Stratigraphy and structure of the Late Precambrian-Early Cambrian clastic metasedimentary rocks of the Baldwin Lake area, San Bernardino Mountains, California
Tyler, David Lynn
Burchfiel, B. C.
Master of Arts
The San Bernardino Mountains are the easternmost range of the Transverse Ranges of southern California, Precambrian crystalline rocks, and Late Precambrian and Paleozoic metasedimentary rocks are exposed in several roof pendants in the Mesozoic plutonic rocks which comprise the bulk of the range. The Late Precambrian - Early Cambrian clastic shelf sequence in chronologic order includes 1) the white quartzite of the Stirling Quartzite Equivalent; 2) the gray quartzite and phyllite of the Wood Canyon Formation; 3) the vitreous white Zabriskie Quartzite; and 4) carbonate ahd schist of the Carrara Formation. These rocks probably constitute a part of the initial deposits along the eastern margin of the Cordilleran miogeosyncline. Middle Cambrian to Permian shelf carbonates overlay the clastic sequence. The Precambrian crystalline rocks and the sedimentary rocks were deformed and metamorphosed to upper greenschist (biotite) grade, probably in Late Masozoic time. The rocks are folded into a northeast-vergent overturned anticline which is overridden by a somewhat later thrust of similar vergenz. Dominantly post-tectonic acid and intermediate plutons of the Mesozoic Sierran magmatic arc intrude the metamorphic rocks. Right-lateral strike-slip faults and gravity slides of Cenozoic age modify the Mesozoic structure. These features are related to the final uplift of the San Bernardino Mountains.