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GMEG - Geology and Geophysics


in the San Francisco Bay Region

In the San Francisco Bay Region Project, paleontologists and geologists work closely to produce accurate geologic maps. Paleontologists provide critical age, stratigraphic, ecologic data about the rocks and the environments in which they formed.

The age of a rock is determined by the use of index fossils which have a short, well-known time of existence. Similarly, the environment is determined by the use of organisms or charateristics which indicate specific environments such as the desert, forest, lake, or marine. Paleontologists must continually study fossils from a variety of times and environments to build a complete picture of the earth's history.

Age and ecological interpretations are based on analysis of single or multiple fossil groups such as calcareous nannoplankton, silicoflagellates, diatoms, radiolarians, foraminifers, and mollusks, which are geologicallt short-lived or inhabit specific environments.

In addition to age and environment, paleontologists can determine the geologic history of an area including movement of faults (active and inactive), erosion or deposition, glacial activity, and the presence of fresh or marine water.

These activities are useful in geologic mapping, recognition of geologic hazards, the search for petroleum and minerals, identification of environmental quality and ecosystems, and understanding of global change and its impact on life.

To learn learn more about paleontology at the U. S. Geological Survey click here.

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Time Scale

Click on map to view explanation.Block Map Link

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