Incipient evolution of the Eastern California shear zone through the transpressional zone of the San Bernardino Mountains and San Gorgonio Pass, California
| dc.contributor.author | Cochran, William J. | en |
| dc.contributor.author | Spotila, James A. | en |
| dc.contributor.author | Prince, Philip S. | en |
| dc.contributor.department | Geosciences | en |
| dc.date.accessioned | 2020-11-04T16:21:36Z | en |
| dc.date.available | 2020-11-04T16:21:36Z | en |
| dc.date.issued | 2020-08 | en |
| dc.description.abstract | The nature of the connection between the Eastern California shear zone (ECSZ) and the San Andreas fault (SAF) in southern California (western United States) is not well understood. Northwest of San Gorgonio Pass, strands of the ECSZ may be migrating south and west into the convergent zone of the San Bernardino Mountains (SBM) as it is advected to the southeast via the SAF. Using high-resolution topography and field mapping, this study aims to test whether diffuse faults within the SBM represent a nascent connection between the ECSZ and the SAF. Topographic resolution of <= 1 m was achieved using both lidar and unmanned aerial vehicle surveys along two Quaternary strike-slip faults. The Lone Valley fault enters the SBM from the north and may form an along-strike continuation of the Helendale fault. We find that its geomorphic expression is obscured where it crosses Quaternary alluvium, however, suggesting that it may have a low rate of yet-undetermined activity. The Lake Peak fault is located farther south and cuts through the high topography of the San Gorgonio massif and may merge with strands of the SAF system. We find that this fault clearly cuts Quaternary glacial deposits, although the magnitude of offset is difficult to assess. Based on our interpretation of geomorphic features, we propose that the Lake Peak fault has predominantly dextral or oblique-dextral motion, possibly with a slip rate that is comparable to the low rates observed along other strands of the ECSZ (i.e., <= 1 mm/yr). Comparing the geomorphic expressions of these faults is difficult, however, given that the erosive nature of the mountainous landscape in the SBM may obscure evidence of active faulting. Based on these observations, as well as the occurrence of other diffuse faults in the region, we suggest that dextral strain is overprinting the actively convergent zone of the SBM, thereby creating a throughgoing connection between the ECSZ and the SAF west of San Gorgonio Pass. | en |
| dc.description.notes | Michael Oskin and Zachery Lifton provided very insightful reviews that greatly improved the quality of this manuscript. We would like to thank the folks at Whitewater Nature Preserve for hospitality and help with discovering the best routes and trails to take to San Gorgonio Peak. We would like to thank NCALM seed proposal data collection and processing services provided by the OpenTopography Facility with support from the National Science Foundation (NSF) under NSF award numbers 1833703, 1833643, and 1833632. Support for this study was provided by NSF grant EAR-1145115 and NCALM seed proposal funding for flying the lidar survey. | en |
| dc.description.sponsorship | National Science Foundation (NSF)National Science Foundation (NSF) [1833703, 1833643, 1833632]; NSFNational Science Foundation (NSF) [EAR-1145115]; NCALM | en |
| dc.format.mimetype | application/pdf | en |
| dc.identifier.doi | https://doi.org/10.1130/GES02121.1 | en |
| dc.identifier.issn | 1553-040X | en |
| dc.identifier.issue | 4 | en |
| dc.identifier.uri | http://hdl.handle.net/10919/100785 | en |
| dc.identifier.volume | 16 | en |
| dc.language.iso | en | en |
| dc.rights | Creative Commons Attribution-NonCommercial 4.0 International | en |
| dc.rights.uri | http://creativecommons.org/licenses/by-nc/4.0/ | en |
| dc.title | Incipient evolution of the Eastern California shear zone through the transpressional zone of the San Bernardino Mountains and San Gorgonio Pass, California | en |
| dc.title.serial | Geosphere | en |
| dc.type | Article - Refereed | en |
| dc.type.dcmitype | Text | en |
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