San Francisco Bay Region Geology and Geologic Hazards

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Fremont and Milpitas - Faulted Quaternary Sediments

One of the ways geologists can tell whether a fault has broken in Quaternary time is to look for Quaternary fossils in the rocks and sediments that are cut by the fault. In Fremont and Milpitas, the Warm Springs Fault cuts gravel deposits (the Irvington Gravels).  These gravel deposits contain many Pleistocene (Ice Age) fossils, including fossils from mammoths, saber-toothed cats, horses, ground sloths, camels, and dire wolves.

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This photo shows the bench along the Warm Springs Fault. The Irvington Gravels make up the ridge to the right (west) of the fault.

 

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A mammoth tooth from the Irvington Gravels in Fremont


Learn more about the Pleistocene fossils found in Fremont.External link - link policy applies

 

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