Pasadena orogeny

File:Digital-elevation-map-so california.svg

Pasadena orogeny is a mountain building event in the Western United States. Conventionally it refers to the formation of mountains in mainly Southern California during the Pleistocene and lasting until the present day; originally it referred to the uplift of the San Gabriel Mountains.

The Pasadena orogeny is a major Late Quaternary-modern event{{sfn|Bohannon|Gardner|2004|p=261}} of mountain formation, which took place in the middle or perhaps late Pleistocene or to the present-day. It is also known as the "Coast Ranges orogeny" or considered to be part of the Cascadian orogeny or Alpide Orogeny.{{sfn|Stille|1936|p=875}} Finally, the term "Pasadena orogeny" is sometimes applied to all very recent orogenies around the Pacific Ocean.{{sfn|Stille|1936|p=849}} The type location is close to Pasadena, California in the Transverse Ranges,{{sfn|Blakey|Ranney|2017|p=186}} and originally referred to the fast rise of the San Gabriel Mountains recorded there.{{sfn|Blakey|Ranney|2017|p=183}}

During this orogeny mountain ranges such as the San Bernardino Mountains, San Gabriel Mountains, San Jacinto Mountains, Santa Monica Mountains, Santa Ynez Mountains{{sfn|Blakey|Ranney|2017|p=31}} and the Transverse Ranges grew, as did the northern Channel Islands{{sfn|Blakey|Ranney|2017|p=31}} such as Catalina Island and San Clemente Island, the Kettleman Hills anticline in the San Joaquin Valley{{sfn|Stille|1936|p=869}} and the Palos Verdes Hills. Sometimes the concept is limited to the uplift of the Transverse Ranges.{{sfn|Blakey|Ranney|2017|p=197}}

The general uplift of mountains over a length of over {{convert|400|km}} is caused by the collision of the North American Plate with other geologic structures that are attached to the Pacific Plate.{{sfn|Blakey|Ranney|2017|p=31}} This orogeny has resulted in the uplift of mostly north-south trending mountain chains, although some east-west trending uplifts are also found such as the Channel Islands and the Transverse Ranges;{{sfn|Stille|1936|p=869}} much of the uplift took place at the edge of basins.{{sfn|Blakey|Ranney|2017|p=181}} The Pasadena orogeny is accompanied by earthquake activity, which includes tsunami hazards.{{sfn|Bohannon|Gardner|2004|p=262}}

Folding accompanying the uplift of the Coast Ranges in Southern California, folding farther north at Morro Bay{{sfn|Blakey|Ranney|2017|p=184}} and the structure of the Santa Barbara Basin and Ventura Basin are consequences of the Pasadena orogeny. The city of Long Beach, California lies within the affected region.{{sfn|Bohannon|Gardner|2004|p=261}}

References

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{{Citation|last1=Marsaglia|first1=K.M.|chapter=Provenance of Sand Deposited in the Santa Barbara Basin at Site 893 during the Last 155,000 Years|date=October 1995|chapter-url=http://www-odp.tamu.edu/publications/146_2_SR/VOLUME/CHAPTERS/sr146pt2_05.pdf|publisher=Ocean Drilling Program|doi=10.2973/odp.proc.sr.146-2.274.1995|access-date=2018-11-20|last2=Rimkus|first2=K.C.|last3=Behl|first3=R.J.|title=Proceedings of the Ocean Drilling Program, 146 Part 2 Scientific Results|volume=146-2|doi-access=free}}

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Category:Orogenies of North America

Category:Natural history of California

Category:Geology of California

Category:Cenozoic orogenies