Occupation of the northern plains during the altithermal climatic episode

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Occupation of the northern plains during the altithermal climatic episode
Tate, Marcia J
Place of Publication:
Denver, CO
University of Colorado Denver
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vi, 96 leaves : illustrations ; 29 cm


Subjects / Keywords:
Anthropology, Prehistoric -- Middle West ( lcsh )
Prehistoric peoples -- Middle West ( lcsh )
Climatic changes -- Middle West ( lcsh )
Anthropology, Prehistoric ( fast )
Climatic changes ( fast )
Prehistoric peoples ( fast )
Middle West ( fast )
bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )


Includes bibliographical references (leaves 82-89).
Submitted in partial fulfillment of the requirements for the degree, Master of Arts, Department of Anthropology
Statement of Responsibility:
by Marcia J. Tate.

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|University of Colorado Denver
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Resource Identifier:
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LD1190.L43 1985m .T37 ( lcc )

Full Text
Marcia J. Tate
B.A., University of Colorado, 1975
A thesis submitted to the
Faculty of the Graduate School of the
University of Colorado in partial fulfillment
of the requirements for the degree of
Master of Arts
Department of Anthropology
! A!
r ,

This thesis for the Master of Arts degree by
Marcia J. Tate
has been approved for the
Department of
Robert E. Hinshaw

Tate, Marcia J. (Master of Arts, Anthropology)
Occupation of the Northern Plains during the Altithermal
Climatic Episode
Thesis directed by Assistant Professor Dennis J. DeSart
The problem of human occupation on the Northern
Plains during the Altithermal climatic episode has
concerned archaeologists for several decades. After
defining the Altithermal climatic episode and providing
a brief overview of the correlative cultural period,
the paper reviews the evolution of theory concerning
human adaptation on the Northern Plains and in its
peripheral areas during the Altithermal. Finally,
an examination of the existing archaeological record
for southwestern Wyoming provides insights into human
adaptation during the climatic episode in this portion
of the Northwestern Plains sub-area of the Northern
Plains. The evidence from southwestern Wyoming indicates
that the area was occupied during the Altithermal
but that occupation was restricted during severe erosional
episodes (droughts). The subsistence strategy for
the period was based upon collecting and small game
hunting with an emphasis on food storage technology
and no evidence for either bison or communal hunting.

I would like to thank my advisor, Dr. Dennis J. DeSart
and the other members of my committee, Drs. Lorna
G. Moore and Robert Hinshaw for their support and
Drs. Ann M. Johnson, H. Marie Wormington, and
James Grady opened their libraries to me, providing
otherwise inaccessible data and valuable advice.
Steven D. Creasman, Paul D. Friedman, Timothy
W. Burchett, and Jude Carino helped me to gather relevant
information, and also advised me on various aspects
of the paper. For this I am grateful.
Thanks are also extended to Powers Elevation and
Petroleum Information for four years of financial
support. Particularly, I am grateful to Dr. Bruce
E. Rippeteau, who encouraged me to undertake the project,
and to George Lapaseotes, who saw it to completion.
A great debt is owed my family for their love
and patience. Special thanks are due my daughter
Sara Roberts, who typed numerous drafts of the manuscript,
and my husband Bill, who in addition to providing
most of the graphics, actively encouraged and supported
me throughout the undertaking.

ACKNOWLEDGEMENTS................................ iv
LIST OF FIGURES...................................vii
INTRODUCTION............................ 1
The Altitherraal as a Climatic
Episode .............................. 5
The Altithermal as a Culture Period.. 7
Cultural Hiatus Theory................. 17
Non-Hiatus Theory...................... 19
Refugia Theories....................... 22
Environment of Southwestern Wyoming.. 36
Physiography and Geology............. 36
Soils................................ 43
Climate.............................. 44
Vegetation........................... 45
Wildlife............................. 47
Cultural Occupation of Southwestern
Wyoming: The Research Questions... 48

Cultural Occupation of Southwestern
Wyoming: The Archaeology Record... 50
IV. SUMMARY AND CONCLUSIONS................. 70
REFERENCES CITED................................. 82
APPENDIX........................................ 90

1 . Northern Plains Culture Area............... 3
2. Culture Chronology and Climatic Episodes.. 8
3. The Wyoming Basin........................ 37
4. Wyoming Physiography...................... 39
5. Graph of Radiocarbon Dates for
Southwestern Wyoming.................... 53

Chapter I
The problem of human occupation on the Northern
Plains during the Altithermal climatic episode has
long been a concern to scientists. In addition to
a long debate about whether or not the phenomenon
actually occurred, scientists from many disciplines
have attempted to describe the nature and causes of
the climatic change, to define its variability, intensity,
and extent, and to ascertain the kinds and amounts
of accompanying environmental changes, particularly
those changes in available water, and in vegetation
and faunal communities. Archaeologists and other
social scientists are interested in the effects of
such broad, environmental changes on humans and the
cultural changes human groups make in response to
changing environments. These adaptations concern
such aspects as the tolerance of human groups to given
environmental parameters, the triggering factors and
mechanisms for cultural change, and finally the manifes-
tations of change, as seen in subsistence practices
and settlement patterns, for example.

In response to Antevs1 (1 948, 1 955) proposal
of the Altithermal as a climatic episode and the corre-
lative climatic model of Bryson et al. (1970), archae-
ologists in the Northern Plains culture area are attempting
to describe the Altithermal as a culture period and,
by means of various theories, to explain the observed
human response to this climatic episode. The theories,
which have developed and evolved over the last several
decades, posit a cultural hiatus on the Northern Plains
during the Altithermal (Mulloy 195'4, 1958 and others),
a cultural non-hiatus (Reeves 1973), and the use of
mountain or ecotonal refugia (Wedel 1961; Hurt 1966,
Benedict and Olson 1978; Buchner 1980 and others).
These theories contain research questions,
implicit therein, some of which will provide a framework
for examining briefly the archaeological record of
southwestern Wyoming, as an example of cultural occupation
during the Altithermal episode. The area of southwestern
Wyoming was chosen for examination for two reasons.
First, as a sub-area of the Northwestern Plains, it
can be included in the Northern Plains culture area,
the subject of the present study. Second, there are
few areas, especially in the western portion of the
Northern Plains for which much information exists
about the Altithermal, either as a climatic episode

Figure 1. Northern Plains Culture Area (Adapted
from Wedel 1961: 23).

or a cultural period. There is a relatively greater
abundance of new information from southwestern Wyoming
on these topics as a result of recent investigations,
than from other areas of the Northern Plains. For
these reasons it is felt that the study of southwestern
Wyoming will yield information about the Altithermal
of relevance to the entire Northern Plains study unit.
Wedel (1961:22-23) has defined the Northern
Plains culture area as including southeastern Alberta;
southern Saskatchewan; southwestern Manitoba; North
and South Dakota; northern Nebraska; extreme southwestern
Minnesota and northwestern Iowa; and Montana, Wyoming
and the northernmost tier of Colorado, west to the
Rocky Mountains. He further noted that ethnologists
have traditionally defined the Plains more broadly,
extending its cultural limits nearly to the junction
of the Mississippi-Missouri rivers on the east and
beyond the Rockies into the Basin and Plateau regions
on the west. Wedel subdivides the Northern Plains
culture area into the Northeastern Periphery, the
Middle Missouri, and the Northwestern Plains (Figure
1 ) For purposes of this study a further definition
of the Northwestern Plains is useful. Mulloy's (1 958:8,9)
historical outline defined the Northwestern Plains
much as Wedel (1961) did later, to include the High
Plains and Missouri Plateau. This includes the eastern
portion of Wyoming. Frison (1978:2,5) includes all

of Wyoming in his description, which will be used
The Altithermal as a Climatic Episode
Based upon erosional and depositional cycles
seen in geological strata, Antevs (1948:76) proposed
that former environments of the American West be divided
into three climatic episodes. The dates used here
result from a later revision (Antevs 1955:328).
Anathermal 10,150-7500 years B.P. (ca. 8000-5500
Altithermal 7500-4000 years B.P. (ca. 5500-2000
Medithermal 4000 years B.P.-present (ca. 2000
Antev's (1955:317) dating procedure included
the study and climatic interpretation of beds and
geological features, assignment of the bed with the
human record to a particular regional climatic age
or phase, and correlation of the relative chronology
of the region with a dated climatic history. The
bracket dates Antevs assigned to the Altithermal episode
are based upon estimates of the rates of lake salinization
and Fries temperature graph.
Antevs (1948:76-80), described the Anathermal
as cooler and wetter than the present climate, with
temperatures gradually rising until the mid-Altithermal.
The Altithermal or "Long Drought" is interpreted as
warmer and drier than present conditions with, tempera-

tures, with gradually declining and moisture generally
increasing during the following Medithermal until
present climatic conditions were reached. He noted,
however, several climatic fluctuations, producing
droughts of lesser duration than the Altithermal "Long
Drought," during the Medithermal (Antevs 1955:330).
Other investigators who have observed these
major postglacial climatic fluctuations, have variously
referred to the phenomenon termed the "Altithermal"
by Antevs (1948) as the climatic.optimum (Sernander
1910), the xerothermic (Sears 1924), the thermal maximum
(Flint and Deevey 1951), the megathermal, and the
ipsothermico or hypsothermal (Deevey and Flint 1 957:182).
Chiarugi,. the Italian botanist proposed the terms
anathermal, hipsomothermal, and katathermal for post
glacial subdivisions in 1936, prior to Antev's suggestion
of the terms presently in use (Antev's 1955).
Antev's (1955:323) climatic model posits a
gradual increase in aridity and temperature during
postglacial times in central North America. The model
of Bryson and colleagues (Bryson et al. 1970:53-56)
by comparison, postulates non-gradual climatic change,
distinguishing a number of climatic episodes with
discernible boundaries. Their model provides a chronology
based on 620 radiocarbon dates found to be associated
with times of environmental change in several regions.
The terms used to define the various episodes are

borrowed from the European Blytt-Sernander sequence
(see Figure 2). Antev's (1955) Altithermal correlates
roughly to the four Atlantic sub-episodes (6500 -
2900 B.C.) of Bryson et al. (1970:63); its hypothesized
peak occurs in Late Atlantic II and early Atlantic
III times. The precise nature, dating, and variability
of the Altithermal and its correlative Atlantic climatic
episode are not presently well understood.
The Altithermal as a Culture Period
Mulloy (1958:219-221) developed the first
historical framework for the Northern Plains, dividing
the prehistory of the region into Early, Middle, and
Late Prehistoric periods with an Altithermal hiatus
between the Early and Middle Prehistoric (Table 1).
Reeves recently (1 983a: 36-37) revised the scheme as
follows. First, the Early Prehistoric period, dating
from 10,000 to 5500 B.C., includes the Clovis, Folsom,
and collective Plano complexes. Early Middle Prehistoric,
dating from 5500 to 1 500 B.C., has been expanded back
in time to cover Mulloy's Altithermal hiatus period,
and include the Mummy Cave, Bitterroot, Oxbow, and
McKean Complexes. The Late Middle Prehistoric, dating
from 1 500 B.C. to A.D. 200-700, is characterized by
such complexes as Pelican Lake, Besant, and Avonlea.
The Late Prehistoric period dates from A.D. 200-700
to 1725.


5000 BC 5000 BC

6000 BC ATLANTIC I 6000 BC
0000 BC

9000 BC 9000 BC
11,000 BC 11,000 BC
Figure 2. Cultural Chronology and Climatic Episodes (Adapted from
Mulloy 1958:219-221; Reeves 1983a:36-37; Frison 1978:83; Antevs 1955:324
and Bryson et al. 1970:63).

