BASIN ANALYSIS OF OLIGOCENE AND LOWER MIOCENE STRATA IN THE GRAPEVINE AND FUNERAL MOUNTAINS, CALIFORNIA-NEVADA

Subsurface stratigraphy, based on well data from Amargosa Valley, Nevada indicates a thick sedimentary package that accumulated in the Amargosa Basin prior to the eruption of the Miocene southwestern Nevada volcanic field. Studies to understand the nature and distribution of these strata are important to regional tectonic interpretations as well as hydrogeologic models of groundwater flow in the basins. Previous studies have investigated analogs to these strata that crop out in the Funeral Mountains and east to the Frenchman Flat area of the Nevada Test Site that are Late Oligocene-Early Miocene in age. From these studies, three main lithologic units have been defined: a lower unit of gastropod and ostracod-rich limestones; a second unit of pebble-cobble conglomerate, coarse sandstone, and siltstone; and an upper unit of volcaniclastic sandstone, ash flow, and airfall tuff. The lower limestone unit represents the initiation of extension, ponding the existing fluvial drainages along the extensional axes of the new basin(s). The middle conglomerate unit represents the development of regional through-going fluvial systems. The upper unit represents attenuation of the crust, great enough to produce regional volcanism. Here we present measured stratigraphic sections that examine the Oligocene-Lower Miocene Titus Canyon Formation of the northern Funeral Mountains and southern Grapevine Mountains, California-Nevada. These stratigraphic sections depict a lithostratigraphy similar to previously described strata in the Funeral Mountains and on the Nevada Test Site. Correlation of these units across southern Nevada and eastern California suggests significant east-west basin development prior to Middle Miocene Basin and Range extension. The presence of these strata in outcrop across this region suggests that intervening basins also contain a significant thickness of these lithostratigraphic units at depth.

[This abstract is an independent product of the CNWRA and does not necessarily reflect the view or regulatory position of the NRC.]