diggle 2014; 1983).
One of the better-known early spatial analyses is the evaluation of World War II German bomb hits in England (Feller 1971). As the bombardment of London continued unrelentingly and some neighborhoods received more hits than others, the public become concerned that German rockets were accurately and precisely hitting their intended targets. Using a gridded map of London the counts of bomb craters per grid square were compared to a Poisson distribution. A statistical analysis showed the clusters of bomb hits, as perceived by the public, were consistent with a Poisson distribution. The Poisson assumes the location of each event, such as a bomb hit, is
58
independent of every other event and each grid square is equally likely to receive an event such as a bomb hit (Feller 1971).
The probability model for the Poisson is represented by the equation:
Where 𝑃(𝑘)=e-λ λk k!
and k = number of items
Lambda (λ) is the mean number of occurrences per unit area. Thus it can be seen that the distribution is dependent on the total number of observations (bomb hits or artifacts in our context) and the area under consideration (crater field or archaeological site). As k, the number of items, increases to infinity the Poisson approximates the binomial distribution.
The excavation grid squares are convenient, providing the counts of artifacts per equal sized areas. For an excavation Block, the predicted number of grid squares with k objects is equal to the probability of k objects times the total number of grid squares. Likewise, contour maps of artifact counts per unit area are also contour maps of probabilities that the artifacts are not randomly distributed per the assumptions for Poisson. The mean count per grid square is the best predictor of a Poisson distribution. The mean and variance of a Poisson are equal. The standard deviation of a Poisson is the square root of the mean. The probability of an artifact count equaling the mean plus three times the standard deviation is approximately 0.0013.
Artifact distributions are described with contour plots of artifact counts. Contours are drawn at a base value of the mean and intervals of the standard deviation creating a probability map. As the number of grid squares and quads increases so will the numbers of rare events. Consequently, as the number of spatial-units increases above ~350-400, five standard deviations are mapped to isolate the rare but expected events.
For a simple, but formal, chi-square goodness-of-fit between archaeological and ethnographic artifact distributions and the Poisson distribution see Stiger 1986. Developed for use with data from extremely small camps and hunter-gatherer residential structures this iterative approach is labor intensive because it selectively removes the data from spatial units in a block that differ greatly from the predicted random distribution (specifically, high or low counts that were statistically significant at the 0.001 level) then it recalculates the chi-square value and repeats. Eventually, no more grid counts give statistically significant chi-square values and the process stops. At Mountaineer, the full iterative process is unnecessary to map virtually all of the statistically significant counts of debitage and bone because these counts decline abruptly from centers of high frequencies. For these artifacts, the highest counts are the least likely to have been caused by a random process.
