Geoscience Reference
In-Depth Information
logical background made her a valuable asset in helping us to unravel
the environmental mysteries at the site and refine the time period dur-
ing which the dinosaurs lived. Javier Guevara is an undergraduate
geology student. In addition to helping us collect fossils, he also
assisted in collecting and documenting the geologic data that would
paint a picture of the ancient environment that the dinosaurs lived in.
Lowell's geological team faced a basic question. Was the embryo
quarry located in the same rock layer that was producing eggs a half
mile away at the flats, or was it contained in a different egg-produc-
ing layer? If it was in the same layer, all the eggs would have been laid
at about the same time, but if it was in a different layer, the site
would contain at least two nesting grounds that had been inhabited
at different times. To find the clues to solve this mystery, we had to
walk on the egg-producing layer all the way from the quarry back to
the flats. We traced the layer that contained the eggs across the
rugged ridges and ravines of the badlands back to the area around
the flats where Lowell had measured the stratigraphic section. It was
easy to follow the layer because of its dark reddish brown color,
muddy texture, and the eggshell fragments that had weathered out
on its surface. After a half hour of careful hiking, we established that
the quarry was in the same layer of mudstone that had produced fos-
silized eggs on the flats. So it seemed as if Auca Mahuevo repre-
sented just one enormous nesting site.
The wind blew mercilessly throughout the night of November 12
and all through the next day. Patagonia was testing our mettle with a
blast of nasty weather. Gusts as high as fifty miles per hour stormed
across the dusty landscape, sandblasting everything in their path,
including our eyes. Many of our tents were blown over or damaged,
so we had to spend much of the day tending to camp.
When the weather calmed, we returned to our work. Over the next
two weeks, we collected dozens more eggs, including both fragments
with patches of fossilized skin from the flats and clusters containing
bones of embryos from the quarry in the badlands. In several
instances, collecting the clusters of eggs required the preparation of
large plaster jackets to protect the eggs during the trip back to the
museum. The primary responsibility for this operation fell to Pablo,
Sergio, and Marilyn Fox. Marilyn is an excellent fossil preparator at
Yale University for Jacques Gauthier. We had known Marilyn for
