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east‐trending dextral faults in the western Great Basin: An explanation for anomalous trends of pre‐Cenozoic strata and Cenozoic faults

1985; Wiley; Volume: 4; Issue: 6 Linguagem: Inglês

10.1029/tc004i006p00547

1944-9194

John H. Stewart,

Geology and Paleoclimatology Research

Two postulated major east trending strike‐slip fault zones, here named the Coaldale and Excelsior fault zones, are delineated mainly on the basis of faults in Cenozoic rocks in eastern California and western Nevada and coincide with apparent major right‐lateral offsets in the distribution and facies of pre‐Cenozoic rocks. Apparent right‐lateral offset of pre‐Cenozoic rocks on the Coaldale fault zone is 60 to 80 km and on the Excelsior fault zone is 45 to 55 km. This offset accounts for major disruption in trends of pre‐Cenozoic rocks in eastern California and western Nevada, a disruption previously interpreted as the result of either an originally curving continental margin or tectonic distortion of originally linear trends by large‐scale bending (oroflexural folding) or by crustal‐scale folding related to north‐east‐southwest compression. Main offset on the Coaldale and Excelsior fault zones appears to be late Mesozoic in age. A pre‐mid‐Cretaceous age is indicated because mid‐Cretaceous and younger plutonic rocks are not cut by major strike‐slip faults on line with the fault zones. Major movement is probably younger than the Dunlap Formation, which is dated paleontologically as Early Jurassic but which may also contain rocks as young as Cretaceous. Local reactivation of the faults in the Cenozoic, perhaps under a different stress regime, accounts for offset of Cenozoic rocks. The Coaldale and Excelsior fault zones terminate major northwest trending late Cenozoic and possibly older faults. The Owens Valley‐White Mountain fault system in eastern California and the Furnace Creek fault zone in southeastern California and westernmost Nevada terminate northward at the Coaldale fault zone. A system of south‐east trending right‐lateral and high‐angle faults in western Nevada, including the Bettles Well fault, terminate southward at the Excelsior fault zone. Major movement on northwest trending faults such as the Furnace Creek and Bettles Well fault may be mostly late Cenozoic in age, but present information does not preclude the possibility that these fault zones initiated prior to, and are offset by, the Coaldale and Excelsior fault system. The unusual trends of pre‐Tertiary rocks and of the Coaldale and Excelsior fault zones in eastern California and western Nevada appear to be restricted to the Walker Lane belt, a broad northwest trending structural zone characterized by right‐lateral shear in western Nevada and eastern California. Possibly initial shear produced the northwest trending faults, and a later “kink” in this system produced oroflexural folding and the east‐trending right‐lateral Coaldale and Excelsior fault zones. This “kink” may have resulted from a change in the stress regime and structural complexities where the shear zone obliquely crossed the Paleozoic continental margin.