Geologic Map Series
Persistent link for this collection
Browse
Browsing Geologic Map Series by Author "Taylor, Richard B."
Now showing 1 - 1 of 1
Results Per Page
Sort Options
Item Geologic Map Series 1. Bedrock Geology of Duluth and Vicinity St. Louis County, Minnesota(Minnesota Geological Survey, 1963) Taylor, Richard B.Duluth, Minnesota, is on the northwest limb of the Lake Superior syncline, a northeast-trending structure of Precambrian age. The north- west limb of the syncline dips 10-20 degrees S.E. toward Lake Superior and is dominated by the Duluth Gabbro Complex, a huge sill-like mass with crescentic outcrop that extends almost 150 miles from Duluth to near Hovland. At Duluth the gabbro complex lies on the Thomson Formation, and apparently was intruded along the surface of unconformity below the Keweenawan rocks. The gabbro complex was formed by multiple intrusion, and consists of an older anorthositic gabbro and a younger layered gabbro and related intrusions. Keweenawan flows above the gabbro mass are cut by diabase sills. The basalt flows at one locality currently are being quarried as a source of crushed rock for concrete aggregate.