Reconstructing Miocene Paleogeography of the Middlegate and Eastgate Basins, NV through Geologic Mapping and Sedimentary Provenance Analysis
Abstract
Effects of continental lithospheric extension and magmatism on sediment dispersal patterns are broadly understood, but complexities such as pre-existing topography and syndepositional deformation challenge efforts to understand basin evolution and sediment routing. This study focuses on Middlegate and Eastgate Basins, two structurally bound non-marine basins in the northern Basin and Range Province (NV, USA). To test lateral stratigraphic correlations within and between Middlegate and Eastgate Basins, measured stratigraphic sections were described throughout four primary study areas. Both Middlegate and Eastgate Basins exhibit upsection changes from dominantly reworked ash, airfall tuffs, and mudstones to sand-dominated reworked ashes and volcaniclastic sandstones. In some localities, lenticular pebble-cobble conglomerate occurs at the top of the section. Interpreted depositional environments range from arid lacustrine environments to higher energy sandy-braided fluvial. Paleocurrent measurements from planar and trough cross-strata and imbricated cobbles indicate a general N-NW paleoflow for both basin depocenters. These findings may suggest that Middlegate and Eastgate Basins were once a continuous depocenter with a paleotopographic high and shared sediment source located to the S-SE. Modal analysis of sandstone compositions and detrital zircon U/Pb geochronology from sandstone and tuff samples will further test this hypothesis for Miocene changes in sediment dispersal and basin partitioning. Volcanic lithics within the basin fill are most likely locally derived from the Oligocene Western Nevada Volcanic Field, with published geochronology showing clustered tuff eruptive ages of ca. 28-29 Ma and 25-26 Ma. In contrast, the presence of metamorphic lithics and pre-Oligocene detrital zircon U/Pb ages would signify external sources outside of the volcanic topography, suggesting more through-going dispersal. Datasets will be synthesized with the regional structural and magmatic history to understand sedimentary basin formation and continental extension within silicic volcanic provinces. These efforts contribute to understanding similar processes in ancient analogs of continental rifting and magmatism, such as the Jurassic Chon Aike igneous province in South America.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T41D0331B
- Keywords:
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- 1165 Sedimentary geochronology;
- GEOCHRONOLOGYDE: 8108 Continental tectonics: compressional;
- TECTONOPHYSICSDE: 8169 Sedimentary basin processes;
- TECTONOPHYSICSDE: 8175 Tectonics and landscape evolution;
- TECTONOPHYSICS