Whitehead, S.J.; Yeager, K.M.; Feagin, R.A.; Huff, T.P.; Paine, J.G.; Schindler, K.S., and Dixon, T.S., Growth fault–induced effects on tidal marsh surficial processes and landscape conversion in the Slop Bowl, Brazoria National Wildlife Refuge, Texas.
The Slop Bowl marsh, located in the Brazoria National Wildlife Refuge on the Texas coast, is an anthropogenically influenced tidal marsh setting that has experienced rapid rates of landscape conversion and loss over the last ∼70 years. This tidal marsh has been affected by recently active faults and several hydrologic barriers (roads, pipeline channels, and active hydrocarbon-extraction well pads). Geophysical field methods and sedimentological analyses were conducted to better understand the effects of these developments on marsh surficial processes. Lithostratigraphy, shallow geophysical data, GPS surveys, radionuclide dating, and organic matter analyses all exhibited influences connected to growth-fault motion. The location and activity of a major growth fault were identified as contributing to subsidence on the downthrown fault block and causing vertical displacement of the marsh surface. Fault motion, in conjunction with the construction of roads, has disrupted the natural hydrologic pathways that once existed. Their combined effects resulted in transition of the land cover over the past several decades from a saline coastal prairie to a tidal marsh–dominant landscape, with continued future submergence anticipated. As the natural laboratory of the Slop Bowl demonstrates, anthropogenic development, neotectonics, and hydrocarbon extraction can have outsized effects on sedimentation processes, with implications for the long-term sustainability of coastal wetland environments in the northern Gulf of Mexico.