INTEGRATING LIDAR, AEROMAGNETIC, AND FIELD DATA TO IDENTIFY STRUCTURAL-LITHOLOGIC DOMAINS WITHIN THE ARCHEAN CARNEY LAKE GNEISS

The Archean Carney Lake Gneiss (2.7-3.8 Ga) in Dickinson County, Michigan is a complex suite of rocks on the southern edge of the Superior Craton, surrounded on three sides by Paleoproterozoic passive-margin sedimentary rocks and covered to the east by Paleozoic sandstone of the Michigan Basin. The Archean and Paleoproterozoic rocks were deformed and intruded during the ~1.85 Ga Penokean Orogeny and, to a lesser extent, during later Yavapai and Mazatzal orogenies. Geologists in the 1950s to 1960s described the Carney Lake Gneiss (CLG) as a granitic gneiss with three facies related to relative abundance of potassium feldspar and plagioclase—red, gray, and composite. Composite gneiss was interpreted to be the more widespread facies and to result from mixing of gray and red gneiss. Remapping and reinterpretation of the area in the context of critical mineral potential is overdue and made difficult by limited access and dense forest and brush that obscure outcrops. Ground mapping has been greatly facilitated by using phone apps with georegistered bedrock geology maps to navigate to desired locations, LiDAR to identify potential outcrops in dense forest and brush, and differential GPS devices to locate field sites with submeter accuracy.

As a further aid to ground mapping, LiDAR and aeromagnetic data are being used in a broader sense. These recently acquired data exhibit variable textures, patterns, and boundaries that likely reflect lithology and structure within the CLG observed in the field. Lineament analysis using 1-meter LiDAR data defines at least 12 morphologic domains, based on orientation and number of lineaments, as well as major topographic boundaries that are likely structurally controlled. Some lineament sets and boundaries defined with LiDAR are expressed in the aeromagnetic data as anomalies that coincide with major lineament trends. While these lineaments often relate to features such as bedding, joints, and faults, their significance and reliability as geologic indicators needs to be further assessed with ongoing field data collection. By integrating robust field observations, aeromagnetic data, and LiDAR, we hope to better differentiate Carney Lake Gneiss into lithologic and structural domains, improve ground mapping, and improve our understanding of the geologic history of this complex terrane.