Lower Keweenawan volcanic rocks of Michigan and Wisconsin
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Abstract
Unconformable sequences of Keweenawan volcanic rocks occur in Michigan and adjacent Wisconsin. The sequences differ in types of rocks, magnetic properties, metamorphic grade, and pattern of structural deformation; they had different vent areas and were deposited in basins that were only partly overlapping. The older sequence includes the Bessemer Quartzite and two newly named formations that are here assigned to the lower Keweenawan. The younger sequence includes the well-known Portage Lake Volcanics and a younger unnamed formation, both of middle Keweenawan age. Formerly the older rocks were interpreted as a fault-repeated part of the Portage Lake Volcanics, but new evidence indicates that these older rocks had been metamorphosed and tilted and were being eroded in middle Keeweenawan time.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Lower Keweenawan volcanic rocks of Michigan and Wisconsin |
| Series title | Journal of Research of the U.S. Geological Survey |
| Edition | 529 |
| Volume | 3 |
| Issue | 5 |
| Year Published | 1975 |
| Language | English |
| Publisher | U.S. Geological Survey |
| Publisher location | Reston, VA |
| Description | 13 p. |
| First page | 541 |
| Country | United States |
| State | Michigan, Wisconsin |
| Online Only (Y/N) | N |
| Additional Online Files (Y/N) | N |
| Google Analytic Metrics | Metrics page |