Regional Geology of Mount Diablo, California: Its Tectonic Evolution on the North America Plate Boundary

Mount Diablo and the geology of the Central California Coast Ranges are the subject of a volume celebrating the Northern California Geological Society’s 75th anniversary. The breadth of research illustrates the complex Mesozoic to Cenozoic tectonic evolution of the plate boundary. Recent faulting and folding along the eastern edge of the San Andreas system have exposed in the mountain a core of Franciscan accretionary wedge complex faulted against Cretaceous and Cenozoic forearc strata. The Memoir includes papers on structure, stratigraphy, tephrochronology, zircon provenance studies, apatite fission track analyses, and foraminifera and calcareous plankton assemblages tied to Cenozoic climate events. Chapters also address the history of geologic work in the area and the resource development of oil and gas, mercury, coal, and sand, and road aggregate.
Miocene stratigraphy and structure of the East Bay Hills, California Available to Purchase
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Published:September 27, 2021
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CiteCitation
J. Ross Wagner, Alan Deino, Stephen W. Edwards, Andrei M. Sarna-Wojcicki, Elmira Wan, 2021. "Miocene stratigraphy and structure of the East Bay Hills, California", Regional Geology of Mount Diablo, California: Its Tectonic Evolution on the North America Plate Boundary, Raymond Sullivan, Doris Sloan, Jeffrey R. Unruh, David P. Schwartz
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ABSTRACT
The structure and stratigraphy of the Miocene formations east of San Francisco Bay have been described in multiple studies for over a century. We integrated the results of past investigations and provide new data that improve understanding of formation age, the timing of deformation, and the amount of dextral displacement on selected faults. New geologic mapping and better age control show that formations previously inferred to be separate units of different ages are correlative, and new names are proposed for these units. Miocene structures associated with the development of the San Andreas transform system exerted significant control on Miocene deposition in the East Bay area. The developing structure created five distinct stratigraphic sections that are differentiated on the basis of differences in the stratigraphic sequence, lithology, and age. The stratigraphic changes are attributed to significant dextral displacement, syndepositional faulting, and distal interfingering of sediment from tectonically elevated source areas. New stratigraphic evaluations and age control show that prior to ca. 6 Ma, the developing fault system created local tectonically induced uplift as well as spatially restricted subbasins. Regional folding did not occur until after 6 Ma. Past evaluations have inferred significant dextral displacement on some of the faults in the East Bay. The spatial relationships between unique conglomerate clasts and known source areas, as well as the distribution of well-dated and unique tuffs, suggest that dextral displacement on some faults in the East Bay is less than previously reported.
- age
- Ar/Ar
- California
- Cenozoic
- correlation
- deformation
- deposition
- depositional environment
- displacements
- East Bay
- faults
- Miocene
- Neogene
- San Andreas Fault
- San Francisco Bay region
- sequence stratigraphy
- stratigraphic units
- structural analysis
- tectonics
- Tertiary
- United States
- San Pablo Group
- Orinda Formation
- Siesta Formation
- East Bay Hills
- Neroly Formation
- Contra Costa Group
- Monterey Group
- Briones Formation
- Mulholland Formation
- Moraga Formation
- Roblar Tuff
- Cierbo Formation
- Pinole Tuff Complex
- Pinole-Palomares Fault
- Indian Valley Member
- Bald Peak Formation
- Garrity Formation