Paleotopography and Hydrocarbon Accumulation: Williston, Powder River, and Denver Basins

THOMAS, GILBERT E., Thomas & Associates, Denver, CO

Recent geomorphic analyses of 1:24,000 scale topographic maps in the three major basins of the northern Great Plains have disclosed a persistent system of basement paleotopographic features that trend north-northeast throughout the region. Superimposed across this system and subtly influenced by it, are the northwesterly trending Laramide structural features.

Paleozoic depositional patterns have been strongly influenced by the paleoridge and trough system formed by the north-northeast features. Mesozoic deposition has also been affected by the ancient subsurface system but in a more subtle manner.

Many of the Paleozoic and Mesozoic hydrocarbon locations in the three basins appear to be the result of paleotopographic control on hydrocarbon accumulation sites. This affect ranges from Paleozoic reef sites in the Williston basin through paleotrough localization of Pennsylvanian Minnelusa production in the Powder River basin to fractured Cretaceous Niobrara production at the Silo field in the Denver basin.

Basement paleotopography is the underlying factor in all deposition and subsequent hydrocarbon migration in any basin. As such, it should be considered a major factor in the exploration for oil and gas.

AAPG Search and Discovery Article #91010©1991 AAPG Rocky Mountain Section Meeting, Billings, Montana, July 28-31, 1991 (2009)