Frison (1978:83) has also recently revised
Mulloy!s original cultural outline. His version uses
the term Paleoindian to describe the Early Prehistoric
period. This is followed by the Early Plains Archaic,
dating from about 5500 to 3000 B.C. A Middle Plains
Archaic, dating from 3000 to 500 B.C., and a Late
Plains Archaic, dating from 500 B.C. to about A.D. 500,
follow. The Late Prehistoric, from about A.D. 500
to historic times, ends the prehistoric sequence.
Frison further subdivides the latter period to describe
a Proto-Historic time. While Reeves (1983a:1) and
others have criticized Frison's use of the term "Archaic"
to describe a temporal period rather than a cultural
stage, numerous regional overviews of the Northern
Plains (e.g., Beckes and Keyser 1983) find this scheme
useful. One of the clear-cut advantages of this organi-
zational framework is its direct correlation of a
cultural period, the Early Plains Archaic, to the
interval 7500 5000 B.P. (5500 3000 B.C.) of the
Altithermal climatic episode that appears to reflect
the duration of the episode's most marked effects
on the Northern Plains (Buchner 1980:43; Benedict
and Olson 1978). The Altithermal as a cultural period,
whether one clearly separates it from other cultural
periods as does Frison (Early Plains Archaic), or
subsumes it within a larger historical context as

does Reeves, is a poorly understood but undeniably
distinct cultural manifestation on the Northern Plains.
The Early Prehistoric or Paleoindian period,
preceding the Altithermal episode, is known generally
by a series of large, lanceolate projectile points
associated with the skeletal remains of large fauna
at kill and butchering sites. Based upon the archaeo-
logical record, lifeways changed little throughout
this period. Small groups practiced a hunting and
gathering economy based on large animals, particularly
mammoth early in the period, and bison, later in the
period. Hallmarks of the period on the plains are
the Clovis, Folsom and various piano complexes (Frison
1978:22-40). The appearance of milling stones late
in the period may indicate increasing reliance on
plant foods (Krieger 1964).
The culture period of the Altithermal, known
as the Early Middle Prehistoric or Early Plains Archaic,
developed on the Northern Plains at the end of the
Pleistocene, when with the extinction of numerous
large mammals, people adapted to a more varied hunting
and gathering subsistence pattern. However, bison
remained the focus of hunting activities throughout
the prehistoric era on the Northern Plains. Site
types dating to the period include camps and bison
kill and butchering stations. The beginning of the
period is marked by a change in projectile point styles

from lanceolate to side-notched types (Frison 1978:41).
The various sub-areas of the Northern Plains shared
a cultural homogeneity during the period, observed
most readily in a distinct, stone tool technological
tradition, which can be described in terms of cultural
complexes (Buchner 1980).
Sites dating to the Altithermal climatic episode
in and around the grasslands of the Northern Plains
are characterized by a large, side-notched atlatl
point variously termed Simonsen (Agogino and Frankforter
1960), Logan Creek (Kivett 1962), Mummy Cave (Reeves
1 969), Bitterroot, and Salmon River Side-notched (Swanson
1962). Those sites in the eastern grasslands are
found from central Manitoba to Kansas along the grasslands
edge. These are frequently grouped as a single cultural
manifestation and termed the Logan Creek complex (Buchner
1980). Similar manifestations distributed along the
eastern slope of the Rocky Mountains from Alberta
to Wyoming are termed Mummy Cave complex sites (Reeves
1969:30-31). The complex includes such side-notched
point types as Blackwater, Pahaska, Bitterroot, and
Salmon River. Among other western complexes relevant
to this study is Mount Albion, (Benedict and Olson
1978), recently defined on the basis of excavations
in the northern Colorado Front Range. The complex
appears to be similar to Mummy Cave complex in subsistence
and locational strategies.

According to Buchner (1980:133), Logan Creek
complex sites include Steeprock Lake and Swan River
(Gryba 1968) in Manitoba; the Itasca Bison Kill in
Minnesota; Simonsen (Agogino and Frankforter 1960),
Cherokee Sewer, and the Lungren site (Brown 1967)
in Iowa; Walth Bay (Ahler et al. 1974) and, Sitting
Crow (Neuman 1 964) in South Dakota; and the type site
(Kivett 1962) and Walker-Gilmore (Champe 1946) in
Nebraska, and others. Logan Creek complex sites are
located at the margins of the grasslands, in outliers
of forests, in major river valleys, or near other
perennial water. Buchner (1980) contends that the
sites are found in regions used only for winter camps
after the Altithermal period. He describes Logan
Creek camp sites as including features such as hearths,
post molds, and middens, and artifacts such as ground
stone, and bone fish hooks, reflecting relatively
extended occupations and diverse subsistence practices.
The hearths often contain dense concentrations of
B. occi-dentalis and occasionally B^ antiquus remains.
There are also diverse faunas and floras represented
at the sites. Deer, mole, birds, turtle, amphibians,
snails, clams, chokecherry, hackberry, wild plum,
hazlenuts, and acorns were all utilized, suggesting
occupations of several seasons' duration.
At the Lungren camp site in Iowa, investigators
found three features. The first was a midden containing

charcoal, broken and burned bone, bison mandibles,
and lithic flakes. Nearby, was a large concentration
of charcoal, bone, and bison teeth. The third feature
was a circular, basin-shaped fire pit, which was filled
with charcoal, ash, burned bones, and lithic debitage
(Brown 1967).
Mummy Cave complex components include Long
Creek and Oxbow Dam in Saskatchewan; the Gap site
and Head-Smashed-In (Reeves 1983b) in Alberta; and
Pretty Creek (Frison 1978), Kobold (Frison 1970),
Myers Hindman (Lahren 1976) and Sorenson (Husted 1969)
in Montana. In Wyoming, there are numerous sites
of this complex. These include the Shoreline, Hawken,
Laddie Creek, and Medicine Lodge sites (Frison 1978),
and Bentzen-Kaufmann (Grey 1962) and Hell Gap Loc. 2
(Haynes et al. 1 967), in addition to the type site
and several others (Buchner 1980:145-147).
The Mummy Cave complex sites are found in
mountainous regions at high elevations and also at
lower elevations in the foothills of the Rocky Mountains
(Reeves 1969). They include communal bison hunting
sites, such as the Head-Smashed-In buffalo jump (Reeves
1983b) and campsites, which are frequently rock shelters.
Generally the only features at Mummy Cave camps are
hearths, although there is rare evidence for habitation
structures (Buchner 1980). At the Shoreline site
in Wyoming, Frison (1978:44) reported remains interpreted

as pithouse features. Reeves (1969) has suggested
that the Mummy Cave sites represent seasonal use by
the same people.
The most complete radiocarbon-dated chronological
record from Early Plains Archaic occupations on the
western plains is found at the Mummy Cave site in
northwestern Wyoming (Wedel et al. 1968), a stratified,
multicomponent rock shelter where the record of human
occupations ranges from the late Paleoindian or Early
Prehistoric to Protohistoric times. At Mummy Cave,
a campsite used largely for mountain sheep hunting
(McCracken et al. 1978:24), investigators found numerous
hearths and a variety of faunal remains in the mid-Alti-
thermal occupations. In addition to mountain sheep,
these included water shrew, jack rabbit, beaver, dog
or coyote, deer, a variety of rodents, and Canada
goose (McCracken et al. 1978:149-150). Bison were
not present in the faunal record at the site. Investi-
gators, Wedel et al. (1968:184) noted an abrupt change
in projectile point styles from the lanceolate Paleoindian
types to the side-notched Archaic types at the beginning
of the period. The earliest date known for the latter
point types at Mummy Cave is 7700 B.P.
While bison are absent in the faunal assemblage
at some of the westernmost Mummy Cave complex sites,
such as the type site, they are well represented at
others. The Hawken site, in the Wyoming Black Hills,

is a classic example of communal bison hunting using
an arroyo trap. The site represents either three
kills in a single season or kills over several years.
Based upon analysis of mandibles, Frison et al. (1976)
posit an early to mid-winter kill. At the nearby
Hawken III butchering site, analysis of mandibles
and fetal materials indicates a spring kill (Frison
Mount Albion complex sites are found in high
mountain parks and in the hogbacks of the Rocky Mountain
Front Range in Colorado. The complex is known from
excavations at the Hungry Whistler and 5BL70 sites
(Benedict and Olson 1978). Other sites with Mount
Albion Complex materials are the Helmer Ranch, Wilbur
Thomas Shelter, Magic Mountain, and the LoDaiska site
(Benedict 1979:8). The diagnostic Mount Albion projectile
point is also known from the Ken Caryl Ranch sites,
near Denver.
The high altitude sites contain mainly game
drive lane features, while the lower elevation sites
are campsites, often in rock shelters. Benedict and
Olson (1978) have suggested a subsistence pattern
in which people, during periods of drought, wintered
at low elevations and moved into the mountains in
the summer in search of game.
There is no clear boundary between the Early
and Middle Plains Archaic periods, both of which are

incorporated in the Early Middle Prehistoric period.
By the end of the Early Plains Archaic a new complex,
Oxbow, appeared on the Northern Plains. The Oxbow
complex extended well into the Middle Plains Archaic
period at sites such as Head-Smashed-In where the
component is last dated at about 2100 B.C. (Reeves
1973; 1983b).

Chapter II
Through time a body of theory has evolved
to attempt to explain the response of human populations
to the phenomenon of the Altithermal climatic episode
on the Northern Plains. This theory building is a
direct result of archaeological investigations and
the subsequent accumulated information of the last
several decades. Theories of cultural hiatus and
non-hiatus, and of refugia, mountain specifically,
and ecotonal generally, are discussed below. These
theories are not mutually exclusive and there is consid-
erable overlap in ideas as the latter build on the
Cultural Hiatus Theory
The possible occurrence of a hiatus in human
occupation between the late Early Prehistoric and
early Middle Prehistoric Periods (Mulloy 1958) was
first proposed by Mulloy (1954:433) in his report
on the McKean site in Wyoming. In the report, he
noted that there was a time span of uncertain length
for which evidence of occupation was lacking and that

this might indicate either abandonment of the area
or merely that the evidence had not yet been discovered.
He further suggested the possibility that abandonment
might be due to climatic conditions making the area
unsuitable for bison. Others, agreed that cultural
abandonment was one possible explanation for the lack
of evidence.
In concert with the ideas of Jennings (1957:284;
Jennings and Norbeck 1955), who suggested that plains
people were reduced to scavenging for food in a Desert
culture pattern during the Altithermal, the concept
of a "cultural hiatus" was further developed by Wedel
(1961 :254-255). He suggested that the Northwestern
Plains was largely reduced to a desert during the
Altithermal which resulted in displacement of native
game animals. Wedel postulated further that during
the period, man either abandoned the area or was reduced
to foraging for anything edible. He warned, however,
that this theory may not apply throughout the area
because certain areas, for example, the Saskatchewan
Basin, may have supported bison hunting populations.
Frison (1978) acknowledged that the hypothesis may
be partially correct, as cultural evidence during
the period appears to be lacking on the open plains
and that this lack can be interpreted as an indication
that climatic conditions did result in the exclusion
of human habitation to a large extent.

Non-Hiatus Theory
Reeves (1973) argued that the lack of pre-3000
B.C. radiometrically-dated sites on the Plains is
indeed more the result of small sampling size, sedimen-
tation, and the paleohydrological sequence, than it
is a migration out of the region in Altithermal times.
According to Reeves, the effects of drought are more
marked in the Prairie grass communities which require
summer rainfall to sustain their forage yield, than
in shortgrass communities whose yield correlates only
with the May/June precipitation maximum. He sees
the main change in the grassland communities during
the Atlantic climatic episode (Altithermal) as a vast
increase in the area of shortgrass plains along with
a general decrease in forage yield, due to changes
within the communities in response to changed spring
precipitation values. While more arid than today,
Reeves concluded that spring precipitation patterns
were not greatly lower and temperature did not fluctuate
Comparing data for cattle during the most
adverse shortgrass forage conditions of the 1930s
droughts and allowing a 50% carryover in forage, Reeves
(1973:1 228) estimated the Northern Plains bison population
at five to ten million during the Atlantic climatic
episode. The increased area of shortgrass plains

compensated for the decreased forage yield and the
bison population remained fairly stable. He further
stated that if mean precipitation values were not
as low as those in modern droughts, the total bison
population may have exceeded that of any other period,
including late Boreal times when they formed the principal
resource base for prehistoric man. Maintenance of
the herd at the level estimated would have supported
a minimum human population of 10,000 to 20,000, according
to his estimates.
In discussing site sampling, Reeves (1973:1237)
suggested that the data are skewed for the area in
the interval 8000 to 1500 B.C. with research tending
to concentrate around the Plains1 peripheries, particularly
along the east flanks of the Rocky Mountains. He
stated that known sites in true shortgrass environments
are limited for the Altithermal period. Reeves further
noted (1973:1246) that the large side-notched projectile
points which characterize the early Middle Prehistoric
period on the plains have, when found in surface manifes-
tations, often been erroneously assigned to later
cultural periods, contributing to the perceived lack
of evidence dating to the period. He stated that
the sampling factor is sufficient to explain the lack
of dated components in the Northern Plains but noted
also that the geological context should be considered.

