Geoscience Reference
In-Depth Information
In the morning, Dave and I said good-bye to his friends, who were off to see
other parts of Montana, and he and I returned to the field site to resume our handi-
work. The fresh familiarity of the previous day made the walk seem shorter, al-
though we also moved a little more quickly in anticipation of learning something
newthatday.Onceatthesite,wefirstusedshovelstouncoverthethinlayerofsed-
iment dumped ontopofourobjective, butsoonset these aside once the white sand-
stone emerged. Replacing the shovels with rock hammers—pointy ends first—and
small hand picks, we began breaking the mudstone closest to the sandstone. Our
goal was to reveal this mystery structure in all of its full three-dimensional glory,
which would answer many of our questions or, more likely, generate a lot more.
While we worked, I kept comparing the whitish structure in front of us to the
flat digital image Dave had sent me the previous month. It definitely was a big,
sandstone-filled tube, cutting across the mudstone around it. Starting from above,
it turned into a horizontal segment, and then twisted down to where the dinosaur
bones resided until just recently. Despite this torsion, its width stayed constant
throughout, at about 30 to 35 cm (12-14 in). If emptied of its sandstone fill and
turned into a hollow tube, it would have been too tight of a fit for Dave or me to
crawl into (especially after the previous night's meal). But it would have been per-
fect for a five-year-old child, or a small dinosaur.
What was its exact form? Before we started, I told Dave that I thought it was
semi-helical, descending with regular turns and not quite making a complete spiral:
more like a water slide rather than a corkscrew. But this was mostly a hunch based
on what I had seen in much smaller invertebrate burrows with similar forms. Was it
wrong for me to apply the same reasoning to something many orders of magnitude
larger? I wasn't sure, considering that this was the first time I had seen something
like this in the geologic record.
I also speculated about trace fossils of other animals that might be there and
connected directly to the supposed dinosaur burrow. For example, modern gopher
tortoiseburrowsplayhostto200to300speciesofotheranimals,makingthemmore
