Plush Ranch Formation
Plush Ranch Formation Stratigraphic range: Late Oligocene-Early Miocene (Arikareean) ~ | |
---|---|
Type | Formation |
Underlies | Caliente Formation (unconformably) |
Overlies | Basement (unconformably) |
Lithology | |
Primary | Conglomerate, sandstone, siltstone, shale |
Other | Limestone, evaporite, interbedded basalt |
Location | |
Coordinates | 34°48′N 119°06′W / 34.8°N 119.1°WCoordinates: 34°48′N 119°06′W / 34.8°N 119.1°W |
Approximate paleocoordinates | 33°48′N 113°36′W / 33.8°N 113.6°W |
Region | California |
Country | United States |
Extent | , Transverse Ranges |
Type section | |
Named for | Plush Range |
Named by | Carman |
Year defined | 1954 |
Plush Ranch Formation (the United States) |
The Plush Ranch Formation is a geologic formation in the Transverse Ranges of southern California. The formation preserves fossils dating back to the Late Oligocene to Early Miocene (Arikareean in the NALMA classification).
Description[]
The formation is the oldest non-marine unit of the Tejon region where the small Plush Ranch Basin is formed by the bounding Big Pine/Lockwood Valley and San Andreas Faults. The unit is composed of alluvial and lacustrine conglomerates, sandstones, siltstones, shales, limestones, and evaporites. Interbedded basalt has been dated by whole-rock and plagioclase K-Ar methods as ca. 26–23 Ma. Northwest of Plush Ranch Basin, on the opposite side of Mount Pinos (which includes exposures of ), Oligocene–Miocene strata are generally mapped as , but are considered equivalent to the Plush Ranch Formation. These strata coarsen upward, from mostly sandstone at the base to coarse conglomerate at the top.[1]
The lacustrine deposits represent the central and eastern parts of the Plush Ranch basin, which received little coarse siliciclastic sediment. Chironomid flies, disarticulated fish, and coprolites indicate a more or less permanent lake.[2]
Atop the Plush Ranch Formation, separated by an angular unconformity, there is the non-marine Caliente Formation, comprising fluvial and lacustrine conglomerate, sandstone, and mudstone, with minor tuffaceous and limestone beds.[1]
Fossil content[]
The following fossils have been reported from the formation:[3]
- Insects
See also[]
References[]
- ^ a b Coffey et al., 2019, p.480
- ^ Old Frazier Borax Mine at Fossilworks.org
- ^ Plush Ranch Formation at Fossilworks.org
- ^ Snyder, 1955
Bibliography[]
- Coffey, Kevin T.; Ingersoll, Raymond V.; Schmitt, Axel K. (2019). "Stratigraphy, provenance, and tectonic significance of the Punchbowl block, San Gabriel Mountains, California, USA". Geosphere. 15 (2): 479–501. Bibcode:2019Geosp..15..479C. doi:10.1130/GES02025.1.
- Snyder, T. E (1955). "A new fossil termite, Parastylotermes frazieri, from California (Isoptera, Rhinotermitidae)". Proceedings of the Entomological Society of Washington. 57: 79–80.
- Geologic formations of California
- Miocene Series of North America
- Miocene California
- Oligocene Series of North America
- Paleogene California
- Chattian Stage
- Aquitanian (stage)
- Arikareean
- Sandstone formations of the United States
- Shale formations of the United States
- Siltstone formations
- Oligocene volcanism
- Alluvial deposits
- Lacustrine deposits
- Paleontology in California