Date of Award
Master of Science (MS)
The upper Mission Canyon and lower Charles Formations of the Madison Group (Mississippian) in central Billings County, North Dakota respectively consist of interbedded limestones and dolostones, and anhydrite. Study of these rocks was limited to Big Stick and T.R. Fields, located on the Billings Anticline, central Williston Basin.
Detailed examinations of cores from a 166 ft (51 m) section within the upper Mission Canyon and lower Charles Formations resulted in the identification of seven lithotypes: echinoderm wackestone-packstone, dolomudstone, dolomitic echinoderm wackestone, grainstone, skeletalpeloidal carbonate, laminated carbonate, and anhydrite. The stratigraphic distribution of lithotypes is consistent throughout the study area.
Deposition took place in sublittoral, littoral and supralittoral environments in a shallow, low-energy, epeiric-sea setting. The depositional history is characterized by 4 successive stages: 1) sublittoral deposition under shallow normal marine conditions; 2) sublittoral deposition in slight topographic depressions under restricted marine conditions of hypersalinity and, possibly, oxygen-deficiency; 3) perilittoral and littoral deposition on a basinward (northwestward) prograding complex of isolated shoals, current channels and protected marine areas, and algal flats; and 4 arid supralittoral deposition on a sabkha and within evaporative ponds.
The studied section was subjected to numerous eogenetic (near-surface) and mesogenetic (deep burial diagenetic processes with complex spatial distributions and temporal relations. Eogenetic diagenesis included micritization, cementation, replacement, dissolution, mechanical compaction, and fracturing. Near-surface diagenetic zones included: sublittoral stagnant and agitated, isolated meteoric/marine water mixing, and hypersaline vadose and phreatic.
Mesogenetic diagenesis included dissolution, neomorphism, replacement, cementation, fracturing, pressure solution and hydrocarbon emplacement. Mesogenetic diagenesis is indicative of a freshwater influx possibly as a result of regional flow through the Madison aquifer.
Eogenetic dolomitization of sublittoral deposits, which was the most prominent diagenetic process, took place through an evaporative reflux mechanism. Minor eogenetic dolomitization of littoral and supralittoral deposits took place by penecontemporaneous, evaporative, and mixing processes.
Three dolomite types identified are: microcrystalline, sucrosic, and saddle dolomite. Microcrystalline and sucrosic dolomite are nearly stoichiometric, whereas saddle dolomite is calcium-enriched. A dynamic mesogenetic environment resulted in the stabilization and enlargement of eogenetic dolomites, and the formation of saddle dolomite.
Stephens, Randall A., "Depositional history and diagenesis of the upper Mission Canyon and lower Charles Formations (Mississippian), Billings County, North Dakota" (1986). Theses and Dissertations. 287.