Abstract: Comparison of Waulsortian Facies of the Appalachian and Williston Basin

TEDESCO, STEVEN A. and ZINKE, SALLY G.

The Waulsortian mounds of the Monteagle Formation of Central Tennessee along the Western side of the Appalachian Basin and the Lodgepole Formation of the Williston Basin demonstrate similarities in geologic setting, associations to basement faulting and similar geophysical characteristics. The Waulsortian mounds of the Monteagle Formation show a northeast-southeast alignment along the eastern flank of the Cincinnati Arch and parallel an ancient shoreline. The regional aeromagnetic map indicates the location of the mounds is closely associated to areas of basement fault junctions. The mounds are typically found on the flanks of shale structural highs. The position of individual mounds present at time of deposition, stratigraphically, varies within the formation and are not restricted to any particular time sequence. Seismic characteristics consist of amplitude variations within and beneath the mound.

The Waulsortian Mounds of the Lodgepole Formation are characterized by the shallow water buildups found in Montana, Manitoba and Saskatchewan and the deeper water buildups found in Montana and North Dakota. The mounds found to date in North Dakota are found at the edge of the False Bakken, a pseudo "structural high". There is evidence of basement faulting on the northeast side of the Eland complex that may have been instrumental in the development of the complex. The mounds in Manitoba an Saskatchewan formed along salt collapse structures relaxed to basement faulting. Seismically, present concepts indicate that there are amplitude variations in the Bakken, and Three Forks contribute to defining areas of possible mound development.

One of the present approaches in the Williston Basin is to explore along the stratigraphic edge of the False Bakken. Based on experience in Tennessee, this is a limited approach to exploration. Tennessee analogs suggest that the mounds will be found from the western edge of the False Bakken (deep water) to the shallow shelf further to the east along the Lodgepole subcrop. This is supported by the mounds such as Daly Field in Manitoba. The number of drill holes that have tested the Lodgepole significantly decrease to the east and south of the Eland Field suggesting this may be where the greater opportunities should exist.

AAPG Search and Discovery Article #90946©1997 AAPG Rocky Mountain Section Meeting, Denver, Colorado