Abstract:

Gum Hollow Delta is a small microtidal, aggradational to slightly progradational, hyperpycnal, tropical-cyclone-dominated delta in Nueces Bay (Texas). The delta formed over the past 80 years following anthropogenically diverted, high sediment-laden stream runoff through Gum Hollow Creek into Nueces Bay. Gum Hollow Delta formed episodically due to high runoff and increased discharge in Gum Hollow Creek and temporarily elevated sea level during Gulf of Mexico tropical cyclones. The delta is 600 m long, 1000 m wide, and 1.6 m thick.

Fifty-one vibracores were taken along four dip transects and two strike transects to delineate the internal sedimentology, architecture, and geochronology of the delta. The delta consists of nine bedsets (tempestites) representing deltaic growth events. Internal stratigraphic correlations were constrained by the identification of significant widespread flooding surfaces and by 137Cs geochronology.

Flooding surfaces formed as storm surges produced short-term base-level rises in Nueces Bay, which were followed by rapid hyperpycnal sedimentation events. Tropical cyclones such as the 1933 Hurricane (Hurricane Eleven), 1945 Hurricane (Hurricane Five), and the 1949 Hurricane (Hurricane Ten) and named hurricanes Alice (1954), Carla (1961), Beulah (1967), Celia (1970), Allen (1980), and Bret (1999) produced significant base-level rises and deltaic depositional events. Distributary-channel avulsions are also associated with the landfall of these tropical cyclones. Comparison of the timing of the deposition of these hyperpycnal tempestites, constrained by 137Cs geochronology, historical aerial photographs, and the historical record of Gulf of Mexico tropical cyclones indicate that the Gum Hollow Delta preserves an 80-year record of storminess.

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