Plains Indian Studies - Smithsonian Institution Libraries

NUMBER 30 197
nent is located in the same locality, it is in a
different arroyo than the one containing the stratified
Polsom, Agate Basin, and Hell Gap components.
During early Paleo-Indian times, or probably
around 12,000 years ago, the Agate Basin locality
was characterized by a deep arroyo with steep
banks and a wide flat bottom with occasional
barriers in the form of knickpoints, which formed
small but effective impediments to large animals
moving up and down the arroyo bottom. This
arroyo was and still is advancing through headward
erosion into a large, relatively flat. Pleistocene
surface.
The arroyo was one of several that ultimately
formed a small, low gradient and intermittent
watercourse known as Moss Agate Creek, which
eventually drained into the Cheyenne River. A
low but prominent divide separates Cheyenne
River and Moss Agate Creek, and from this exposed
location the timbered slopes of the southern
Black Hills are quite visible across the Cheyenne
River. Present at the site, during Polsom times at
least, were the heather vole {Phenacomys intermedius)
and the red-backed vole {Cluthrionomys gapperi),
which strongly suggest a more shrublike
understory at that time in contrast to the sagebrush
and grass cover today. Shrubs could have
been of importance to Paleo-Indian hunters in
providing material to build structures to augment
the natural topography for bison procurement.
The old arroyo at the Agate Basin site locality
began to aggrade during Clovis times and continued
until the youngest known cultural component.
Hell Gap, was buried by 3 to 5 meters of
alluvium. Studies have not yet been able to determine
when the system began to degrade, but
old trenches revealed in profiles suggest that when
it did, part of the aggraded deposits were removed.
This may have been an Altithermal period
phenomenon. There are, in fact, some geological
deposits present in the site locality that
have produced artifact material diagnostic of the
Altithermal or early Plains Archaic periods. However,
these deposits have not yet been properly
studied.
The trenches into the Paleo-Indian alluvium
were later filled and another period of degradation
began that ultimately produced the present
topography. The present main arroyo chose a
somewhat different course, which removed entirely
some of the older deposits, partially exposed
others, and in some places left the old deposits
intact. This situation confused earlier investigators,
who assigned separate site designations to a
large number of Paleo-Indian site exposures that
were, in reality, closely interrelated by the arroyo
system. Soils and climate provided food for optimum
winter range conditions for bison and, in
turn, provided ideal topographic features for winter
bison trapping.
The old arroyo at Agate Basin was the scene of
many separate Paleo-Indian bison kills that varied
in the number of animals taken. One Polsom
kill, for example, contained about eight animals.
The original Agate Basin site component may
have contained over 100 animals, but this very
likely represented more than one procurement
event. The one known Hell Gap component contained
between eight and ten bison. As mentioned
above, the one in situ Clovis component is in
another location and appears to be a spring or
early summer camp site. They were utilizing
bison but we do not know the means of procurement.
However, there is a high probability that
further site investigations will reveal Clovis components
underlying the other Paleo-Indian components.
The study of bison remains in Polsom, Agate
Basin, and Hell Gap components points unequivocally
to winter kills. Fortunately, there are adequate
samples of young animals and, in addition,
fetal material to help establish animal ages at the
time of death. It is suggested that the animals
were first butchered and then frozen. The units
were piled and used as needed. Obviously, the
meat piles required protection; evidence suggests
that the hunters may have camped alongside the
meat piles, withdrawing food as needed. The
wide, flat-bottomed arroyo would have provided
a satisfactory camping location during the winter
months.