Andrew,
That's very interesting about the color of fossil shells. It looks almost
as bright as many recent specimens of irradians.

What is the website for the Univ. of Arizona group?

David

>Aydin and David,
>
>The orange color is probably not original. Organic pigments don't usually
>last for thousands of years. It may be iron oxide (rust) instead. We had a
>Conch-L discussion on "Red shells, blue shells" a year or two ago.
>
>When referring to the age of beach shells, I meant ordinary beach shells.
>The Pliocene Epoch ended about 2.0 million years ago; the Miocene Epoch
>about 5.1 million years ago, according to Harland et al. (1982). So any
>Chesapecten shells you see are more than two million years old.
>
>If you are interested in Michal Kowalewski's work and in what you can do
>with long-dead shells, consult the website of the CEAM taphonomy group at
>the University of Arizona, where he researched before finding a job at
>Virginia Tech. He did a lot of work in the Gulf of California (Mexico), and
>also in Brazil. Michal says that growth bands of shells can be used like
>tree rings, in this case as a record of past temperature and salinity.
>Since one shell bank can contain abundant shells ranging in age from the
>present back to several thousand years ago, we can in principle decipher
>the climatic history of a location over a period of thousands of years.
>This could be very useful in determining the natural state of areas for
>which we have no data before they were changed by nearby agriculture,
>industry, housing developments, etc. But this research is very new -- and
>you read it first on Conch-L!
>
>Andrew K. Rindsberg
>Geological Survey of Alabama
>
>Reference
>
>Harland, W. B., Cox, A. V., Llewellyn, P. G., Pickton, C. A. G., Smith, A.
>G., & Walters, R., 1982, A geologic time scale: London, Cambridge
>University Press, xi + 131 pp.