Posted: Feb 28, 2010 2:07 pm
by theropod
This post is a related follow-up to the above, also previously a part of the archive.

Details of field work in vertebrate paleontology:

One summer we had a volunteer on a dig crew that was a little ignorant of the methodology we employed when recovering vertebrate fossils. I think in this case we had located the left front leg of a Triceratops horidus from the radius down (maybe there were couple phalanges missing I can't remember). This semi articulated set of fossils was not all visible in an exposed state, and unfortunately this was the extent of that particular find.

When we started laying out a grid and taking measurements before we even started digging this person got the strangest look on his face, and stood in silence watching. When we began a stratigraphic site examination and still weren't actually digging to uncover the bones he couldn't stand it any more. A string of questions followed, which we answered as we continued our preparatory work.

We explained that we were laying out the grid so that we would be able to reconstruct the depositional data at a later date. We showed him that we could determine if the fossils were deposited to their current position as a result of water transport and if so what sort of actions had taken place to leave the fossils in their present positions. The grid, we explained, would allow us to construct a map that would allow us to better understand what had happened so long ago, and document the whole affair. We went into detail to show him that if there was a great deal of this particular triceratops would could not currently see we would be able to determine if, or how much, scattering has taken place, and maybe the reasons for that scattering.

We didn't have to spend near as much time explaining the stratigraphics, as we actually had him help with that. When he saw the layering with diverse types of sediments and how we we recording these layers from well above to well below the horizon in which the fossils had been found he had a "light bulb" moment. We showed him how there had been multiple ash falls and overbank flooding and the distinction each layer exhibited. We did out best to show how we could tell by the clastic characteristics what forces had worked to leave this data. In the process of collecting this data we stuck a layer of heavily lignitic material that clearly represented a long stable period in which a great deal of organic matter had been laid down without disturbances. In this layer we located several thin coal seams with embedded tiny amber nuggets. This volunteer then became much more interested in the sedimentology than recovering the bones.

The entire point being that without the associated data one collects as a fossil is recovered all one has is a dinosaur bone. A dinosaur bone, alone, only tells us that a dinosaur died and here's the bone. However when one collects every scrap of information that is available we can tell if the dinosaur was fossilized where it fell, if scavengers spread the remains out or carried off portions thereof, if the bones were transported to their final resting place by a flood and how intense this flood may have been, and a great many other data points. Far too many lay persons think all there is to collecting fossils is to dig 'em out of the ground. Of all the fossils I saw recovered none of the data points suggested anything other than deposition by natural causes.