Thomas E. Ewing

Hass-Pratt Distinguished Lecturer

Thomas E. Ewing

Vice President, Sections 2012-14 156 Thomas E. Desktop /Portals/0/PackFlashItemImages/WebReady/ewing-thomas-2.jpg?width=200&height=235&quality=75&mode=crop&encoder=freeimage&progressive=true

“From the detailed stratigraphy of the Yeguna Formation to the tectonic development of West Texas, I’ve been fortunate to work in areas that teach us a lot about rocks, basins and hydrocarbons, and we’re still finding new plays and provinces.

“I would like to bring to a wider audience the neat things I’ve found in the geology of Texas, including West Texas and the Gulf of Mexica, and give back to our society the great stories about the earth and how its wealth has created our modern society.”

Tom Ewing, noted geoscientist and author, is owner and operator of Frontera Exploration Consultants in San Antonio. In his 35-year career, Ewing’s primary research interest has been integration of structural and stratigraphic history in the evolution of major petroleum-producing basins. He also has a long-standing interest in the geology of San Antonio, and Central and South Texas – integrating surface and subsurface data, and applying it to historical development of the area.

The Bureau of Economic Geology recently released Ewing’s book, “Texas Through Time – a full-color, lavishly illustrated look at the geology of Texas and its relation to human history and human needs,” and “Landscapes, Water and Man: Geology and History in the San Antonio Area of Texas.”

During his tenure with the Bureau of Economic Geology, 1980-84, he worked on the Gulf Coast expansion faults and over-pressured reservoirs, and co-authored “Atlas of Texas Oil Reservoirs” and complied the Tectonic Map of Texas. Ewing previously worked with an exploration team for Venus Oil in the expanded Yegua Trend, achieving significant successes at Vidor Ames, Nome and Constitution fields. The team also worked in West Texas, Kansas and Oklahoma. He has worked with clients in New Mexico, as well as regional ground-water studies in Texas.

Ewing is currently the AAPG Gulf Coast Section president(2016-2017). He is a past president of Sections for AAPG and previously served as president for both the Energy Minerals Division and the Division of Professional Affairs.

He is a three-time recipient of the AAPG A.I. Levorsen Award and recipient of the Distinguished Service Award. He also received Honorary membership from GCAGS and the South Texas Geological Society.


Video Presentation


  • 41250 Comparison of the hydrocarbon systems and geometries of the complex intracratonic West Texas (Permian) Basin and the complex postrift subsidence basins of the Gulf Coast / Gulf of Mexico yield useful insights for basin evolution and play development. The West Texas basin contains source rocks in the Ordovician and Devonian, but much generation comes from the Late Mississippian, Pennsylvanian and Permian basinal sediments. These were deposited in a poorly ventilated remnant basin during compression and strike-slip of the Ancestral Rocky Mountains orogeny, and subsidence of the intracratonic Permian Basin. Maturation resulted from Permian intracratonic subsidence, with hydrocarbons sealed from later leakage by late Permian salt and a fortunate tectonic setting. By contrast, the major Jurassic source rocks of the Gulf basins are at the base of the postrift subsidence, and are matured by further subsidence. Later Cretaceous source rocks (Eagle Ford) are mature in the main Gulf basin, but again lie near the bottom of the thick sedimentary package in the area. The younger part of the succession yields mostly gas formed during outbuilding of the shelf margin by Cenozoic deltaic progradation. No cap is present on the basin (except for subsalt plays), and seepage is widespread. A Tale of Two Basins: Sources and Timing of Petroleum and Natural Gas Generation in the Mature Gulf Coast/Gulf of Mexico and West Texas (Permian) Basins
    A Tale of Two Basins: Sources and Timing of Petroleum and Natural Gas Generation in the Mature Gulf Coast/Gulf of Mexico and West Texas (Permian) Basins
  • 41251 The West Texas (Permian) Basin is a complexly structured intracratonic (IC) basin with prolific oil and natural gas production. It began as a subsidence basin ('Tobosa Basin') from Middle Ordovician to Devonian time, a response to the Cambrian rifting that separated Gondwana and Laurentia. In the Pennsylvanian to early Permian, it formed part of the Ancestral Rocky Mountains (ARM) orogen. The Texas-New Mexico segment of the ARM contains small to medium basement-cored uplifts, folds, thrust faults and two trends of strike-slip faults, with a pattern that is consistent with SW-NE compression. The largest thrust fault known in the basin is SW-vergent, and faces the deepest part of the Delaware Basin. This direction of compression is similar to that observed in the southern Oklahoma part of the ARM, which shows NE-vergent thrusting and left-lateral faulting. This SW-NE compressive stress is grossly inconsistent with the northwestward convergence of the Ouachita-Marathon thrust belt southeast of the ARM. The ARM-generating stress may have originated either from the Pacific side (by flat subduction) or from strong continental collision in the Appalachian Orogen. Lines of weakness generated during the Proterozoic and/or Cambrian concentrated stress and created the complex structures. The West Texas branch of the ARM is buried by over 2.5 km of post-deformational Permian strata -- the Permian Basin. Subsidence began during ARM deformation, then increased in rate and continued to the end of the Permian. Permian subsidence resulted in the maintenance of isolated deep-water marine basins until Late Permian time. The Marathon orogen also subsided, and shed little clastic material into the basin. Despite Mesozoic basin-margin modifications, the Permian isopach pattern suggests a bowl-shaped subsidence centered on the Central Basin axis of uplift. The size and shape of the Permian Basin are similar to other IC basins (Illinois, Michigan, Williston). Similar to some IC basins, the central basin area hosts a 1100-Ma mafic complex, which was subjected to compression in Pennsylvanian time. Sinking of a mafic crust or its subjacent lithosphere, begun during compression, may have been a driving force for Permian subsidence. Over most of the basin, later Permian subsidence was responsible for putting source rocks into the oil window. Further maturation to gas occurred within the deep basins generated by ARM deformation and Marathon thrust loading. Tectonics and Subsidence in the West Texas (Permian) Basin, A Model for Complex Intracratonic Basin Development
    Tectonics and Subsidence in the West Texas (Permian) Basin, A Model for Complex Intracratonic Basin Development
  • 41249 The Yegua Formation (Late Middle Eocene) is a minor siliciclastic progradation of the Gulf of Mexico shelf margin between the larger Early Eocene and Oligocene shelf-margin progradations. During Yegua time (and unlike the other units of the Middle and Late Eocene), four to eight sea-level fluctuations with a 100-300 ka period alternately pushed marine rocks toward the basin margins and pushed deltaic sedimentation to and past the shelf edge. Because of limited to moderate sand supply and the flat coastal plains, the updip (highstand) depositional complexes are nearly entirely separated from the downdip (lowstand) shelf-edge deltas and slope fans. Maximum flooding surfaces can be mapped over much of the area and correlated along and across the basin. The Yegua is truly a laboratory for sequence stratigraphy. A number of plays in the downdip and 'mid-dip' (incised valley complexes) trends have produced over 4 TCF of gas and condensate, and new discoveries await the return of exploration capital. The Yegua story is significant to all those interested in siliciclastic stratigraphy in passive-margin settings. Yegua Formation (Late Middle Eocene) in the Gulf Coast Basin, as a Type Laboratory for Sequence Stratigraphy in Hydrocarbon Exploration
    Yegua Formation (Late Middle Eocene) in the Gulf Coast Basin, as a Type Laboratory for Sequence Stratigraphy in Hydrocarbon Exploration