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Stratigraphic Analysis and 3d Interpretation of Coastal Plain Delta Architecture, Neslen Formation, Floy Canyon, Utah

Kimber O'Brien
Geology/Petroleum Geology, Colorado School of Mines, Golden, CO, USA
[email protected]

Abstract

Edmonds (2011) developed a numerical model that classifies fluvial deltas into two types on the basis of the fractional thickness of topset and foreset strata: topset-dominated and foreset-dominated. The model is based on the initial water depth, gradient of the sediment-water interface, and discharge. Topset-dominated deltas form in shallow water and contain a high proportion of distributary channels and interdistributary muds. In contrast, foreset-dominated deltas form in deeper water and contain a high proportion of distributary mouth bars and have a thin veneer of delta plain strata. Depending on input conditions, a delta can transfer from topset to foreset-dominated along a basinward transect.

Through field reconnaissance, an exceptionally well exposed outcrop of a topset-dominated delta that was deposited in a coastal plain setting has been identified in the Neslen Formation in Floy Canyon, Utah. This outcrop provides an opportunity to quantitatively document the stratigraphic architectures and internal facies distributions of this type of delta; thereby offering a natural laboratory to test Edmonds' predictions of the stratigraphic architecture of a topset-dominated delta. Edmonds' model can be enhanced by producing a dataset of facies proportions, juxtapositions with architectural features and an analysis of reservoir connectivity. The data acquired from the outcrop can then be used to gain a better understanding of topset-dominated systems as reservoirs for future hydrocarbon exploration. The basinward transition from a topset to a foreset-dominated delta has implications for the net sand content and connectivity of deltaic systems. A sister study will be conducted on a foreset-dominated delta.

AAPG Search and Discovery Article #90199 © 2014 AAPG Foundation 2014 Grants-in-Aid Projects