According to Reeves (1973:1237), the geological
contexts of sites dating to 3000 to 1 500 B.C. can
be grouped into those occurring in alluvial sediments
contained within stream terraces, such as Oxbow, and
those in aeolian sediments, such as Head-Smashed-In
and Signal Butte. Periods of alluviation correlate
with the re-advance of the Alpine glaciers at about
6000 and 3000 B.C. and are separated by a major erosional
interval in which streams degraded their flood plains.
Reeves explains that sites of this age in flood plains
have either been destroyed or deeply buried and that
the aeolian accumulation sites are mostly single component
sites, all of which are associated with buried erosional
Reeves (1 973) further explained that archaeological
complexes dating to about 5500 to 3000 B.C. (Altithermal
period) and characterized by side-notched atlatl points,
occur on the plains peripheries and are either earlier
or contemporaneous with the earliest dated (3000 B.C.)
Oxbow complex components. As Oxbow components have
Mummy Cave and Bitterroot side-notched point types
in association, he believes that Oxbow developed in
situ out of a preceding complex similar to those in
the Rocky Mountains and on the Northeastern Periphery
of the Northern Plains.
Reeves (1973:1245) has suggested that Oxbow
is derived from the Mummy Cave complex. Others, trace

it to more eastern origins, such as Logan Creek (Buchner
1 980).- Late in the period Oxbow is found at some
sites with the McKean complex (Reeves 1973), which
is known from sites such as Mummy Cave in Wyoming
to be present by about 2500 B.C. (Wedel et al. 1 968;
McCracken et al. 1978).
In summary, Reeves (1973) believes that there
is adequate evidence for occupation of the plains
during the Early Middle Prehistoric or the Early Plains
Archaic. He postulates a viable but smaller bison
population with the same basic human subsistence strategy,
i.e., communal bison hunting, as earlier and later
populations practiced. He concludes that while population
numbers, group size and density might have changed,
the concepts of either a cultural hiatus or a forager
adaptive strategy are not applicable.
Refugia Theories
The concept of "refugia" areas was introduced
by Wedel (1961:255) as areas in the plains where local
conditions may have permitted the continuation of
earlier lifeways. Hurt (1966:110) further developed
the idea, noting that certain areas, those near springs
and rivers originating in mountainous areas, areas
of relatively higher elevations in the west, and those
located on the northern and eastern plains peripheries
provided better access to water than the remainder

of the plains and may have attracted animal and human
populations during droughts.
The concept of the Rocky Mountains as a human
refuge area throughout the Altithermal was first suggested
by Huscher and Huscher (1 941 :228-229) Hurt (1 966:1 10-111 )
recognized the possibility of climatic cycles within
the Altithermal, that is, of short alternating wet
and dry periods, and the subsequent discontinuous
use of mountain refuge and other areas. Benedict
and Olson's (1978) recent study suggests an alternation
of population density between dry lowlands and moist
Benedict and Olson (1978) defined the Mount
Albion complex on the basis of excavations at the
Hungry Whistler and 5BL67 sites in the Colorado Front
Range. The complex, of which a large side-notched
projectile point, which is both notch and basally
ground is the chief diagnostic, is known from surface
collections and excavations at high elevation sites
and from excavations at rockshelters and open campsites
in the eastern foothills of the Front Range in Colorado,
particularly in the hogbacks west of Denver.
In search of an origin for the Mt. Albion
complex, Benedict concluded that it evolved at some
distance from its Colorado locales in a drought-susceptible
region, and while its origin is not yet known, it
is related to contemporary cultures at the northern

tree limit and perhaps in the forests of the Great
Lakes (Benedict and Olson 1978:74). He interpreted
his data as suggesting that its appearance about 3800
B.C. coincided with a shift in human population from
dry environments in many parts of the west to regions
of relatively high precipitation.
Benedict and Olson (1978) have postulated
that Mt. Albion groups wintered in the eastern foothills
of the Front Range and in mountain parks east of the
divide and that use of the subalpine forest, and alpine
tundra was seasonal, in summer and fall, for game-drive
hunting and gathering of wild plant foods. This is
a subsistence pattern essentially similar to the Mummy
Cave complex adaptation.
Based upon 225 radiocarbon dates from 110
archaeological sites in western North America, Benedict
estimated the population density in the Altithermal.
The derived population curves and pedalogical data
from the Hungry Whistler and 5BL70 sites, support
a hypothesis of an Altithermal with two severe droughts
(Benedict and Olson 1978). This possibility has also
been raised by the Mazama ash section of the Crowsnest
Pass site temperature curve from southwestern Alberta
(Buchner 1980:152).
According to Benedict (Benedict and Olson
1978:184), the aridity maxima occurred about 7000-
6500 B.P. (5000-4500 B.C.) and 6000-5500 B.P. (4000-

3500 B.C.). He believes that the second drought was
most severe and resulted in reduced occupation of
the Great Basin, the Columbia and Colorado Plateaus,
and the prairie-forest ecotone, and possibly in short-term
abandonment of the western plains and dry interior
plateaus with concomitant population maxima in moist
refugia areas, such as the Rocky Mountains and Pacific
Northwest. He sees the Altithermal as a period of
rapidly fluctuating climate rather than a uniform
long drought.
Benedict (Benedict and Olson 1978:179) concludes
that the twin concepts of the "long drought" and the
Altithermal "cultural hiatus" in western North America
are no longer tenable. He asserts that most Altithermal
archaeological sites are in or near forested areas
and forest-grassland ecotones, with the exceptions
occurring near water sources. Benedict believes that
western North America was never massively abandoned
but that significant population fluctuations did occur.
He sees the Wyoming Basin and the shortgrass plains
of eastern Colorado, however, as either uninhabited
or sparsely inhabited throughout the Altithermal.
Further, he has suggested that if the Wyoming Basin
was occupied, it was part of the Great Basin culture
area during the Altithermal maximum (6000-5500 years

Buchner (1980) conducted an extensive study
of the effects of the Altithermal or Atlantic episode
on the Northern Plains which included synthesizing
the available paleoecological data, mostly palynological,
and using multivariate statistical techniques to recon-
struct climatic patterns for the period. The palynological
record for the period, according to Buchner, indicates
that at the height of the Wisconsin glaciation, there
were spruce forests at scattered intervals throughout
central North America. The warming trend at the end
of the Pleistocene marked the appearance of grassland
flora in the south-central United States. The grasslands
spread east and west, but mainly northward. Based
upon estimates of maximum prairie expansion by McAndrews,
Ritchie, and Wright, and the palynological site data,
Buchner estimated that the grasslands achieved a maximum
penetration about 7000-6500 B.P. at 200 km north and
100 km east of its modern limits. In the west, elevation
of the tree line occurred. From this it is also concluded
that the peak of heat and aridity was time transgressive
south to north.
Using the Multiple Regression technique, Buchner
(1980:62) took the modern frequencies of Picea, Pinus,
Betula, Populus, Gramineae, Chenopodiineae, Ambrosieae,
and Artemisia from 107 surface sites in Aspen Parkland
and Boreal Forest in Saskatchewan and Manitoba, and
calculated the percentage of these independent variables

in the total pollen count of each site. Dependent
variables, determined for each site, were precipitation
during growing season, yearly snowfall, yearly sunlight,
potential evaporation, July mean temperature, degree
days above 42 F, and length of the growing season.
The Multiple Regression program of the S.P.S.S. package
was used to process the data. The resulting transfer
functions were applied by Buchner (1980:65) to pollen
data from a deep core at Crowsnest Lake, southwest
Alberta and a temperature graph was constructed.
In summary, Buchner's (1980) completed statistical
reconstruction of mean climatic parameters indicates
that maximum temperature and aridity occurred at 6500-3900
B.C. In addition to a temperature increase of 2F
during the Altithermal or Atlantic episode, precipitation
declined by 25%, the growing season was warmer and
longer by one week, and there were fewer storms.
These conditions were associated with increased force
and frequency of prevailing westerly winds. The cumulative
effect resulted in increased rates of transevaporation
and aeolian activities. According to Buchner, these
changes are consistent with an increase in the dominance
of warm, dry Pacific air in the prairie region from
the present pattern of five months a year to seven.
During this period the eastern U.S., Arizona and possibly
Wyoming were cooler and wetter. The pattern occurred
abruptly, became locked in due to an expansion of

the circumpolar vortex, and was perpetuated as a result
of increased solar activity in the latter half of
the period.
Buchner (1980:86) asserts that the reconstructed
climatic values correspond closely with recorded major
modern droughts and that the same mosaic of regionally
differential climates is observed in the present.
He concludes that the persistence of warmer temperatures
and lighter precipitation increased the frequency
and severity of droughts by 400%. The reduction of
solar activity between 4450 and 4220 B.C. (Mazama
eruption) raises the possibility of a mid-Atlantic
cool spell.
The climatic pattern reconstructed for the
period resulted in an overall floral capacity reduction
to one-fourth its former potential, according to Buchner
(1980:203), and affecting most heavily the shortgrass
plains. The dessication of the grasslands is seen
as having caused a commensurate depletion of the plains
bison herds by lowering their winter- survival and
their vitality during breeding and gestation. Buchner
believes the herds may have been reduced until communal
hunting was no longer productive. He further posits
that, as a response to a reduced carrying capacity,
bison clustered where the grasses were densest and
that their size gradually diminished.

Buchner's (1980:118) underlying assumption
is that man's technology did not change appreciably
from the period preceding the onset of the Atlantic
or Altithermal (about 8000 to 5500 B.C.) to that following
it (about 3000 to 1500 B.C.). Like Reeves (1973),
he postulates a nomadic lifeway centering on bison
hunting using communal techniques, when feasible-.
He believes populations shifted their activity rounds
to those areas of the greatest density of plant and
animal life.
According to Buchner (1980) these refugia
occurred in grassland margins and river valleys, at
higher elevations, and near perennial springs. Precipi-
tation was higher at the northern and eastern peripheries
of the plains. Due to denser vegetative cover in
these areas, the effects of increased temperature
and aridity were less marked and the variety of large
game regionally and seasonably available increased.
He further believes (1980:154) that those sites falling
near the Altithermal peak are situated in "double
refuge" areas, which are characterized by at least
two of the refugia attributes.
In western areas of higher elevation where
increased precipitation and decreased transevaporation
are the norm, populations larger than the preceding
period could have been supported, according to Buchner
(1980). He agrees with Wells (1970), who notes that

in lower elevations in the west, notably in the Laramie
Basin, rainfall may have increased during the Altithermal
due to the deployment of major air masses and the
rain shadow effect of the Rocky Mountains.
Buchner's (1980) second hypothesis is that
river valleys in the plains run east-west and should
contribute to culture contact evidence at the eastern
and western grasslands margins, while north-south
travel would follow the grassland peripheries. He
first examined sites collectively grouped as the Logan
Creek complex and extending from Manitoba to Kansas.
These grassland sites are in settings traditionally
considered to be winter habitats, but artifacts and
plant remains indicated year-round occupation during
the Altithermal, according to Buchner, who believes
that Logan Creek complex peoples, like the bison,
spent most of the year in areas that were later exclusively
winter camps. While bison numbers were reduced, he
feels that probably greater densities existed in these
refugia than elsewhere. According to this theory,
the result was less nomadism, larger camps, and increasing
dependence on local flora.
Next, Buchner (1980) examined western sites
of the Mummy Cave and assorted other complexes (Bitterroot,
Salmon River, Mt. Albion), located mainly along the
eastern flank of the Rocky Mountains from Alberta
to Colorado. Vegetation changes here during the Alti-

thermal were, according to the investigator, slight
compared to the eastern grasslands. The most dramatic
change was the northern penetration of the grasslands
into Alberta.
Whereas Reeves (1973) believes the grasslands
were occupied during the Altithermal, Buchner disagrees,
asserting that even those sites that appear to be
in open grasslands, are in fact in refuge areas.
For example, he cites the Head-Smashed-In bison jump
in the southwestern Porcupine Hills, 5 km from the
Oldman River, an area he claims has the highest carrying
capacity of any Alberta rangeland. He agrees with
Benedict (Benedict and Olson 1978) that mountain sites
probably represent groups who summered at higher altitudes
where water and a variety of game were available.
Unlike Frison (1978), Buchner believes that in colder
weather the same peoples perhaps moved to lower elevations
into forest outliers, as in the Black Hills, for communal
bison hunting.
To demonstrate the climatic change-settlement
shift correlation, Buchner (1980) studied site distri-
butions for three consecutive climatic episodes.
He found evidence for homogenous site distribution
and use of both refuge and non-refuge areas in the
period immediately before and after the Altithermal.
Further, he demonstrated cultural continuity throughout
these periods. Whereas the large, side-notched projectile

