Complex Fluvial-Lacustrine Interactions as Revealed by Outcrop to Subsurface Analysis of the Renegade Tongue, Green River Formation, Uinta Basin, Utah

Abstract

The Early Eocene Renegade Tongue of the Green River Formation in the Uinta Basin, northeast Utah, is a fluvial siliciclastic dominated interval, interpreted as a fluvial megafan depositional system, interbedded with carbonate and siliciclastic lacustrine facies. Stratigraphy of the Green River Formation is poorly understood due to complex and variable spatial and temporal relationships between fluvial and lacustrine deposits. The complexity of these fluvial-lacustrine deposits is assigned to frequent climate-driven lake level fluctuations, as combined with longer-frequency up-dip controlled progradation and aggradation of the fluvial fans system, and lower-frequency autogenic processes, such as fan lobe and channel avulsions. Detailed outcrop measured sections, photomosaics and GPS surveys yield an understanding of the sedimentary facies, facies associations, channel architecture, and stacking patterns. Optical thin section microscopy and X-ray fluorescence (XRF) analysis integrated with stratigraphic descriptions enabled more detailed characterization of facies and stratigraphy. This study combines a detailed dataset across ca 5 miles in Nine Mile Canyon, Utah, with basin-scale correlations and comparison across ca 80 miles. The detailed facies and facies associations were used in conjunction with subsurface log data suites to provide a better understanding of vertical trends, lateral variability, and correlation of the fluvial complex within the Renegade Tongue. The descriptions and interpretations of the interval were compared with other fluvial intervals within the Green River and Wasatch Formations, which provide valuable insights into the variability observable in other fluvio-lacustrine interfaces.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016