Date of Award
Master of Science
Geological and Environmental Sciences
Dr. William B. Harrison III
Dr. Charles A. Sternbach
Dr. B. Charlotte Schreiber
Masters Thesis-Open Access
The Richfield Member of the lower Middle Devonian Lucas Formation is represented in the subsurface of northeast Isabella County, Michigan as a 180-foot-thick sequence of Interbedded limestone, dolomite and anhydrite. Richfield lithofacies within the study area reflect deposition in a complex patchwork mosaic of evaporative supratidal, in tertid al, shoal, and subtidal environments.
The present variations in Richfield porosities were caused almost entirely by post-depositlonal diagenetic changes. The carbonate units have undergone pervasive dolomltlzation of mud matrix, leaching of allochems, and extensive anhydrite void -fillin g . The best porosity developments are associated with partial to complete dolomitizatlon of the carbonate mud. Replacement of dolomlcrite by anhydrite and later dissolution of replacement fabric anhydrite also contributed to secondary porosity within the carbonate reservoirs. Compaction and dewatering of the primary sulfates provided the source for the anhydrltizing solutions which produced diagenetic cements.
Sullivan, Kevin James, "Petrography, Diagenetic History, and Development of Porosity in the Richfield Member of the Lower Middle Devonian Lucas Formation, Northeast Isabella County, Central Michigan Basin" (1986). Masters Theses. 1348.