Geoscience Reference
In-Depth Information
and study. Excavating a fossil is called quarrying and means digging
around a bone or skeleton that is buried near the surface of the
ground and encasing it in a protective jacket of toilet tissue and plas-
ter bandages. First, tissue is placed over the fossil bones and moistened
to form a protective layer between the fossils and the plaster bandages,
and then the bandages are applied. Once the bandages dry, the jacket
can be lifted out of the ground and transported safely back to a
museum without damaging the fossils inside. The time required to
quarry out a dinosaur skeleton often depends on the hardness of the
surrounding rock and the size of the specimen. During this expedition
we would eventually need to both prospect and quarry.
Our first day in the field we uncovered nothing new and exciting.
Luis and his crew found scraps of fossil bone: some fragments of tur-
tle shell, small pieces of shell from a dinosaur egg, and armor plates
from ancient crocodiles. Rodolfo and his team found the tail section
from the skeleton of a small sauropod called a titanosaur, not a bad
discovery but not significant enough for a team of collectors to
spend a whole week excavating.
By looking at the clues in the rock layers, Lowell noticed a good geo-
logic reason for why we were finding only fragments of bone. The lay-
ers of rock around the
puesto
were composed primarily of cemented
sand, gravel, and even small boulders that had been deposited by fast-
running rivers or streams on an ancient alluvial fan or wedge of debris
that lay fairly close to some small mountains or hills. Alluvial fans are
found at the mouth of many mountain canyons today. Lowell knew
that swift, turbulent currents are required to carry such large objects
and that these would destroy most skeletons of dinosaurs and other
animals being carried along in the river. So, these rock layers, although
beautiful, were probably not the best place to look for well-preserved
fossil skeletons. Nonetheless, these layers of sand and gravel some-
times contain pockets of mudstone and siltstone, deposited by slow
eddies in quiet parts of the channel, where more complete fossil
skeletons can be preserved. However, from the top of outcrops near the
puesto,
we could see another extensive set of glowing reddish brown
badlands off in the distance, and we thought that they might contain
more complete fossil skeletons, if we could find a way to get to them.
On the morning of November 9, we drove off in that direction. As
we bounced back toward the main road from Neuquen, we passed a
