--> --> Abstract: The Age, Geometry, Kinematic, and Regional Tectonic Setting of the Glacier Lakes and Gemini Fault Zones, Central Sierra Nevada, California, by M. A. Pachell; #90925 (1999)

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PACHELL, MATTHEW A., Utah State University, Department of Geology, Logan, Utah

Abstract: The Age, Geometry, Kinematic, and Regional Tectonic Setting of the Glacier Lakes and Gemini Fault Zones, Central Sierra Nevada, California

This research focuses on two kilometer-scale sinistral strike-slip faults in the central Sierra Nevada batholith, California. The research objectives are to understand the relationship between the age, geometry, and kinematics of these northeast striking brittle faults to larger, ductile, north-south striking, dextral shear zones. Previous research indicates that the dextral shear zones formed from oblique subduction within the late Cretaceous magmatic arc and may have allowed pluton emplacement through tensile voids that correspond to P orientations in Riedel-type shear zones. The brittle faults this study examines appear to have conjugate orientations to the larger ductile shear zones and may correspond to an R' Riedel orientation. Previous investigations of similar brittle faults in the area suggest that they nucleated and slipped soon after pluton emplacement, and therefore may be genetically linked to the dextral shear zones. This relationship is important because it may document changing deformation styles within one deformational event. That is, ductile deformation may have yielded to brittle deformation as the plutons cooled. Detailed geologic mapping and dating of metamorphic minerals within the faults may resolve the age and structural relationships of the brittle and ductile fault systems.

This research is unique because it focuses on the interactions of exhumed fault systems that formed at upper- to mid-crustal depths. It addresses how fault systems interact under transpressive stresses and helps clarify the complex geometries and rates of growth of major strike-slip fault systems at changing crustal temperatures and pressures. This bears direct application to mineral and hydrocarbon exploration by providing a better understanding of fractured reservoirs. 

AAPG Search and Discovery Article #90925©1999 AAPG Foundation Grants-in-Aid