Geoscience Reference
In-Depth Information
basic geological features. The paleontological and geological teams
then split up and began their separate operations.
The first task for our fossil collectors was backbreaking. Luis and
Rodolfo wanted to expose a large area of the egg-bearing layer at the
quarry where we had found the embryos on our previous trip, but this
would involve considerable excavation. At the nose of the ridge where
the embryos had been found, most of the mudstone layer containing
the eggs was buried under three to four feet of other rock. This spot
was not easily accessible, so we could not use a bulldozer to clear off
the overburden. We all knew that a more primitive approach would be
required.
With everyone pitching in, we hauled the picks and shovels up
the ridge and set to work. Our goal was to expose an area of the egg
layer about thirty feet long by fifteen feet across, which would
require us to remove about thirty to forty tons of overlying rock. It
was a long, hard day, but with about ten people helping, we were
nearing the top of the egg layer by the end of the afternoon. Once we
got close to the top of the egg-bearing layer, we would trade our picks
and shovels for smaller rock hammers, chisels, and dental tools to
excavate the eggs without breaking them. But we could begin that
job the next day.
A mile away on the other side of the field area, Lowell and the geo-
logical team were doing some digging of their own, though fossil eggs
were not their quarry. Several hundred feet of sandstone and mud-
stone layers lay on top of the egg-bearing mudstone, but we had not
had time to measure or collect magnetic samples from these layers
during our first trip. Our intent now was to continue measuring the
rock layers above the egg-bearing layer and collect more samples for
magnetic analysis. Starting just above the same layer that contained
the egg quarry, we began working our way up the ridges.
Lowell described the rock types and measured the thickness of the
layers for the stratigraphic section. Julia Clarke and Alberto Gar-
rido, an Argentine graduate student in geology from the University of
Cordoba, collected rock samples for paleomagnetic analysis. Alberto
is a handsome, soft-spoken young man in his late twenties who, in
addition to his general geological training, is familiar with the rocks
of this region because he grew up in the area and has volunteered as
one of Rodolfo's field assistants since he was a teenager.
