Type Geologic formation Country United States | Overlies Bedrock (California) Named for Lake Merced | |
Underlies Colma Formation (California) Region San Francisco Bay Area
of California,
Oregon,
Washington (state) Primary Sedimentary rock (California) | ||
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.
Contents
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"
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.
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.
Fossils
It preserves fossils dating back to the Neogene period.