point complexes represented an abrupt culture change
along the western flanks of the Rocky Mountains during
the Altithermal, he noted that they are represented
at sites in the eastern grasslands margins at an earlier
period and in association with Plano artifacts. From
this, he concluded that the Mummy Cave complex represents
a continuation of the technology, economy, and basic
lifeway established much earlier, with the side-notched
point a mere stylistic attribute, introduced to an
indigenous complex from the eas.t, probably by way
of the river systems.
The appearance of the side-notched complex
in the east predates its western counterpart by 400
to 900 years and is found in association with Plano
types throughout the eastern plains in sites from
the Dakotas to Texas and further east in the Woodlands.
Buchner (1980:165-166) stated that by 6500 B.C., side-
notched projectile points and end scrapers were incor-
porated into the Plano Dalton assemblage at Woodland
sites and that basic continuities in the rest of the
lithic and faunal assemblages argue for in situ develop-
ment. By 6500 B.C., the start of the Atlantic Climatic
episode (Bryson, et al. 1970:63), he posits that both
diversified early side-notched/Dalton hunter-gatherers
from the eastern woodlands and nomadic plains hunters
used the grassland-forest ecotone in winter when the
bison gathered there. This culture contact is reflected

in sites along the eastern grasslands which contain
large side-notched projectile points in association
with Agate Basin and Cody complex (Plano) forms.
Buchner (1980) had suggested that during the
period of climatic amelioration at the end of the
Altithermal, Oxbow sites, distributed from the eastern
slopes of the Rockies to northwestern Ontario in refugia
and non-refugia areas, share a majority of traits
with those of earlier side-notched point assemblages.
He sees the Oxbow projectile point as a stylistic
evolution from earlier Logan Creek and Mummy Cave
styles, which in turn are probably descended from
an eastern style. The appearance of the associated
McKean complex, accepted as a clearly western manifes-
tation, he has interpreted as a reoccupation of the
grasslands after the Altithermal.

Most of southwestern Wyoming consists of lands
administered by the federal government. Because cultural
resources investigations on such lands are mandated
by federal legislation and due primarily to intensive
efforts in the area on the part of energy developers,
the archaeological data base in southwestern Wyoming
has expanded greatly in the last decade. This is
not to imply that existing information is wholly adequate
for understanding the culture history of the area,
as only a very small percentage of federal lands in
the area has yet been sampled. However, in comparison
to many areas of the Northern Plains, e.g., southeastern
Wyoming or northeastern Colorado, the information
presently available for southwestern Wyoming provides
a small window to the past not everywhere available.
The physiographic province of the Wyoming
Basin is characterized as an extension of Great Plains
topography westward through the opening between the
Bighorn and Laramie mountain ranges (Thornbury 1965:323),
a similar opening east of the Uinta Mountains provides

a corridor for relatively easy access to the Colorado
Plateau (Fenneman 1931). Culturally, southwestern
Wyoming lies on the periphery of the Northwestern
Plains and Great Basin culture areas as defined by
Frison (1978) and Willey (1966), respectively. That
the area has been variously influenced by cultural
trends of both areas is demonstrated in the residual
cultural material manifested. Therefore, the selection
of the archaeology of southwestern Wyoming as an example
of the culture history of a sub-area of the Northwestern
Plains during the Altithermal climatic episode was
made based on availability of information, and not
because the area can be considered to be truly typical
of the Northern Plains. However, as stated above,
the area, can be rightly treated as part of the Northern
Plains culture area and while some environmental and
cultural aspects may vary from those of the grasslands
proper, others will be very similar.
The various theories discussed herein as pertaining
to human occupation and adaptation on the Northern
Plains and peripheral areas during the Altithermal
climatic episode suggest numerous research questions,
many of them applicable to an examination of the archae-
ology of southwestern Wyoming. Following a brief
environmental description of the area intended to
provide a frame of reference for the reader, research
questions that will guide the following discussion

of southwestern Wyoming archaeology are listed categor-
ically, within appropriate problem domains.
Environment of Southwestern Wyoming
Thornbury (1965) defined four physiographic
provinces in the United States Rocky Mountain system,
the: Northern Rocky Mountains, Middle Rocky Mountains,
Wyoming Basin, and Southern Rocky Mountains. The
Wyoming Basin and portions of the Middle Rocky Mountains
occupy southwestern Wyoming (Figure 3). In western
Wyoming the Overthrust Belt of the Middle Rockies
extends southward into north-central Utah, terminating
at the Uinta Mountains. The Wyoming Basin is partly
subdivided into separate structural and topographic
basins by fingers of the Middle Rockies in the north
and Southern Rockies in the southeast (Fairbridge
1975:629). The major basins are the Green River Basin
on the west, and the Great Divide (Red Desert) and
Washakie Basins on the east.
Physiography and Geology
The Overthrust Belt is comprised of a series
of north-northeast trending ridges of thrust plates
and valleys which are underlain by Paleozoic and Mesozoic
strata. Elevations range from a high of almost 90 0 0
feet in the foothills of western Wyoming to a low
of 6100 feet on the Bear River floodplain on the Wyoming-
Utah border. Dominant landforms include the Sublette

Figure 3. The Wyoming Basin (Adapted from
Fairbridge 1975: 628).

and the Tunp Ranges on the north and west, and Commissary
and Oyster Ridges on the east (Rubey et al. 1971-1).
Upper Cretaceous and lower Tertiary age formations,
consisting of fluvially carried muds, sands, and gravels,
are exposed on valley floors within the area. The
deposits comprising the Tertiary formations tend to
be conglomerates weathered out of a sedimentary matrix,
forming lag pavements or interfluvial ridges (Treat
et al. 1982:15).
The Overthrust Belt contains two major drainage
systems which are separated by the Bear River Divide.
The eastern portion is drained by the Hams Fork and
Black Fork Rivers, which flow into the Green River
and subsequently into the Colorado River. The western
portion of the area is drained by the Bear River,
which flows into the Great Salt Lake (U.S. Department
of the Interior 1 979). There are numerous permanent
streams in the area, including Twin, Sage, and Yellow
Creeks, which flow into the Bear River; and Soda Hollow,
which joins Muddy Creek and later, the Green River.
The Green River Basin (Figure 4), also known
as Bridger Basin, is a large structural and topographic
basin occupying all of that portion of the Wyoming
Basin west of the Rock Springs Uplift (Fenneman 1931 :136).
The basin, which extends from southern Wyoming into
northeastern Utah and northwestern Colorado, is bordered
by the Wind River Range on the north; the Rock Springs

Figure 4. Wyoming Physiography

Uplift to the east; the Uinta Range on the south;
and the Oyster Ridge hogback which forms the eastern
extent of the Overthrust Belt, on the west. Elevations
in the basin range from 6000 to 9100 feet.
The floor of the basin is largely a plain
developed by erosion of flat-lying strata. Near the
river, portions are eroded into badlands (Fenneman
1931:145). Surface geology in the Green River Basin
is primarily Tertiary age outcrops of gray, green,
and pink mudstones and sandstones: and white to buff,
cherty limestones (Burchett in Brechtel et al. 1984:9).
The Green River formation is the source of the Laney
shale gravels found outcropping near Pilot Butte and
of the alluvial deposits along the Green River, which
are associated with the surficial Wilkins Peak member.
Also, in the western portion of the basin, both rims
of Green River formation and escarpments of Wasatch
formation are present (Treat et al. 1982:16).
The dominant drainage of the Green River Basin
is the perennial Green River, a tributary of the Colorado
River. Major tributaries of the Green River are the
Blacks Fork, Muddy Creek, and Hams Fork.
The Rock Springs Uplift is an immense north
trending anticlinal fold which forms a structural
divide between the Great Divide and Washakie Basins
on the east, and the Green River Basin on the west
(Lewis 1961:87). At the center of the uplift is a

low depression, Baxter Basin, with a low elevation
of about 6300 feet. Ridges and mountains in the uplift
areas range to more than 8600 feet.
The surface geology of the Baxter Basin is
primarily manifested in deposits of the Mesa Verde
group, specifically, in ascending order the Late Cretaceous
age Baxter shale, Blair, Rock Springs, Ericson, and
Almond formations (Smith 1961:101). The outer edges
of the uplift contain a broad belt of sandstone escarp-
ments. In the northern part of the uplift are lava
capped buttes and mesas, cinder cones, and sand dunes,
erosional remnants of the Tertiary age Leucite Hills
(U.S. Department of the Interior 1979).
The major drainage in the Rock Springs Uplift
is Bitter Creek, which flows west to the Green River.
Its tributaries include Horsethief Canyon, Deadman
Wash, Long Canyon, and Salt Wells Creek.
The Great Divide Basin lies on the Continental
Divide and is bordered on three sides by uplifts:
the Wind River Range and Sweetwater Arch on the north,
the Rawlins Uplift and Sierra Madre Range to the east,
and the Rock Springs Uplift to the west (Figure 4).
Elevations in the basin range from about 6500 to 8000
The surface geology of the Great Divide Basin
is characterized by Tertiary age strata, i.e., Wasatch
formation, comprised of gray mudstones and muddy sandstones

(Burchett in Brechtel et al. 1984:11). A combination
of lake deposits, aeolian sands, and gravel deposits
comprise the surface materials of the basin. The
exposed Wasatch and Battle Spring formations terminate
in the Rock Springs Uplift rim where the Lewis shale
and Fort Union formations are exposed (Treat et al. 19-
The Great Divide Basin, or Red Desert, is
an area of low relief, actually a hydrologically closed
basin, containing several smaller basins and lake
deposits (Fenneman 1931:143). These include Alkali,
Buffalo, and Lost Creek Basins, and Tenmile and Black
Rocks Flats (Brechtel et al. 1984). Another prominent
feature is the Killpecker dune field, a series of
stabilized and active dunes running eastward across
the basin, from the western margin of the Green River
Basin, across the Rock Springs Uplift, and into the
Red Desert. The feature, primarily sand of the Laney
member of the Green River formation, covers some 170
square miles (Ahlbrand 1974:52).
Major water sources in the Great Divide Basin
include the Chain-of-Lakes area and other playa lakes.
The internal character of the area's drainage depends
solely on deficient precipitation (Fenneman 1931:144).
Between the Great Divide Basin on the north
and the Colorado border on the south is the synclinal
Washakie Basin, a structural but not a topographic

feature. Within the structural depression the higher
and younger strata of the Green River and Bridger
formations remain, forming huge outward facing cuestas
up to 1 000 feet high. Where the cuesta is highest,
it bears local names: Laney rim and Cathedral Bluffs
on the north, Washakie Mountain on the east, Pine
Bluff on the west, and Table Rock on the northwest.
The Washakie Basin terminates at the anticlinal Cherokee
Ridge on the south. The great cuestas described here
are exceedingly dissected in places, forming badlands
and isolated buttes (Penneman 1931:144-145).
The Washakie* Basin is drained by the Little
Snake River which flows into the Yampa on its way
to the Green River. The intermittent Muddy Creek
forms the major tributary of the Little Snake in the
Washakie Basin.
The soils of southwestern Wyoming are generally
shallow. Small areas of deep soils occur where eroded
particles accumulate, as in alluvial fans. Soil formation
is a result of weathering of parent materials of which
five types are present in the region: 1 ) residual
sandstones and shales, occupying 85 percent of the
area; 2) alluvium, occupying about 13 percent of the
region; 3) aeolian sands, in about one percent of
the area; 4) residual volcanic pumice and wyomingite,

at less than one percent of the region, and; 5) loess
silts, which also occupy less than one percent of
the area (U.S. Department of the Interior 1979).
Soil structure is weak in stability or non-
existent. Most soils in the region have some level
of salinity and alkalinity, although the relative
percentages vary. Most soils also contain some calcium
carbonate, often concentrated in a subsoil zone.
Significant rates of soil erosion occur in the region,
in the form of water action on steep, poorly vegetated
slopes and wind erosion on sand dunes (U.S. Department
of the Interior 1979).
The climate of southwestern Wyoming is semi-arid
to arid. The area is characterized by cold, dry winters;
hot, dry summers; and a short growing season. Average
annual precipitation ranges from 8.7 inches on the
Rock Springs Uplift to about 12 inches in the Overthrust
Belt. Precipitation is heaviest in the spring months,
and while much of it occurs as rain, snowfall averages
45 to 55 inches per year (National Oceanic and Atmospheric
Administration 1982; Lowers 1960).
Average January temperatures range from a
low of about 15 F in the Green River Basin and the
Overthrust Belt to almost 21 F in the Great Divide
Basin. July average temperatures range from about

