Tuesday, March 15, 2011

It's What Follows "We Don't Know" That Matters

Paleontologist Alton Dooley of the Virginia Museum of Natural History is leading ground breaking work (literally) at the Carmel Church Quarry in Virginia.  The week-long dig that Dooley ran last week with his wife, son, and four college students is featured in this morning’s  Washington Post (March 15, 2011).  The video accompanying the story makes clear the conditions under which this dig took place.  No lounging on warm sand in the sun, and no frolicking in the surf for these college students who went fossil hunting on their spring break.  This is messy and difficult work as the mud-caked boots and hands testify.  It’s also rewarding in terms of the fossils found.   Dooley described some of each day’s finds on his blog Updates from the Vertebrate Paleontology Lab.

At the Carmel Church site, a Middle Miocene bed of the Calvert Formation is exposed (see Trochim and Dooley, Diatom Biostratigraphy and Paleoecology of Vertebrate-bearing Miocene Localities in Virginia, Jeffersoniana, No. 23, 2010).  An initial striking feature of the site is its remarkable concentration of marine fossils, among them, according to the article, 17 whale and dolphin species, and many fish species, including more than a dozen kinds of shark.  As the Post article described it,
Some of the fossils are pressed together, overlapping, as if they had settled to the bottom on top of one another.  Some have bite marks, evidence that the carcasses had been eaten by sharks or other scavengers.
Clearly, there’s an abundance of fossils here; Dooley notes in the Day 3 posting on his blog that even the author of the Post piece, Eric Niler, during his visit to Carmel Church, stumbled upon a sturgeon bone fossil.

A second remarkable aspect of Carmel Church, given that the Calvert Formation was laid down when the area was under water, is the “unusual abundance of terrestrial animals and plants” that have been found here, relative to other Calvert Formation sites.  (Dooley, Barstovian (Middle Miocene) Land Mammals from the Carmel Church Quarry, Caroline County, Virginia, Jeffersoniana, No. 18, 2007.)  Dooley has offered a possible explanation,
Carmel Church is the westernmost known exposure of the Calvert Formation, and is therefore possibly the nearest to the paleoshoreline as well.  (Jeffersoniana, No. 18)
I guess the logic is that terrestrial creatures swept out to sea, for whatever reason and in whatever condition (dead or alive), would be more likely to be found here rather than places farther from shore.

But the mystery that seems to most envelop Carmel Church is why this site has such an incredible concentration of animal (mostly marine) species.  In the Post piece, Dooley is quoted as stating frankly, “We don’t know how they got here.”

To my mind, part of the beauty of science is what follows such an admission of ignorance, that is, the challenge of looking for answers among possible natural causes.  Just as with a Carmel Church dig, it’s a messy procedure.  This one involves asking questions, fashioning and testing hypotheses, making mistakes and correcting them, and, perhaps, coming up with an explanation that gains traction.

And Dooley is looking for answers.  The article closes with a couple of sentences that wonderfully capture some of the essence of this process.
“We have some partial explanations,” Dooley said with a smile.  “But I’ve gotten used to being wrong.”

I have tweaked the syntax in several sentences after first uploading this post.  It's the price I pay for being in a hurry.

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