GLACIOTECTONIC STRUCTURAL ANALYSIS OF DEVILS LAKE, NORTH DAKOTA

The ice-shoved terrain south of Devils Lake was formed by the last advance of the late Wisconsinan glaciers approximately 12,000 years ago. Two series of ice-shoved ridges and associated source depressions (lake basins) formed during this event. Glacial thrusting was facilitated by high pore-water pressures within the underlying Spiritwood Aquifer. Many of these ice-shoved features formed from proglacial and subglacial thrusting. Our current knowledge of these processes at the subglacial interface and within the subglacial materials is somewhat deficient, especially the kinematics of deformation within the Devils Lake Mountain (DLM) area. This study focuses on conducting a microstructural analysis of Wisconsinan tills from the Sullys Hill and Devils Lake Mountain areas of North Dakota. Currently, we have collected oriented till samples from the southeastern flank of DLM and from a kame exposure on Sullys Hill. Preliminary microstructural analysis from DLM reveals: discrete shears, till pebbles, galaxy or turbate structures, clast haloes, pressure shadows, crushed quartz grains, boudins, faults, and plasma fabrics. Field observations and microstructural evidence indicates deformation within a subglacial environment.

Regional mapping and Landsat TM imagery was utilized in conjunction with the microstructural analysis. Glaciotectonic structures of the Devils Lake area were analyzed through Landsat TM imagery.