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A New Interpretation of the Stratigraphic Architecture of the Williams Fork Formation, Piceance Basin, Colorado

Cantwell, Jon 1; Evans, Lesley W.1; Cumella, Steve 2
1 Williams E&P, Denver, CO.
2 Bill Barrett Corporation, Denver, CO.

Integration of core data, outcrop studies, image-log interpretation, and subsurface-log correlations results in a dramatically new view of the stratigraphic architecture of the Williams Fork Formation in the Piceance Basin of western Colorado. The Williams Fork Formation is generally viewed as a continuous, regressive, sedimentary sequence that transitions from the marine facies of the underlying Iles Formation upwards through a series of paludal, coastal and fluvial facies. The new interpretation places a significant erosional unconformity (sequence boundary) at about the midpoint of the Williams Fork stratigraphic column. The erosion carved out valleys with vertical relief greater than 200 feet in some areas. These incised valleys were subsequently filled with sand-rich fluvial deposits (possibly from braided streams) and capped by a sequence of marine-influenced facies associated with the Lewis seaway lying to the northeast. This new interpretation provides a new set of stratigraphic markers that further subdivides the Williams Fork Formation.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009