Several
teams of three were assigned to dig geologic trenches today as part of our
continuing effort to understand in detail the structural and sedimentary history
of the Olorgesailie Basin. While our excavation trenches tend not to be very
deep (we try to dig through the least amount of overburden as possible), geologic
trenches often climb the entire hillside, and we try to pick the tallest slopes
that will crosscut the most amount of sediment. Also, while excavation trench
sizes (length and width) are determined by the distribution of fossils and
artifacts within the site (the Elephant Site, with its nine extensions, is
now about a hundred square meters), geologic trenches are usually only a meter
to a meter and a half wide. 
Thus
they resemble knife cuts going straight up the hillside. We are interested
primarily in the sediment layers of Members 7 through 10 this season, a complex
series of events starting around 780,000 years ago, that have bearing on many
of the sites we are currently excavating, and have on our list to do in the
near future.
Work
also continued on the Member 11 sites A11-10 and 15. The "C"
sand layer at Site A11-10 is yielding many tools and fragments of bone and
tooth. A partial lower jaw of a large antelope or horse was uncovered this
afternoon. Additional clusters of stone tools are being uncovered, making
the excavation crowded with specimens. We are going to have to lift at this
site tomorrow. An advance crew went to the site this afternoon to place a
new datum for removing the artifacts. Because of the geometry of the site,
we had to place the datum within the boundary of the old excavation. Normally
we wouldn't have wanted to do this, but there was no other way to see the
entire excavation from a single transit position. 
After
we were done setting the new datum, and had verified its position on the coordinate
grid, we did a little numbering of the artifacts and bones to get a head start.
We got through 134 specimens before the light gave out, and we were not even
a quarter of the way done.
Bright and early tomorrow for the lift.
-RP