Date of Award
Master of Science
Geological and Environmental Sciences
Dr. William B. Harrison III
Dr. John D. Grace
Dr. W. Thomas Straw
Masters Thesis-Open Access
The Upper Keweenawan Jacobsville Formation source areas were mixed source terranes with dominant terrane types changing regionally in relative abundances of sediment contribution. Dominant source terranes were older sediments, including a weathered soil zone, Upper Keweenawan Freda Sandstone and other recycled sandstones; plutonic Precambrian basement rocks;. Middle Keweenawan Portage Lake Volcanics; and the chlorite to staurolite grade metamorphic rocks and iron ranges of Michigan’s upper peninsula.
Depositional environments of the formation's four facies types range from fluvial to deltaic/lacustrine. Sediments were in transport for a short distance, resulting in grain freshness and angularity, moderate sorting and preservation of unstable sediments. Rapid erosion and deposition caused rock immaturity, an abundance of fresh, coarse feldspars and a wide range of alteration in a single species of feldspar. Two major basins of deposition were partially separated by a plutonic to metamorphic terrane highland. Major source areas were to the southeast of the western end of the outcrop belt and to the south of the eastern two-thirds of the outcrop belt.
Lindsay, "The Provenance of the Jacobsville Formation of the Upper Peninsula of Michigan through a Petrographic Study" (1986). Master's Theses. 1331.