Late Quaternary variability in coastal changes along the Texas Gulf coast
Odezulu, Christopher Ikechukwu
Anderson, John B
Doctor of Philosophy
The majority of the coastal barriers in Texas are retreating landwards, only a few are stable or progradational. The barriers are responding to both external (allogenic) forcings such as relative sea-level and sediment supply, and internal (autogenic) basinal mechanisms such as antecedent topography, regional subsidence, wave climate, offshore profile, and anthropogenic effects. The central Texas coast is characterized by stable barriers whereas the upper and south Texas coast is dominated by transgressive barriers. These changes along the Texas coast became prominent in the mid-late Holocene when the rate of sea-level rise decreased. Man-made activities such as the construction of jetties and dams exacerbate the more recent changes. Transects of sediment cores that extend from back-barrier to beyond the toe of the shoreface were investigated to examine the Holocene evolution and the response of Follets Island (an end member transgressive barrier) and Matagorda Peninsula through North Padre Island (an end member of the stable barrier) to allogenic forcings. Radiocarbon ages are used to constrain the timing and rates of shoreface progradation and retrogradation. The Late Quaternary stratigraphic architecture of the Texas coast varies regionally despite a similar sea-level history. Our data shows that sea level and sediment supply played a major role in the evolution of the Texas coast. The central Texas coast-shoreface experienced high-frequency progradation and retrogradation in the mid-late Holocene whereas upper Texas coast experienced continuous flooding and landward shifts in shoreline. Based on sand budget estimates, only barriers on the central Texas coast are currently stable; upper and south Texas coastal barriers have limited sand thickness and are currently retreating landwards. With the impact of anthropogenic effects on sand delivery to the coast, some barriers are on the verge of disappearing within a few centuries given projected rates of sea-level rise.
Texas coast; barrier island; Transgressive Ravinement; Texas mud blanket; Overwash; More... Sediment supply; Continental Shelf; Sea Level; Antecedent topography; Shoreline; Shoreface; Flooding surface; Sand Budget; Parasequences; Progradation; Retrogradation; Numerical modeling; Radiocarbon dating; 210 b analysis. Less...