Unnamed Prospect (MRDS 10174098), Gold Butte District, Clark Co., Nevada, USAi

Regional Level Types
Unnamed Prospect (MRDS 10174098)	- not defined -
Gold Butte District	Mining District
Clark Co.	County
Nevada	State
USA	Country

Age: Pleistocene (0 - 2.588 Ma)

Description: Unit is present in all counties. Some counties divided the alluvium into younger and older units, and some did not. For those that did not, or used other generalized terms for Quaternary rocks, the unit Qal has been used for the general undivided alluvium. Additionally, when polygons have been edited and changed to alluvium, Qal was used as the general value; hence it now is present in all counties. Qya-Younger alluvium: Map unit is used in Churchill, Elko, Esmeralda, Eureka, Humboldt, Lander, and Lincoln Counties where geologic information suggests better-defined younger versus older alluvium. It is mostly interchangeable with Qal, except that it implies some specifically younger Quaternary deposits.

Comments: Original map source: Crafford, A.E.J., 2007, Geologic Map of Nevada: U.S. Geological Survey Data Series 249, 1 CD-ROM, 46 p., 1 plate; Scale 1:250,000.

Lithology: Major:{coarse alluvium,fine alluvium}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

Age: Cenozoic (0 - 23.03 Ma)

Lithology: Sedimentary rocks

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Age: Miocene (5.333 - 15.97 Ma)

Description: Alluvial fan conglomerate distinguished by abundant clasts and boulders of Gold Butte Granite (Yg) shed to the NW from the Gold Butte area. Outcrop patterns suggest alluvial fan originated in the Cedar Basin area in Gold Butte. Mostly tan to tan-gray coarse conglomerate with coarse sand matrix of decomposed granite. Locally interbedded with lenticular coarse pebbly sandstone beds. Granite boulders typically sub-rounded and range in size from a few centimeters to as much as 5 m diameter, commonly concentrated as lag on hillsides. Also includes boulders of garnet gneiss. Exposed thickness about 90 m. Interbedded near top with and overlain by Gold Butte basalt flows (Tbgb), dated at about 9 Ma. Rests unconformably on coarse-grained Thoc deposits that include a tuff dated at 10.94 ± 0.06 Ma just below the unconformity in Quail Spring Wash (40Ar/39Ar, M. Kunk, written communication, 2000)

Comments: Part of Overton Arm. Deposits not studied in detail; herein are informally grouped as rocks of Overton Arm. Include sandstone, limestone, gypsum and conglomerate, deposited in basin in vicinity of Overton Arm, Virgin Basin and Temple Basin, southeast of the Lake Mead fault system. Largest and stratigraphically highest exposures of limestone are mapped separately as Hualapai Limestone (Th). The eastern margin of basin is defined by highlands of the South Virgin Mountains and Hiller Mountains, where coarse-grained deposits mostly lap onto older rocks. Coarse-grained deposits also lap against southeast side of Cleopatra volcano (Tvc). Western margin of basin is uncertain because rocks are tilted and faulted along the east side of the Black Mountains; however, coarse-grained deposits there suggest western margin was nearby. Basalts intercalated near the top of the conglomerate facies (Toac) are about 8 to 9 Ma (Tb). Locally, in area west of Gold Butte, deposits unconformably overlie Horse Spring-age deposits in Overton Arm. However, elsewhere in basin the basal part of unit is older and is probably laterally equivalent to the Horse Spring rocks (Plate 2).

Lithology: Conglomerate

Reference: Beard, L.S., R.E. Anderson, D.L. Block, R.G. Bohannon, R.J. Brady, S.B. Castor, E.M. Duebendorfer, J.E. Faulds, T.J. Felger, K.A. Howard, M.A. Kuntz, and V.S. Williams. Preliminary Geologic Map of the Lake Mead 30' X 60' Quadrangle, Clark County, Nevada, and Mohave County, Arizona. U.S. Geological Survey Open-File Report 2007-1010 version 1.0. [151]