Enhanced map unit correlation and basin history interpretations from detrital zircon U-Pb data: Cenozoic strata of the Death Valley National Park area, California and Nevada, USA

Session: Advances and Applications in Geochronology for Interpreting Stratigraphic and Basin Records (Posters)

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Abstract:

Cenozoic sedimentary strata in the Death Valley National Park (DVNP) region remain poorly constrained by modern geochronologic data; this is particularly true for strata that predate local volcanism and thus lack intercalated volcanic deposits. However, recent studies by the authors have demonstrated that maximum depositional ages (MDAs) calculated from detrital zircon U-Pb data provide viable estimates of depositional age for pre-volcanic map units exposed in the DVNP region and across Nevada. Such units contain young volcanogenic zircon grains likely derived via ash-fall from eruptions that occurred elsewhere in the Great Basin. We build on these previous studies and present new detrital zircon U-Pb data for Eocene to Miocene strata exposed in the Indian Buttes area of the northern Funeral Mountains. The new data yield a suite of upward-younging MDAs (from ~45.6 Ma at the base of the section to ~12.2 Ma near the top of the section) that allow for enhanced correlation of the strata to other Cenozoic map units in the Grapevine Mountains, Funeral Mountains, and surrounding ranges. Paired with a detailed understanding of regional map unit relations, depositional facies associations preserved by host strata, and multiple types of provenance data, we use the new age constraints to inform the tectono-sedimentary history of the DVNP region. The data support two discrete phases of basin evolution. First, relict paleovalleys that had been incised into pre-Cenozoic contractional terranes were passively filled by Eocene-Oligocene (ca. 45.6 to 25.9 Ma, and perhaps younger) fluvial deposits of the Titus Canyon Formation and Rocks of Porter Mine. These deposits correlate to Eocene-Oligocene strata of the newly recognized Fallout Hills basin of southern Nevada; together, the basins define a regionally extensive paleovalley (basin) network that occupied rugged topography of the Cordilleran hinterland. The paleovalley deposits were subsequently deformed, uplifted, and eroded during a period of tectonic reorganization beginning ca. 17-16 Ma that marked the transition from contraction to oblique extension within the Cordillera. A second phase of deposition beginning ~16 Ma, accompanied by voluminous local volcanism, was then accommodated by a network of extensional basins that overprinted the former basin network.