Paper No. 9
Presentation Time: 11:00 AM


MAHON, Robert C., Geology and Geophysics, University of Wyoming, Dept. 3006, 1000 E. University Ave, Laramie, WY 82071-2000 and LINK, Paul K., Department of Geosciences, Idaho State University, Pocatello, ID 83209,

The Saddle Peak Hills 7.5’ quadrangle was mapped at 1:24,000-scale and compiled in ArcGIS, with partial funding by USGS EdMap #G11AC20185. The quadrangle is located in the southeasternmost corner of Death Valley National Park and encompasses NPS land and wilderness areas as well as BLM land and Areas of Critical Environmental Concern. The quadrangle’s accessibility, the exceptional exposures of a diversity of geologic units and structural features, and over 60 years of geologic work by Lauren Wright, Bennie Troxel and others, make this a commonly visited area for field trips and geologic investigations. Normal-fault-bounded ranges expose bedrock in three locations: the Saddle Peak Hills, Sperry Hills and Salt Spring Hills. There are exceptional exposure of Mesoproterozoic to Cambrian sedimentary rocks including the Pahrump Group – Crystal Spring Formation (~1070 Ma), newly named Horse Thief Springs Formation (~770 Ma), Beck Spring Dolomite (~740 Ma), and Kingston Peak Formation (~710-635 Ma). Ediacaran to Cambrian rocks include the Noonday Dolomite up to the Cararra Formation.

The quadrangle is located at the junction of three major tectonic provinces: the Basin and Range to the north and east, the Transverse Ranges to the west, and the Mojave Province to the east. The junction of two major transform faults, the Garlock Fault and the Southern Death Valley Fault Zone, is less than 1km to the south of the quadrangle boundary. Inferred Mesozoic compressional tectonism (C-1) is evident in south-southeast trending folds. The oldest extensional (E-1) episode includes down-to-the-west normal faults, which are generally flat lying at present. E-2 includes northwest-striking normal faults and similarly oriented Miocene (ca. 12.6-12 Ma) trachytic dikes as well as volcanic rocks, and monolithologic breccias of landslide-origin inferred to fill paleograbens. E-3 includes north-striking normal faults. E-4 includes inferred north- and northwest-striking range-bounding normal faults along the west sides of the Saddle Peak, Sperry and Salt Spring Hills. Effects of late Neogene transpression in the Avawatz Mountains (T-1) may be evident in pervasive northwest oriented cleavage in the Kingston Peak Formation and in Neogene dikes throughout the quadrangle.

  • Mahon and Link, GSA13 FINALsmall.pdf (13.2 MB)