Back to work today, after yesterday's R'n'R.
We
hit our target at Site 15 today; the paleosol layers that contained the elephant
fossils we originally excavated. Just within this layer we began uncovering
fossils very different from those above. While the microfauna are present
in this layer as well, we are uncovering bones of large grazing animals, which
is consistent with the switch from diatom-rich sediments to soils. We are
going to excavate the layers following the contours of sediments from here
on out, instead of sticking to arbitrary 5 cm thick spits. This is done to
ensure that artifacts and fossils are properly assigned to the correct sedimentary
environment, as well as to aid our attempts to reconstruct the landscape of
the basin at this period. Continued excavation should soon uncover the level
with the curious stone cobbles.
Our
microfuana project continues, with our concentration shifting to the sieving
of samples from several of last year's fossil sites. Bags of sediment taken
from the excavations are analyzed for both fragments of bone and stone tools.
A useful byproduct of our microfaunal analysis is that small flakes
of stone tool, which would have ordinarily gone unnoticed, can also be recovered
at the same time as the bone. Thus we not only can reconstruct ancient environments
with our efforts, but also determine if a sufficiently large number of stone
tools are going unnoticed to warrant careful examination of all of the previously
excavated sediment.
The
transit expedition to place three datum points in Locality B, which we had
tentatively planned for today, had to be postponed until tomorrow. While checking
the data from the test run, we noticed a 7 cm discrepancy between the elevation
values we were reading on our instruments and those we had recorded. While
a 7 cm error may not seem like a whole lot at distances of over a football
field in length, remember our instrument is sensitive to changes of only 5
mm, at distances of up to a kilometer. We were worried that the transit might
need adjustment. So today we tested the transit and the team at two known
points in our camp. They were able to gauge the elevations of the test points
to within 3 mm, well within the confidence limit of the machine. We believe
that there has been some disturbance in the position of one of the test datums
we used. Since we haven't visited these transit sites in nearly 6 years, it
is possible that some movement due to small earthquakes has occurred that
has altered the elevation of one or both of the points to create the error
we were noticing. The important thing is that the transit works.
-RP