126 D30. Recent Advances in Structural Geology (Posters)

Monday, 11 October 2021
2:30 PM - 6:30 PM
Exhibit Hall A

REVISED GEOLOGIC MAP OF THE MINERAL KING PENDANT, SOUTHERN SIERRA NEVADA, CALIFORNIA, INDICATES EXTREME STRUCTURAL IMBRICATION OF A PERMIAN TO MID-CRETACEOUS VOLCANO-SEDIMENTARY SEQUENCE

Paper number: 126-8
Program: Technical Sessions
Time: 2:30 PM – 6:30 PM

Authors

Abstract

The Mineral King pendant is an ~15-km long, NW-striking assemblage of Permian to mid-Cretaceous metavolcanic and metasedimentary rocks that form a steeply dipping wall rock screen between large mid-Cretaceous plutons of the Sierra Nevada batholith. Pendant rocks are generally well-bedded, and characterized by NW-striking, steeply dipping, bedding-parallel cleavage and flattening foliation, and steeply NW-plunging stretching lineation. NW-elongate lithologic units with well-developed parallel bedding and an absence of prominent faults or shear zones suggests a degree of stratigraphic continuity. However, U/Pb zircon dating of felsic metavolcanic and volcanosedimentary rocks across the pendant indicates a complex pattern of structurally interleaved units with ages ranging from 276 Ma to 100 Ma.

We utilize a compilation of 39 existing and new U/Pb zircon ages and 4 reported fossil localities to construct a revised geologic map of the Mineral King pendant that emphasizes age relationships rather than lithologic (e.g. Sisson and Moore, 2013) or stratigraphic (e.g. Busby-Spera and Saleeby, 1987) correlations. We find that apparently coherent lithologic units are lensoidal and discontinuous, and cryptically interleaved at meter to km scales. Along-strike facies changes and depositional unconformities combine with km-scale tight folding and structural imbrication to create a complex map pattern with numerous discordant units.

Discrete faults or major shear zones are not readily apparent in the pendant, although such structures would seem necessary to produce the structural complications revealed by our new mapping and U/Pb dating. We interpret the Mineral King pendant to be structurally imbricated by a combination of km-scale tight to isoclinal folding and cryptic thrust(?) faulting, accentuated by, and eventually obscured by, pervasive flattening and vertical stretching that preceded and accompanied emplacement of the bounding mid-Cretaceous plutons. Close juxtaposition of rhyolite tuffs deposited subaerially at ~100 Ma and large granitic plutons crystalized at ~11 km depth at 98 Ma (Klemetti et al., 2013) suggests that the final phase of deformation involved very rapid downward displacement of Mineral King pendant rocks during upward emplacement of granitic plutons.

Geological Society of America Abstracts with Programs. Vol. 53, No. 6

doi: 10.1130/abs/2021AM-367655

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