A moderate amount of bone has started showing up in both pits, although since we’re mostly working in deeply weathered material we usually can’t tell yet what kinds of bones we have. But we are getting some interesting – and identifiable – elements from the northeast corner of the pit.
I pulled out the weathered, indurated chunk shown above this morning. When I turned it over I realized that it’s two articulated vertebrae. They are mid-range thoracic vertebrae, probably somewhere around the 5th or 6th thoracics (which would make them around the 12th or 13th vertebrae overall). They come from a whale that probably wasn’t fully mature, based of the detached epiphyses between them. They’re also pretty large for a Carmel Church whale, bigger than “Sinistra” and probably comparable to “Popeye” (which were both adults). They are also consistent with the ribs we removed yesterday. In fact, we’ve now pulled parts of at least six ribs from this area that all seem to come from one individual whale.
But today’s most remarkable find was not even a fossil. These whale bones have been coming out of a drainage ditch in the northeast corner of the site, with the initial bones found just below a large rock. In the photo at the top, Ashley is resting her feet on this rock.
When we started digging here on Monday, I assumed that the rock was set here by the quarry over 20 years ago for erosion control; big rocks are not exactly uncommon in a rock quarry! I noticed that the visible edges were rather rounded, but I figured that was a result of sitting in a drainage ditch for 20 years.
As I worked I started noticing some strange things about the rock and its relationship to the fossils. As you can see in this photo I took yesterday, the fossils are pressed tightly up against the rock on at least two sides:
Today I discovered that some of these fossils were actually articulated bones, and that they were in many cases actually in contact with the rock and even slightly above it. I realized that there was no way this rock had been dumped here during quarrying operations. The rock was actually in place, in the Calvert Formation; it’s part of the Carmel Church conglomerate!
It’s hard to express just how huge this boulder is; I’d guess it’s at least 10 times larger than the next largest rock we’ve found in the bonebed. In an effort to find out just how big it really is, I started cleaning off the top surface, but ran into a problem:
See the small round object on top of the rock, just below and to the left of the scale bar? Here it is up close:
It’s actually a small patch of apparently in-place Calvert Formation, complete with a small whale vertebra.
This rock causes an interesting geological dilemma. I did a quick calculation to figure out how much the visible part of the rock weighs (remember, I haven’t found the end of it), and came up with about 1,700 pounds. How does a rounded boulder that size end up in a marine deposit surrounded by silts and clays, and whale skeletons?
Of course, this means we’re going to need more data. Are there other rocks this size in the quarry? If so, why in 22 years haven’t we found anything else even close to this size? This is the farthest to the east we’ve ever dug in the quarry, so are we looking at a lateral grain-size gradient? These are new questions I’m going to have to consider as we attempt to work out the depositional environment at Carmel Church, which will hopefully move us closer to understanding the origin of the bonebed.