A Palynostratigraphic Investigation of Holocene Coastal Texas Bays: Implications for Future Coastal Change

Abstract

Although the Gulf of Mexico is one of the most studied basins in the world, a majority of the focus has been driven by petroleum exploration and/or on seismic and sedimentological facies models. Rarely has the intent of previous studies been to characterize the Holocene climatic record of coastal Texas. Of those studies that discuss Holocene vegetation change, the majority focus on the Mississippi River Delta, the Edwards Plateau or central Florida, leaving an absence of insight to western Gulf of Mexico climate changes. The Texas coastline stretches 595 km across almost 4° of latitude and the strong northwestern precipitation gradient results in a diverse coastal vegetation assemblage. We provide a detailed palynological record of Holocene climate for southeast and coastal Texas, based upon four subaqueous sediment core transects from within Baffin Bay, Corpus Christ Bay, and Trinity Bay, south to north, respectively. Our marine record from dinoflagellates in Corpus Christi Bay, Texas found convincing evidence that the bay’s coastal barrier island was compromised for several hundred years due to a rapid pulse of sea-level rise. Statistical results of combined marine (dinoflagellate) and terrestrial (pollen and spores) records from Trinity Bay, Texas and Corpus Christi Bay, Texas show that they had similarly-composed assemblages, but that these assemblages first appeared at different times. These environments transitioned through the Holocene from herbaceous-dominated assemblages to arboreal-dominated, as early as 8.4 ka within Corpus Christi Bay, and 3.8 ka within Trinity Bay. Furthermore, our results indicate that coastal Texas’ climate operated semi-independently from central Texas regions during the Holocene, and is primarily driven by a coast-wise gradient of precipitation and evapotranspiration. A final study of Baffin Bay, Texas shows that it experienced similarly timed vegetative shifts as seen in Corpus Christi Bay, located <60 km to the north. Sample-to-sample shifts in arboreal-herbaceous abundances in this record were shown to be likely correlated with the climatic effects of changing solar>irradiance.