The Williston basin is a large intracratonic basin located in North Dakota, Montana, and Saskatchewan. The sedimentary and tectonic histories of the Williston basin have been resolved

End_Page 1014------------------------------

through the analysis of well data. Sedimentation rates, sediment lithologies and densities, and structural imprinting have all influenced the geometry of the Williston basin. With this background information, a subsidence model for the basin has been proposed. Mechanisms controlling the subsidence history appear to be a combination of a thermal mode and a mechanical mode. The thermal aspect of basin subsidence is related to factors associated with subsurface heating and cooling of the lithosphere through time. A noted property of thermal-induced subsidence is the relation of square root of age to depth of sediments. The mechanical aspect of basin subsidence is related to tectonic rifting and normal faulting.

An important component of the thermal history of the Williston basin is the relation between thermal heating and hydrocarbon maturation of the sediments within the basin. The organic-rich sediments accumulating within the subsiding basin will be subjected to increasing depth of burial through time, and concurrently experience increased heating induced by the geothermal gradient. Application of the "liquid-window" concept to hydrocarbon generation in the Williston basin gives an indication of the potential for hydrocarbon accumulation. Petroleum production data have confirmed this hypothesis.

End_of_Article - Last_Page 1015------------