In the Desert Queen area, Tertiary volcanic and sedimentary strata rest nonconformably on Mesozoic metasedimentary-metavolcanic and plutonic basement. Quaternary sediments onlap the bedrock units. The Mesozoic basement is exposed directly west of the quadrangle in the footwall of the east-dipping Desert Queen fault zone. An erosional surface of moderate relief (i.e., hundreds of meters) is developed on the Mesozoic rocks, above which rests the Tertiary section. The Tertiary section is a heterogeneous mix of volcanic and sedimentary rocks, with a total of thickness of ~2–3 km. Only middle to late Miocene rocks are exposed in the quadrangle, but Oligocene units have been observed in deep wells in the area and altered sedimentary rocks of probable Eocene age crop out directly west of the map area. Although significant lateral variations exist, the Tertiary section exposed within the quadrangle can be grouped into several discrete packages. In ascending order, these include:

Tephras (i.e., ash-fall deposits) are common in the late Miocene section and facilitate dating and correlation of stratigraphic units through geochemical fingerprinting. The capping ~7.5 Ma ash-flow tuff is one of the youngest pyroclastic deposits in the region. It forms a resistant cap on the ridges and mesas to the south of the Desert Queen basin and appears to underlie the basin itself, as evidenced by several small exposures along the western margin of the basin. It provides an important marker from which to gauge the magnitude of late Miocene to recent extension.

The Quaternary sediments in the area are dominated by lacustrine deposits of Pleistocene Lake Lahontan. Most of the closed basins in the Great Basin contained numerous pluvial lakes during the Pleistocene. However, lacustrine deposits older than those of the late Pleistocene (Sehoo) cycle were not observed in the Desert Queen area. During the Sehoo highstand, Lake Lahontan reached a maximum altitude of about 1330 m submerging much of the map area. Lake Lahontan deposits include beach gravels and sands and lacustrine silt and mud. Quaternary alluvial deposits include alluvial fans of different ages. In the central part of the map area, two small areas contain tufa mounds aligned ~NNE, parallel to the predominant structural grain in the area. These tufa mounds may mark the sites of late Pleistocene hot springs that issued along NNE-striking normal faults.

The structural framework of the Parran quadrangle is dominated by NNE-trending gently to moderately tilted (<10° to ~60°) fault blocks bounded by moderately to steeply dipping normal faults. Most of the faults accommodated relatively minor offset (i.e., hundreds of meters or less), but the east-dipping Desert Queen fault zone in the westernmost part of the quadrangle accommodated 2–3 km of normal displacement. West-tilted fault blocks dominate the area within and proximal to the Desert Queen basin. Bedding and layering show a distinct NNE-trending structural grain in accord with tilting along the NNE-striking normal faults. The Dessert Queen geothermal system is probably controlled by both a step-over (or relay ramp) within and horse-tailing southern termination of the Desert Queen fault zone.

Faulds, J.E., Koehler, R.D., Dellerman, N.P., and Green, H.L., 2022, Geologic map of the Parran quadrangle, Churchill County, Nevada: Nevada Bureau of Mines and Geology Open-File Report 2022-02, scale 1:24,000, 6 p.

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