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Geologic Map of the Northern Snake Range Metamorphic Core Complex, White Pine County, Nevada and Millard County, Utah
 
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Product Code: OF2025-02

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Title: Geologic Map of the Northern Snake Range Metamorphic Core Complex, White Pine County, Nevada and Millard County, Utah

Author: Jeffrey Lee
Year: 2025
Series: Open-file reports
Version: 2025-02
Format: 35" x 61" color; text, 24 pages
Scale: 1:62,500

This 1:62,500 scale geologic map of the northern Snake Range metamorphic core complex, White Pine County, Nevada and Millard County, Utah, is a compilation of 10.5 published 1:24,000 scale 7.5’ quadrangle geologic maps of the northern Snake Range, White Pine County, Nevada and Millard County, Utah. This geologic map covers ~386,226 acres (~1563 km2).The ~45-km-long NNW-trending northern Snake Range is separated from the southern Snake Range by Sacramento Pass. To the north, the northern Snake Range is bounded by Pleasant Valley, to the east by Snake Valley, and to the west by Spring Valley. The northern Snake Range includes the Mount Moriah Wilderness Area, which encompasses 81,082 acres (332 km2) and includes The Table, an extensive plateau at ~11,000 ft (~3353 m) and Mount Moriah, at 12,067 ft (3679 m) the highest point in the range.

Exceptional exposures and a well-known stratigraphic framework make the northern Snake Range an archetypal metamorphic core complex, which records a Paleogene-Neogene history of high magnitude WNW-ESE-extension. The principal structure in the range is the low-angle top-to-the-SE normal slip décollement or detachment fault, the northern Snake Range décollement (NSRD),that juxtaposes a lower plate of metamorphosed and ductilely thinned and stretched Neoproterozoic to Ordovician metaclastic, marble, and calc-schist rocks intruded by Mesozoic and Cenozoic plutons and dikes beneath an upper plate of normal faulted weakly metamorphosed Middle Cambrian to Permian miogeoclinal rocks unconformably overlain by unmetamorphosed Tertiary sedimentary and volcanic rocks.

Across the range, the NSRD defines a NNW-trending asymmetric dome with ~5249 ft (~1600 m) of relief. Magnificent exposures of ductilely thinned and horizontally stretched Neoproterozoic to Ordovician strata in the lower plate possess a mylonitic foliation and stretching lineation which record WNW-ESE ductile extension and vertical thinning. Ductile extensional deformation in these strata show that strain markedly increases west to east across the range. Along the western flank of the range, strata have been thinned to ~40% of their original stratigraphic thickness. In sharp contrast, along the eastern flank of the range, strata have been thinned to as little as ~5% of their original stratigraphic thickness and extended horizontally as much as ~2400%. In the northwestern part of the range, the ductile extensional strain dies out in the lower plate and older, Late Cretaceous foliations, intersection lineations, isoclinal recumbent folds, and minor thrust faults are exposed. In the upper plate, at least two generations of normal faults, that record primarily WNW-ESE extension, cut Middle Cambrian to Permian miogeoclinal rocks, and unconformably overlying Tertiary sedimentary and volcanic rocks. These normal faults are well-exposed along the ridges straddling drainages in the southern part of the range, and in klippe in the northern part. The late Eocene to middle Miocene Sacramento Pass Basin, located along the southern flank of the range, and isolated middle Miocene sediments along the eastern flank of the range, record the exhumation and unroofing of this metamorphic core complex. During the late Pleistocene, Lake Bonneville and an age equivalent lake lapped onto the eastern and western pediment, respectively, of the range. The origin and tectonic evolution of the NSRD, lower plate ductile extension, and upper plate normal faulting have been topics of research for ~60 years, yet these topics still remain controversial.

© Copyright 2025 The University of Nevada, Reno. All Rights Reserved.

Original Product Code: OF2025-02