METHODS FOR RECONSTRUCTING HOLOCENE SEA LEVELS IN SOUTH TEXAS

Reconstructing past sea levels is important in understanding how coastal systems respond to sea-level changes as well as placing constraints on geophysical models of past ice sheets and the rheology of the Earth. Reconstructions of past sea levels also allow coastal planners to better understand the nature and cause of recent elevated rates of relative sea-level rise. Traditional methods of reconstructing past sea levels within the Gulf of Mexico have been limited to the dating of basal peats, beach ridges, and estuarine deposits. Basal peats are common in the northeastern Gulf of Mexico but become sparser towards the west and south, particularly in South Texas. The relationship between beach ridges and estuarine deposits is often ambiguous and as a result the interpretation of such features is hotly debated. Here we present two methods of reconstructing past sea levels that have not been previously applied to the Gulf of Mexico. These two methods include the use of isolation basins and algal mats. We review their utility and compare results obtained from these two methods with previously published records of sea-level change in the northwestern Gulf of Mexico.