Title

Deformation across the western Mina deflection: field studies in the Huntoon Springs quadrangle, California-Nevada

Presenter Information

Eliya Hogan

Document Type

Oral Presentation

Location

SURC Ballroom A

Start Date

17-5-2012

End Date

17-5-2012

Abstract

The Mina deflection (MD) defines a major right step in the NW-trending eastern California shear zone (ECSZ)-Walker Lane belt (WLB) dextral system, and transfers fault slip from the ECSZ to the WLB along ENE- and NW-trending faults. Three models have been proposed to explain this fault slip transfer: (1) the displacement transfer model suggests that Pliocene slip was transferred along NE-striking normal faults, (2) the transtensional strain model suggests that Pleistocene strain was transferred by extension-dominated transtension in the west and wrench-dominated transtension in the east, and (3) the rotational block model suggests that slip was transferred by clockwise rotating blocks bounded by NE-striking sinistral faults. New geologic mapping and structural studies in the Huntoon Springs quadrangle (HSQ) of the western MD evaluate these hypotheses. Here, Pliocene andesite lavas, basalt lavas, and unconformably underlying Miocene ignimbrite are cut and offset by primarily high-angle ENE-striking sinistral faults and by lesser NW-striking normal faults. Sinistral faults are identified by linear fault traces, alternating scarp-facing directions, sinistral offsets of normal faults, fractures, and volcanic units, and by the presence of extensional basins at releasing steps, or pop-up structures at restraining steps. Normal faults are identified by sinuous fault traces, the lack of lateral offset along strike, or as connecting faults between left-stepping sinistral faults. Major NE-striking sinistral faults documented in the HSQ may be related to block rotation, but further study is required to verify this hypothesis.

Poster Number

3

Faculty Mentor(s)

Jeff Lee, Wendy Bohrson, Anne Egger

Additional Mentoring Department

Geological Sciences

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Deformation across the western Mina deflection: field studies in the Huntoon Springs quadrangle, California-Nevada

SURC Ballroom A

The Mina deflection (MD) defines a major right step in the NW-trending eastern California shear zone (ECSZ)-Walker Lane belt (WLB) dextral system, and transfers fault slip from the ECSZ to the WLB along ENE- and NW-trending faults. Three models have been proposed to explain this fault slip transfer: (1) the displacement transfer model suggests that Pliocene slip was transferred along NE-striking normal faults, (2) the transtensional strain model suggests that Pleistocene strain was transferred by extension-dominated transtension in the west and wrench-dominated transtension in the east, and (3) the rotational block model suggests that slip was transferred by clockwise rotating blocks bounded by NE-striking sinistral faults. New geologic mapping and structural studies in the Huntoon Springs quadrangle (HSQ) of the western MD evaluate these hypotheses. Here, Pliocene andesite lavas, basalt lavas, and unconformably underlying Miocene ignimbrite are cut and offset by primarily high-angle ENE-striking sinistral faults and by lesser NW-striking normal faults. Sinistral faults are identified by linear fault traces, alternating scarp-facing directions, sinistral offsets of normal faults, fractures, and volcanic units, and by the presence of extensional basins at releasing steps, or pop-up structures at restraining steps. Normal faults are identified by sinuous fault traces, the lack of lateral offset along strike, or as connecting faults between left-stepping sinistral faults. Major NE-striking sinistral faults documented in the HSQ may be related to block rotation, but further study is required to verify this hypothesis.