Abstract
Examination of cores from the Sabine Uplift, East Texas Basin, and outcrops and near-surface cores taken by the USGS from the north-central Texas outcrop belt identified four separate siliciclastic depositional systems during the Cenomanian-Turonian. Deposition during the lower Cenomanian Maness system was focused on the western margin of the Sabine Uplift, with a delta identified in Rusk County. The middle Cenomanian Woodbine system is found in outcrop on the western side of the DFW Metroplex and is thought to be the source of the sandstone reservoirs in the giant East Texas Field. Following the major sea-level transgression that drowned the Woodbine deltas and subsequent deposition of the organic-rich lower Eagle Ford marlstones, deltas from the upper Cenomanian Harris system prograded as far south as southern Madison County. The sea-level highstand at the Cenomanian-Turonian boundary trapped sediments at their updip source, producing a widespread hiatus. Siliciclastic deposition was re-initiated during the middle to upper Turonian. Known as the Sub-Clarksville system, deposition was focused along the East Texas Basin axis and on the southwest side of the Sabine Uplift in Tyler and Polk counties.
Production studies performed during development of the Eagle Ford unconventional resource have found that the zones containing less than 35% clay that have a high frequency of thin limestones are among the highest producers. Near the San Marcos Arch on the north end of the main producing region, two clay-rich, non-productive mudstones have been identified, a thin lower clay-rich unit between the primary Eagle Ford producing zone and the underlying Buda Limestone that is associated with instability issues during horizontal drilling, and a thick upper clay-rich unit at the top of the lower Eagle Ford. Thickness maps indicated that the clays originated from the north, but it was not initially apparent as to their precise origin. Biostratigraphic analysis of the lower clay-rich unit in multiple cores identified early Cenomanian micro-ammonites and nannofossils that were also found within the Maness in cores taken from the East Texas field. The upper clay-rich unit was dated as late Cenomanian and tied to the delta of the Harris system in Madison County. On the San Marcos Arch, the age-equivalent rocks to the Woodbine and Sub-Clarksville systems cannot be differentiated by lithology from other Eagle Ford marlstones and limestones.
Biography
Richard Denne is Program Director of the Gulf Basin Depositional Synthesis Project (GBDS), an industry-supported research project at the University of Texas Institute for Geophysics (UTIG) that assembles and synthesizes well, seismic, and other data to establish a basin-scale depositional history of the Gulf of Mexico. His research focuses on integrating biostratigraphic, geochemical, and lithostratigraphic data to understand Cretaceous depositional systems and on applying biostratigraphy to determine the paleoenvironments and relative ages of Cenozoic and Mesozoic marine systems. Richard holds a B.S. in Geology from the University of Iowa and a Ph.D. from Louisiana State University. He began his career at Exxon in 1990 and served as Marathon Oil’s chief biostratigrapher, after which he left industry in 2016 for Texas Christian University where he held the Endowed Chair in Petroleum Geology and was Director of the TCU Energy Institute. He joined the University of Texas in March 2025.
Cost: Members – $10 | Non-Members – $25 | AIPG Student Members – free
Participants who attend the full webinar will receive a certificate for 0.1 CEU / 1 PDH.
To earn NY State CEUs, you must attend the entire webinar, including the Q&A, and complete a brief assessment afterward with a score of at least 70%. The assessment link will be shared in the chat box at the end of the webinar. Multiple attempts are allowed.
Once registered, you will receive the Zoom link with your email receipt and a reminder on the day of the webinar.
Save $ by joining AIPG!
 |
2/17/2026 |
| When: | February 17, 2026 12:00 Noon Central Time |
| Where: | United States |
| Presenter: | Dr. Richard Denne, Program Director of the Gulf Basin Depositional Synthesis Project (GBDS) |
| Contact: | Cathy Duran cld@aipg.org (303) 412-6205 |
REGISTER (here).
