Remagnetization of the coast range ophiolite and lower part of the Great Valley Sequence in northern California and southwest Oregon

1987 ◽  
Vol 92 (B5) ◽  
pp. 3487 ◽  
Author(s):  
Leah S. Frei ◽  
M. C. Blake
Keyword(s):  
Northern California ◽  
Coast Range ◽  
Coast Range Ophiolite ◽  
Southwest Oregon ◽  
Great Valley

Field and petrographic reconnaissance of Franciscan complex rocks of Mount Diablo, California: Imbricated ocean floor stratigraphy with a roof exhumation fault system

2021 ◽  
Author(s):  
John Wakabayashi
Keyword(s):  
Fault System ◽  
Normal Faults ◽  
Coast Range ◽  
Franciscan Complex ◽  
The North ◽  
Tectonic Window ◽  
Coast Range Ophiolite ◽  
Great Valley Group ◽  
Clastic Sedimentary ◽  
Great Valley

ABSTRACT Franciscan subduction complex rocks of Mount Diablo form an 8.5 by 4.5 km tectonic window, elongated E-W and fault-bounded to the north and south by rocks of the Coast Range ophiolite and Great Valley Group, respectively, which lack the burial metamorphism and deformation displayed by the Franciscan complex. Most of the Franciscan complex consists of a stack of lawsonite-albite–facies pillow basalt overlain successively by chert and clastic sedimentary rocks, repeated by faults at hundreds of meters to <1 m spacing. Widely distributed mélange zones from 0.5 to 300 m thick containing high-grade (including amphibolite and eclogite) assemblages and other exotic blocks, up to 120 m size, form a small fraction of exposures. Nearly all clastic rocks have a foliation, parallel to faults that repeat the various lithologies, whereas chert and basalt lack foliation. Lawsonite grew parallel to foliation and as later grains across foliation. The Franciscan-bounding faults, collectively called the Coast Range fault, strike ENE to WNW and dip northward at low to moderate average angles and collectively form a south-vergent overturned anticline. Splays of the Coast Range fault also cut into the Franciscan strata and Coast Range ophiolite and locally form the Coast Range ophiolite–Great Valley Group boundary. Dip discordance between the Coast Range fault and overlying Great Valley Group strata indicates that the northern and southern Coast Range fault segments were normal faults with opposite dip directions, forming a structural dome. These relationships suggest accretion and fault stacking of the Franciscan complex, followed by exhumation along the Coast Range fault and then folding of the Coast Range fault.

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.

III.—Recent Observations on the Glaciation of British Columbia and Adjacent Regions

1888 ◽  
Vol 5 (8) ◽  
pp. 347-350 ◽  
Author(s):  
Geo. M. Dawson
Keyword(s):  
British Columbia ◽  
Glacial Period ◽  
Coast Range ◽  
Coast Mountains ◽  
One Stage ◽  
Queen Charlotte Islands ◽  
Glacier Ice ◽  
Inland Ice ◽  
Great Valley ◽  
The U.S

Previous observations in British Columbia have shown that at one stage in the Glacial period—that of maximum glaciation—a great confluent ice-mass has occupied the region which may be named the Interior Plateau, between the Coast Mountains and Gold and Eocky Mountain Kanges. From the 55th to the 49th parallel this great glacier has left traces of its general southward or southeastward movement, which are distinct from those of subsequent local glaciers. The southern extensions or terminations of this confluent glacier, in Washington and Idaho Territories, have quite recently been examined by Mr. Bailley Willis and Prof. T. C. Chamberlin, of the U.S. Geological Survey. There is, further, evidence to show that this inland-ice flowed also, by transverse valleys and gaps, across the Coast Range, and that the fiords of the coast were thus deeply filled with glacier-ice which, supplemented by that originating on the Coast Range itself, buried the entire great valley which separates Vancouver Island from the mainland and discharged seaward round both ends of the island. Further north, the glacier extending from the mainland coast touched the northern shores of the Queen Charlotte Islands.

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