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.