62 F in the Overthrust Belt and Green River Basin
to about .66 F in the Rock Springs Uplift and Great
Divide Basin (National Oceanic and Atmospheric Admini-
stration 1982). Winds blow from the west and southwest
fairly constantly at an average speed of 12 to 14
miles per hour (Lowers 1960).
Kuchler (1964) defined the regional biome
for southwestern Wyoming as sagebrush steppe. Three
of Cary's (1917) Life Zones: the Canadian, the Tran-
sition, and the Upper Sonoran, further describe the
The lower range of the Canadian zone is found
on the upland ridges of the Overthrust Belt and the
uplands to the east (Burchett in Brechtel et al. 1984:16).
Here, lodgepole pine (Pinus murrayana) and aspen (Populus
tremuloides) are present on north facing slopes.
Sagebrush (Artemisia sp. ) and grasses are common on
south facing slopes (Cary 1917:40-41). Along permanent
streams, aspen is found in association with cottonwood
(Populus sp.), willow (Salix sp.), boxelder (Acer
negundo), hawthorn (Craetaegus sp.), and dogwood (Cornus
spp.). Understories and grassland species, which
provide the majority of the Overthrust Belt vegetation,
include serviceberry (Amelanchier alnifolia), mountain
mahogany (Cercocarpus sp.), and many forbs and grasses

(Roper et al. 1983:17; Brechtel et al. 1984). Prominent
grasses are thickspike wheat grass (Agropyron dasysta-
chyum) Letterman needlegrass (Stipa lettermani).
Sandberg bluegrass (Poa sandbergii), bluebunch wheatgrass
(agropyron spicatum), and Indian ricegrass (Orsyzopsis
hymenoides) (Treat et al. 1982:23-24).
Transition zone species occupy the lower slopes
of the mountains and uplifts at the edges of the basins.
These include, in addition to the dominant sagebrush
(Artemisia s£.), yellow pine (Pinus scopulorum), Rocky
Mountain juniper (Juniperus scopulorum), willow (Salix
s£.), mountain mahogany (Cercocarpus s£.), currant
(Ripes S£.), rabbitbrush (Chrysothamnus s£.), wheat-
grasses (Agropyron sp.), and numerous forbs and other
grasses (Cary 1917:32-37), many previously noted.
The upper Sonoran zone occupies the broad
Green River, Great Divide and Washakie Basins of south-
western Wyoming. Vegetation most commonly encountered
here includes sagebrush (Artemisia sjd. ) saltbush
(Atriplex S£.), greasewood (Sarcobatus vermlculatus),
rabbitbrush (Chrysothamnus §£.), prickly pear cactus
(Opuntia sj3.), and numerous grass species. Juniper
(Juniperus sp.) is found on dry slopes and willow
(Salix sp.) grows along streams (Cary 1917:18-37).

Present day large game animals in southwestern
Wyoming include pronghorn antelope (Antilocapra americana),
mule deer (Odocoileus hemionus), elk (Cervus canadensis),
and moose (Alces alces). Antelope forage year-round
throughout the area, browsing primarily on sagebrush,
and also on other vegetation. Mule deer are distributed
throughout the area and elk are found both in the
subalpine zone and at lower elevations, in the sagebrush-
covered hills. Moose are found only in the western
third of the area, confined mainly to riparian zones
along major drainages (U.S. Department of the Interior
The most common small mammals presently found
in the region are the longtail weasel (Mustela frentata),
striped s.kunk (Mephitus mephitus) badger (Taxidea
taxus ), coyote (Canis latrans), bobcat (Lynx rufus),
red fox (Vulpes fulva), whitetail prairie dog (Cynomys
leucurus), Richardson ground squirrel (Spermophilus
richardsonii), Uinta ground squirrel (Spermophilus
armata), least chipmunk (Eutamius minimus), whitetail
jackrabbit (Lepus townsendii), and deer mouse (Peromyscus
miniculatus) (U.S. Department of the Interior 1979).
Reptiles in the area are represented by a
variety of lizards and snakes. Common among them
are the sagebrush lizard (Sceloporus graciosus), desert
shorthorned lizard (Phrynosoma douglassi), prairie

rattlesnake (Crotalus viridis) Great Basin gopher
snake (Pitophus melanoleucus), and garter snakes (Tham-
nophis sp.). Amphibians are represented by the tiger
salamander (Ambystoma tigrinum), leopard frog (Rana
pipiens), and the Great Basin spade-footed toad (Scaphiopus
intermontanus), common in the lowlands. The cutthroat
trout (Salmo clarki) is an example of a fish species
native to the Green River (U.S. Department of the
Interior 1979).
Some of the species listed above are known
prehistorically and ethnographically. The importance
of antelope as a game animal, for example, is well
documented at archaeological sites in the area, as
is a heavy dependence on rabbits.
Cultural Occupation of Southwestern Wyoming;
The Research Questions
As stated above, the various theories pertaining
to cultural occupation of the Northern Plains during
the Altithermal climatic episode suggest numerous
research questions, several of which will provide
a framework for the examination of southwestern Wyoming
archaeology. These research questions can be grouped
into major problem domains which include the nature
and/or extent of any human occupation of the Wyoming
Basin during the Altithermal; the nature of the Altithermal
climatic manifestation in the area, and; the nature
of cultural adaptations, particularly in terms of

subsistence strategies and settlement, or site distribu-
tion. These problem domains and research questions
are interlinked in that climate affects environment.
Environment, in turn, imposes physical constraints
to which people must adapt, largely in cultural ways,
in order to occupy a given area successfully.
The first problem domain, which concerns the
nature and/or extent of human occupation in the Wyoming
Basin during the Altithermal, includes the following
research questions. Was the Wyoming Basin totally
abandoned during the Altithermal? If the area was
not uninhabited during the period, was it then sparsely
occupied? Is it likely that any lack of sites or
low site frequency during the Altithermal results
from the consequences of the erosional/depositional
cycles associated with the climatic fluctuations of
the period?
The second problem domain concerns the nature
of the Altithermal climatic manifestation. Was the
Altithermal, as evidenced in southwestern Wyoming,
comprised of two major droughts? Was the nature and
intensity of the climatic manifestation uniform throughout
the broader, Wyoming Basin and adjacent areas? If
there were two major droughts affecting southwestern
Wyoming during the period, is there any evidence for
resulting population density fluctuations?

The third problem domain encompasses questions
pertaining to cultural adaptations in southwestern
Wyoming during the Altithermal, specifically, subsistence
strategies and site distribution. Did the subsistence
strategy and technology of the period remain the Northern
Plains communal bison hunting pattern of earlier and
later periods? Or, were inhabitants of the area reduced
to a foraging strategy? Finally, were mountain or
ecotonal refugia preferred site locations?
Cultural Occupation of Southwestern Wyoming:
The Archaeology Record
To address the first problem domain, concerning
human occupation or the postulated abandonment of
the Wyoming Basin during the Altithermal, the radiocarbon
record of the area must be examined. In 1978, Frison's
synthesis of the Northwest Plains (Prehistoric Hunters
of the High Plains) was published, in which he rigorously
gathered available radiocarbon data for sites in and
around Wyoming. Since that time, a great amount of
archaeological investigation has occurred in the state.
The State of Wyoming is currently in the process of
compiling a comprehensive, updated listing, but it
is not yet ready for distribution (Feathers, personal
communication 1985). Fortunately, and perhaps more
germane to the issue, is the recent publication of
radiocarbon dates for the Wyoming Basin compiled by
Metcalf-Zier Archaeologists, Inc. (Zier et al. 1983),

a fairly complete document, containing dates from
various institutions, companies, and individuals.
Western Wyoming College also compiles radiocarbon
dates for the area. For the purposes of the present
study, published Western Wyoming College dates (Mackey,
Sail, and Creasman 1982; Creasman and Garvey 1983)
not already included in the Zier et al. (1983) listing
have been, added, as have several additional dates
from this writer's research as Principal Investigator
for the Tenneco Oil Company Unit #1 and Frontier Pipeline
Trench Inspection projects (Burchett 1982; Brechtel
et al. 1984), and that of others (Schroedl 1984).
Dates known to be from sites outside southwestern
Wyoming have been deleted from the sources. Collectively
(see Appendix A), these data represent not all, but
a majority of the radiocarbon dates presently available
for southwestern Wyoming.
The combined listing (Appendix A) includes
278 radiocarbon dates from archaeological components
at about 150 sites in Carbon, Fremont, Lincoln, Sublette,
Sweetwater, and Uinta counties. Following numerous
others (Benedict and Olson 1978; Mackey, Sail, and
Creasman 1982; Mackey et al. 1982, Creasman and Garvey
1 983; and Zier et al. 1 983 ), the assumption here is
that frequency of dates can be interpreted as reflecting
very general trends in intensity of occupation despite
any distortions that factors such as differential

preservation and discovery potential might cause to
the data base.
Of the 278 dates, 38, or 14 percent, are from
components dating to the Early Plains Archaic period,
which correlates with the major portion of the Altithermal
climatic episode. From this it is clear that the
Wyoming Basin was indeed inhabited during the period.
The frequency of radiocarbon dates for this period
compares with 7 dates, or 3 percent, for the preceding
Paleoindian period and 47 dates, or 17 percent, repre-
senting components of the following Middle Plains
Archaic period.
A graph of radiocarbon date frequencies by
time period (Figure 5) indicates that population densities
were low in southwestern Wyoming during the Paleoindian
period. This is followed by a rather marked increase
in Altithermal period dates (Early Plains Archaic-early
Middle Plains Archaic) which approaches those of the
following post-Altithermal or late Middle Plains Archaic
period and indicates general stability of populations
for both of these periods, an observation Creasman
and Garvey (1983:33) made based upon an earlier graph.
These findings do nothing, however, to contradict
a hypothesis of sparse occupation of the Wyoming Basin
for the period, as put forth by Benedict (Benedict
and Olson 1978:175). Based on the radiocarbon dates
(Figure 5), population densities, although showing

Late Late Middle Early
Prehistoric - Plains Plains Plains Raleoindian
' Archaic Archaic Archaic
Figure 5. Graph of Radiocarbon Dates for Southwestern Wyoming

general increases through time, must be described
as relatively low until the end of the Late Plains
Archaic or beginning of the Late Prehistoric periods,
when there is a marked increase in radiocarbon dates,
interpreted here as a marked increase in human population
density. This is consonant with the earlier studies
of Mackey, Sail, and Creasman (1 982); Mackey et al. (1 982),
and others.
While sampling error may still be a concern,
the known radiocarbon record in southwestern Wyoming
is not believed to be a result of research bias.
As Zier et al. (1 983: 1 2) have stated, research bias
does not appear to be a serious problem. Although
the selection of sites for excavation has not been
truly random, it has been dictated largely by placement
of energy development projects and not by research
interests. This results in the selection of locations
for primarily geological, as well as topographic,
access and surface ownership attributes rather than
cultural potential (Tate and Rippeteau 1984).
As to the concern that erosional/depositional
cycles associated with the Altithermal may have differ-
entially destroyed or obscured sites when compared
to earlier or later periods, the radiocarbon data
available do not appear to support that idea. Zier
et al. (1983) noted that because sites of increasing
antiquity could be expected to be less well preserved

and more difficult to locate, the radiocarbon curve
should show a marked trend from a few dates of great
age to many dates of recent age. They further observed
that while the actual data show a general correspondence
to this expectation, there are marked fluctuations
in date frequency. Mackey et al. (1982), Mackey,
Sail, and Creasman (1982:23), and others have demonstrated
definite and sharp declines in date frequencies during
periods interpreted as erosional episodes at the beginning
and end of the Altithermal and increases in date frequen-
cies in the mid-Altithermal and post-Altithermal periods,
seen also in Figure 5. The decline in date frequencies
are not seen as resulting from erosional removing
of occupations because many sites that contain both
mid and post-Altithermal occupations, but no inter-
vening ones, display no evidence of eroded strata
that would erase evidence of occupation (Creasman
Evidence of relevance to the second problem
domain, concerning the nature of the Altithermal climatic
manifestation in southwestern Wyoming, has emerged
from geomorphic, soil sediment and pollen data derived
from some recent archaeological site excavations in
the area. To date, the most complete record of environ-
mental change comes from the Deadman Wash (48SW1 455)
and Tenmile Draw (48SW1668) sites located on the eastern
edge of the Rock Springs Uplift. Among the most important

