Geologic map of the eastern Tehachapi Mountains, patterned: Supplement 4 from 'Geology of the Eastern Tehachapi Mountains and Late Cretaceous-Early Cenozoic tectonics of the southern Sierra Nevada Region, Kern County, California' (Thesis)

Many geologic studies have inferred that the California continental margin in the vicinity of the western Mojave Desert was tectonically disrupted after emplacement of the Cretaceous Cordilleran batholith and prior to Neogene displacements on the San Andreas fault system. The causes of this regional deformation, however, are poorly understood. Located along the northern margin of this disrupted region at the southern end of the comparatively little deformed Sierra Nevada batholith, the eastern Tehachapi Mountains are ideally situated to study the possible mechanisms of this disruption. In view of this, the geology and structure of the eastern Tehachapi Mountains were investigated using geologic field mapping at scales of 1:6,000 through 1:24,000, detailed petrographic studies, and structural and kinematic analysis of deformation fabrics and structures in the field and in the lab. The study area is divided by a generally N trending shallowly SE dipping ductile-cataclastic fault zone called the Blackburn Canyon fault into the eastern Tehachapi gneiss complex in the footwall and the Oak Creek Pass complex in the hangingwall. The eastern Tehachapi gneiss complex is composed of two different sequences of metasedimentary rocks that have been intruded by three generations of plutonic rocks. The Brite Valley group metasedimentary rocks consist largely of pelites and graphitic quartzite with subordinate marble. The Antelope Canyon group metasedimentary rocks consist of a lower section composed mostly of thinly laminated dirty quartzite overlain by an upper section of marble. The earliest intrusive rocks in the area (group I orthogneisses) are lithologically diverse and include granite augen gneiss, garnetiferous hornblende diorite gneiss, and hornblende biotite quartz diorite gneiss. Both groups of paragneiss and the group I orthogneisses are intruded by group II plutons of the Tehachapi Intrusive Complex. The Tehachapi Intrusive Complex is composed of comagmatic gabbro, quartz diorite, and tonalite and it is inferred to ...