A transect of metamorphic rocks along the Copper River, Cordova and Valdez Quadrangles, Alaska: A section in The United States Geological Survey in Alaska: Accomplishments during 1982

Circular 939
By: , and 

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Abstract

The lower Tertiary Orca Group is juxtaposed against the Upper Cretaceous Valdez Group along the Contact fault system (Winkler and Plafker, 1974, 198; Plafker and others, 1977)(fig. 33). In both groups, turbidites are the dominant rock type, with lesser mafic volcanic rocks (table 10). The Valdez Group, on the north, has traditionally been considered to be of higher metamorphic grade than the Orca Group (Moffit, 1954; Tysdal and Case, 1979; Winkler and Plafker, 198; Winkler and others, 1981). In 1982, we made a transect across the regional strike of the rocks and the contact between the two groups. The transect area follows the Copper River for 85 km from the Cordova quadrangle north into the Valdez quadrangle and extends for about 25 km on either side of the river (fig. 33). We planned, by systematic sampling of the area, to examine the metamorphic differences between the Orca and Valdez Groups. We found, however, that a strong thermal metamorphic event has overprinted and obscured regional metamorphic relations. We believe intrusion of Tertiary granite (fig. 33) to be responsible for this metamorphism. (Figures 33 and 34 and tables follow this article.)

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title A transect of metamorphic rocks along the Copper River, Cordova and Valdez Quadrangles, Alaska: A section in The United States Geological Survey in Alaska: Accomplishments during 1982
Series title Circular
Series number 939
DOI 10.3133/70180210
Year Published 1984
Language English
Publisher U.S. Geological Survey
Publisher location Alexandria, VA
Contributing office(s) Alaska Science Center Geology Minerals, Alaska Science Center
Description 6 p.
Larger Work Type Report
Larger Work Subtype USGS Numbered Series
Larger Work Title The United States Geological Survey in Alaska: Accomplishments during 1982 (Circular 939)
First page 52
Last page 57
Country United States
State Alaska
Other Geospatial Copper River