Kayla Lockmiller, MS3

TOC, C/N, δN15, and δC13 of Shales from the Mississippian Michigan Formation, Western Michigan

The Mississippian Michigan Formation in Wyoming, Michigan, is composed of thick layers of gypsum with thin layers of dolomite and shale. Samples of shale from each of three units at Michigan Natural Storage Company were collected and analyzed to help determine the environment of deposition. Depositional proxies used were total organic carbon (TOC), carbon/total nitrogen (C/N) ratios, δ13C, and δ15N. TOC (0.20 - 0.51%) indicates low productivity of organic matter. C/N (3.97 – 8.50) and δ13C (-22.77 to -25.38 VPDB) imply a carbon input from mixed marine and freshwater sources. δ15N (1.77 – 3.77 % Air) remains enigmatic; however, it may also indicate a mix of sources. The lack of terrestrial land plant indicators suggests an arid environment with little vegetation. An arid environment would promote the evaporation of seawater, producing gypsum. Freshwater influx into the brine would halt gypsum precipitation and allow for the deposition of shale with mixed carbon sources.

Faculty Mentor: Patricia Videtich, Geology

Page last modified August 2, 2013