The Brawley Formation is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

in the

Colorado Desert The Colorado Desert is a part of the larger Sonoran Desert located in California, United States, and Baja California, Mexico. It encompasses approximately , including the heavily irrigated Coachella, Imperial and Mexicali valleys. It is home to ...

Southern California Southern California (commonly shortened to SoCal) is a geographic and Cultural area, cultural List of regions of California, region that generally comprises the southern portion of the U.S. state of California. Its densely populated coastal reg ...

, located in northwestern

Imperial County Imperial County is a county located on the southeast border of the U.S. state of California. As of the 2020 census, the population was 179,702, ranking as the least populous county in Southern California. The county seat and largest city is ...

and eastern

San Diego County San Diego County (), officially the County of San Diego, is a county in the southwest corner of the U.S. state of California, north to its border with Mexico. As of the 2020 census, the population was 3,298,634; it is the second-most populous ...

Geology

Sandstone and

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...

of the Brawley Formation accumulated between ~1.1 and ~0.6–0.5 Ma in a delta on the margin of an arid Pleistocene lake. It is in the

San Jacinto Fault Zone The San Jacinto Fault Zone (SJFZ) is a major strike-slip fault zone that runs through San Bernardino, Riverside, San Diego, and Imperial Counties in Southern California. The SJFZ is a component of the larger San Andreas transform system and ...

area, including in the San Felipe Hills.

Fossils

It preserves

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

from the

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

Epoch of the

Quaternary Period The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...

, during the

Cenozoic Era The Cenozoic Era ( ; ) is Earth's current geological Era (geology), era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, Insect, insects, birds and flowering plant, angiosperms (floweri ...

Geology

Fossils

See also

References

Further reading