New evidence for Early Paleozoic orogeny in the eastern Klamath terrane, northern California
The Grey Rocks outlier, in the east-central part of the Trinity mafic-ultramafic complex, has two localities in which metamorphosed and strongly deformed rocks lie unconformably between the Trinity complex and overlying, less deformed, volcanic and sedimentary sections. At one locality, a bouldery metaconglomerate and schistose sedimentary melange consist of detritus derived from Trinity serpentine, gabbros, and dikes. Foliation is vertical, striking discordantly beneath mafic submarine flows and a thick argillite section assigned questionably to the Mississippian Bragdon formation. At the second locality, interbedded argillite, thin discontinuous flows, and hyaloclastic lapilli tuffs are metamorphosed and isoclinally folded. Steep foliation is truncated beneath the gently dipping base of the Grey Rocks submarine volcanic pile. Undeformed dikes cut the folded sequence and enter the Grey Rocks volcanics, possibly as late feeders. The Grey Rocks lavas and volcanic breccias have been compared with the Early Devonian Copley greenstone of the Redding section. Timing of the orogenic event or events is poorly constrained. Accepting a questionable correlation between the submarine volcanics and the Copley greenstone, the orogenic event(s) would be Early Devonian or older. Clasts in the schists and conglomerates at the first locality are clearly derived from gabbros and dikes considered by some workers to be Silurian. The folded sequence at the second locality contains no Trinity complex detritus and rests on a strong, low-angle, schist and mylonite zone that truncates the Silurian( ) dike and gabbro complex.
- OSTI ID:
- 5019010
- Report Number(s):
- CONF-9305259-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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