PRE-HOLOCENE AND HOLOCENE POLLEN RECORDS OF VEGETATION HISTORY FROM THE FLORIDA PENINSULA AND THEIR CLIMATIC IMPLICATIONS

Pre-Holocene sediments may be found in sinkhole lakes or filled sinkho les in the Florida peninsula. Lake Tulane in south-central Florida yie lded a core of 18.5 m under 22./m of water. The core extends from the present to ca. 50,000 yr B.P. It is age controlled by twenty radiocarb on dates. The pre-Holocene shows alternating peaks of Pinus (pine)-dom inated and Quercus-Ambrosia (oak-ragweed)-dominated vegetation. The pi ne peaks correlate in detail with Heinrich events H1 to H5. This demon strates linkage between continental and oceanic climate events. The pi ne peaks are thought to link with periods of relatively high precipita tion and warm Gulf water during ice advances. Oak-ragweed peaks are th ought to indicate aridity when the Gulf and North Atlantic surface wat ers were cooled by meltwater from retreating ice sheets. Lake Grizelle is a filled sinkhole with several climatic episodes recorded in polle n counts which are separated from the Holocene by a hiatus marked by t hick sand. It is representative of a category of fossil lakes in Flori da which promise to contain long and perhaps interglacial pollen recor ds. Sheelar Lake records the end of the Wisconsin and the assembling o f a species-rich forest of mesic trees such as Fagus (beech) close to, or south of, their present southern geographic limits. This forest is believed to be ancestral to the mesic deciduous forest which invaded eastern North America in the next 3000 yr.