This is a Hybrid Event

Meeting Location:
PGS
15375 Memorial Dr.
Houston, TX 77079

Meeting Time: 11:30 to 1:00
Registration Begins at 11:30
Lunch Served at 11:30
Presentation starts at Noon

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Speaker: John Snedden, PhD, Research Professor, Institute for Geophysics, Jackson School of Geoscience, The University of Texas at Austin

Co-Authors: Chris M. Lowery and Timothy F. Lawton, and the GBDS Research Team

Until recently, information about the end of the Cretaceous was based upon investigation of global outcrop sections.  New subsurface drilling and characterization from well cores and logs in the Gulf of Mexico Basin have greatly illuminated the end Cretaceous event. However, the paleogeography of the late Maastrichtian just prior to bolide impact is less well understood and is of great importance in terms of modeling the resulting distribution and composition of the Chicxulub impact material as well as tsunami and seiche wave height. Here we examine the Maastrichtian strata in the basin, synthesizing lithostratigraphic and chronostratigraphy, tectonic plate reconstructions, global and local sea level history, paleoclimate, and depositional systems.  Our new Maastrichtian paleogeographic reconstruction shows the basin prior to the Chicxulub impact at a time of globally high sea level, with widespread deposition of deepwater chalks and shallow marine carbonates and local siliciclastic shorelines fed by the nascent Cordilleran belt. Stratigraphic correlations of wells and outcrops illustrate the range of paleoenvironments from coastal plain to deep marine. As much as 610 m (2000 ft) of Maastrichtian and Campanian section is mapped around the basin, reflecting accommodation provided by basin subsidence, salt deflation, and paleo-physiography. A large thickness of carbonates accumulated in the basin center, with steep shoreline to basin gradients particularly in Mexico. At the end of the Cretaceous, carbonate paleoenvironments probably covered 96% of the Gulf of Mexico basin, with less than 4% of the area likely occupied by siliciclastic systems, a distribution that evolved from the early Cretaceous. Our maps thus explain dominance of carbonate breccia and chalks in K/Pg boundary units deposited over the basin sites proximal or distal to the Chicxulub impact crater.  This also elucidates the large impedance contrast and high amplitude seismic response of the K/Pg boundary horizon, mappable over vast portions of the basin.  

Speaker Biography: John Snedden, PhD, The University of Texas at Austin
Dr. Snedden is co-principal investigator for the UT-Austin Gulf of Mexico Basin Depositional Synthesis (GBDS) research consortium of 20 companies and federal agencies. He has over 30 years of industry experience with Mobil and ExxonMobil, including 11 years in research. John’s technical specialties include sequence and seismic stratigraphy, sedimentology, reservoir characterization, reservoir connectivity analysis, and unconventional resource evaluation. He has worked in 20 different global basins.   His ten-plus years of UT work has supported important research in deepwater exploration in the USA and Mexico, exploitation of onshore unconventional resource plays, and reservoir compartmentalization and connectivity in field development and carbon storage.   

John received his BA, MS, and PhD in geology at Trinity University, Texas A&M, and Louisiana State University, respectively. He has published over 40 scientific papers; he is the first author on 25 of these. He has also served as technical chair of several large AAPG and GCS-SEPM conventions. John is lead author of a book called The Gulf of Mexico Sedimentary Basin: Depositional Evolution and Petroleum Applications, published by Cambridge University Press in 2019.  In 2021, he was awarded the Doris Malkin Curtis Medal recognizing his outstanding contributions to the understanding of the Gulf of Mexico Basin.  In April 2023 John was honored at the GCAGS GeoGulf Convention with The Donald R. Boyd Medal for Excellence in Gulf Coast Geology. 

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