Abstract

When examining outcrop belts that will ultimately be used as paralic/deltaic reservoir analogs it is critical to accurately identify 1) the type of ancient deposition system, and 2) spatio-temporal changes in position within the system evidenced by stratal heterogeneities. Carefully tracking variations in both the stratigraphy and ichnology helps identify sub-environments within these complex coastal depositional systems. Identifying fluctuating sub-environments is significant because it allows us to better predict areas prone to sand vs. mud deposition and probable sandbody-shale geometries, resulting in better reservoir models. By integrating sedimentology, ichnology, and high-resolution imagery (GigaPan photopanoramas, drone photogrammetry) in laterally extensive outcrop belts we can reveal typical architectural elements and in some cases quantify their geometries. This integrated technique helps us determine the relative effects of forcings such as fluvial floods, waves, and tides that controlled sandbody-shale geometries, and variations in salinity that help us refine paleoenvironmental models. Key surfaces can also be identified and tracked across outcrop belts. In this talk I present several examples from outcrops containing transitional shallow-marine to continental paralic/deltaic deposits of the Cretaceous Western Interior Seaway. These include a mixed fluvial-flood dominated to tidally modified delta in the Loyd Formation and tidally modified shallow-marine to continental deposits of the Sego Formation, both found along the Rangely Anticline, CO. Estuarine deposits of the Neslen Formation in the Book Cliffs of UT are also examined. The implications for modeling these systems and controls on reservoir quality are discussed.

Speaker Bio

Dr. Peter Flaig is a sedimentologist/stratigrapher and photographer. He earned his BS and MS at the University of Wisconsin, Milwaukee. His MS Thesis focused on changing fluvial style across the Permian-Triassic boundary in the Transantarctic Mountains of Antarctica. Pete earned his PhD at the University of Alaska-Fairbanks working on outcrops of Cretaceous, dinosaur-bearing coastal plain deposits on the North Slope of Alaska that also serve as viscous to heavy oil reservoirs. Pete came to UT-Austin in 2009 to work at the Quantitative Clastics Laboratory, Bureau of Economic Geology’s where he is a Research Scientist in charge of the shallow-marine to fluvial research program. Pete’s has spent many field seasons examining shallow-marine to continental-fluvial sediments deposited along the shoreline of the Cretaceous Western Interior Seaway found in laterally-extensive outcrops in UT, CO, and WY that serve as outcrop analogs for oil and gas reservoirs. Recent work has taken him to Patagonia to examine similar Cretaceous-aged sediments. He typically uses a combination of sedimentology, ichnology, and high-resolution imagery in his research, some examples of which he will show you today.