INTEGRATED SURFACE DRAINAGE IN NORTHWEST FLORIDA'S KARSTIC GULF COASTAL LOWLANDS LINKED TO SHIFTING SUBTROPICAL STORM TRACKS IN RESPONSE TO HIGH-LATITUDE POST-GLACIAL CLIMATE CHANGE

Magnetic analysis of sediment cores from an inundated mid-river sinkhole in northwest Florida's karstic Gulf Coastal Lowlands reveals temporal fluctuations in the concentration of detrital titanomagnetite. Higher and more variable concentrations of titanomagnetite coincide with elevated Gulf of Mexico (GoM) sea-surface temperature (SST) during the Bølling-Allerød interval and the early Holocene. A hiatus in titanomagnetite deposition and subaerial weathering of sinkhole deposits coincides with GoM SST cooling during the Younger Dryas. Paleoclimate records and numerical models indicate that high-latitude cooling during the Last Glacial Maximum and the abrupt Younger Dryas event is associated with a southward displacement of the Atlantic Warm Pool (AWP) and decreased precipitation in the subtropical North Atlantic. Conversely, a warm tropical North Atlantic and northward propagation of the AWP is associated with increased rainfall and tropical cyclone activity. We attribute fluctuations in the concentration of titanomagnetite in the Aucilla River to changes in the frequency and/or intensity of regional precipitation events. Increased precipitation from ca. 14.3–12.5 and after 10.6 calendar years before present (cal yr BP) was sufficient to integrate disconnected surface channels, sinkholes, and subterranean conduits to form a channelized fluvio-karst drainage system capable of transporting detrital titanomagnetite. Reduced precipitation from ca. 12.5–11.5 cal yr BP restricted flow to subsurface karst channels and conduits. We hypothesize that the observed temporal fluctuations in the concentration of titanomagnetite are linked to north–south shifts in the prevailing storm tracks as the subtropical jet migrated in response to high-latitude post-glacial climate change. Increased understanding of changes in the frequency and magnitude of storm events in the northeastern GoM in relation to changing SST will help differentiate potential climatic forcing functions including solar insolation and ocean and atmospheric circulation changes in the GoM.