| Orinda Formation Stratigraphic range: Miocene | |
|---|---|
| Type | Geologic formation |
| Underlies | Moraga Formation |
| Overlies | Tice Shale, of Monterey Formation Group |
| Lithology | |
| Primary | coarse conglomerates |
| Location | |
| Region | Alameda County and Contra Costa County, California |
| Country | United States |
| Type section | |
| Named for | Orinda, California |
The Orinda Formation is a Miocene epoch geologic formation in the Berkeley Hills of the East Bay region of the San Francisco Bay Area, California. [1]
It is found within Alameda County and Contra Costa County. [1] [2]
The Orinda Formation is a coarse alluvial conglomerates sedimentary formation. It underlies the volcanic Moraga Formation. [3]
It preserves fossils dating back to the Miocene epoch of the Neogene period. [4]
The Orinda Formation is prone to landsliding due to intrinsic properties such as its weak cohesive strength and low friction angle. Landslides less than or equal to 10 acres in size occur as slides, slumps, and earthflows on dip or parallel to dip slopes. In the formation, landslides greater than or equal to 10 acres in size are common to very common and occur as slumps and slides on anti-dip slopes.
Moraga is a town in Contra Costa County, California, in the San Francisco Bay Area. The town is named in honor of Joaquín Moraga, member of the famed Californio family, son of Gabriel Moraga, and grandson of José Joaquín Moraga, famous 18th century expeditionaries of Alta California. As of 2010, Moraga had a total population of 16,016 people. Moraga is the home of Saint Mary's College of California.
Orinda is a city in Contra Costa County, California, United States. The population was 17,643 at the 2010 census, and was estimated in 2019 to have increased to 19,926.
Vasquez Rocks Natural Area Park is a 932-acre (377-hectare) park located in the Sierra Pelona Mountains in northern Los Angeles County, California. It is known for its rock formations, the result of sedimentary layering and later seismic uplift. It is located near the town of Agua Dulce, between the cities of Santa Clarita and Palmdale. The area is visible from the Antelope Valley Freeway. It has been used as a location for films and television programs on many occasions.
The Portuguese Bend region is the largest area of natural vegetation remaining on the Palos Verdes Peninsula, in Los Angeles County, California. Though once slated for development including the projected route of Crenshaw Boulevard, the area is geologically unstable and is unsuitable for building.
A mudflow or mud flow is a form of mass wasting involving "very rapid to extremely rapid surging flow" of debris that has become partially or fully liquified by the addition of significant amounts of water to the source material.
Robert Sibley Volcanic Regional Preserve is located in the Berkeley Hills of the East Bay region of the San Francisco Bay Area, California. The park is part of the East Bay Regional Parks District (EBRPD), covers 928 acres (3.76 km2), and lies east of Oakland, partly in Alameda County and partly in Contra Costa County. It can be entered from Oakland via Skyline Boulevard, or from Contra Costa County via Old Tunnel Road.
Simi Valley is a synclinal valley in Southern California in the United States. It is an enclosed or hidden valley surrounded by mountains and hills. It is connected to the San Fernando Valley to the east by the Santa Susana Pass and the 118 freeway, and in the west the narrows of the Arroyo Simi and the Reagan Freeway connect to Moorpark and Ventura, California. The relatively flat bottom of the valley contains soils formed from shales, sandstones, and conglomerates eroded from the surrounding hills of the Santa Susana Mountains to the north, which separate Simi Valley from the Santa Clara River Valley, and the Simi Hills.
The Rincon Formation is a sedimentary geologic unit of Lower Miocene age, abundant in the coastal portions of southern Santa Barbara County, California eastward into Ventura County. Consisting of massive to poorly bedded shale, mudstone, and siltstone, it weathers readily to a rounded hilly topography with clayey, loamy soils in which landslides and slumps are frequent. It is recognizable on the south slopes of the Santa Ynez Mountains as the band at the base of the mountains which supports grasses rather than chaparral. Outcrops of the unit are infrequent, with the best exposures on the coastal bluffs near Naples, in the San Marcos Foothills, at the Tajiguas Landfill, and in road cuts. The geologic unit is notorious as a source of radon gas related to its high uranium content, released by radioactive decay.
The Alum Bluff Group is a geologic group in the states of Georgia, Florida, and Alabama. It preserves fossils dating back to the Neogene period.
The Ringold Formation is a geologic formation in Eastern Washington, United States. The formation consists of sediment laid down by the Columbia River following the flood basalt eruptions of the Columbia River Basalt Group reaching up to 1,000 feet (300 m) thick in places. It preserves fossils dating back to the Neogene period.
The Chatsworth Formation is a Cretaceous period sandstone geologic formation in the Simi Hills and western Santa Susana Mountains of southern California.
The Claremont Shale is a Miocene epoch geologic formation in the Berkeley Hills of the East Bay region of the San Francisco Bay Area, California.
The Moraga Formation or Moraga Volcanics is a Pliocene epoch volcanic geologic formation in the Berkeley Hills of the East Bay region of the San Francisco Bay Area, California.
The Mulholland Formation is a Pliocene epoch geologic formation in the Berkeley Hills and San Leandro Hills of the East Bay region of the San Francisco Bay Area, California. It is found within Alameda County and Contra Costa County.
The Briones Formation is a Late/Upper Miocene epoch geologic formation of the East Bay region in the San Francisco Bay Area, California.
The Crowder Formation is a geologic formation in the Central and Western Mojave Desert, in northern Los Angeles County and eastern San Bernardino County, in Southern California.
The Topanga Canyon Formation is a Miocene epoch geologic formation in the Santa Monica Mountains, Simi Hills, Santa Ana Mountains and San Joaquin Hills, in Los Angeles County, Ventura County, and Orange County, southern California. It is primarily composed of hard sandstone with some inter-bedded siltstone.
The San Pablo Formation is a Late/Upper Miocene epoch geologic formation of the East Bay region in the San Francisco Bay Area, California.
The San Francisquito Formation is a geologic formation in northern Los Angeles County, California.
Lamorinda AVA is an American Viticultural Area in the San Francisco Bay Area located due east of the Berkeley Hills in Contra Costa County encompassing the region around the cities of Lafayette, Moraga and Orinda. The name Lamorinda is a portmanteau from the names of the three locales defining the region: Lafayette, Moraga, and Orinda. The AVA is a sub-region within the existing San Francisco Bay AVA and the larger, multicounty Central Coast AVA stretching approximately 30,000 acres (47 sq mi) with 46 commercially-producing vineyards that cover approximately 139 acres (56 ha). The USDA plant hardiness zone for the AVA is 9b. The AVA was proposed as the growers in the area found the wider San Francisco Bay and Central Coast AVA titles too generic and not indicative of its terroir. The Lamorinda AVA was officially established in February 2016 by the Alcohol and Tobacco Tax and Trade Bureau (TTB).
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