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Seismic Stratigraphic Analysis of the Yoakum/Lavaca Canyon System, South Texas, USA


The Yoakum/Lavaca canyon system is composed of two ancient, superimposed submarine canyons located in the subsurface of Lavaca and DeWitt counties, Texas. The Yoakum/Lavaca canyon system's initial formation was described previously as a response to sudden interruption of incoming sediment supply from the lower Wilcox Rockdale delta system, followed by a period of rapid transgression causing instability and slope failure at the time of Upper Wilcox deposition during the Late Eocene. Analysis of stratigraphic relationships from well data and morphology of the Yoakum/Lavaca canyon system in two dimensional (2D) seismic reflection data has provided an opportunity to propose a new explanation for the initiation of slope failure that excavated the base of the canyon system. The Chicxulub impact event is linked to the Cretaceous-Paleogene (KPg) mass extinction and is believed to have induced massive slope failures across the Yucatan platform and surrounding continental margins. This study considers the possibility that initiation of the Lavaca canyon system, the older canyon system, was a result of the induced seismicity from the Chicxulub impact event ~66 Ma. Structure of the Yoakum/Lavaca canyon system is easily identified on 2D high-resolution seismic reflection data. The Lavaca Canyon is interpreted to incise through an underlying Albian age carbonate platform. Seismic data reveals the Cretaceous-Paleogene boundary as a high amplitude, continuous reflection that truncates seismic reflectors below. Other stratal terminations, found at the base of the canyon system, suggest that slope failure of the final Cretaceous carbonate platform resulted in the initial canyon excavation. Interpretation of seismic stratigraphic relationships and well penetrations of the canyon system has provided robust constraints on timing of excavation and fill of the entire Yoakum/Lavaca canyon system. This work provides the first comprehensive depositional synthesis of the canyon complex utilizing both subsurface seismic and well log data.