Statistical Characterization of Channel-Belt Clustering in the Fluvial lower Wasatch Formation, Uinta Basin, Utah
Jesse R. Pisel
Colorado School of Mines, Department of Geology and Geological Engineering, Chevron Center of Research Excellence, Golden, Colorado, USA
The Eocene lower Wasatch Formation of the Uinta Basin contains exceptional outcrops of low net-sand content fluvial strata. This study quantitatively documents the stratigraphy of a 7 km wide by 300 meter thick strike-oriented outcrop to develop a quantitative database that can be used to improve our knowledge of how some fluvial systems evolve over geologic time scales. Data used to document the outcrop are: (1) 550 meters of decimeter to half meter scale resolution stratigraphic columns documenting grain size and physical sedimentary structures; (2) detailed photopanels document architectural style and lithofacies types in the outcrop; (3) thickness, width, and spatial position for all channel belts in the outcrop, and (4) directional measurements of paleocurrent indicators.
Two channel-belt styles are recognized: lateral and downstream accreting; both of which occur as either single or multi-story. Floodplain strata consist of overbank fines and sand-rich crevasse splay deposits. Key upward and lateral characteristics of the outcrop documented herein are the following. First, the shapes of 243 channels are documented. The average width, thickness and aspect ratios of the channel belts are 110 m, 7 m, and 16:1, respectively. Second, channels are documented to spatially cluster. 9 clusters are documented using a spatial statistic. Stratal surfaces can be correlated from mudstone units within the clusters to time-equivalent floodplain strata adjacent to the cluster demonstrating that clusters are not confined within fluvial valleys. Finally, proportions of floodplain and channel belt elements underlying clusters and channel belts vary both laterally and vertically throughout the outcrop.
AAPG Search and Discovery Article #90183©2013 AAPG Foundation 2013 Grants-in-Aid Projects