| Mehrten Formation | |
|---|---|
| Stratigraphic range: Neogene | |
| Type | Formation |
| Location | |
| Region | California |
| Country | United States |
The Mehrten Formation is a geologic formation in California that is a type of inverted relief. It consists primarily of andesitic clastic and pyroclastic materials, deposited by volcanic activity that filled ancient rivers and valleys. Over time, the rock from these deposits proved more resistant to erosion than the surrounding land, leaving behind ridges that follow the paths of the former river channels, resembling inverted river meanders.
It was originally described in 1939 in Geology and Ground-Water Hydrology of the Mokelumne Area, California, Piper et. al.
Naturalist John Muir described the formation as "dead rivers" in his writings.
The Eagle Sandstone, originally the Eagle Formation, is a geological formation in Montana whose strata date back to the Late Cretaceous. It is a light to brownish gray to pale yellow-orange, fine-grained sandstone. It contains areas of crossbedding and local shale members. It contains large sandy calcareous concretions. Its thickness varies from 100 to 350 feet due to the lens nature of the individual sandstone layers and local interbedded sandy shale layers.
The Pungo River Formation is a geologic formation in North Carolina. It preserves fossils dating back to the Middle Miocene.
The Okeechobee Group is a geologic group in Florida. The group preserves fossils dating back to the Neogene period. This group of formations in the Everglades were deposited when high tropical water started to return in the Late Zanclean Period.
The Deadwood Formation is a geologic formation of the Williston Basin and Western Canada Sedimentary Basin. It is present in parts of North and South Dakota and Montana in the United States, and in parts of Alberta, Saskatchewan, and southwestern corner of Manitoba in Canada. It is of Late Cambrian to Early Ordovician age and was named for exposures in Whitewood Creek near Deadwood, South Dakota. It is a significant aquifer in some areas, and its conglomerates yielded significant quantities of gold in the Black Hills of South Dakota.
The Hoback Formation is a geologic formation in west-central Wyoming, located within the Hoback Basin. It formed as a result of increased sedimentation rates from the Laramide Orogeny and preserves fossils dating back to the late Paleogene period, through the early Eocene.
The Ely Springs Dolomite is an Ordovician period geologic formation in the Southwestern United States.
The Colton Formation is a geologic formation in Utah. Its age is based on its position between the Upper Cretaceous-Paleocene North Horn Formation and overlying Green River Formation.
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. The California portion is composed of a variety of sediments deposited on the coast of the San Francisco Bay Area in a small basin, which was split into two halves by the San Andreas Fault.
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 Etchegoin Formation is a Pliocene epoch geologic formation in the lower half of the San Joaquin Valley in central California.
The Modelo Formation is a Miocene geologic formation in the Simi Hills and western Santa Susana Mountains of southern California, including under parts of Los Angeles.
The Tulare Formation is a Pliocene to Holocene epoch geologic formation in the central and southern San Joaquin Valley of central California.
The La Jolla Group is a group of geologic formations in coastal southwestern San Diego County, California.
The Poway Group is a geologic group in San Diego County, Southern California. It preserves fossils dating back to the Paleogene period.
The Montezuma Formation is a geologic formation in California, just north of the confluence of the Sacramento and San Joaquin Rivers. The formation contains early Pleistocene deposits consisting of "poorly sorted, poorly consolidated clayey sand, silt, and pebble gravel." It is ranked "high" in "Potential Sensitivity for Paleontological Resources."
The San Benito Gravels is a Quaternary Epoch geologic formation in California.
The Palm Spring Formation is a Pleistocene Epoch geologic formation in the eastern Colorado Desert of Imperial County and San Diego County County, Southern California.
The Turlock Lake Formation is an Early Pleistocene geologic formation in the Sierra Nevada foothills in Sacramento County, California. Cities in/over the formation's area include Citrus Heights, Carmichael, and Roseville.
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