Friday, July 31, 2009

FOSSIL MOLLUSKS IN CALIFORNIA

Well since this blog was all my idea I guess I should go first. My name is Charles Powell and I work for the Western Earth Surfaces Team of the U.S. Geological Survey in Menlo Park, California. My degrees are in geology, but most of my work is a hybrid between geology and biology. I use mollusks and other invertebrate fossils to solve geologic questions. Right now I’m involved in a project that is trying to make a four dimensional (length, width, depth, and time) map of the San Andreas fault between the San Francisco Bay area and the Tehachapi Range north of Los Angeles. That is, we’re trying to figure out what the San Andreas fault looked like in the past and how it evolved.

My part of this project is to look at formations of similar age on either side of the San Andreas fault to figure out how they correlate and how far the San Andreas fault has moved since they were deposited. I’ve picked the Purisima Formation on the coast near Santa Cruz and the San Joaquin Formation in the Central Valley near Kettleman City. These rock units are of similar age, but standard correlation between the two using extinct species doesn’t work well because the temperatures that were present at both places were significantly different and so their faunas were different. The Purisma Formation was deposited along a cool water, open coast, while the San Joaquin Formation was deposited in an interior shallow bay that had higher temperatures. I’m currently working on a detailed biostratigraphy of both units and will then try to track temperatures shifts – cool to warm, warm to cool – and then develop a pattern of these changes for the two sites. With luck the patterns will be similar and I’ll be able to correlate them. That’s the beginning, but it’s enough for my first blog post. Check back to see what other scientists and students of Eastern Pacific mollusks are doing, and I’ll fill you in on how my work continues and what else I’m doing.

Charles Powell

1 comment:

corteziensis said...

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