scholarly journals Late Cenozoic tephrochronology of the Mount Diablo area within the evolving plate-tectonic boundary zone of northern California

2021 ◽  
Author(s):  
Andrei M. Sarna-Wojcicki ◽  
Raymond Sullivan ◽  
Alan Deino ◽  
Laura C. Walkup ◽  
J. Ross Wagner ◽  
...  
Keyword(s):  
San Francisco ◽  
Volcanic Field ◽  
Northern California ◽  
Stratigraphic Sequence ◽  
Source Areas ◽  
Northern Nevada ◽  
Southern Nevada ◽  
Tephra Layers ◽  
California Coast Ranges ◽  
Tectonic Boundary

ABSTRACT We present a tephrochronologic/chronostratigraphic database for the Mount Diablo area and greater San Francisco Bay region that provides a spatial and temporal framework for geologic studies in the region, including stratigraphy, paleogeography, tectonics, quantification of earth surface processes, recurrence of natural hazards, and climate change. We identified and correlated 34 tephra layers within this region using the chemical composition of their volcanic glasses, stratigraphic sequence, and isotopic and other dating techniques. Tephra layers range in age from ca. 65 ka to ca. 29 Ma, as determined by direct radiometric techniques or by correlation to sites where they have been dated. The tephra layers are of Quaternary or Neogene age except for two that are of Oligocene age. We correlated the tephra layers among numerous sites throughout northern California. Source areas of the tephra layers are the Snake River–Yellowstone hotspot trend of northern Nevada, southern Idaho, and western Wyoming; the Nevadaplano caldera complex of central Nevada; the Jemez Mountains–Valles Caldera in northwestern New Mexico; the Southern Nevada volcanic field and related source areas in eastern California and west-central Nevada; the Quien Sabe–Sonoma volcanic centers of the California Coast Ranges; and the young Cascade Range volcanic centers of northeastern California and Oregon.

scholarly journals Miocene stratigraphy and structure of the East Bay Hills, California

2021 ◽  
Author(s):  
J. Ross Wagner ◽  
Alan Deino ◽  
Stephen W. Edwards ◽  
Andrei M. Sarna-Wojcicki ◽  
Elmira Wan
Keyword(s):  
San Francisco ◽  
Fault System ◽  
Geologic Mapping ◽  
Stratigraphic Sequence ◽  
Source Areas ◽  
Significant Control ◽  
Bay Area ◽  
San Andreas ◽  
East Bay ◽  
Elevated Source

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.

Northern California Coast Ranges, Domain 4

2007 ◽  
Author(s):  
Earl B. Alexander ◽  
Roger G. Coleman ◽  
Todd Keeler-Wolfe ◽  
Susan P. Harrison
Keyword(s):  
San Francisco ◽  
Northern California ◽  
Coast Range ◽  
Klamath Mountains ◽  
California Coast ◽  
Mountain Ranges ◽  
The North ◽  
Coast Ranges ◽  
California Coast Ranges ◽  
Great Valley

The Northern California Coast Ranges domain is in a mountainous region in which most of the mountain ranges are aligned north–south, or more precisely north, northwest– south southeast, curving around the Klamath Mountains into Oregon where the domain branches to north–south and northeast–southwest trends on the northwest side of the Klamath Mountains. It extends about 600km from the Golden Gate at the entrance to San Francisco Bay north to about the Coquille River in Coos County and nearly to the North Umqua River in Douglas County, Oregon. The domain corresponds to a physiographic region that is bounded by the Pacific Ocean on the west, the Coast Range of Oregon and Washington (Orr and Orr 1996) on the north, the Klamath Mountains on the northeast, the Great Valley of California on the southeast, and on the south by the drainage outlet of the Sacramento and San Joaquin rivers through the Carquinas Straight and San Pablo Bay. Serpentine is scattered in relatively small ultramafic bodies throughout the Northern California Coast Ranges and is concentrated along some of the major faults. For 200 or 300 km south from the Klamath Mountains, the Northern California Coast Ranges region is a rectangular strip 90–110 km wide between the Ocean and the Great Valley of California. The Klamath Mountains crowd the region to a narrow strip only 10 or 12 km wide in Del Norte County. Most of the mountain ranges have approximately concordant summits that are tilted up toward the east–northeast. Therefore, the highest altitudes are on the east, just south of the Klamath Mountains. North Yolla Bolly at 2397 m (7865 feet) and South Yolla Bolly at 2466 m (8092 feet) have the highest summits. Both of these and some neighboring mountains have cirques and moraines indicative of glaciation on their north slopes. There is no evidence of glaciation in any areas with serpentine rocks. Only the Rogue and Klamath rivers cut from east to west all of the way across the Northern California Coast Ranges, except for a few smaller streams such as the Chetco and Smith rivers that have headwaters in the Klamath Mountains.

scholarly journals Networks within networks: scaling response operations in the lightning complex fires in northern california, August 2020

2021 ◽  
Vol 331 ◽  
pp. 04016
Author(s):  
K. Comfort Louise
Keyword(s):  
San Francisco ◽  
Distribution Systems ◽  
Extreme Event ◽  
Electrical Power ◽  
Incident Management ◽  
Northern California ◽  
California Department ◽  
Wildfire Risk ◽  
The Impact ◽  
Large Sections

Wildfire risk has increased dramatically in California over more than two decades, 2000 - 2021, reflecting the intense impact of climate change on the state’s environmental and ecological systems. Most urgent is the impact of wildfire at the wildland-urban-interface (WUI), and the challenge to prevent cascading disaster for regions connected via interdependent lifelines of transportation, communications, electrical power, water, sewer, and gas line distribution systems that characterize geographic regions. To what extent do large, multi-organizational, multi-jurisdictional networks of organizations learn from experience and adapt their performance in response to the dynamic conditions of an actual extreme event? This article identifies four types of networks operating in the 2020 Lightning Complex Wildfires in northern California and documents the rapid escalation of risk and costs based on a preliminary analysis of the 209 incident reports filed by California Department of Forestry and Fire Protection (CalFire) for the SCU Fire that engulfed large sections of five counties in the southeastern San Francisco Bay Region. The article concludes that Interagency Incident Management Networks provide essential intelligence to support local management of operations in the dynamic context of wildfire risk.

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