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GEOREF RECORD

Paleozoic seas of central Idaho

Clyde P. Ross
Paleozoic seas of central Idaho
Geological Society of America Bulletin (1962) 73 (6): 769-793

Abstract

Some recent paleogeographic maps indicate that central Idaho was part of a major geosyncline throughout Paleozoic time. This concept, apparently based on thick marine accumulations far apart on the margins of the region, is inconsistent with field data. Within the area of the Idaho batholith, Permian(?) volcanic rocks rest either on batholithic rocks or on the Belt Series. The Belt Series rocks have furnished the xenoliths in the batholith. To the W., upper Paleozoic and Mesozoic strata are invaded. Along the eastern margin, S. of lat. 45 degrees , thick Paleozoic strata are intruded by the batholith. These locally exceed 30,000 ft. in thickness and thin eastward. They have many variations. Those close to the batholith, especially those high in the sequence, are regarded as of nearshore origin, The Paleozoic strata in southeastern Idaho, more than 17,000 ft. thick, are broadly similar except that Cambrian strata there are thicker and more widespread. The part of central Idaho N. of the vicinity of lat. 45 degrees has no known Paleozoic strata. Northern Idaho has only a few outcrops of beds of Cambrian age. The differences in thickness and character between Paleozoic strata in S.-central and southeastern Idaho and those in western Montana and Wyoming (less than 7500 ft. thick) suggest a hinge line near the eastern boundary between Idaho and Montana with a shelf to the E. and a trough to the W. In S.-central Idaho this trough had a maximum width of 90 mi. and a western shore roughly at the E. margin of the batholith. This trough wedged out northward a little beyond lat. 45 degrees . Thus the area of the present Idaho batholith has been a positive block since Precambrian time, comparable to but apparently of longer duration than the geanticline in northern Nevada, Any invasion of the positive block in Idaho by marine waters during the Paleozoic was local and brief, except perhaps along the western border. Uncertain correlations within the area of the batholith leave open the possibility of some deposition there early in Paleozoic time.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 73
Serial Issue: 6
Title: Paleozoic seas of central Idaho
Author(s): Ross, Clyde P.
Pages: 769-793
Published: 1962
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
Accession Number: 1962-011126
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus., table
N42°00'00" - N49°00'00", W117°15'00" - W111°04'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from Bibliography and Index of North American Geology, U. S. Geological Survey, Reston, VA, United States
Update Code: 1962
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