A FACIES DESCRIPTION AND HOLOCENE HISTORY OF THE NUECES BAY-HEAD DELTA, TEXAS

Accelerated coastal retreat associated with recent climate change has the potential to affect both human and natural systems. Approximately 40% of the global population lives within 100 km of a coast. Ongoing loss of coastal resources associated with recent climate change has led to an increase in awareness of the importance of preserving coastal systems. Most studies have focused on the impacts of recent climate change in coastal areas associated with the increasing rates of sea-level rise. However, other factors associated with climate change have the potential to influence coastal systems. A climatic change marked by a period of aridity is thought to have occurred at 2.6 ka resulting in the back-stepping of the deltas in the Gulf of Mexico. This study attempts to quantify the flux of sand delivered to the Nueces delta across this 2.6 ka event using grain-size analysis. Additionally, facies correlations obtained from sediment cores will be used to map the movement of the bay-head delta over the last 5 ky. Studying the Nueces delta in Corpus Christi, TX also presents a unique opportunity to characterize the facies architecture of a bay-head delta.

Nueces bay is located in central Texas along the Gulf of Mexico. The Gulf of Mexico has experienced increasing sea-level rise during the Holocene even when accounting for glacio-isostatic adjustment. The early Holocene sea-level rise was punctuated by two rapid rates of increase, known as high-stands. The Gulf of Mexico has experienced a relatively steady increase in sea-level for the past 5 ky. The main contributing factor to change in the estuaries in the southern and central Texas Gulf Coast has been climate change during this period. Six geoprobe cores and thirty-one vibracores have been described and the descriptions used to make facies correlations from the front of the delta to approximately 12 km inland. Additionally, 4 km of seismic data were collected in the bay itself and within the distributary channels. Radiocarbon dating was used to constrain the timing of deposition. Four distinct have been defined based on relative grain size and type of fauna. The correlated defined facies have been used to characterize the delta front architecture. Interpreted seismic data indicates progradation sequences and channel migration sequences during the delta’s past.