Merced Formation
Stratigraphic range: Pliocene,
Neogene Period
TypeGeologic formation
UnderliesColma Formation (California)
OverliesBedrock (California)
Lithology
Primarysedimentary rock (California)
Location
RegionSan Francisco Bay Area
of California,
Oregon,
Washington (state)
CountryUnited States
Type section
Named forLake Merced

The Merced Formation is a geologic formation in California, and also in Oregon and Washington state. It is named for Lake Merced, a natural lake on the western San Francisco coastline.

Geology

California

In the coastal San Francisco Bay Area of California the Merced Formation was deposited in a small sedimentary basin that formed along the San Andreas Fault during the last two million years during the Pliocene age of the Neogene period, in the Cenozoic Era. USGS.gov: "San Andreas Fault and Coastal Geology, from Half Moon Bay to Fort Funston: Crustal Motion, Climate Change, and Human Activity" [1]

The fault cut the basin into two pieces and moved the pieces apart. It is found on the east side of the fault in western San Francisco and northern San Mateo County. On the west side of the fault it was carried 20 miles (32 km) north to the Bolinas headlands of western Marin County.[1]

Fort Funston is on a bluff made up of exposed sedimentary rocks of the Merced Formation, in San Francisco within the NPS Golden Gate National Recreation Area.[1]

Fossils

It preserves fossils dating back to the Neogene period.[2]

See also

References

  1. 1 2 3 Geologic Trips.com: Merced Formation in San Francisco and the Bay Area
  2. ↑ Various Contributors to the Paleobiology Database. "Fossilworks: Gateway to the Paleobiology Database". Retrieved 17 December 2021.


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