>Good. Then fish fossils are definitely associated with the laminae which
>have been interpreted as annual varves. Now, do we see annual varves
>accumulating today which also have interbedded dead fish which might
>potentially become fossils under the right conditions? We need a
>credible model/mechanism for the preservation of dead fish until they
>eventually get buried if the varve theory survives.
>
>I am also surprised that the laminae were not destroyed by bioturbation
>if this was a lake-bottom environment of slow accumulation.
>
That argument has been tried, but the bottoms of the lakes is assumed to
have been anoxic, and eutrophic due to accumulation of H2S in denser
hypersaline water below. When the lake turned over, probably annually, the
surface waters would become toxic, and there would be mass mortalities,
which would subsequently become entombed in sediments. I know the evidence
for this kind of environment is substantial and that there is a good model
for this kind of environment in a modern lake in Africa. But I don't know
if preserved fish have been found in the sediments there. As far as
floating versus sinking, Brand has done the most extensive studies of which
I am aware on thanatology (really gross stuff). He gave a talk on this at
GSA a couple of years ago in New Orleans. He knows how long things float,
how fast they disarticulate and when they sink under a bunch of different
conditions. Most fish do float because they have swim bladders which
accumulate gases. But fish without bladders will probably never float. No
bioturbation, because no biota.
Art
http://chadwicka.swau.edu