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E. E. Brabb

Publications and source records attributed to E. E. Brabb.

At least 19 recordsLinked to original sources
USGS2007

Geologic Map and Map Database of Eastern Sonoma and Western Napa Counties, California

Introduction This report contains a new 1:100,000-scale geologic map, derived from a set of geologic map databases (Arc-Info coverages) containing information at 1:62,500-scale resolution, and a new description of the geologic map units and structural relations in the map area. Prepared as part of the San Francisco Bay Region Mapping Project, the study area includes the north-central part of the San Francisco Bay region, and forms the final piece of the effort to generate new, digital geologic maps and map databases for an area which includes Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, Santa Cruz, Solano, and Sonoma Counties. Geologic mapping in Lake County in the north-central part of the map extent was not within the scope of the Project. The map and map database integrates both previously published reports and new geologic mapping and field checking by the authors (see Sources of Data index map on the map sheet or the Arc-Info coverage eswn-so and the textfile eswn-so.txt). This report contains new ideas about the geologic structures in the map area, including the active San Andreas Fault system, as well as the geologic units and their relations. Together, the map (or map database) and the unit descriptions in this report describe the composition, distribution, and orientation of geologic materials and structures within the study area at regional scale. Regional geologic information is important for analysis of earthquake shaking, liquifaction susceptibility, landslide susceptibility, engineering materials properties, mineral resources and hazards, as well as groundwater resources and hazards. These data also assist in answering questions about the geologic history and development of the California Coast Ranges.

Scientific Investigations Map↗
USGS2006

Geologic map of the San Francisco Bay region

The rocks and fossils of the San Francisco Bay region reveal that the geology there is the product of millions of years at the active western margin of North America. The result of this history is a complex mosaic of geologic materials and structures that form the landscape. A geologic map is one of the basic tools to understand the geology, geologic hazards, and geologic history of a region. With heightened public awareness about earthquake hazards leading up to the 100th anniversary of the 1906 San Francisco earthquake, the U.S. Geological Survey (USGS) is releasing new maps of the San Francisco Bay Area designed to give residents and others a new look at the geologic history and hazards of the region. The “Geologic Map of the San Francisco Bay region” shows the distribution of geologic materials and structures, demonstrates how geologists study the age and origin of the rocks and deposits that we live on, and reveals the complicated geologic history that has led to the landscape that shapes the Bay Area.

California↗
USGS2001

Geologic maps and structure sections of the southwestern Santa Clara Valley and southern Santa Cruz Mountains, Santa Clara and Santa Cruz Counties, California

This digital map database, compiled from previously published and unpublished data, and new mapping by the authors, represents the general distribution of bedrock and surficial deposits in the mapped area. Together with the accompanying text file (scvmf.ps, scvmf.pdf, scvmf.txt), it provides current information on the geologic structure and stratigraphy of the area covered. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:24,000 or smaller.

Miscellaneous Field Studies Map↗
USGS2001

Magnetic stratigraphy of the lower middle Eocene (type Ulatsian) Vacaville Shale, Solano County, California

Mallory (1959) designated exposures of the Vacaville Shale on Ulatis Creek, northwest o Vacaville, California, as the type section of his lower middle Eocene Ulatisian benthic foraminiferal stage. Magnetic samples were taken from the 75 m of exposed section, and yielded a stable remanence held mainly in magnetite which passed a reversal test. The section showed two normal zones and three reversed magnetozones. Based on calcareous nannofossils and planktonic foraminifera, we correlate the type Ulatisian with Chron C20r-C22r (45.0-50.5 Ma), which is latest early Eocene to early middle Eocene on the global time scale. Our data calibrate what has been previously suggested by micropaleontologists: the base of the Ulatisian in the Vacaville Shale is 2 million years older (50.5 Ma) than it is in Media Agua Creek in the Temblor Range (48.5 Ma), and that the top of the Ulatisian is a million years younger (46.5 Ma) in the Vacaville section then it is at Media Agua Creek (47.5 Ma). This is another example of the problems with time-transgressive benthic foraminiferal stages.

Book chapter↗
USGS2001

Magnetostratigraphy of the Eocene-Oligocene San Lorenzo and Vaqueros formations, Santa Cruz Mountains, California; implications for California biostratigraphic zonations

The San Lorenzo and Vaqueros formations in the Santa Cruz Mountains are the only place in the Pacific Coast that provide a superposed record of the middle Eocene to late Oligocene Narizian, Refugian, and Zemorrian benthic foraminiferal stages, and also yields planktonic microfossils that can be used to correlate these strata with the global time scale. Magnetic samples were taken from three stratigraphic sections spanning the entire formation: the type section of the Twobar Shale and Rices Mudstone members of the San Lorenzo Formation at Kings Creek, the thickest section along the San Lorenzo River, and the upper part of the section along Zayante Creek. After overprinting was removed, a stable remanence was obtained which passed a reversal test and fold test. Our results suggest an age of 36.5 Ma for the early/late Narizian boundary, 35.5 Ma for the Narizian/Refugian boundary, 32.5 Ma for the Refugian/Zemorrian boundary, and 30.0 Ma for the early/late Zemorrian boundary, consistent with results reported from other regions. However, the beginning of the Vaqueros Stage is demonstrably time transgressive, with typical Vaqueros molluscs (e.g., Turritella inezana) first occurring as early as 29.5 Ma in the Santa Cruz Mountains, while they first occur at 27.5 Ma in Ventura County, and 17.5 Ma in Orange County, California.

Book chapter↗
USGS2000

Geologic map and map database of the Palo Alto 30' x 60' quadrangle, California

This digital map database, compiled from previously published and unpublished data, and new mapping by the authors, represents the general distribution of bedrock and surficial deposits in the mapped area. Together with the accompanying text file (pamf.ps, pamf.pdf, pamf.txt), it provides current information on the geologic structure and stratigraphy of the area covered. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:62,500 or smaller.

California↗
USGS1999

How useful is landslide hazard information? Lessons learned in the San Francisco Bay region

Landslides, worldwide and in the United States, are arguably the most costly natural hazard. Substantial landslide information is available, but much of it remains underutilized, as a disconnect exists among geologists, decision makers, and the public. The lack of a national landslide insurance policy exacerbates this situation and promotes litigation as the principal recourse for recouping landslide-damage losses. The U.S. Geological Survey's landslide investigation in the San Francisco Bay region of California provides a context for making suggestions on how Earth science information could be used more effectively.

International Geology Review↗