information derived from the site excavations was
the evidence of two erosional uncomformities, believed
to define the beginning and end of the Altithermal
and the height of xeric climatic conditions in southwestern
Wyoming. The earlier uncomformity is dated ca. 7500-7000
years B.P. (5500-5000 B.C.) and was found at Deadman
Wash; the later unconformity dates to ca. 4700-4500
B.P. (2700-2500 B.C.) and was discovered at Tenmile
Draw (Creasman 1984:41).
Soil sediment analysis was conducted at several
sites (Deadman Wash, Tenmile Draw, 48SW4492) in connection
with the Trailblazer Pipeline project. The analysis,
undertaken to determine the depositional environment
of site strata, demonstrated that the period between
the early and late erosional episodes was one of soil
aggradation, and that in non-alluvial situations,
deposition resulted from aeolian transport. About
half-way between the erosional episodes, dunal deposits
stabilized. During this relatively mesic interval,
a paleosol developed. Based upon radiocarbon dates
from this horizon and Albrandt's work at the Killpecker
dune field, this distinctive paleosol has been dated
to about 5800-5500 B.P. (3800-3500 B.C.) (Creasman
Creasman (1984:45) has shown that pollen analysis
from strata at site 48SW4492 supports the geomorphic
and soil sediment data. The pollen analysis indicates

that just prior to 8000 B.P., arboreal pollen frequencies,
particularly Pinus pollen, began to decrease indicating
a deterioration of early Holocene mesic conditions,
and continued until the raid-Altithermal paleosol was
encountered. Then an increase in arboreal pollen,
especially Pinus and Artemisia, at the expense of
Cheno-ams, was noted. The return to xeric conditions
was manifested in a decrease in arboreal and Artemisia
pollen frequencies, until just after 4500 B.P. when
the pollen record once more provided evidence of more
mesic conditions.
Pollen analysis from other sites in southwestern
Wyoming supports the findings at 48SW4892 (Creasman
et al. 1983:163). Linda Scott's analysis, conducted
as part of this writer's Frontier Pipeline investigations
at site 48UT872 in the Green River Valley (Brechtel
et al. 1984:257), revealed a tendency toward higher
Pinus pollen accumulations in features dated ca. 5540
and 4720 B.P. when compared to frequencies from features
dated 7520 and 6130 B.P. This is interpreted as indicating
a xeric period early in the Altithermal, followed
by a more mesic environment later in the period.
The combined soil sediment, geomorphic, and
pollen data compiled by Creasman (1984) and others
indicates an Altithermal sequence in southwestern
Wyoming that is characterized by two erosional episodes
or droughts occurring about 7500-7000 B.P. and 4700-4500

B.P., with a more mesic, but still arid interval at
6000-5500 B.P.
Information, based primarily on geological
studies, from the Copper Mountain Site (Zier and Zier
1 980) located just northeast of the area comprising
southwestern Wyoming, in the Owl Creek Mountains of
central Wyoming, provides a view of the Altithermal
manifestation in marked contrast to that seen in south-
western Wyoming. The site straddles an intermittent,
south-flowing tributary of the East Fork of Dry Creek
and later joins the Wind River. Known also as Guffy
Peak II, the site is rare archaeologically, because
it evidences human occupation over a considerable
time depth, and geologically, because its geologic
section includes most of the Holocene, with large
segments of pre-Altithermal and Altithermal soil (Zier
et al. 1984:20).
Five major stratigraphic units were identified
at the site. The boulder and cobble deposits of Unit
I, indicate high energy stream runoff at the end of
the Pleistocene, of an extent and intensity not seen
since. The clay sediments forming the lowest member
of Unit II, which unconformably overlie Unit I, are
interpreted as suggestive of a change in climatic
regime. This soil developed in humid, well drained
conditions which were cooler and moister than present
climatic conditions. Overlying this basal member

are three, thin depositional units composed of calcareous,
azonal soils, the investigators feel can be identified
with the Altithermal soils described by earlier investi-
gators in the area. These soils, separated by minor
erosional surfaces, indicate periods of relative geomorphic
stability during the Altithermal. Further, evident
episodes of fluvial deposition suggest water flowed
in the main channels of the stream during portions
of the period. The investigators believe that fluvial
channel widths were constant over time, showing that
stream runoff in the Holocene did not vary greatly
and that the narrow width of the modern stream channels
indicates exceptional aridity with a stream flow now
as low as any time in the Holocene (Zier et al. 1984).
Zier et al. (1984:22) conclude that a semi-arid
climate has predominated in the area since the onset
of the Altithermal with no evidence, however, for
long periods of drought more severe than that of the
last century. The geologic record for the area, then,
provides no evidence for a protracted Altithermal
drought period.
From the data presented here, it appears that
the Altithermal climatic manifestation in southwestern
Wyoming is similar to the two-drought episode postulated
by Benedict (Benedict and Olson 1 978) for the Rocky
Mountains. However, a short distance away, in central
Wyoming, studies at the Copper Mountain site indicate

that the nature and/or intensity of Altithermal climatic
effects there were considerably different. The contrasting
data support Wells (1 970) finding of a complex postglacial
pattern in Wyoming, where sites in the mountains and
foothills, and those subject to the rainshadow effect
from nearby mountains may be characterized by more
moderate climates than at present. It is apparent,
that close examination is needed to regionally characterize
the Altithermal, in areas of vast environmental diversity,
such as Wyoming. As stated, there appear, based on
existing data, to have been two major droughts manifested
in southwestern Wyoming during the Altithermal episode,
at least for those portions of the area for which
data are presently available.
The radiocarbon record for the area (Figure
5) shows decreased date frequencies at the beginning
and end of the Altithermal period correlating to the
two proposed drought periods and an increased date
frequency toward the middle Altithermal period. These
phenomena, observed by earlier investigators (Mackey,
Sail, and Creasman 1982, and others) can be interpreted
as commensurate population fluctuations attributable
to the climatic and subsequent environmental changes.
The. third problem domain concern cultural
adaptations, particularly subsistence strategies and
site distribution or settlement patterns. The subsistence
strategy and technology characteristic of human adaptation

on the Northern Plains throughout the prehistoric
period has been communal bison hunting. However,
communal bison kill or butchering/processing sites
in southwestern Wyoming are rare. The best known
of these are the Finley and Wardell sites (Frison
1 978) in the Green River Basin, which date to the
Paleoindian and Late Prehistoric periods, respectively.
Not only are there no communal kill or butchering
sites known in southwestern Wyoming during the Early
Plains Archaic period, but there are no bison in the
repbrted site faunas. Because much of southwestern
Wyoming can be characterized as a sagebrush steppe,
which provides favored forage for antelope, this is
the large game animal more often reported in site
faunas, including those of the Altithermal period.
Communal antelope hunting and processing is documented
at several sites in the area including Eden Farson
and Bridger Antelope Trap (Frison 1978). However,
the earliest known site of this type is the Austin
Wash (48UT390) site dated by Schroedl (1984) at about
A.D. 760.
The question of whether inhabitants in the
Wyoming Basin or elsewhere on the Plains were reduced
to a foraging strategy during the Altithermal is first
a matter of definition. Binford (1980) has suggested
that there are two basic principles employed by hunters
and gathers in carrying out their subsistence strategies.

Foragers, generally highly mobile groups, who live
in warmer climates characterized by no seasonal food
shortages, "map on," by moving consumers to resources.
Collectors, found in temperate and colder climates
characterized by seasonality and food shortages, employ
a "logistical" procurement strategy, moving resources
to consumers, thereby necessitating a developed food
storage technology. Binford (1980:18) believes that
the ratio of foragers to collectors is correlated
to the length of the growing season; as the season
decreases, the role of logistical strategies within
the subsistence system increases. While still mobile,
collectors are seen as utilizing base camps and a
variety of associated, single activity sites for procure-
ment of resources and storage. Zier et al. (1983:88-89)
correctly noted that while the collector model has
already been used to describe collector lifeways in
the Overthrust Belt, that its application can be extended
to include the Wyoming Basin. Thus, if Wedel (1961)
was not distinguishing foraging from collecting and
was instead referring, as one suspects he was, to
a strategy of small bands making seasonal gathering
rounds to utilize a wide range of ecosystems, his
description is probably accurate, at least for the
Wyoming Basin.
Although Altithermal settlement and subsistence
patterns are still poorly understood, recent investigations

at several sites and particularly at the Deadman Wash
Site (48SW1455), have provided considerable information
about the nature of subsistence activities during
the Altithermal. Deadman Wash (Armitage et al. 1982),
a multi-component site dating from ca. 8500-500 B.P.,
contains four Altithermal components documenting extensive
base camps.
These occupations are characterized by an
increased density of groundstone tools and ratio of
groundstone to flaked lithics over earlier and later
periods, and by the occurrence of plant processing
or storage pits, purposefully dug with no oxidation
or charcoal present. These features, known from sites
in the Great Basin as well as in Wyoming (Armitage
et al. 1982:52), have been described as larger than
firepits, and filled with dark sand, seed, and fragments
of animal bone.
The Deadman Wash site also produced temporally
diagnostic, side-notched dart points and large, side-
notched knives, since documented at several Wyoming
Altithermal sites. Finally, the faunal assemblage
of the Altithermal components evidences a wide range
of animals (no bison) but a low relative mean weight
compared to later periods. This evidence in combination
with the special use pits and the high proportion
of plant processing to hunting type tools leads to
the interpretation of subsistence activities dominated

by plant gathering and processing, supplemented by
hunting available game. Creasman (in Armitage et
al. 1982:187) suggested that the base camp was used
seasonally, sometime between spring and fall, based
on its plant processing focus and that based upon
recovered lithic materials, inhabitants traveled over
a wide area within southwest Wyoming.
Evidence from other sites along the Trailblazer
pipeline (Rock Springs Uplift-Great Divide Basin-Rawlins
Uplift) complements the studies at Deadman Wash.
Here investigators found that while the macrofloral
and pollen data revealed no clear patterns in vegetal
resource utilization through time, the number of plant
types utilized diminished through time, being highest
in the Paleoindian and Early Archaic periods. They
also found that while antelope, mule deer, mountain
sheep and rabbits were present in faunal assemblages
dating to the Altithermal period, these sites frequently
evidenced much higher proportions of rabbit-sized
animals. For example, 83 percent of all bone at 48SW4492
was identified as rabbit size or smaller mammal (Creasman
et al. 1983).
There are two important, newly discovered,
Early Plains Archaic period habitation sites, 48SW5175
(Creasman, personal communication 1985) and the Split
Rock Ranch Site (Eakin 1 984), presently under investigation
in Wyoming. They are significant because they contain

pit house structures, among the first dating to this
period in the area. The only other site of this type
known here is the Shoreline site, mentioned earlier,
on the east edge of the study area. As reported by
Frison (1978:44), limited investigations at the Shoreline
site revealed pit house features. Excavation of one
of the features produced a fire hearth dated to about
5200 B.P. and a single large, side-notched projectile
Site 48SW5175, located in the Baxter Basin
area of the Rock Springs Uplift, produced the remains
of a single pithouse with an interior slab-lined hearth
with deflector, dating to about 5130 B.P. Diagnostic
artifacts include side-notched projectile points (Creasman,
personal communication 1985).
The Split Rock Ranch Site (48FR1484) is located
in the Sweetwater River Valley in the Sweetwater Arch
area of central Wyoming. Here investigators found
at least four and probably more pithouse remains.
The numerous features present at the site include
probable postholes, storage pits, roasting pits, and
hearths. Identifiable bone has been recovered from
the pit structures and elsewhere at the site. Preliminary
analysis of the bone and lithic materials indicates
heavy use of small mammals and wild plant materials.
Among other artifacts, the site has yielded diagnostic
side-notched projectile points (Eakin 1984).

