Holocene sea-level history and the evolution of Sabine Lake and Calcasieu Lake; east Texas and west Louisiana, USA and the glacial retreat history of Maxwell Bay, South Shetland Islands, Antarctica: Implications for ice cap thickness, retreat, and climate change
Milliken, Kristy Lynn Tramp
Anderson, John B.
Doctor of Philosophy
The history of relative sea-level rise along the northern Gulf of Mexico must be constrained in order to determine the relative effects of eustatic sea-level rise, subsidence, antecedent topography, and sediment supply variations on fluvial--bay-shoreline sedimentary systems. This study adds important additional sea-level indicators for the past 10 kyrs in addition to compiling the extensive pre-existing data from the literature. The northern Gulf of Mexico data from the modern shoreline is compared western and eastern Gulf of Mexico datasets to determine the relative difference in subsidence rates over the past 4 kyrs. Subsidence differences are negligible. Furthermore, quantification of the antecedent topography provides a means to account for its effects on sedimentary architecture and the evolution of the Sabine and Calcasieu river-bay systems. The record of eustasy potentially indicates 3 to 4 meter-scale rapid rise intervals during the early Holocene. Subsequent to 7.5 ka, the progradation and retrogradation of the sedimentary systems must be attributed to sediment supply variations (climate change). From 7.5 ka to ∼3 ka, the east Texas, west Louisiana climate oscillated between sub-humid to sub-arid to produce greater than modern sediment flux manifested as deltaic deposits in the modern estuaries. Important future applications of this study include comparison to the nature and timing of fluvial-deltaic retreat in other estuaries along the Gulf of Mexico and Atlantic coasts. The South Shetland Islands, off the western side of the Antarctic Peninsula, are separated by glacial troughs carved during glacial maxima. These glacial troughs are currently fjords which contain a glaciomarine sedimentary record. Age constraining the sediments provides a retreat history of the ice cap for the past 15 kyrs including rates and magnitude of retreat for sub-polar glacial systems. Furthermore, the timing of the migration of sub-glacial polar (cold-based) glacial conditions southward is constrained to ∼10kyr. This has important implications for Holocene glacial flow rates and ice shelf stability in the Antarctic Peninsula region.