Editing Transverse Ranges (section)

==Geology==
{{More citations needed section|date=January 2021}}
[[File:Traverse Ranges, Mojave Desert, Silverwood Lake.jpg|thumb|View west of the eastern portion of the San Bernardino and San Gabriel Mountains, with the [[Mojave Desert]] on the right and [[Silverwood Lake]] near the boundary. The [[San Andreas Fault]] runs straight up the middle toward the horizon.]]
[[File:Sanandreas.jpg|thumb|The San Andreas Fault trends more east-west where it cuts through the Transverse Ranges.]]

===Tectonics===
The Transverse Ranges result from a complex of tectonic forces and [[Southern California faults|faulting]] stemming from the interaction of the [[Pacific Plate]] and the [[North American Plate]] along the dextral (right slip) [[San Andreas Fault]] system. Their orientation along an east–west axis as opposed to the general northwest–southeast trend of most California ranges results from a pronounced left step in the San Andreas Fault that occurred in the [[Pliocene]] ({{circa|4}} million years ago) when southern reaches of the fault moved east to open the [[Gulf of California]].<ref>{{Cite journal|last1=Larson|first1=Roger L.|last2=Menard|first2=H. W.|last3=Smith|first3=S. M.|date=1968-08-23|title=Gulf of California: A Result of Ocean-Floor Spreading and Transform Faulting|journal=Science|language=en|volume=161|issue=3843|pages=781–784|doi=10.1126/science.161.3843.781|issn=0036-8075|pmid=17802622|bibcode=1968Sci...161..781L |s2cid=31863250 }}</ref> The crust within the Pacific Plate south of the ranges can not easily make the left turn westward as the entire plate moves northwestward, forcing pieces of the crust to compress and lift.

Prior to this shift of the fault to create the left bend, northwest–southeast trending rock belts in all of the Transverse Ranges began to rotate clockwise in the right shear of Pacific Plate – North American Plate motion.<ref name=":3">{{Cite journal|last1=LUYENDYK|first1=BRUCE P.|last2=KAMERLING|first2=MARC J.|last3=TERRES|first3=RICHARD|date=1980-04-01|title=Geometric model for Neogene crustal rotations in southern California|journal=GSA Bulletin|language=en|volume=91|issue=4|pages=211|doi=10.1130/0016-7606(1980)91<211:gmfncr>2.0.co;2|bibcode=1980GSAB...91..211L |issn=0016-7606}}</ref><ref name=":0">{{Cite journal|last1=Luyendyk|first1=Bruce P.|last2=Kamerling|first2=Marc J.|last3=Terres|first3=Richard R.|last4=Hornafius|first4=J. Scott|date=1985|title=Simple shear of southern California during Neogene time suggested by paleomagnetic declinations|journal=Journal of Geophysical Research|language=en|volume=90|issue=B14|pages=12454|doi=10.1029/jb090ib14p12454|bibcode=1985JGR....9012454L |issn=0148-0227}}</ref><ref>{{Cite journal|last=LUYENDYK|first=BRUCE P.|date=1991-11-01|title=A model for Neogene crustal rotations, transtension, and transpression in southern California|journal=GSA Bulletin|language=en|volume=103|issue=11|pages=1528|doi=10.1130/0016-7606(1991)103<1528:amfncr>2.3.co;2|bibcode=1991GSAB..103.1528L |issn=0016-7606}}</ref> This tectonic rotation began in Early Miocene Time and continues today.<ref>{{Cite journal|last1=HORNAFIUS|first1=J. SCOTT|last2=LUYENDYK|first2=BRUCE P.|last3=TERRES|first3=R. R.|last4=KAMERLING|first4=M. J.|date=1986-12-01|title=Timing and extent of Neogene tectonic rotation in the western Transverse Ranges, California|journal=GSA Bulletin|language=en|volume=97|issue=12|pages=1476|doi=10.1130/0016-7606(1986)97<1476:taeont>2.0.co;2|bibcode=1986GSAB...97.1476S |issn=0016-7606}}</ref> The total rotation is about 90° in the Western Transverse Ranges and less (about 40°) in the eastern ranges.<ref>{{Cite journal|last1=CARTER|first1=JAMES N.|last2=LUYENDYK|first2=BRUCE P.|last3=TERRES|first3=RICHARD R.|date=1987-02-01|title=Neogene clockwise tectonic rotation of the eastern Transverse Ranges, California, suggested by paleomagnetic vectors|journal=GSA Bulletin|language=en|volume=98|issue=2|pages=199|doi=10.1130/0016-7606(1987)98<199:nctrot>2.0.co;2|bibcode=1987GSAB...98..199C |issn=0016-7606}}</ref> [[Santa Catalina Island (California)|Catalina Island]] shows the most rotation: almost 120°.<ref name=":0" />

