Information Circular 47. Compositions of Rift-Related Volcanic Rocks of the Keweenawan Supergroup Atop the St. Croix Horst, Southeastern Minnesota

Abstract

This information circular summarizes stratigraphic and geochemical information obtained in the 1980s and early 1990s from Mesoproterozoic volcanic rocks associated with the Midcontinent rift system. These rift-related rocks comprise the St. Croix horst, a major structural feature now mostly buried by a thin cover of generally flat-lying sedimentary rocks of Paleozoic age. Although the studies described herein were completed 10 to 15 years ago, the results have never been published. This report is intended to correct that omission.