Evidence for regional Mesozoic extension in the eastern Mojave Desert, California: The Riggs ductile detachment fault
- Univ. of South California, Los Angeles, CA (United States). Dept. of Geological Sciences
The Riggs fault (Kupfer, 1960) is a complex low-angle structure in the Silurian Hills, approximately 25 km north of Baker in SE California, and in the northern Halloran Hills east of the Silurian Hills. Important structural characteristics of the fault are: (1) juxtaposition of metamorphosed Paleozoic miogeoclinal strata over older units (Eocambrian, Proterozoic metasedimentary rocks; Proterozoic basement rocks); (2) evidence for two episodes of fault displacement (ductile: pre-mid-Cretaceous or ( ) pre-mid-Jurassic; brittle: Miocene); and (3) the localized development of a lower-plate chaos zone. The older episode of faulting, the focus of this abstract, is characterized by knife-sharp ductile contacts where not overprinted by younger, brittle deformation. This episode was coeval with the formation of the chaos structure described by Kupfer, who recognized its geometric similarities to the chaos structure beneath faults in the Death Valley area. The Silurian Hills chaos is a zone, generally a few hundred meters thick, of footwall rocks cut by a myriad of bedding-subparallel faults. Stratigraphic section is cut out along the faults, but for the most part an upward younging stratigraphic order is maintained. Upper-plate transport is believed to have been generally westward. The chaos is intruded by mid-Cretaceous Teutonia granitic rock ([approximately]95 Ma), thus setting an upper age constraint for both it and the older episode of Riggs faulting. Earlier workers have interpreted the Riggs fault as a younger-over-older thrust fault. The authors believe that it is a previously unrecognized, regional extensional detachment fault of Mesozoic age. Counterparts of the deep-seated ductile fault lie in areas N and S of Baker within the Soda, Avawatz( ), and Old Dad Mtns.
- OSTI ID:
- 5422869
- Report Number(s):
- CONF-9305259--
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Journal Name: Geological Society of America, Abstracts with Programs; (United States) Vol. 25:5; ISSN GAAPBC; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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