The tectonic origin of the Western Transverse Ranges microplate, southern California: Sedimentologic evidence of rotation
- Univ. of California, Los Angeles, CA (United States). Dept. of Earth and Space Sciences
Most workers currently working on the problem of Southern California tectonic history and development are in agreement that the Western Transverse Ranges are allochthonous. The major point of contention revolves around the question of the distance the various terranes have traveled and their point of origin. Two tectonic models have been developed over the years to explain the emplacement of the WTRM: (1) accretion of exotic, far-traveled terranes; or (2) rotation, possibly with a small amount of translation, of a native or locally-derived terrane. Both of these reconstructions rely heavily on paleomagnetic data, with minimal input from field studies of sediment provenance or depositional systems. Examination of published reconstructions and models reveals that each would require a totally different provenance for sediments, and radically divergent transport directions for these sediments. Thus, examination of Cretaceous sediments exposed in the Western Transverse Ranges provides an independent test of the models, and will contribute to the resolution of the controversy. Paleocurrent measurements from several different tectonic blocks all yield a northerly flow direction. Removal of approximately 90[degree] of clockwise rotation and 70 km of right-lateral slip would align these data with westerly flow indicators in Cretaceous conglomeratic fan deposits in the San Diego area. Analysis of point count data indicate a mixed provenance for these rocks, both the conglomerates, and the associated sandstone units. Data indicate mixed magmatic arc/recycled orogen, as well as dissected/transitional arc as the dominant provenance terranes. These data are consistent with deposition in a Cretaceous forearc basin, which, in the reconstruction, would have been located immediately west of the San Diego area. Tertiary rotation and right-lateral offset have slivered the margin, and transported the forearc basin northward, forming the present Western Transverse Ranges.
- OSTI ID:
- 5342616
- Report Number(s):
- CONF-9305259-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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