Middle and Late Paleozoic Marginal Basin Systems
Published:January 01, 1990
1990. "Middle and Late Paleozoic Marginal Basin Systems", Paleozoic and Early Mesozoic Paleogeographic Relations; Sierra Nevada, Klamath Mountains, and Related Terranes, David S. Harwood, M. Meghan Miller
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Details of the stratigraphy, depositional setting, and clastic petrography of the upper Paleozoic Schoonover sequence in the Independence Mountains, northern Nevada, provide the basis for a better understanding of the paleogeography of the continental margin of western North America during the late Paleozoic.
The Schoonover sequence represents the northernmost exposures of the Golconda allochthon, which was thrust over the outer edge of the continental margin of western North America during the Permo-Triassic Sonoma orogeny. The Schoonover sequence, like the Havallah sequence and other units of the Golconda allochthon, is an imbricated assemblage of thrust-bound packages of radiolarian “ribbon” chert, basaltic greenstone, silty limestone turbidites, and siliciclastic sandstones that range in age from Late Devonian to Early Permian.
Detailed mapping, and facies and petrographic analysis of lithostratigraphic units, combined with paleontologic control, indicate that the Schoonover sequence consists of a coherent stratigraphic succession of basinal deposits with paleogeographic ties to the autochthonous shelf margin and to a volcanic arc. Latest Devonian- to earliest Mississippian-age basaltic and andesitic greenstones and tuffaceous sedimentary rocks form the stratigraphic base of the sequence and are succeeded by Lower Mississippian siliciclastic sandstones. The petrography of these sandstones indicates that they consist of mixed detritus derived from volcanic and continental shelf source terranes, indicating the proximity of an arc to the continental margin. In addition, stratigraphic relations between autochthon and allochthon indicate that the Schoonover basin evolved adjacent to the continental shelf throughout the late Paleozoic, its history punctuated by periods of basaltic volcanism and pulses of continent-derived clastic input. The onset of the Sonoma orogeny resulted in closure of the basin and emplacement of its deposits on the continental margin.