As stated, the subsistence strategy of the
period appears to have been centered on a seasonal
round of hunting and gathering activities, but seasonality
and resource-use scheduling are as yet poorly understood.
Further research at the two habitation sites may shed
light on both of these aspects of subsistence practices
and settlement patterns.
In the concern with site distribution or settlement
patterns, numerous sampling surveys have been conducted
in recent years in southwestern Wyoming for the purposed
of developing predictive models of prehistoric site
locations. Rainer's study of the Overthrust Belt,
cited in Zier et al. (1983:91), revealed a pattern
of sites located near water, especially large, intermittent
drainages; a tendency of sites to be situated on slopes
with south and east aspects, at elevations generally
under 7200 feet; a preference for the occupation of
areas in juniper breaks; and a correlation of sites
to areas of ecological diversity. Zier and Peebles'
( 1 982) study of the Bear Divide area produced the
same results in regard to the variables of aspect
(south) and elevation.
Peebles, Hummer and Metcalf (1983:159) studied
a 10% sample of 23,000 acres in the Green River Basin.
There, they found that the most significant environmental
variables in site location were vertical distance

to dependable water, slope, relief, view, and presence
of juniper.
In the Washakee Basin, Peebles, Angulski,
and Metcalf (1983:146) found the environmental variables
of elevation and presence/absence of sand dunes to
be the most potent indicators. Sites were generally
found below 7400 feet and were often associated with
sand dunes.
Intensive archaeological investigations were
conducted for the Trailblazer pipeline, which crosses
portions of the Rock Springs and Rawlins Uplifts,
and the southern portion of the Great Divide Basin.
Here, investigators (Creasman et al. 1983) found that
80% of sites from all periods are located within the
Rock Springs Uplift and along the southern edge of
the Rawlins Uplift, areas where there is a diverse
topography of sand dunes, ridges and hills, and ephemeral
drainage valleys, and fewer sites are in the Great
Divide Basin between. Sites were found mainly in
dunes and on slopes and hillsides.
The studies discussed above, while of general
value to an understanding of prehistoric site distribution
in southwestern Wyoming, do not address the problem
of period-specific site location. They do, however,
indicate that the environmental variables used to
define "refugia" (Buchner 1980 and others) were probably
of value to this semi-arid region's occupants throughout

the prehistoric era and that the importance of these
refugia-comprising elements to Altithermal period
inhabitants was probably merely relatively greater
than in other periods.
Of greater relevance to the present study
is a recent analysis of site distribution in southwestern
Wyoming. The study indicates that the interior basins
of southwestern Wyoming, far from being abandoned,
were heavily used during the Altithermal period.
More importantly, when radiometric dating information
is added to the site distribution data, it appears
that most, if not all of the interior basin sites
date to the mid-Altithermal mesic interval, discussed
earlier, a tendency the author believes to be true
for all Altithermal sites in southwestern Wyoming
(Creasman 1984:47-48).
It is apparent that the multiple-function
base camps of the period are located in areas that
can be defined in terms of Buchner's (1 980) ecotonal
refugia. The Deadman Wash Site is located on the
edge of the Rock Springs Uplift on the west bank of
Deadman Wash, an ephemeral tributary of Bitter Creek,
just north of its confluence with Tenmile Draw. The
site is in a stabilized sand dune formation on the
edge of a marsh environment, thus allowing exploitation
of two environments. Further, there are five distinct
vegetation types and their accompanying fauna, in

the vicinity of the site. Investigators believe,
"The site's location afforded excellent prehistoric
access to water, travel routes, and varied topography
and ecology" (Armitage et al. 1982:47).
The pit house habitation sites, previously
discussed, can also be considered to be in refugia
locations. Site 48SW5175 is situated in the southern
portion of the Baxter Basin in the Rock Springs Uplift
with intermittent streams, including the semi-permanent
Sweetwater Creek, nearby. The site is on a southeast
facing ridge slope in a grassland setting with juniper
occurring on the steeper slopes to the west (Creasman,
personal communication 1985).
The Split Rock Ranch Site (Eakin 1984) lies
between the Granite Mountains on the north and the
Green Mountain on the south, in the Sweetwater Arch
of south-central Wyoming. The site is on the permanent
Sweetwater River, which provided a year-round water
supply, even during the Altithermal. The dominant
vegetation is grasslands and there is a hogback area
nearby, providing an ecological transition zone to
the mountains further north.

Chapter IV
The effects of the warm and dry postglacial
climate episode defined by Antevs (1948) as the Alti-
thermal, dating from about 7500-4000 years B.P., have
resulted in a body of archaeological theory concerning
the human response to this phenomenon.
Based on Mulloy's (1958) original cultural
framework, Reeves' (1983a) Early Middle Prehistoric
and Frison' s (1 978) Early Plains Archaic periods correspond
to the Altithermal. During this time, the Northern
Plains and its sub-areas shared a cultural homogeneity
demonstrated in similar lithic technological complexes,
which include the Logan Creek complex (Buchner 1980)
of the eastern grasslands and such western complexes
as Mummy Cave (Reeves 1969) and Mount Albion (Benedict
and Olson 1978). While the Logan Creek complex sites
contain evidence of habitation features, these are
rarely evidenced in sites of the western complexes.
Bison, present in the Logan Creek complex sites and
the easternmost of the Mummy Cave complex sites, are
absent in the faunal assemblages of the westernmost
components of this complex. Sites of all the various

complexes provide evidence for exploitation of a wide
variety of fauna and flora during the period.
It is apparent that the Altithermal climatic
episode had demonstrable effects upon the floral and
faunal communities of the Northern Plains, effects
which conditioned human adaptive responses. In an
effort to explain the human response, a body of theory
has evolved. The individual building blocks of this
theory are summarized below.
Beginning with the related concepts of a cultural
hiatus (Mulloy 1954) or a reduction in the available
fauna forcing Plains peoples to practice a foraging
subsistence strategy (Wedel 1961) during the Altithermal,
there were two directions future theories might take.
One was the non-hiatus theory, as presented by Reeves
(1973), who posited that neither the Northern Plains
nor the bison hunting strategy of earlier and later
cultural periods was abandoned. Reeves offered small
sampling size, sedimentation and the paleohydrological
sequence as reasons for the low number of radiometrically
dated sites for this time on the Plains. He documented
the occurrence of some sites dating to the Altithermal,
however, and postulated smaller bison and possibly
human populations for the period but a continuation
of the same basic human subsistence strategy of earlier
and later periods, i.e., communal bison hunting.

The concept of "refugia," as areas in the
plains where local conditions allowed the continuation
of established lifeways, was introduced by Wedel (1961).
Following Huscher and Huscher (1941), Benedict (Benedict
and Olson 1978) from the more generalized refugia
concept went on to articulate the specific mountain
refugia idea, explaining settlement and subsistence
patterns throughout western North America and postulating
a two-major-drought Altithermal, where human groups
from areas such as the Plains and Great Basin retreated
to mountain refugia.
Hurt (1966) formulated the refugia theory
most applicable to the Northern Plains which defined
refugia as areas on the eastern and western peripheries
of the plains, at higher elevations in the west, and
with a perennial water supply. Termed by this writer
as "ecotonal refugia," this theory was recently developed
by Buchner (1980), who used available paleoecological
data and multivariate statistical techniques to reconstruct
Altithermal climatic patterns for the Northern Plains.
From this he postulates a severe xerography for mid-post-
glacial central North America with a commensurate
response by humans, who responded to changes in avail-
ability of water, and floral and faunal resources
by exploiting more heavily the ecotonal refugia areas
at the grasslands peripheries.

The topography of the Wyoming Basin, can be
considered an extension of the Great Plains (Thornbury
1965). Further, the Northwestern Plains culture area
has been defined to include the area (Frison 1 978).
However, in many respects, southwestern Wyoming must
be considered not strictly typical of the Northern
Plains, being transitional to both the Northern Plains
and the Great Basin. The archaeology of the area
during the Altithermal episode was chosen for examination
because its recently expanded data base provides oppor-
tunities for the study of the Altithermal manifestation
and its effect upon a regional culture history which
is not readily available in many areas of the Northern
Plains. Further, as a sub-area of the Northwestern
Plains culture area, its archaeological record can
be viewed within the context of the greater Northern
Plains prehistory.
The Wyoming Basin is comprised of a series
of large basins separated and surrounded by various
uplifted areas. The climate is semi-arid and vegetation
is typically a sagebrush steppe. There are permanent
drainages and springs throughout the area but also
large areas with only intermittently available water.
The archaeology of southwestern Wyoming was examined
in terms of the nature and/or extent of human occupation
during the Altithermal, the nature of the Altithermal

climatic manifestation, and subsistence strategies
and site distribution during the period.
On the basis of presently available radiocarbon
dates, the presence of human populations in southwestern
Wyoming has been conclusively demonstrated. While
the data indicate relatively sparse populations for
the period compared to the Late Prehistoric period,
there is a considerable increase in population indicated
over the preceding Paleoindian period, a size approaching
that indicated for the subsequent Middle Plains Archaic
period. The data also show declines in date frequencies
for periods interpreted as erosional episodes at the
beginning and end of the Altithermal and increases
in frequencies in the mid and post-Altithermal periods.
Further, the lower frequencies associated with the
inferred erosional periods are seen as not resulting
from removal of evidence by erosion, as studies (Creasman
1 984) at sites with both mid and post-Altithermal
and no intervening occupations indicate otherwise.
Based on geomorphic, soil sediment, and pollen
analysis from recent archaeological investigations
in the area, it appears that the Altithermal in south-
western Wyoming is characterized by two major droughts
as per the Benedict model (Benedict and Olson 1978).
These are believed to date to about 7500-7000 and
4700-4500 years B.P. (Creasman 1984). The lowered
radiocarbon date frequencies during portions of the

climatic episode support the two drought concept for
southwestern Wyoming. However, information from nearby
central Wyoming (Zier et al. 1984) indicates no evidence
for a protracted Altithermal drought period there,
which supports Wells (1970) findings of a complex
Altithermal climatic pattern for Wyoming and demonstrates
the need for continued studies to better define Altithermal
environmental variability in this diverse region.
Examination of the southwestern Wyoming archae-
ological record indicates that the subsistence strategy
of human groups during the Altithermal emphasized
neither bison, which were apparently not in the area
at the time, nor the communal hunting of any other
animal. It was, instead, focused on activities dominated
by plant gathering and processing supplemented by
hunting available game (Armitage et al. 1982), most
frequently rabbit-sized or smaller mammals (Creasman
et al. 1983). There is evidence for the logistical
organization described by Binford (1980) for collectors,
manifested in the appearance of large base camps with
multiple storage features and sites with habitation
features (Armitage et al. 1982; Creasman, personal
communication 1985; Eakin 1984).
Recent studies of site distribution indicate
that the environmental attributes defining refugia
were probably always of importance in this semi-arid
region. While, the basins of southwestern Wyoming

were not abandoned, at least during the postulated
mid-Altithermal mesic interval (Creasman 1984), it
is apparent that the semi-permanent base camps and
habitation sites are located in areas that can be
considered to be refugia, areas with a perennial water
supply and two or more ecological zones to be exploited.
It should be noted here, that the refugia areas in
any period were probably universally favored, although
in times of less climatic stress, such areas may have
played a relatively lesser role in the survival of
animal and human populations.
The evidence for an Altithermal climatic episode
in western North America appears to be irrefutable.
While a basic understanding of its nature is at hand,
knowledge of its precise temporal distribution is
still somewhat imprecise and information pertaining
to regional differences in the intensity and patterning
of the climatic manifestation is still sorely lacking.
On the basis of available palynological informal
tion, Buchner (1980) has convincingly argued that
while the grasslands area increased, its carrying
capacity and available water supplies decreased.
He has also shown that there is not only an absolute
but a relative increase in the number of grassland
sites in the period following the Altithermal.
The available archaeological evidence based
upon site distribution and site assemblages for the

period indicates that human populations clustered
in refugia at the eastern and western peripheries
of the plains and that the human subsistence focus
shifted to include a more eclectic range of vegetal
and animal resource exploitation, no doubt in response
to decreased availability of bison.
As Buchner has noted (1 980), it is not likely
that arguments of erosion of sites or mistyping of
artifacts from surface sites can account for a lack
of sites in the grasslands when there are known Altithermal
components a few miles away, in some cases. Buchner
also contests Reeves (1973) contention of skewed site
sampling of the area due to a research bias favoring
the east flanks of the Rockies. Research bias or
not, there has yet to be an adequate sampling of the
grasslands as a whole. The only areas within the
grasslands proper for which there has been sampling
that might at some future time approach statistically
significant levels, and much of this sampling is not
truly random, are public lands. Further, in many instances
these lands are badlands, i.e., parts of the Williston
Basin, formed by erosion in the last few thousand
years, with only post-Altithermal soils remaining
(Albanese in Floodman, Tate and Williams 1982).
As recently as 1980, however, Buchner (1980:153)
noted that the only site known to be actually within
the shortgrass plains at the peak of the Altithermal

