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Posted by on Sep 14, 2013 in Book Review, Geology, Science | 1 comment

Darwin’s Doubt – Chapter 2 – Part 1

Ah, it was a very near thing today.  I don’t feel good and I’m tired, but I have a chance to write, so here we go.

The end of chapter 1 is just an introduction to chapter 2.  So, lest someone say, “He didn’t read the whole thing.” I did.  It’s just not relevant to anything.

This post is about the introduction to chapter 2.

The title of this chapter is “The Burgess Bestiary”.  This is obviously named after the famous Burgess Shale, which is a geological formation of shale rock.  But when most people say “Burgess Shale”, they are referring specifically to one of the fossil beds.

First, let me give  quick primer on the Burgess Shale.  This a formation in southwestern Canada about 150 miles west of Calgary.  It is a member of the Stephen formation and about 505 million years old.  It’s considered to be in the middle Cambrian (which lasted from 541.0 ± 1.0 to 485.4 ± 1.9 million years ago).  It is best known for some truly fascinating fossils.

As I’ve talked about in the past, fossilization is a rare event anyway.  Especially of the soft parts of organisms.  We mostly get bones, shells, and teeth.  Which is part of the problem, all the truly early organisms didn’t have hard parts at all.  What makes the Burgess Shale fossil beds so interesting is that they do contain fossilized bodies of organisms… that don’t have bones or shells.  A mere 14% of the fossils recovered have hard parts.  The fossils also show what may be a nearly complete ecosystem with sessile (non-mobile) filter feeders, small mobile organisms and a few large-bodied predators.

Recent evidence indicates that oxygen was present during the fossilization process and other factors may have prevented decomposition of the organisms.  Here’s a good primer on the fossilization of the Burgess Shale organisms.  And some information on the specific geology and fauna of the shale bed.

That’s basically it for the introduction to Chapter 2.  The next post in the series will start with Meyer’s “The Bestiary”.

As always, if you have any questions, please let me know.

The rest of the series.

  • Dave’s Not Here

    Under the “recent evidence” link, the abstract actually lists anoxia of the sediment/water interface and below as a factor in preservation. However, anoxia of the whole water column (the explanation given in Wonderful Life) is no longer accepted.