FUSULINIDS FROM THE UPPER PART OF THE BROOM CREEK FORMATION (PERMIAN?): A PALEOECOLOGICAL AND BIOSTRATIGRAPHIC ASSESSMENT OF A CARBON STORAGE INTERVAL IN THE WILLISTON BASIN

This is part of a student-led analysis and assessment of the Broom Creek and Amsden Formations in the subsurface of the Williston Basin in west-central North Dakota. The Broom Creek Formation has been selected as a potential carbon storage unit because of the porosity and permeability of aeolian and nearshore sand facies commonly occurring in the middle and upper part of the formation (which currently functions as a saline aquifer). Project CarbonSAFE was an initiative sponsored by the DOE and local and state agencies and carried out by the EERC, and the initiative resulting in the selection of the Broom Creek. The formation occurs over 6000 ft. down in the subsurface and overlies the Amsden Formation (Pennsylvanian) which consists on many similar facies, and is overlain unconformably by the Opeche Formation wich consists or a thick interval of redish siltstones and anhydrite. The Broom Creek has great potential for carbon storage because of its depth, the high porosity and permeability of the aeolian facies, and other interbedded facies functioning as seals (siltstones & anhydrite layers). The Broom Creek lacks detailed stratigraphic assessment as it was never exploited for hydrocarbons. Just below the unconformity with the overlying Opeche, facies in Broom Creek appear to become more significantly marine than most of the underlying formation. Facies consist of cherty dolostone, and anhydrite cemented quartz arenite. These facies contain abundant fossils, including brachiopods, crinoids, and lenses and layers of fusulinids. Fusulinids occur in both the sandstone and dolostone, and in the sandstones the fossils show external abrasion suggesting at least minor amounts of transport. Past studies of fossils in the Broom Creek were not done in the Williston Basin, but instead were carried out in nearby outcrops and basins in Wyoming. Fusulinids have been found to undergo rapid evolution through the fossil record. As a result, fusulinids are beneficial to use to figure out the biostratigraphy of this region and understand past environments.