Bedrock Geologic Map of the Port Wing, Solon Springs, and parts of the Duluth and Sandstone 30' X 60' Quadrangles, Wisconsin

About 3 km of underlying Mesoproterozoic strata, including the Gogebic iron range, and about 10 km of Neoarchean rocks, exposed in the southernmost part of the map area lie to the southeast of the horst. The nearly flat-lying continental red beds of the Oronto and Bayfield Groups, the youngest strata of the Keweenawan Supergroup, overlie the volcanic rocks. A wealth of geologic data exists for the area as a result of many individual studies over the last hundred years, but much has remained unpublished in theses, dissertations, and other reports of limited availability.

This map has incorporated most of that data (see list of data sources) and includes results of our investigations conducted from 1992 to 2000. Our studies were designed to fill gaps in existing data and reconcile conflicting interpretations on some aspects of the geology of the region. The purpose of this map is to complete digital coverage of quadrangles with significant exposure of rocks of the Midcontinent rift in Wisconsin and Michigan at a scale of 1:100,000.

[Summary provided by the USGS.]