Evolution of Devonian carbonate-shelf margin, Nevada

Abstract

The north-trending, 550-km-long Nevada segment of the Devonian carbonate-shelf margin, which fringed western North America, evidences the complex interaction of paleotectonics, eustasy, biotic changes, and bolide impact–related influences. Margin reconstruction is complicated by mid-Paleozoic to Paleogene compressional tectonics and younger extensional and strike-slip faulting. Reports published during the past three decades identify 12 important events that influenced development of shelf-margin settings; in chronological order, these are: (1) Early Devonian inheritance of Silurian stable shelf margin, (2) formation of Early to early Middle Devonian shelf-margin basins, (3) progradation of later Middle Devonian shelf margin, (4) late Middle Devonian Taghanic onlap and continuing long-term Frasnian transgression, (5) initiation of latest Middle Devonian to early Frasnian proto-Antler orogenic forebulge, (6) mid-Frasnian Alamo Impact, (7) accelerated development of proto-Antler forebulge and backbulge Pilot basin, (8) global late Frasnian semichatovae sea-level rise, (9) end-Frasnian sea-level fluctuations and ensuing mass extinction, (10) long-term Famennian regression and continent-wide erosion, (11) late Famennian emergence of Antler orogenic highlands, and (12) end-Devonian eustatic sea-level fall. Although of considerable value for understanding facies relationships and geometries, existing standard carbonate platform-margin models developed for passive settings elsewhere do not adequately describe the diverse depositional and structural settings along the Nevada Devonian platform margin. Recent structural and geochemical studies suggest that the Early to Middle Devonian shelf-margin basins may have been fault bound and controlled by inherited Precambrian structure. Subsequently, the migrating latest Middle to Late Devonian Antler orogenic forebulge exerted a dominant control on shelf-margin position, morphology, and sedimentation.