LATE PALEOZOIC BASIN EVOLUTION IN SOUTHWESTERN LAURENTIA: A PROGRESS REPORT

The southwestern margin of Laurentia experienced several episodes of tectonism during late Paleozoic time. This resulted in formation, filling, uplift, and abandonment of several spatially overlapping basins during the time between the Antler and Sonoma orogenies. Sedimentary packages from these basins are now exposed in many of the ranges of eastern Nevada. Much work has been done to document basin-bounding unconformities and structures within the basins across northeastern and east-central Nevada. The extent of basin sediments and distribution of lithofacies constrain the tectonic forces driving basin subsidence.

Here, we present an overview of the Mississippian to early Permian basins exposed in eastern Nevada. Basin deposit extents and lithofacies are plotted on published palinspastically reconstructed maps (McQuarrie and Wernicke, 2005) that restore Basin and Range extension and Walker Lane translation. The Kinderhookian to Meramecian Antler Foreland basin is dominantly deep marine black shale with turbidites locally; these siliciclastic facies grade eastward into carbonates. In contrast, the Chesterian successor basin is dominated by fluvio-deltaic conglomerate and sandstone, grading eastward into shale. These clastic facies are mostly replaced in Morrowan to Atokan time by shallow-water carbonates of the Ely-Bird Spring basin. Conglomerate beds in the northwestern part of the Ely-Bird Spring basin are a noteworthy exception. Desmoinesian strata are missing across much of the area, except a few places where the deep marine Hogan Formation is preserved. The Missourian to Asselian Lower Strathearn basin contains shallow-water limestone, sandstone, and conglomerate. Facies distributions within these basins shed light on tectonic processes that led to deformation of southwestern Laurentia throughout late Paleozoic time.