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Chapter C in Geological Survey research 1967

Professional Paper 575-C

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Abstract

Low-grade metamorphic rocks of the blueschist facies grade upward to the sole of a great thrust fault along the eastern margin of the Coast Ranges in northern California and southwestern Oregon. The gradation is defined by three textural zones of increasing reconstitution in metagraywacke, and by two metamorphic mineral zones, lawsonite and pumpellyite. The metagraywacke of textural zones 1 and 2 is clearly Franciscan Formation on the basis of lithology and age, and grades into thoroughly reconstituted rocks of textural zone 3 that herein are named the South Fork Mountain Schist. The blueschist probably formed in a zone of cataclasis and anomalously high water pressures under the thrust fault, rather than in the generally postulated zone of extreme depth of burial. Water in excess of that required to form pumpellyite and lawsonite was available for serpentinization of ultramafic rocks emplaced in the thrust fault.

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Additional publication details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Chapter C in Geological Survey research 1967
Series title:
Professional Paper
Series number:
575
Chapter:
C
Year Published:
1967
Language:
English
Publisher:
U.S. Geological Survey
Contributing office(s):
Wisconsin Water Science Center
Description:
p. 251
Larger Work Type:
Report
Larger Work Subtype:
USGS Numbered Series
Larger Work Title:
Geological Survey research 1967
Country:
United States
Online Only (Y/N):
N
Additional Online Files (Y/N):
N