Abstract: Fold System in Southern Sierra Nevada Batholith, California

Joseph C. Nellis

The Paleozoic (Permian-Carboniferous) folded rocks in the area of Lake Isabella, Kern County, California, are part of a roof pendant resting in the southern end of the Sierra Nevada batholith. The mapped area contains six major rock units: marble, slate, gneiss, andalusite schist, impure quartzite, and quartz diorite. The marble unit is the most conspicuous of the metamorphic rocks and arcuate lenses of this unit appear within structural folds.

The major features in the area are the batholith and the fold system. Stereographic projection of the rock attitudes shows that the folds went through two episodes of deformation but belong to a single system. The fold axes of the large-scale folds, plotted from relict beddings, are essentially the same as the fold axes of the small folds.

Field evidence and the east-west variation of the polymorphs sillimanite and andalusite indicate that metamorphism was gradational and more intensive toward the east. During the last phases of the progressive metamorphism and deformation the amplitudes of the isoclinal folds became greater and the earlier structures were partly obscured.

The geologic history of the study area comprises: (1) deposition of sedimentary rocks; (2) folding and metamorphism; (3) intrusion of the batholith; and (4) regional uplift, faulting, and erosion.

AAPG Search and Discovery Article #90964©1978 AAPG Rocky Mountain Section Meeting, Salt Lake City, Utah