Stratigraphic and Structural Framework of the Clemente-Tomas and Corsair Growth Fault Systems in the Texas Continental Shelf

Olabisi Ajiboye and Seiichi Nagihara
Department of Geosciences, Texas Tech University, MS 1053, Lubbock, Texas 79409–1053, U.S.A.

The Clemente-Tomas and Corsair growth fault systems in the Texas continental shelf run roughly parallel to the shoreline. The structural development and sedimentation history of some parts of these fault systems have not been investigated in detail. The present study attempts to characterize the sedimentary structure and stratigraphy in one of those parts; an 867 mi² (2245 km²) section within the Mustang Island federal lease area. A 3D seismic volume, well logs from 36 boreholes, velocity survey data from 26 wells and paleontological data from 16 wells were interpreted for this investigation. Integration of these datasets enabled us to identify 6 chronostratigraphic horizons in the Miocene and Pliocene.

Structure maps and sedimentary isopach maps were generated from them. Additional time constraints in deeper sediments were examined on seismic sections.

Based on the observations from our study area and comparison with those from previous studies on other segments of the Clemente-Tomas and Corsair fault systems, we infer two stages of structural evolution in these fault systems. The first is the active growth faulting period in the early to middle Miocene when the basic framework of the two fault systems was set. The older Clemente-Tomas growth fault was initiated by basinward evacuation of a shale mobile substrate in the late Oligocene through the early Miocene. A part of the evacuated shale body developed into a diapiric ridge. Further downslope evacuation of the shale substrate lead to mobilization of the sediments overlying the basinward flank of the shale ridge, and resulted in the primary Corsair fault. This ridge is probably equivalent to the Brazos Ridge that trends along the two fault systems in the northeast Texas shelf. There is much similarity in the basic structural framework involving the two growth fault systems between the present study area and the northeast Texas shelf. The second stage is the period of relative quiescence that followed. By the middle to late Miocene, movement of both growth fault systems slowed down considerably, as sedimentation had slowed down. Diapiric movement of the shale ridges still took place episodically and resulted in formation of graben faults in younger sediments. The last major movement of the Corsair system occurred in the Pliocene, while Clemente-Tomas system has been inactive for a longer period.

AAPG Search and Discovery Article #90158©2012 GCAGS and GC-SEPM 6nd Annual Convention, Austin, Texas, 21-24 October 2012