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Geology of the Three Forks quadrangle, Montana, with sections on petrography of igneous rocks

Professional Paper 370

By:
and

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Abstract

The Three Forks quadrangle at the head of the Missouri River, has a long stratigraphic succession. The oldest rocks are Precambrian gneiss, derived from arkosic sandstone, and amphibolite, probably altered from mafic sills and lava flows. The unmetamorphosed sedimentary rocks range in age from late Precambrian to Recent, have an aggregate thickness of about 11,000 feet, and underlie about 85 percent of the quadrangle. The only systems not represented are Ordovician, Silurian, and Triassic.

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Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Geology of the Three Forks quadrangle, Montana, with sections on petrography of igneous rocks
Series title:
Professional Paper
Series number:
370
Year Published:
1963
Language:
ENGLISH
Publisher:
United States Government Printing Office
Description:
iv, 143
Country:
United States
State:
Montana
Other Geospatial:
Three Forks Quadrangle