Title: Geologic map of the Sixmile Canyon quadrangle, White Pine County, Nevada
Author: Jeffrey Lee, Scott Johnston, and Elizabeth L. Miller
Year: 2023
Series: Open-File Report 2023-08
Version:
Format: map sheet: 35.5 x 25 inches, color; text: 8 pages, b/w
Scale: 1:24,000
This 1:24,000-scale geologic map of the Sixmile Canyon 7.5-minute quadrangle is located along the west-central flank of the northern Snake Range metamorphic core complex and the eastern part of Spring Valley. The northern Snake Range metamorphic core complex exposes a low-angle normal-slip detachment fault, the northern Snake Range décollement (NSRD), that juxtaposes an upper plate of unmetamorphosed Middle Cambrian to Permian miogeoclinal rocks cut by normal faults and a lower plate of metamorphosed and ductilely thinned and stretched Neoproterozoic to Middle Cambrian metaclastic and marble rocks intruded by Mesozoic and Cenozoic plutons and dikes.
In the map area, the lower plate to the NSRD is composed of Early to Middle Cambrian metaclastic and marble rocks exposed across the northern half of the quadrangle and in a lower plate window in Negro Creek. Cretaceous pegmatites and aplites, and Eocene rhyolite porphyry and mafic dikes crosscut lower plate metasedimentary rocks in the northern part of the map area. In the lower plate, the mapped foliation and lineation changes character across the Sixmile Canyon quadrangle. On the northwestern flank of the range in the map area, the late Eocene–late Oligocene ductile thinning and stretching deformation fabrics, characteristic of most of the lower plate exposed across the northern Snake Range (Lee et al., 2017), have died out. Here, an older penetrative deformational fabric, defined by a foliation that dips more steeply west compared to bedding, is exposed. The intersection of these two planes defines a NNW-trending intersection lineation. In the Lower Cambrian metaclastic rocks, quartz grains in quartzites exhibit a stretching lineation along the intersection lineation, defining an intersection-stretching lineation (Lee, 1990). Southward along the western flank of the range to the Fourmile Canyon area, bedding is progressively transposed into a moderately to shallowly west-dipping mylonitic foliation and the intersection-stretching lineation progressively rotates into a WNW-ESE trending stretching lineation (Lee, 1990). The upper plate, composed of Middle Cambrian to Permian miogeoclinal rocks cut by normal faults, is exposed in the southern part of the map area and in a few klippe in the northern part. At least two generations of normal faults cut the upper plate rocks. Exposed on the western flank of the range and in Spring Valley are older alluvial deposits of Quaternary age and lacustrine, sand, and gravel lake deposits equivalent(?) in age to late Pleistocene Lake Bonneville.
This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program under STATEMAP award number G21AC10873.
Suggested citation:
Lee, J., Johnston, S., and Miller, E.L., 2023, Geologic map of the Sixmile Canyon quadrangle, White Pine County, Nevada: Nevada Bureau of Mines and Geology Open-File Report 2023-08, scale 1:24,000, 8 p.
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