is Walth Bay, dated at about 7010 years B.P. He claims
that all others are either typologically or radiometrically
late in the Altithermal, post 6000 years B.P.
Nor can the data from southwestern Wyoming
be used to infer that the Northern Plains grasslands
were occupied at the height of the Altithermal. First,
southwestern Wyoming is not grasslands primarily,
but sagebrush steppe. Second, it is likely that a
hunting and gathering subsistence strategy was in
all periods at least as important, as big game hunting
in this Great Basin peripheral area. Finally, while
there is definite evidence for occupation of the Wyoming
basins, it presently appears to be limited to the
relatively mesic, mid-Altithermal period (Creasman
1984), as noted earlier, and true base camps appear
to be in refugia settings.
What can be inferred from the southwestern
Wyoming data that pertains to the greater Northern
Plains is that bison were likely absent from grasslands
areas most affected by extreme aridity and water shortages,
even though their presence is well documented for'
the preceding and succeeding periods, as in the case
of southwestern Wyoming. It is further likely that
human populations did not occupy the grasslands proper
during periods of drought, just as they do not appear
to have occupied the basins of southwestern Wyomig
during major erosional episodes, but instead exploited

the better watered refugia areas. While a dependence
on bison was maintained throughout much of the Northern
Plains, unlike southwestern Wyoming, there is evidence
throughout the area for increased use of vegetal foodstuffs
and small game, as seen in southwestern Wyoming.
In addition to demonstrating occupation during
the Altithermal, the data from southwestern Wyoming
argue convincingly for a two-drought Altithermal,
a collecting and small game hunting subsistence strategy
which emphasized development of a food storage technology,
and use of refugia. The apparent lack of bison in
the period is probably a direct result of a changed
environment and the subsistence strategy described
is seen as a cultural adaptation to this environmental
change. Therefore, the southwestern Wyoming archaeological
record has made a significant contribution to an under-
standing of the nature of the Altithermal climatic
episode, the resulting environmental change, and the
human cultural response in one part of the Northern
The present thinking on the subject of the
Altithermal has evolved from a great deal of time
and effort expended in the pursuit of knowledge derived
from various scientific techniques and disciplines,
as well as archaeology. This has also involved some
healthy speculation. In this regard we must agree
with Taylor, who stated that, "...interpretations

are both justified and required... Other disciplines
are constantly reworking their hypotheses and forming
new ones upon which to proceed with further research"
(Taylor 1948:157).
The archaeological data, from which the interpre-
tations presented herein are derived, comes from small
numbers of sites in many cases. Needed is a great
deal more information about the Altithermal and subsequent
human adaptations. On the Northern Plains generally
and in southwestern Wyoming as well, vastly more site
sampling; more radiocarbon dating of occupations,
especially those associated with geologic erosional
unconformities; and more widespread use of ancillary
disciplines and the specialized techniques that can
provide geological and palynological data, for example,
are necessary if we are to one day truly understand
both the Altithermal climatic episode and the subsequent
human response. Particularly useful would be development
of a palynological sequence for the grasslands proper,
based upon samples from either archaeological or non-
archaeological sites.
Regarding the present state of knowlege, however,
the author is in agreement with Creasman, who finds
that observed, "...changes in climatic conditions
and associated changes in cultural adaptation not
only define the Altithermal as a distinct climatic
episode but as a distinct prehistoric cultural period"

(Creasman 1984:54). Thus, though these phenomena
are imperfectly known as yet, they are definitely

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Years B.P. Site No. /Name Reference Lab Number
11 ,830410 Pine Spring Sharrock (1966) GKO-355**
11,280+280 U.P. Mammoth Irwin (1971) 1-499
96951195 Pine Spring Sharrock (1966) GXO-354
9026H18 Finley Frison (1978) SMU-250
89501220 Finley Prison (1978) RL-574
8020+90 48SW4492 Creasman (1983) Beta-5391
7520+90 48UT872 Brechtel et al. (1984) Beta-7867
7290+115 Maxon Ranch Creasman (1981)
6870+120 48UT372 Bleacher (1982) Beta-3320
6840+90 Deadman Wash Armitage et al. (1982) Beta-3924
6600+110 48CR1946 Sender et al. (1982) Beta-3738
6480+340 48UT370 Schroedl (1984) Beta-7270
64601130 48SW1668 J. Miller (1982) Beta-3012
6310+210 48SW1153 J. Miller (1982) Beta-3139*
6270+150 48CR1946 Sender et al. (1982) Beta-3704
6260+280 48CR1946 Sender et al. (1982) Beta-3708
6150+120 48CR1946 Sender et al. (1982) Beta-3705
6150+90 48SW5019 Creasman (1983) Beta-5392
6130+90 48UT872 Brechtel et al. (1984) Beta-7870
6000+140 Deadman Wash Armitage et al. (1982) Beta-3009
5900+80 48SW5020 Creasman (1983) Beta-5394
5810130 48CR1 946 Sender et al. (1982) Beta-3706
5750+190 48CR3405 Sender et al. (1982) Beta-2692
5690+100 48UT375 Angulski (1982) Beta-3323
5680+70 48SW2590 Creasman (1983) Beta-4794
5640110 48CR936 Creasman (1981) UGa-2641
5630+120 48CR3961 Creasman (1983) Beta-5438
5600+70 48SW5700 Brechtel et al. (1984) Beta-7952
5590 120 80-WY512b Sender et al. (1982) Beta-2039
5560280 48SW2590 Creasman (1982) Beta-3622*
5560 100 48CR3405 Sender et al. (1982)
5540 150 48UT872 Brechtel et al. (1984) Beta-7871
5530140 Deadman Wash Armitage et al. (1982) Beta-3133
552080 48SW4491 Creasman (1983) Beta-5390
552070 48SW1028 Greer et al. (1982) Beta-2744
551070 48SW1900 Creasman (1983) Beta-5695
5490 120 48UT375 Angulski (1982) Beta-3322
5360 100 48UT375 Angulski (1982) Beta-2434
5300110 48UT370 S. Miller (1982) Beta-3319
529575 48SW2590 Creasman (1983) Beta-4795
5220 150 Shoreline Frison (1978) RL-689
517080 48UT638 Burchett (1982) Beta-5081

Years B.P. Site No./Name Reference Lab Number
5130+160 48CR3482 Van Ness {1981) Beta-3725
5130+120 48CR1946 Sender et al. (1982) Beta-3855
5040+160 48UT63 Metcalf et al. (1981) RL-1160
494080 48SW1668 J. Miller (1982) Beta-3013
4890+240 48UT199 Schroedl (1984) Beta-7 276
4840+80 48SW5697 Brechtel et al. (1984) Beta-7951
4820 120 48CR3722 Vlcek & Merewether (1980) Beta-2087
4720670 48UT872 Brechtel et al. (1984) Beta-7869*
469070 Halfway Hill 8 Pastor & Lewis (1981) Beta-2429
4670 120 48UT779 Schroedl (1984) Beta-6945
4610 140 48SW5006 Creasman (1983) Beta-5395
4540 110 Scoggin Frison (1978) RL-174
448070 48LN329 Creasman (1983) Beta-5462
4400 100 48SW1028 Greer et al. (1982) Beta-2745
4380 170 48CR2200 Creasman (1983) Beta-5398
4330 140 48SW142 Metcalf (1975) RL-546
4320 180 48SW2369 Greer (1981) Beta-2007
4310 120 48CR3493 Metcalf-Zier (n.d.) Beta-3772
4290 150 48UT370 Schroedl (1984) Beta-7278
429070 48CR3962 Creasman (1983) Beta-5443
429060 48FR1603 Brechtel et al. (1984) Beta-8222
4210130 48SW5699 Brechtel et al. (1984) Beta-7947
419080 48SW5703 Brechtel et al. (1984) Beta-7948
418070 48FR1600 Brechtel et al. (1984) Beta-8221
416090 48SW5213. Brechtel et al. (1984) Beta-7956
4140390 48CR873 Creasman (1983) Beta-5400
3920540 48SW1091 O'Brien (1982) Beta-3347
3860 110 48FR1468 Brechtel et al. (1984) Beta-8219
385090 48CR3962 Creasman (1983) Beta-6097
3810 70 48SW4381 Creasman (1983) Beta-5166
380070 48LN1037 Creasman (1983) Beta-5167
379080 48SW3813 Decker & Vlcek (1982) Beta-3719
378590 48CR513 McGuire & Joyner (1981) UGa-3629
375575 48SW1695 Creasman (1982) Beta-3775
375090 48SW2590 Creasman (1982) Beta-3620
372060 48CR1929 Creasman (1983) Beta-5441
367070 48SW5701 Brechtel et al. (1984) Beta-7953
363580 Pine Spring Sharrock (1966) GXO-356
363070 48FR1468 Brechtel et al. (1984) Beta-8220
360070 48CR1929 Creasman (1983) Beta-5442
3455125 Cow Hollow Schock et al. (1982) UGa-3670
339060 48SW1029 Greer et al. (1982) Beta-2738
3360180 48SW1153 J. Miller (1982) Beta-3141
335570 Cow Hollow Schock et al. (1982) UGa-3568
3320100 48SW1457 Greer et al. (1982) Beta-2930
3160130 48SW1153 J. Miller (1982) Beta-3138
3160130 48CR40 Creasman (1982) Beta-3138*
315070 48SW5044 Brechtel et al. (1984) Beta-7955
310090 48SW3555 Decker & Vlcek (1982) Beta-3456
3030 120 48OT390 Reiss & Sanders (1982) Beta-2445
2870 130 Deadman Wash Armitage et al. (1982) Beta-3131*

Years B.P. Site No./Name Reference Lab Number
2870+90 48SW1448 Creasman (1982) Beta-3528*
2780190 48UT375 Angulski (1982) O'Brien (1982); Creasman Beta-2431
2740 100 48SW1091 Beta-3615*
2740 100 Deadman Wash Armitage et al. (1982) Beta-3010
266050 Cutthroat Spgs Decker & Vlcek (1982) Beta-3458
2640300 Deadman Wash Acmitage et al. (1982) Beta-3124*
2590+90 48SW3268 Greer (1981) Beta-2095
2580180 Deadman Wash Armitage et al. (1982) Beta-3130
256060 48UT872 Brechtel et al. (1984) Beta-7868
24401140 48SW2624 Greer (1981) Beta-2084
24101120 48SW2369 Greer (1981) Beta-2006
23801110 48LN531 Brock (1981) Beta-2449
23601450 48LN695 Creasman (1983) Beta-5463
23601180 48SW5025 Creasman (1983) Beta-5403
2350180 48SW2590 Creasman (1982) Beta-3624
23201130 48LN397 Greer (1981) Beta-1630
23101110 48SW1688 Creasman (1983) RL-1497
22701200 48SW5023 Creasman (1983) Beta-5405
22501100 48SW2369 Greer (1981) Beta-2008
22101180 48LN771. Sanders et al. (1982) Beta-3808
21901240 48CR698 Creasman (1982) RL-1494
2140190 Deadman Wash Acmitage et al. (1982) Beta-3129
21301170 48SW2590 Creasman (1982) Beta-3618
2130190 48LN484 Sanders et al. (1982) Beta-3380
2120170 48SW5702 Brechtel et al. (1984) Beta-7954
207080 48SW1091 O'Brien (1982) Beta-3616
2070180 48CR3768 Black (1982) Beta-5294
2060+110 48CR3779 Black (1982) Beta-5295
2010 100 48SW283 Metcalf (1975) RL-547
1975 55 48SW1229 Creasman (1981) UGa-2640
1880 90 48SW5215 Brechtel et al. (1984) Beta-7972
1850 70 48LN297 Greer (1981) Beta-1632
1845 60 Lost Quarry Metcalf & Hilman (n.d.) UGa-2050
1840 120 48SW5057 Brechtel et al. (1984) Beta-7988
1820 110 48SW1211 Creasman (1982) RL-1496
1820 80 48UT375 Angulski (1982) Beta-2435
1810 70 48CR3482 Van Ness (1981) Beta-3726
1115-lb 48SW1184 Creasman (1981) UGa-2642
175060 48SW1433 Creasman (1981) Beta-3527
174060 48UT390 Reiss and Sanders (1982) Beta-3324
173575 48SW1229 Creasman (1981) UGa-2643
1710200 Deadman Wash Armitage et al. (1982) Beta-3125*
1710100 48LN484 Sanders et al. (1982) Beta-3380
168090 48UT194 Brechtel et al. (1984) Beta-7949
168080 48CR2785 Bradley (n.d.) Beta-3057
167060 Lost Quarry Metcalf & Hilman (n.d.) UGa-2051
165090 48CR2200 Creasman (1983) Beta-5399
164090 48SW2049 Decker & Vlcek (1982) Beta-3449
1610 50 48SW2665 Tucker (1982) Beta-2439
1580110 48SW5215 Brechtel et al. (1984) Beta-7873
1580*110 Wardell Frison (1973) RL-102