Date of Award
Master of Science
Geological and Environmental Sciences
Dr. Richard V. McGehee
Dr. W.D. Kuenzi
Dr. L.J. Schmaltz
Masters Thesis-Open Access
Precambrian X tectonites deformed between thermal domes in the northern Black Hills 1.7 B.Y.B.P. display variably trending isoclinal folds cross-cut by southeast trending slip-folds developed in discrete shear zones. Eugeosynclinal sedimentary rocks consisting of shale, quartzarenite , sublitharenite, and graywacke were metamorphosed to phyllite, quartzite, and metagraywacke during two syntectonic phases and one post-tectonic phase. The earliest syntectonic metamorphism was associated with development of isoclinal folds and may have produced amphibolite or greenschist facies. It was succeeded by retrograde metamorphism of greenschist facies syntectonic with and post-tectonic to development of southeast trending folds.
Mica, chlorite, iron oxides, and graphite are strongly developed parallel to isoclinal' fold axial planes and quartz c-axes display preferred orientation related to isoclinal fold axes. These minerals display weaker preferred orientation related to southeast trending folds. Chloritoid, Mn-garnet, chlorite, and mica display random orientation and may have developed concurrently with ubiquitous post-tectonic quartz veins.
Cookman, Richard G., "Structural Analysis of Precambrian Metasedimentary Rocks of the Swede Gulch Formation, Nahant, South Dakota" (1981). Masters Theses. 1837.