| Briones Formation | |
|---|---|
| Stratigraphic range: Miocene | |
| Type | Geologic formation |
| Underlies | San Pablo Formation |
| Location | |
| Region | Contra Costa County, California |
| Country | United States |
| Type section | |
| Named for | Briones Hills |
The Briones Formation is a Late/Upper Miocene epoch geologic formation of the East Bay region in the San Francisco Bay Area, California. [1]
It is found in western Contra Costa County. [1]
The formation preserves fossils dating back to the Late/Upper Miocene epoch of the Neogene period. [2] Common fossils in the area include Spisula, Calyptraeidae, Clinocardium, and S. falcata. [3] The presence of shell beds and mollusk fossils suggests the area was once under a shallow bay, with relatively uniform levels of salinity and sand porosity. [4] The shell beds form a conglomerate in a calcerous sandstone matrix; today, this conglomerate is a major component of notable geological features in the Bay Area, including Mission Peak. [5]
The base of the formation includes sandstone and siltstone in distinct, parallel layers. [5] The sandstone is unique in its relative coarseness and light coloration. Some areas also include a pebble conglomerate. [3]
The Tularcitos syncline is a significant geological feature in the southern part of the formation. The high level of deformation, compared to the northern area, suggests that there was significant metamorphic activity, enabling the formation of laumontite. [4]
The vegetation present in the area is primarily annual grasses and forbs. The soil, which is primarily composed of sand, is considered "excessively drained" because of its high permeability and high levels of runoff. Today, the land is used primarily for grazing. [6]
The exposed geology of the Capitol Reef area presents a record of mostly Mesozoic-aged sedimentation in an area of North America in and around Capitol Reef National Park, on the Colorado Plateau in southeastern Utah.
The Morrison Formation is a distinctive sequence of Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone, and limestone and is light gray, greenish gray, or red. Most of the fossils occur in the green siltstone beds and lower sandstones, relics of the rivers and floodplains of the Jurassic period.
Rainbow Basin is a geological formation in the Calico Peaks range, located approximately 8 miles (13 km) north of Barstow in the Mojave Desert in San Bernardino County, California.
The Geology of Bangladesh is affected by the country's location, as Bangladesh is mainly a riverine country. It is the eastern two-thirds of the Ganges and Brahmaputra river delta plain stretching to the north from the Bay of Bengal. There are two small areas of slightly higher land in the north-centre and north-west composed of old alluvium called the Madhupur Tract and the Barind Tract, and steep, folded, hill ranges of older (Tertiary) rocks along the eastern border.
The Coyote Mountains are a small mountain range in San Diego and Imperial Counties in southern California. The Coyotes form a narrow ESE trending 2 mi (3.2 km) wide range with a length of about 12 mi (19 km). The southeast end turns and forms a 2 mi (3.2 km) north trending "hook". The highest point is Carrizo Mountain on the northeast end with an elevation of 2,408 feet (734 m). Mine Peak at the northwest end of the range has an elevation of 1,850 ft (560 m). Coyote Wash along I-8 along the southeast margin of the range is 100 to 300 feet in elevation. Plaster City lies in the Yuha Desert about 5.5 mi (8.9 km) east of the east end of the range.
The Vaqueros Formation is a sedimentary geologic unit primarily of Upper Oligocene and Lower Miocene age, which is widespread on the California coast and coastal ranges in approximately the southern half of the state. It is predominantly a medium-grained sandstone unit, deposited in a shallow marine environment. Because of its high porosity and nearness to petroleum source rocks, in many places it is an oil-bearing unit, wherever it has been configured into structural or stratigraphic traps by folding and faulting. Being resistant to erosion, it forms dramatic outcrops in the coastal mountains. Its color ranges from grayish-green to light gray when freshly broken, and it weathers to a light brown or buff color.
The Sespe Formation is a widespread fossiliferous sedimentary geologic unit in southern and south central California in the United States. It is of nonmarine origin, consisting predominantly of sandstones and conglomerates laid down in a riverine, shoreline, and floodplain environment between the upper Eocene Epoch through the lower Miocene. It is often distinctive in appearance, with its sandstones weathering to reddish-brown, maroon, pinkish-gray, tan, and green. Since many of its sandstones are more resistant to erosion than many other regional sedimentary units it often forms dramatic outcrops and ridgelines in many local mountain ranges.
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 Galisteo Formation is a geologic formation in New Mexico. It contains fossils characteristic of the Bartonian stage of the Eocene epoch, Duchesnean in the NALMA classification.
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 Orinda Formation is a Miocene epoch geologic formation in the Berkeley Hills of the East Bay region of the San Francisco Bay Area, California.
The Kern River Beds Formation is a Neogene Period geologic formation in the southeastern San Joaquin Valley, within Kern County, California.
The Chanac Formation is a Cenozoic Era sandstone geologic formation in the southeastern San Joaquin Valley, within Kern County, 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 La Jolla Group is a group of geologic formations in coastal southwestern San Diego County, Southern California. Its locations include the coastal La Jolla San Diego region.
The Stadium Conglomerate is a geologic formation in San Diego County, California. It is found at the northern end of Mission Valley near San Diego Stadium.
The Cook Inlet Basin is a northeast-trending collisional forearc basin that stretches from the Gulf of Alaska into South central Alaska, just east of the Matanuska Valley. It is located in the arc-trench gap between the Alaska-Aleutian Range batholith and contains roughly 80,000 cubic miles of sedimentary rocks. These sediments are mainly derived from Triassic, Jurassic and Cretaceous sediments.
The Alajuela Formation, originally Alhajuela Formation (Tau), is a Late Miocene geologic formation in the Panama Canal Zone of central Panama.
The Vasquez Formation (Tvz) is a geologic formation cropping out at the eponymous Vasquez Rocks in southern California. The formation dates to the Late Oligocene to Early Miocene.
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