Lower Keweenawan volcanic rocks of Michigan and Wisconsin

Journal of Research of the U.S. Geological Survey
By:

Links

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

Additional publication details

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
Additional metadata about this publication, not found in other parts of the page is in this table