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Re: causes of K-T ferns
The thing that really bugs me about the volcanic derivation of the iridium
anomaly is where are the bentonite layers that one would expect at the
boundary? Is there that much iridium in volcanoclastic rocks that would
give the same signal in Montana, Italy, and other places in a layer only a
couple centimeters thick? Has anyone looked closer in to the Rockies for
bentonites that are thick, correlative with the boundary layer, and are
enriched in iridium? How many bentonites have actually been investigated
for iridium enrichment?
Second, as far as the overgrazing by Triceratops causing the fern spore
spike, where are all the Triceratops that should be near or at the
boundary? If there are suddenly enough Triceratops to overgraze an area
that size, where are they all? Plus, wouldn't you then expect there to be
fern spore spikes earlier in the Lancian, where we do find lots of
Triceratops? Or maybe places where there is bentonite that proves there
was an eruption? Has anyone looked at deposits of the last major eruption
of Yellowstone or even Mt. St. Helens for a modern analogue to the fern
Last thing: as far as I know, and it may not be all that far yet, there
aren't any definite lambeosaurines that have been found in rocks of Lancian
age. Same thing with centrosaurines. It seems difficult for
lambeosaurines to be "eaten to death" by a predator that they never even
met. They were surely accustomed to the tyrannosaurids that were their
contemporaries. It seems to me that they were lost due to background
extinction. Any thoughts?
There sure seems to be a lot of work that needs to be done in the rocks
before the extinction to see what exactly changed during the extinction.
University of Wisconsin-Madison
Department of Geology and Geophysics
1215 W. Dayton St.
Madison, WI 53706