Variation of "Growth Fault" Structural Styles in the Texas Gulf Coast Basin

Thomas E. Ewing

Significant regional variability exists within the overall theme of Gulf Coast growth faulting. Detailed mapping and regional seismic interpretation of selected areas in growth-fault trends of onshore Texas illustrate this variability, which can be related to patterns of oil and gas fields and overpressure occurrence.

Several basic styles of growth faulting are observed in the Tertiary sequence of the Texas Gulf Coast. The most distinctive are glide-fault systems, which display a basal detachment below highly faulted and rotated, usually sand-rich and hydrocarbon-bearing, strata. Most glide systems show rapidly migrating highs following the basal detachment, an "escalator" model (Vicksburg, Sarita, Corsair), but others involve domino-style extension similar to Great Basin models (Yegua, Lobo). Other areas show rotated blocks on listric faults, which may sole into a deep glide plane at great depth (Frio), often downdip of ridges of mobile shale (Zapata Wilcox). Still other growth faults are only slightly listric, have slight block rotations, and may root at great depth (Dewitt Wilcox). More local gr wth faulting also occurs along the margins of salt- or shale-withdrawal basins, or as compactional faulting related to shale ridges.

Factors that control structural styles must include the nature of the pre-progradation substrate, presence of salt- or shale-related bathymetric features on the old continental slope, the rate and spatial variation of sediment loading, and the relative excess of sedimentation over subsidence. Presence of thick mud sequences in the substrate favors shaleridge development and glide-fault systems. Slope features localize the faulting trend and may concentrate it over the slip-face of the slope feature. The spatial variance of sedimentation may determine the geometry of faulting and initiate salt or shale movement. The relative excess of sedimentation over subsidence determines the magnitude and timing of the fault systems.

AAPG Search and Discovery Article #91036©1988 GCAGS and SEPM Gulf Coast Section Meeting; New Orleans, Louisiana, 19-21 October 1988.