Bedrock Geology of the Esther Lake Area, Cook County, Minnesota

Abstract

Six students from the 2014 Precambrian Research Center Field Camp spent five days, from August 3-9, mapping the Esther Lake area in northeast Minnesota. Dr. Phillip Larson, an adjunct assistant professor at University Minnesota Duluth and senior geologist for Duluth Metals Limited, oversaw the work and directed students to better cover the area. In total, about four square miles were mapped at 1:10,000 scale using mapping techniques of land traverse, shoreline traverse around lakes, and outcrop sampling. A total traverse distance of about 45 kilometers was traveled in the mapping of 247 outcrop around 6 lakes. The purpose of the map was to build upon Grout and other (1959) reconnaissance-level mapping from the1930s and create the first detailed map of the Esther Lake Area including the North Shore Volcanic Group, Cucumber Lake granophyre intrusion, and three other intrusive dikes displaying similar characteristics to the Beaver Bay Complex along with several sills similar to the Crocodile Lake gabbro intrusion. The primary objectives were to outline contacts of the sequences and differentiate the intrusive bodies along with lithological emplacement.