Abstract: Wind Energy Control of Contemporaneous Carbonate Coastal Facies: Williston Basin Mississippian and Caicos Bank Holocene

S. Duff Kerr, R. Michael Lloyd, Ronald D. Perkins

Carbonate sediments of the middle Mississippian Mission Canyon Formation of the Williston basin (USA and Canada) exhibit contrasting depositional fabrics and corresponding constituents in coastal facies tracts on opposite sides of the basin. These contrasts closely parallel differences in certain coastal deposits of Holocene age on the Caicos Bank, B.W.I. The different depositional fabrics have different attributes as hydrocarbon reservoirs, and differing architecture which requires adjustments in techniques for reservoir definition.

The configuration of the Caicos Bank causes the source of energy on the shallow bank top to be mainly wind derived. Oolites and other coated grains form in shoal and shoreline settings open to prevailing winds. Coastal settings of the platform interior in the lee of prevailing winds develop mud-dominated shorelines typified by the tidal-flat complex.

In the Williston basin, a cratonic sag basin, the Madison Group records carbonate-evaporite sequences deposited on a low-relief ramp. The Mission Canyon Formation consists of at least two orders of shoaling-upward sequences, which include major hydrocarbon traps. The basinward stepping sequences on the south side of the basin consist of mud-dominated tidal-flat facies tracts. On the north and northeast sides of the basin, the prograding coastal facies tracts are dominated by coated grains, significant parts of which are represented as island shoals. The Williston basin is remote from the continent margin and from major oceanic tidal and current systems. Therefore, the principal source of energy controlling grain type and sediment distribution is likely wind derived. A wind source from the southwesterly quadrant is indicated.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994