Mid-Cretaceous unconformities in the East Texas Basin and the Sabine Uplift


The analysis of electric-logs from wells in the East Texas Basin indicate the presence of at least three mid-Cretaceous unconformities along the margins of the basin. These unconformities include the pre-Woodbine (mid-Cenomanian), the pre-Eagle Ford (late Cenomanian), and the pre-Austin (pre-Coniacian) unconformities. Electric-log evidence for these unconformities indicates that depositional hiatuses and erosion was minimal to nonexistent in the center of the basin, with increasing erosion towards the flanks of the East Texas Basin. The mid-Cenomanian unconformity appears to be related to the Vail, et al. (1977), mid-Cenomanian sea level drop and the MCU of Buffler, et al. (1980). The evidence for this unconformity therefore lends credence to a worldwide unconformity resulting to a large degree from eustatic sea level changes. The structure of the East Texas Basin indicates that the Sabine Uplift had several episodes of tectonic uplift during the time of deposition of the Washita Group and the following mid-Cretaceous Woodbine and Eagle Ford Groups. The Sabine Uplift and its associated faults caused a westward shift in the axis of the East Texas Basin throughout the mid-Cretaceous as the basin was tilted. The Sabine Uplift was no longer tectonically active during Austin Chalk time, as this formation unconformably overlies the underlying mid-Cretaceous units