Mammoth Rub Update - Society for California Archaeology

32
1998:23, 28).
The Red Hill site is interesting because of its higher
elevation and association with what may be a much older
uplifted terrace. The polished surface of the Red Hill boulder
measures about 1 m square and is almost completely covered
with lichen. Lichens have been slow to colonize the polished
surfaces of the lower rubbing rocks at Mammoth Rocks and
Jasper Rock. The fact that the polished surface at Red Hill is
almost completely obliterated from view by lichen growth
suggests that the rubbing rock has gone unused for a much
greater period of time than have the rocks further below on
QMT5.
Current Research
During summer 2004, I am again working with a
volunteer crew in the 4x4 m exposure at Jasper Rock. The
exposure is being expanded in order to make it safe enough
to continue the deeper excavation. Tom Origer’s fall 2004
fieldclass will return to the site, and by the end of this year,
we hope to have a better idea of what is to be found in the
deeper depths of the site. However, given the difficulty and
depth of the excavation, we may not have many answers until
next year.
Also in summer 2004, Jack Meyer of Sonoma State
University excavated a column sample from the 4x4 m
exposure at Jasper Rock. The excavated sample will be
subjected to flotation analysis. As part of this same project, we
hope to obtain a radiocarbon date from soil in the lower
cultural component (i.e., from the lowest layer of the site that
we know to be cultural).
Meyer will also conduct flotation analysis of a column
sample I excavated at Mammoth Rocks in fall 2002. At
Mammoth Rocks, I excavated a single 1x1 m control unit
adjacent to a heavily-polished rock face. In my excavation, I
encountered a 0-48 cm dark brown topsoil (Rohnerville
Loam) overlying a compacted yellow loam subsoil. I
recovered several chert flakes in the 0-20 cm levels, and
quite a few more in the 45-70 cm levels. The chert flakes in
the subsoil appear to have come from CA-SON-1713, a green
chert source (with evidence of quarrying) located about 250
m north of Mammoth Rocks. The chert flakes found in the
topsoil were brown and gray in color, and came from
elsewhere in the area.
Drs. Marvin Rowe and Karen Steelman of the Department
of Chemistry, Texas A&M University, have agreed to use
their plasma-chemical extraction (PCE) method in an attempt
to date samples of the polished rocks by direct AMS
radiocarbon measurement (Rowe 2001; Rowe and Steelman
2002). They have had great success in the past at extracting
and dating organic carbon from pictographs using the PCE
method, and may be able to apply it to the polished rock
samples with the same results. They will work with samples
from both Jasper Rock and Mammoth Rocks.
SCA Newsletter 38(4)
Vernal Pools as Rancholabrean Wallows
Included among California’s most precious natural
resources are the state’s vernal pools, seasonally flooded
depressions found on ancient Ice Age soils with an
impermeable layer such as a hardpan or claypan. The origin
of the pools has always been a bit of a mystery, and there are
several theories that have been offered to explain them.
During earlier times, these features in the Central Valley
were often referred to perhaps derisively as “hogwallows”
just as similar features were referred to as “buffalo wallows”
on the Great Plains (Anonymous 1998:15). I have recently
added a new theory to the mix. In 2003, I hypothesized an
association between vernal pools and ancient Rancholabrean
wallows (Parkman 2003b). My reasoning began with an
observation at Mammoth Rocks in 2001. 20 The site contains
an unusual wetland depression which measures about 0.5 ha
in size. The depression is encircled by four loci of polished
rocks. As unlikely as it may seem, I believe the depression
may be a relic wallow left over from the late Pleistocene. If
that is the case, then its presence helps explain the rubbing
rocks that encircle it.
Contemporary rubbing rocks are typically associated with
the bathing and grooming behavior of megafauna. For
example, African elephants wallow at waterholes in order to
coat themselves in mud, then, as the mud dries, they rub it off
against a hard object, often a large boulder. This helps
remove extoparasites from the animal’s skin. Bison often use
dry wallows for a similar purpose.
I suspect that Ice Age mammoth and bison had similar
practices to their modern-day counterparts. If so, then it
seems probable that some of California’s vernal pools began
as animal wallows. In the case of those that did not, it seems
likely that they served as useful waterholes in late spring and
early summer, and would have thus been affected by the very
presence of the megafauna (e.g., African elephants are known
to enlarge and “improve” waterholes).
California’s vernal pools are typically associated with late
Pleistocene soils and landforms (Anonymous 1998:18;
Holland 2000:31-32; Stone 1990:91). While some of the
Pleistocene pools have undoubtedly filled in over time, it is
likely that many of these depressions have survived through
the ages. The use of the vernal pools by megafauna during
the late Pleistocene would have maintained many of the
pools’ depressions until the time of the megafauna’s
extinction, perhaps as late as 10,000 CALYRBP. The repeated
use of the wallows by the megafauna would have prevented
the California flora from colonizing the depressions for any
length of time. However, upon the demise of the megafauna,
and for the past ten millennia, the plants would have been
free to move in and colonize the abandoned wallows. It is
likely that plant adaptations and ecological dynamics
mitigated against the in filling of many of the pools. Thus, if
my hypothesis is accurate, many of California’s vernal pools
were born of abandoned wallows at the dawn of the
Holocene. I am currently exploring how best to investigate
this aspect of the Rancholabrean Hypothesis.