Fluvial Sequence Stratigraphy and Depositional Systems of the Tertiary Duchesne River Formation, Northern Uinta Basin, Northeastern Utah

Takashi Sato and Marjorie A. Chan
University Village, Salt Lake City, UT

An upward-coarsening, continental sequence of lacustrine through fluvial systems is both a common and important target for hydrocarbon exploration. The juxtaposition of lower organic-rich lacustrine source rock and the overlying coarse-grained fluvial sandstone reservoir creates favorable conditions for upward hydrocarbon migration and accumulation. The Eocene to earliest Oligocene strata of the Uinta Basin exhibits this same upward coarsening sequence which includes the Green River, Uinta and Duchesne River formations in ascending order. The Duchesne River Formation represents the last 'Lake Uinta' intermontane basin fill, comprised primarily of braided and meandering fluvial deposits. The formation also contains significant tar sands in Asphalt Ridge (e.g. alluvial facies) of the eastern Uinta Basin, likely sourced from the organic-rich lacustrine Green River shales. Duchesne River depositional facies are: alluvial fan conglomerates, fluvial channel sandstones, flood plain mudstones, and lacustrine carbonates. Complex depositional systems and drainage patterns result from multiple clastic sources of the Uinta Mountains in the north, Split and Blue Mountain in the northeast, and the Sevier orogenic belt to the west. The extensive exposures are conducive to studies of: (1) fluvial sequence stratigraphy, (2) correlation and distribution of depositional facies, and (3) controls on the facies distribution (e.g. tectonics, climate). Collectively, the Duchesne River example has important applications for exploring similar subsurface fluvial reservoir systems, and for understanding the history of the late-stage basin filling.

AAPG Search and Discovery Article #90169©2013 AAPG Rocky Mountain Section 62^nd Annual Meeting, Salt Lake City, Utah, September 22-24, 2013