Affiliation:
1. U.S. Geological Survey, 525 South Wilson Avenue, Pasadena, California 91106, USA
2. U.S. Geological Survey, 520 North Park Avenue, Tucson, Arizona 85719, USA
3. University of California, Riverside, 900 University Avenue, Riverside, California 92521, USA
Abstract
Abstract
The San Gorgonio Pass region of southern California is a locus of extensive Quaternary deformation within a multi-strand section of the San Andreas fault zone. The geomorphology of the San Gorgonio Pass region reflects the complicated history of geologic events in the formation of this structurally complex region. We define fault-bounded blocks in San Gorgonio Pass and focus on two that are characterized by extensive crystalline bedrock outcrops with similar bedrock lithologies. These two blocks are separated by the San Bernardino strand of the San Andreas fault. Morphometric variables, including local relief, slope, slope distribution, and surface roughness, consistently demonstrate distinctions between the bedrock upland regions of the two blocks. Geologic observations of the region highlight differences in Quaternary units within the two blocks, reflective of the differing surficial processes active in each block. Within the Kitching Peak block, the morphology highlights a lineament that we informally name the Lion Canyon lineament. This boundary more clearly differentiates the two regions, as compared to the mapped San Bernardino strand, and may represent the previously active strand or bounding structure in this section. The distinction in morphology and surficial processes leads to our interpretation that the Kitching Peak and Pisgah Peak blocks have experienced different uplift histories. This further leads to the conclusion that the San Bernardino strand, broadly defined, has been integrated, at some point in the past, with the Banning strand, allowing for through-going rupture along the fault system. This connectivity may have occurred along the Burro Flats section of the San Bernardino strand or the Lion Canyon lineament. The fault connection along the mapped trace of the San Bernardino strand is not currently evident at the surface, however, suggesting that the integration has been disrupted. We propose this is due to intervals of N-S compression in the region, manifest as slip along the San Gorgonio Pass fault zone and other regional faults. We present evidence for lateral displacement along the San Bernardino and Banning strands of the San Andreas fault, discuss the implications of these displacements, and propose a sequence of fault activity, including multiple phases of activity along the San Bernardino and Banning strand pathway to account for the structural complexity and lack of surficial fault continuity.
Publisher
Geological Society of America
Reference84 articles.
1. Magnetostratigraphy and biochronology of the San Timoteo Badlands, southern California, with implications for local Pliocene–Pleistocene tectonic and depositional patterns;Albright;Geological Society of America Bulletin,1999
2. San Andreas fault zone in San Gorgonio Pass, southern California;Allen;Geological Society of America Bulletin,1957
3. Bacheller, J., II
I, 1978, Quaternary geology of the Mojave Desert-eastern Transverse Ranges boundary in the vicinity of Twentynine Palms, California[M.S. thesis]: Los Angeles, University of California, 157 p., scale 1:24,000.
4. Classified point cloud and gridded elevation data from the 2005 B4 Lidar Project;Bevis,2017
5. Soils and Geomorphology;Birkeland,1999
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