Speaker: Peter P. Flaig, Research Scientist at the Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin

Subject: Characteristics and Controls on Depositional Systems of the Strawn Group in the Fort Worth Basin and Eastern Shelf of the Permian Basin


Upper Strawn deposits found in core from Stonewall and King Counties include a mixture of quartz-rich and carbonate-rich deposits. Quartz-rich sandstones are typically trough to current-ripple or modified current-ripple cross-stratified, with some inclusive intervals of well-developed herringbone cross-stratification. Single to double mud-drapes on sedimentary structures, mud rip-up clasts, and mud balls are common. Some sandbodies are moderately to heavily bioturbated with a diverse and abundant trace-fossil assemblage, and exhibit relict bedding. All traces are known from marine or brackish-water environments. Carbonate-dominated intervals, ranging from bioturbated packstones to cross-bedded grainstones, are largely comprised of skeletal components including fragments of crinoids, brachiopods, bryozoans, mollusks, and fusilinid foraminifera; ooids are also present in some intervals. These carbonate-dominated intervals are commonly quartz-rich and may interfinger with quartz-rich sandstone intervals which are commonly trough-to-ripple cross-stratified or parallel-laminated, and also contain mud drapes, mud clasts, and mud balls. Bioturbated wavy-to lenticular bedded siltstones and flaser-bedded sandstones are interbedded with the quartz-rich and carbonate -rich sandstones. Stratal characteristics coupled with the interfingering nature of these deposits suggest that they record tidally modified deltaic to open backbarrier depocenters that interfinger with carbonate factories along a shallowly-dipping tidal shelf and ramp. Gamma-ray logs, shale volume logs (VSH), resistivity logs, density logs (RHOB), and photovoltaic factor logs (PEF) are consistent with stacked coarsening-upward successions that reflect migrating-switching delta lobes that interfingered with shelf carbonates prior to deposition of the overlying Canyon Group sequences. Newly refined net sandstone maps developed from VSH logs near the Katz field showcase the evolution of deltaic parasequences in the Upper Strawn


Peter P. Flaig is a Research Scientist at the Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin. His specialty is clastic sedimentology and stratigraphy of depositional systems from the hinterland to the shelf, including deposits of fluvial, deltaic, and complex coastal to shelf systems. His Master’s work took him to the Central Transantarctic Mountains of Antarctica where he examined fluvial sedimentation across the Permian-Triassic boundary. During his PhD research on the North Slope of Alaska Peter collaborated with paleontologists to help identify the ancient depositional systems and ecosystem of the dinosaur-bearing Prince Creek Formation. He joined the Bureau of Economic Geology in 2009 for a 2 year Jackson School postdoctoral fellowship, and then spent 7 years as lead scientist on fluvial, deltaic, and shallow marine research at the Quantitative Clastics Laboratory Industrial Associates Consortium. Peter now works for the State of Texas Advanced Resource Recovery program and Alaska North Slope Integrated Projects program.

Peter’s research focuses on deposits of clastic and mixed carbonate clastic systems and typically integrates sedimentology, ichnology, paleopedology, high-resolution image capture and analysis (e.g. drone photogrammetry), and petroleum geology. He has worked extensively on deposits of the Cretaceous Western Interior Seaway from Texas through the southwestern US (UT, CO, WY), Canada, and into Alaska. Peter has also investigated strata deposited across the Paleocene-Eocene Thermal Maximum in Wyoming and Texas, reservoirs in the Eastern Shelf of the Permian Basin, the Brookian Megasequence on the North Slope of Alaska, the Cretaceous-Tertiary of Patagonia, and Permo-Triassic deposits of Antarctica.    

Peter’s contact information is–email: [email protected], telephone: 512-471-9622, Address: Bureau of Economic Geology, The University of Texas at Austin, University Station, Box X, Austin, TX, 78713-8924.