Date of Award


Document Type


Degree Name

Master of Science (MS)



First Advisor

W.L. Moore


The Tilston interval sediments were deposited on the eastern flank of the Williston basin of North Dakota, Manitoba and Saskatchewan. The interval (Osagian) is composed of a basal carbonate and upper anhy drite in the predominantly carbonate Mississippian Madison Formation. The interval consists of four major facies (subtidal, shoal, tidal flat and supratidal anhydrite), and two geographically restricted facies (lagoonal and elastic) and represents a regressive sequence.

Tilston deposition began with the subtidal facies, deposited on a broad, shallow shelf. As the sea regressed this was followed by deposition of the shoal facies. Further regression resulted in the deposition of the tidal flat facies. The final regressive stage of the Tilston is marked by the deposition of the widespread supra tidal anhydrites and a local elastic facies. The western extent of the regression occurs at approximately 102° west longitude. This area is also interpreted to be the position of the shelf break at the end of Tilston deposition.

Possibility for additional Tilston production outside of known producing areas is indicated by: (1) the Tilston production in Canada and from the North Souris field near the international border in Bottineau County, North Dakota, (2) the scattered shows throughout the study area, (3) the porous zones or facies in the interval, (4) the impermeable anhydrite cap, and (5) the association with an angular unconformity on the subcrop portion of the interval.

The assessment of the petroleum potential of the Tilston interval revealed four potential types of hydrocarbon traps. The first two types, paleogeomorphic and wedge-out, are located at the subcrop portion of the Tilston interval. The third type of trap is due to a combination of a porous zone capped by anhydrite. The fourth type, a stratigraphic trap, is the result of updip porosity change.

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