Bedrock Geology Map of the Knife Lake Group and Related Intrusions near Kekekabic Lake: Lake County, Minnesota

Abstract

This map was created by undergraduate students attending the Precambrian Research Center Field Camp in the summer of 2015 under the guidance of Mark Jirsa, Minnesota Geological Survey. Reconnaissance mapping at a scale of 1:24,000 was conducted by the authors in the Boundary Waters Canoe Area Wilderness (BWCAW) in the vicinity of Kekekabic Lake. The goal of this endeavor was to uncover the regional geologic history of Neoarchean rocks of the Knife Lake Group that have been influenced by volcanism and intruded by igneous bodies. An additional goal was to acquire an understanding of the contact between the Mesoproterozoic Duluth Complex and other Proterozoic intrusions, and the Knife Lake Group. Nearly 220 outcrops were examined in the course of 8 days by traveling approximately 130 miles by canoe and land traverses to con rm the internal lithologic variability, contact relationships, stratigraphic facing, and structure. The area primarily contains etasedimentary, metavolcanic, and intrusive rocks of the Neoarchean Knife Lake Group. Metasedimentary rocks including graywacke, slate, sandstone and conglomerate that were deposited in alluvial fan, fluvial, and subaqueous environments. Metavolcanic rocks include largely porphyritic, mafic and intermediate flows that shed detritus to the sedimentary units. The metasedimentary and metavolcanic units are intruded by polyphase intrusions, which also contributed detritus to some sedimentary rocks. The Neoarchean rocks were intruded by Proterozoic diabase dikes and the Duluth Complex.