PBS-SEPM 2026 February Luncheon - John Holbrook

"The Geology Behind the Vistas of the Palo Duro Canyon, West Texas" - John Holbrook, Texas Christian University
 
Abstract
Triassic strata of the Tecovas and Trujillo formations in the Palo Duro Canyon of West Texas record deposition dominated throughout by upperflow-regime channel flow. These strata provide an opportunity for new insights into the architecture, floodplain/channel processes, vertical profiles, palaeohydrology and taphonomy typical of broader upper-flow-regime-dominated fluvial systems. Thicker channel-fills (ca 2 m, aspect ratio ca 24) host upper-plane-bed, symmetrical antidune, breaking-antidune, chute-and-pool, and cyclic-step structures. The thinner channel-fill population (<1 m, aspect ratio ca 35) comprises upper-plane-bed and some antidune structures.  Some of the larger channel fills developed low-angle downstream-accreting bars, with rare examples of laterally accreting side-attached bars. This appears to be the first documentation of an ancient upper-flow-regime side-attached bar. A generalized vertical sequence for large upper-flow-regime channel stories has upper-plane-bed structures above the basal scour, transitioning upward into higher flow regime structures (for example, antidunes, cyclic steps, etc.), then back to a mix of upper-plane-bed and antidunes or lower-flow-regime structures towards the top. The Tecovas Formation and overlying Trujillo Sandstone both bear layers of cross-cutting laterally amalgamated valley fills, multivalleys, and are separated by a regional sequence boundary.  Large and flashy discharge was the likely cause for supercritical-flow conditions instead of excessive slopes. Rivers in both the Tecovas and Trujillo formations record a fluvial system developed in a tropical to subtropical megamonsoonal environment. The tendency for preservation of metre-scale channel-fills and catastrophic inundations of floodplains and lakes in single floods has also made the Dockum Group a prolific preserver of large Triassic vertebrates.
 
Bio
John Holbrook is a Professor in the Department of Geological Sciences at Texas Christian University.  He previously served as a Professor at both University of Texas at Arlington and Southeast Missouri State University, and has held adjunct/guest professor positions at Enugu State University, Nigeria; St Petersburg State University, Russia; University of Texas at Dallas; and Hebrew University, Jerusalem.  His research interests are field oriented, focusing mostly on both modern and ancient fluvial-deltaic systems and physical stratigraphy.  He is a ‘World’s Top 2% Scientist’ for 2020, 2021, and 2025 according to the Stanford/Elsevier ranking, and a highest-ranked (top 3%) scholar in his field and overall according to ResearchGate 2022-present.  Current interests include controls on architecture and permeability trends in sediments, quantifying fundamental sedimentary processes at small and large scales, pathways to preservation of modern processes in the stratigraphic record, the origin of stratigraphic sequences, and tectonic and climatic impacts on rivers and deltas.  He has worked directly in these areas in over 20 countries.  He applies his research widely across petroleum, geothermal, and environmental issues, and is well published, well cited (<6400), and active professionally in each of these fields.  He has thus far graduated 44 M.S. and four Ph.D. thesis students.  He gained his B.S. at the University of Kentucky, his M.S. at the University of New Mexico, and his Ph.D. at Indiana University, all in Geology.  He was PI for the NSF Research Coordination Network for research in geothermal energy from sedimentary basins. He has served on several committees at SEPM, GSA, and AAPG.  He is a past member of GSA Council, past Chair of the GSA Sedimentary Geology Division, past Chair of the GSA Publications Committee, and is a GSA Fellow.  He has served SEPM on SEPM Council and as President of Gulf Coast and Mid-Continent sections, and he teaches short courses and serves/chaired committees for AAPG.  He is a licensed Professional Geologist and served as Vice Chair of the Board of Geologist Registration in Missouri.   He works on numerous funded research projects globally and has sat proposal review panels for PRF, AAPG, NSF, and USGS. He was an AAPG Distinguished Lecturer in 2015/2016, teaches AAPG short courses in fluvial and sequence stratigraphy, and won the Madsen Award for Best Oral Presentation at the annual meeting (ACE) in 2019.  He is an experienced expert witness, working in multiple Fortune-500 environmental litigations.