Southern California Coast Ranges, Domain 3

2007 ◽  
Author(s):  
Earl B. Alexander ◽  
Roger G. Coleman ◽  
Todd Keeler-Wolfe ◽  
Susan P. Harrison
Keyword(s):  
San Francisco ◽  
Southern California ◽  
Golden Gate ◽  
California Coast ◽  
The North ◽  
Transverse Ranges ◽  
Coast Ranges ◽  
Domain 3 ◽  
California Coast Ranges ◽  
Great Valley

The Southern California Coast Range domain is a mountainous region with subparallel ridges aligned north–south, or more precisely north, northwest–south, southeast, and with intervening valleys that are controlled by strike-slip faulting. It extends about 400 km from the Golden Gate at the entrance to San Francisco Bay south to the Transverse Ranges that have east–west trending ridges. The domain corresponds to a physiographic region about 400 km long and 100 km wide that is bound by the Pacific Ocean on the west, the Great Valley of California on the east, on the north by the drainage outlet of the Sacramento and San Joaquin Rivers through the Carquinas Straight and San Pablo Bay, and on the south by the Transverse Ranges. Ridges in the Southern California Coast Ranges generally have nearly level crests (Page et al. 1997), but they range considerably in height up to about 1500 m on some of the higher peaks. No streams from the Great Valley cross the Southern California Coast Ranges to the Ocean; the Great Valley drains through the Carquinez Straight and Golden Gate at the north end of these ranges. The larger streams in the Southern California Coast Ranges drain from the Santa Clara Valley, Salinas Valley, and Cuyama Valley to the San Francisco, Monterey, and San Luis Obispo bays. Only relatively small streams drain to the Great Valley, but some of them have large alluvial fans in the valley. There are many Tertiary-faultbound valleys and basins among the mountain ranges. Some of the more prominent basins are the Santa Maria basin, Carrizo Plains, Paso Robles basin, and Watsonville basin. Serpentine is scattered in relatively small bodies throughout the domain and is concentrated along some of the major faults and in the New Idria area (locality 3-12). Climates range from cool and foggy along the coast to warm inland, with hot and dry summers inland from the fog belt.

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.

Neogene volcanism on the eastside of Mount Diablo, Contra Costa County, California

2021 ◽  
Author(s):  
Raymond Sullivan ◽  
Ryan P. Fay ◽  
Carl Schaefer ◽  
Alan Deino ◽  
Stephen W. Edwards
Keyword(s):  
Middle Eocene ◽  
Volcanic Rocks ◽  
Calc Alkaline ◽  
Stream Channels ◽  
California Coast ◽  
Late Pliocene ◽  
The North ◽  
Great Valley Group ◽  
California Coast Ranges ◽  
Great Valley

ABSTRACT Two spatially separated areas of Neogene volcanic rocks are located on the northeast limb of the Mount Diablo anticline. The southernmost outcrops of volcanics are 6 km east of the summit of Mount Diablo in the Marsh Creek area and consist of ~12 hypabyssal dacite intrusions dated at ca. 7.8–7.5 Ma, which were intruded into the Great Valley Group of Late Cretaceous age. The intrusions occur in the vicinity of the Clayton and Diablo faults. The rocks are predominantly calc-alkaline plagioclase biotite dacites, but one is a tholeiitic plagioclase andesite. Mercury mineralization was likely concomitant with emplacement of these late Miocene intrusions. The northern most outcrops of Neogene volcanic rocks occur ~15 km to the north of Mount Diablo in the Concord Naval Weapons Station and the Los Medanos Hills and are probably parts of a single andesite flow. A magnetometer survey indicates that the flow originated from a feeder dike along the Clayton fault. The lava flow is flat-lying and occu pies ancient stream channels across an erosional surface of tilted Markley Sandstone of middle Eocene age. New radiometric dates of the flow yield an age of 5.8–5.5 Ma, but due to alteration the age should be used with caution. The flow is a calc-alkaline andesite rich in clinopyroxene and plagioclase. What appear to be uplifted erosional remnants of the flow can be traced northeastward in the Los Medanos Hills across a surface of tilted Cenozoic rocks that eventually rest on formations as young as the Lawlor Tuff dated at 4.865 ± 0.011 Ma. This stratigraphic relationship suggests that the andesite flow is probably late Pliocene in age and was impacted by the more recent uplift of the Los Medanos Hills but postdates the regional folding and faulting of the rocks of Mount Diablo. In terms of timing, location, and composition, the evidence suggests these two areas of dacitic and andesitic volcanics fit into a series of migrating volcanic centers in the California Coast Ranges that erupted following the northward passage of the Mendocino Triple Junction.

Klamath Mountains, Domain 5

2007 ◽  
Author(s):  
Earl B. Alexander ◽  
Roger G. Coleman ◽  
Todd Keeler-Wolfe ◽  
Susan P. Harrison
Keyword(s):  
Klamath Mountains ◽  
Cascade Mountains ◽  
California Coast ◽  
The Pacific ◽  
The Pacific Ocean ◽  
P Domain ◽  
Coast Ranges ◽  
California Coast Ranges ◽  
Great Valley ◽  
Eastern Edge

Domain 5 has mountains on the west aligned in broad arcs; in the eastern Klamath Mountains this arcuate pattern is not as evident. The outer arc curves from the triple junction of the California Coast Ranges, Great Valley, and Klamath Mountains in western Tehama County around through Del Norte County, where it is within a few kilometers of the Pacific Ocean, to Douglas County in Oregon. This western edge of the Klamath Mountains marks a boundary with the California Coast Ranges. The eastern edge of the Klamath Mountains forms a boundary with the Cascade Mountains. The southern, or southeast, boundary is where sediments of the Great Valley lap over the Klamath Mountains in Shasta and western Tehama counties. Serpentine rocks are more extensive in the Klamath Mountains than in any other domain or physiographic province in North America. Through the middle of the Tertiary, the Klamath Mountains were eroded to a nearly level plain called the Klamath peneplain (Diller 1902). According to Diller, the Klamath peneplain and the submerged coastal area that had been accumulating sediments were uplifted slightly during the Miocene, and erosion reduced the northern California Coast Ranges to a nearly level plain which he called the Bellsprings peneplain, noting that it is practically continuous with the Klamath peneplain. Subsequently discovered sediments of the Weaverville formation were deposited in a depression, or graben, in the Klamath Mountains during the Oligocene, indicating that uplift of the Klamath peneplain must have begun during the Paleogene, before the Miocene. Uplift was intermittent, allowing time for the erosion of broad valleys in less resistant rocks between episodes of uplift. Concordant summits, or mountains with summits of nearly equal elevation, are the evidence that led Diller (1902) to suspect a former peneplain. Although the mountain summits in any particular area are nearly equal or subequal, there is a general increase in summit elevation from the coast inland to 2.5–2.7 km. The altitude of Mt. Eddy on the eastern edge of the Klamath Mountains is 2751 m and that of Mt.

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