T266 Best Student Geologic Mapping Competition (Posters)

Tuesday, 27 September 2016
9:00 AM - 6:30 PM
Exhibit Hall E/F

SLATE MOUNTAIN AND NORTHERN SAND SPRINGS RANGE, NEVADA GEOLOGIC MAPS CLARIFY KEY CROSS-CUTTING RELATIONS IN THE CORDILLERAN HINTERLAND

Paper number: T266-8
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

The Sand Springs Range (SSR) and Slate Mountain (SM) are located in the Cordilleran hinterland, within the Sierran magmatic arc, and in the western Great Basin. Recent 1:8000-scale geologic mapping for a 2015 undergraduate research project and for part of 2016 field camp documents two key timing relations: 1) amphibolite facies metamorphism and coeval deformation is a regional event (D1) that predated Cretaceous plutons, 2) a low-angle fault forming klippen that cross-cuts S1 in northern SSR is a Luning-Fencemaker belt (LFTB) thrust fault (D2), not a detachment fault. A tied grid of cross-sections accompanies geologic maps.

The northern SSR contains metamorphic tectonites (andalusite schist, foliated marble, garnet biotite quartz schist, and meta-rhyolite sills dated at 237 Ma; Satterfield, 2002), Cretaceous intrusive igneous, and Tertiary intrusive and extrusive igneous map units. The Sand Springs granitoid pluton, dated at 81-90 Ma (John, 1992; Satterfield, 2002), sharply cross-cuts S1, D1 folds, and a low-angle fault. However, abundant Tertiary and Cretaceous sills which intruded parallel to steep S1 typically terminate at the low-angle fault. Mapped relations demonstrate the fault is pre-Cretaceous: a) two sills thicken upward before terminating at the fault, b) sills in the upper plate of the thrust do not terminate at the fault, and c) a Tertiary sill cross-cuts the fault. NE- and NW-trending folds, the characteristic LFTB sequence, deform the thrust and tectonites.

SM contains map units similar to southern SSR units: hornblende schist containing stretched pebble conglomerate, foliated marble, a lineated granitoid, meta-rhyolite, and Tertiary igneous rocks. Granitoid mineral lineations parallel hornblende schist stretching and mineral lineations, indicating the granitoid lineation is metamorphic. The 81-82 Ma Slate Mountain granitoid pluton is porphyritic and not lineated (John, 1992). Overall NE-trending SM metamorphic foliation (S1) could be one limb of a large NE-trending D2 fold. Several map-scale NW-trending D3 folds warp this limb. Fairview Peak rupture (1954) fault scarps cross-cut the range front. Shutter ridges document older right-lateral slip.

D1 and coeval amphibolite facies metamorphism correlate with eastern Sierra Nevada structures and predate LFTB thrusting and folding.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-286527

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