A Precambrian diamictite below the base of the Stillwater Complex, southwestern Montana
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Abstract
The metasedimentary rocks of Precambrian age below the base of the Stillwater Complex, southwestern Montana, contain a metamorphosed diamictite similar to diamictite in strata of late Precambrian and Early Cambrian age in Canada and the Western United States. The diamictite consists of a quartz-cordierite matrix containing an average 10-15 percent of rock fragments diverse in shape, size, angularity, lithologic types, and textures. The diamictite unit is poorly sorted, crops out discontinuously for 14 miles, and locally has a crude layering containing dropstones. Its origin is debatable, but the rock is suggestive of glacial marine deposition. The minimum age of the diamictite of the complex is 2,750 m.y. from U-Pb determination on zircon of intrusive quartz monzonite, the maximum 3,140 m.y. as determined on zircon from metasedimentary rocks interbedded with the diamictite.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | A Precambrian diamictite below the base of the Stillwater Complex, southwestern Montana |
| Series title | Journal of Research of the U.S. Geological Survey |
| Volume | 1 |
| Issue | 4 |
| Year Published | 1973 |
| Language | English |
| Publisher | U.S. Geological Survey |
| Publisher location | Reston, VA |
| Description | 12 p. |
| First page | 403 |
| Last page | 414 |
| Country | United States of America |
| State | Montana |
| Other Geospatial | Stillwater Complex |
| Online Only (Y/N) | N |
| Additional Online Files (Y/N) | N |
| Google Analytic Metrics | Metrics page |