A mechanism proposed for the rotation event is capture of the subducting Monterey plate by the outboard Pacific plate. Because the Monterey plate was then beneath southern California, the capture resulted in pulling of the overlying crust out and northward from the rest of California.<ref>{{Cite journal|last1=Nicholson|first1=Craig|last2=Sorlien|first2=Christopher C.|last3=Atwater|first3=Tanya|last4=Crowell|first4=John C.|last5=Luyendyk|first5=Bruce P.|date=1994-06-01|title=Microplate capture, rotation of the western Transverse Ranges, and initiation of the San Andreas transform as a low-angle fault system|journal=Geology|language=en|volume=22|issue=6|pages=491|doi=10.1130/0091-7613(1994)022<0491:mcrotw>2.3.co;2|bibcode=1994Geo....22..491N |issn=0091-7613}}</ref>

===Rocks===
Rocks of the Transverse Ranges exhibit extreme differences in geologic age and composition, varying from sedimentary rocks in the western Santa Ynez and volcanic rocks in the Santa Monica Mountains to primarily granitic and metamorphic rock in the central and eastern segments, including the San Gabriel and San Bernardino Mountains.

The oldest basement (deepest) rocks are of [[Proterozoic]] age, and are found in the San Gabriel Mountains and the San Bernardino Mountains. The [[Jurassic]]-[[Cretaceous]] [[Franciscan Assemblage]] is found in the western section of the ranges and is the presumed basement in this segment. Exposed plutonic rocks from the [[Mesozoic]], mostly granites, can be found on [[Mount Pinos]] and generally in regions east of [[Tejon Pass]]. The youngest rocks are [[Cenozoic]] sedimentary and volcanic rocks that can be found throughout the ranges.

The western segment is distinctive for the large thickness of Cretaceous and Cenozoic sedimentary rocks, estimated to be up to 10 kilometers.<ref name=":1" /> The thickest deposits of these are in the Santa Barbara Channel and Ventura basin. These are mostly marine in origin with a marked change to [[red beds]] of river systems of [[Oligocene]] age in the western and central segments.

[[Limestone]]s and [[Dolomite (rock)|dolomite]]s of the marine Miocene [[Monterey Formation]] are found in the Santa Ynez Mountains and in the Coast Ranges to the north.

===Faults===
[[File:SoCal Transverse Ranges.svg|thumb|Transverse Ranges segments shown as shaded with bordering faults. Catalina not usually included in the province but it has similar geologic faults. |left]]The distinctive feature of the Transverse Ranges besides their anomalous orientation is that they are bounded by east-west trending faults. Most are left slip, [[strike slip faults]]. In the western and central segments many of the faults are [[thrust fault]]s.<ref name=":1" /><ref name=":2" /> Faults in the Coast Ranges and Peninsular Ranges trend northwest-southeast and butt into the east-west trending faults of the Transverse Ranges. Because all of these faults are considered active and seismic but they do to cut each other, the only geometry that satisfies that observation is if the east-west faults and Transverse Ranges are rotating clockwise with respect to the faults outside that province.<ref name=":3" />

Between the western segment and the Peninsular Ranges to the south is the complex Malibu Coast—Santa Monica—[[Hollywood fault]], which exists as the border between these two mostly geologically unitary provinces.<ref name="Barth2002">{{cite book|title=Contributions to Crustal Evolution of the Southwestern United States|last1=Meigs|first1=Andrew J.|last2=Oskin|first2=Michael E.|publisher=Geological Society of America|year=2002|isbn=978-0-8137-2365-5|editor-last=Barth|editor-first=Andrew|pages=281–7|chapter=Convergence, block rotation, and structural interference across the Peninsular-Transverse Ranges boundary, eastern Santa Monica Mountains, California|chapter-url=https://books.google.com/books?id=1ZPoZUE-jJAC&pg=PA281}}</ref> These faults are part of the same thrust fault system south of the northern Channel Islands of San Miguel, Santa Rosa, and Anacapa Islands.<ref name=":1" /> North of the western segment the bounding faults are left slip [[Santa Ynez Fault|Santa Ynez]] and Pine Mountain Faults. The [[San Gabriel Fault]] and San Andreas bound the central segment. The eastern segment is bounded by the Pinto Mountain Fault in the north and the Salton Creek Fault in the south.

===Petroleum===

The large thickness of marine sediments in the western segment have made it a habitat for oil. Several dozen fields are found onshore and offshore, particularly in the Santa Barbara Channel and Ventura Basin. Much oil has pooled in the Monterey Formation, which is produced onshore and offshore. In the eastern Santa Barbara Channel oil is held in younger sedimentary rocks. The [[Los Angeles Basin]] south of the western segment, formed during rotation of that segment away from the Peninsular Ranges.<ref name=":3" /> It is also a site of prolific oil production. The California Geologic Survey states:

<blockquote>Great thicknesses of [[Cenozoic]] petroleum-rich sedimentary rocks have been folded and faulted, making California one of the [[California oil and gas industry|most important oil-producing areas]] in the United States.<ref name=CGPNote36>[http://www.conservation.ca.gov/cgs/information/publications/cgs_notes/note_36/Documents/note_36.pdf ‘’California Geologic Provinces,’’ Note 36, page 2] {{webarchive|url=https://web.archive.org/web/20161222132418/http://www.conservation.ca.gov/cgs/information/publications/cgs_notes/note_36/Documents/note_36.pdf |date=2016-12-22 }}</ref></blockquote>