Charlie Kerans | Impact of a 40-year Program of Carbonate Field Research

Sea Level and Climate Patterns During the Last Interglacial for the Bahamas-Caicos Archipelago: Impact of a 40-year Program of Carbonate Field Research Abstract: Carbonate strata host a rich record of paleoclimate and past sea level during the Last Interglacial (LIG) across the Bahamas-Caicos Archipelago (BCA). Current models of ice sheet history and glacioisostatic adjustment across the LIG can be significantly improved by a detailed whole-island/cross-archipelago understanding of this record. Field data from Great Inagua, the Caicos Platform, San Salvador Island, and Abaco are leveraged here with cross-BCA DEM data and airborne lidar imagery to provide new estimates of relative sea level (RSL). Essential improvements in GIA models and global mean sea level (GMSL) estimates can derive from these data. However, the myopic focus on GMSL may be, in part, a distraction from the insights gained into past climate states and wave/wind energy in the western North Atlantic during the LIG vs. the mid-late Holocene. Before covering the BCA story, a vignette of the JSG carbonate group’s path to arrive at this focus on Pleistocene RSL and paleoclimate will emphasize the importance of field-based research and education in reaching these insights. The BEG Reservoir Characterization Research Lab began detailed characterization of carbonate outcrops and subsurface datasets in 1987 and has continued pushing science and technological boundaries in outcrop digital characterization and stratigraphic analysis. The Permian Basin, the Cretaceous and Jurassic of the GOM and Middle East, and most recently the Holocene-Pleistocene of the BCA have been significant “testing grounds” for this research. Much of this work has enhanced our field educational curriculum and been improved by it. This combined expertise in carbonate outcrop characterization has enabled interrogation of Pleistocene stratigraphy across the BCA in a way not previously possible, allowing a more complete reconstruction of the archipelago’s dynamic relative sea level history. The BCA MIS 5e RSL record is shown to include an early +4 m highstand, followed by a short-lived fall to +1m, and then a peak highstand of at least +6, but more likely +8-10 m, before a rapid forced regression dropped SL below the top of the platforms. The previous suggestion of a northward gradual increase in peak MIS 5e RSL from 2.2 m in the southwest to above 6.5 m in the north is challenged, suggesting a need for reassessment of recent GIA models. The dramatically more energetic aeolian and wave-generated deposits of the MIS 5e could be of equal or greater importance relative to GMSL in assessing climate impacts of a warmer world as compared to their mid-late Holocene counterparts.