MICRO-STRUCTURAL RESEARCH FOR HEART MOUNTAIN MOVEMENT IN THE MADISON, DINWOODY, AND CHUGWATER FORMATIONS, NORTHWESTERN WYOMING

The Heart Mountain Detachment, located along the eastern edge of the Absaroka Range in northwest Wyoming, continues to baffle researchers despite of the plethora of studies that have been undertaken in order to understand it better. The detachment surface has been identified by stratigraphic relationships, and micro-structural studies in the Sunlight Basin provide evidence of some of the complex processes involved in the movement within a local area close to Eocene volcanic sources. This project searches for microscopic evidence (e.g. calcite twinning, quartz deformation, as well as other microstructures and micro-textures) for deformation and brecciation in lowermost part of the allochthon (and uppermost part of the autochthon) in an area roughly 12 kilometers east of sites of earlier studies, and thus farther away from the volcanic sources which may have played a role in initiation of the movement. The goal of this work is to collect local information at the microscopic level in order to understand better the nature of the block movement in this area.