A typical cross section based on magnetic data of lower and middle Keweenawan volcanic rocks, Ironwood area, Michigan

Journal of Research of the U.S. Geological Survey
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Abstract

A north-trending aeromagnetic profile of a sequence of east-striking Keweenawan volcanic rocks near Ironwood, Mich., can be matched to a calculated profile over a model consisting of a series of dipping layers. (The dips were those measured by H. A. Hubbard along the north-trending valley of the Black River.) Remanent and induced magnetizations of 39 oriented cores from the Black River valley were determined by K. G. Books; felsite from Chippewa Hill and basalt from Algonquin Falls of middle Keweenawan age have normal Keweenawan magnetization and lower Keweenawan Powder Mill rocks have reverse magnetization. In the model these magetizations were assigned to 26 layers which alternated with very weakly magnetized layers. The best match of the calculated composite anomalies of remanent and induced magnetization and the aeromagnetic profile occurs if a deeper block of steeply dipping Powder Mill rocks is assumed to underlie the middle Keweenawan flows.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title A typical cross section based on magnetic data of lower and middle Keweenawan volcanic rocks, Ironwood area, Michigan
Series title Journal of Research of the U.S. Geological Survey
Volume 3
Issue 5
Year Published 1975
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Description 4 p.
First page 543
Last page 546
Country United States
State Michigan
Online Only (Y/N) N
Additional Online Files (Y/N) N
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