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Reef madness (was RE: K/T revisited, was: Re: DINOSAUR digest 3382)
> From: email@example.com [mailto:firstname.lastname@example.org]On Behalf Of
> David Marjanovic
> Didn't the corals (which also have planktonic
> larvae) need the entire Paleocene or so to form the first full-size Cenozoic
True, but that may in part be due to longer-term changes in ocean chemistry.
Here's the condensed version: the oceans have two main
phases as far as which form of CaCO3 is easier to produce. These are calcite
oceans vs. aragonite oceans. Calcite oceans (which tend
to be associated with both higher mid-ocean ridge activity and higher sea
levels) favor organisms that put down massive amounts of
calcite; aragonite oceans (with lower mid-ocean ridges and generally lower sea
levels) favor aragonite.
During the Jurassic and Early Cretaceous we had aragonite oceans, and
scleractinian corals flourished. In the later Early K and the
Late K, there was a shift to calcite seas, the scleractinians did worse, but
the rudists (and inoceramids) bloomed. Even after the
K/T extinction, the oceans were still in the calcite phase, but the main
calcitic reef formers present (rudists) had been clobbered.
The scleractinians had to wait for the oceans to shift back to aragonitic mode
before they could put down lots of reef material
Hope this helps,
Thomas R. Holtz, Jr.
Senior Lecturer, Vertebrate Paleontology
Department of Geology Director, Earth, Life & Time Program
University of Maryland College Park Scholars
Building 237, Room 1117
College Park, MD 20742
Phone: 301-405-4084 Email: email@example.com
Fax (Geol): 301-314-9661 Fax (CPS-ELT): 301-405-0796