Full Title: Geologic Map and Description of Structure and Stratigraphy, La Madre Mountain, Spring Mountains, Nevada
Compiler: Gary Axen
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One sheet, 30" x 46", scale 1:25,000. From text: The rocks of the La Madre Mountain area can be divided into three groups: I) allochthonous lower Permian to middle Cambrian carbonates, 2) upper Paleozoic and Mesozoic, dominantly siliciclastic marine or non-marine strata which are autochthonous or parautochthonous, and 3) post-orogenic sediments. Petrographic and outcrop study of Ordovician-Devonian(?) Mountain Springs Formation and Pogonip Group (?) rocks in the Red Spring thrust plate indicate the presence of a subaerial unconformity of unknown duration. Devonian beds mark the transition from dominantly dolomitic rocks below to dominantly limey rocks above. The Late Jurassic-Early Cretaceous(?) synorogenic conglomerate of Brownstone Basin (new name) was deposited in thin fluvial channels with three source terranes: I) an erosionally breached fold in the autochthon, along with other local autochthonous sources, 2) Eocambrian clastic rocks of the Wheeler Pass thrust plate, and 3) the Red Spring thrust plate (Davis, 1973). Clastic dikes and thrust-bounded lenses of cataclastic autochthonous lithologies are present locally in the bases of both major thrust sheets, but are more common in the Keystone plate. Landslide-breccia deposits thought previously to be Mesozoic (Davis, 1973) are probably Tertiary…
Published: 4/01/1985
Pages: 17 plus 1 sheet
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