Kaskaskia rock sequences in the Williston basin, North Dakota, comprise most major carbonate facies, fabrics, and porosity types. Stratigraphic units discussed are the Mission Canyon, Ratcliffe, Frobisher Alida, Bakken, Birdbear, Duperow, Winnipegosis, and the Ashern formations. All of these have produced substantial amounts of hydrocarbons except the Ashern Formation. Slabs of cores show different facies, fabrics, and some porosity types associated with each.
Kaskaskia sequence deposits represent a period of waxing and waning sedimentation during overall transgression and regression of the late Paleozoic. Facies represented, except for the Ashern, are cyclic, composed of supratidal, intertidal, and subtidal depositional settings. Ashern facies are supratidal to highest intertidal. Some facies can be further subdivided into high/low or shallow/deep. Special facies types include stromatoporoid and evaporite, both supratidal and deep. Facies and fabrics vary considerably throughout the sequence, both interformationally and intraformationally. Mudstones, wackestones, and packstones are most common although grainstones and boundstones also occur. Within textural constraints, each fabric contains their respective amounts of skeletal and nonskeletal allochems. Because of frequent and sharp facies changes, it is important to discriminate among different facies that superficially have similar fabrics. Examples are deep/shallow evaporites, or supratidal/subtidal oolites and pisolites. Peloidal wackestones/grainstones, skeletal wackestones/packstones, and mottled mudstones are the prevalent fabric types. Significant sedimentary structures include burrows, flat pebble interclasts, desiccation cracks, bird’s-eye structures, and collapse breccias.
Porosity types common to all, except for the Ashern and Bakken, are intercrystal, interparticle, moldic, vuggy, and breccia. Significant porosity in the Ashern and Bakken formations is from fractures.
