Orbiting debris and K-T

[Ralph Chapman <MNHAD002@SIVM.SI.EDU>]

Dana Pagel was wondering about the lack of large numbers of carcasses at
the K-T boundary and what it says about mass extinctions. Not much, I'm
afraid. For a while Kay Behrensmeyer and I have been doing taphonomic
simulations that mimic the process of fossilization in typical vertebrate
deposits over normal time-averaging periods of 1000+ years. Kay and Alan
Cutler made a presentation at the last Snowbird conference where they
developed a model showing that, given average death rates in population
of about 5-10% or more per annum, a mass extinction that takes everything
out will only increase the detrital bone rain into the deposits at a rate
of 20 times the average and, over 1000+ years, will not show up at all. We
are building this into the simulations that are showing the same thing.
Now, you get concentrations normally and with mass extinctions if there isd
a mechanism for piling them all up in a very small area. However, you get
that frequently in non-mass extinction times also (see various bone beds),
so it would have to be something that concentrates the bone with a signature
that would support the mass extinction. For example, a biiiiig bone
accumulation associated with evidence for a huuuuuuuuge tsunami, might
do the trick but we know of nothing of the like, so far. The simulations
are just getting moving, the first paper was in the Taphonomy short course
volume put out by the Paleo Society, and i gave a talk at GSA last year on
the interaction between taphonomic time-averaging and the apparent
morphometric variability in fossil samples. I'm anticipating 3-4 papers
using them this year (going into review that is, not coming out).

Ralph Chapman, NMNH