Abstract

The truncated southwestern edge of the Roberts Mountains allochthon is exposed in the Northern Ritter Range pendant in the eastern Sierra Nevada, structurally overlying parautochthonous rocks of the Cordilleran miogeocline. The Northern Ritter Range pendant exposes units that have the same stratigraphic affinities and structural relationships as rocks of the Antler orogenic belt in Nevada.

Paleozoic metasedimentary rocks exposed in the pendant consist of two major units: (1) a structurally complex, disrupted chert and argillite unit interpreted to be correlative with the Roberts Mountains allochthon; and (2) a stratigraphically coherent siliceous and calcareous unit, the Rush Creek sequence, that is interpreted to be part of a transitional outer shelf and slope assemblage of the lower Paleozoic Cordilleran miogeocline. In the Northern Ritter Range pendant, the Roberts Mountains allochthon structurally overlies the Rush Creek sequence along a north-striking, steeply dipping fault zone that may be a preserved remnant of the Roberts Mountains thrust, which in north-central Nevada emplaced the allochthon over outer shelf and slope strata of the Cordilleran miogeocline during the Late Devonian–Early Mississippian Antler orogeny.

These stratigraphic and structural belts are truncated on the southwest side of the pendant by the Gem Lake shear zone, a northwest-trending dextral strike-slip fault associated with the Cretaceous Sierra Nevada batholith. The Northern Ritter Range pendant thus defines both the southwestern limit of the Antler orogenic belt and the westernmost exposures of parautochthonous miogeoclinal rocks in the central Cordillera.

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