Peat records of late Holocene climate and sea level change in South Florida.

摘要

This dissertation explores the late Holocene climate, sea level, and paleoecology of southern Florida. Proxy records of climatic and environmental change are employed to reconstruct the past climates and hydrological regimes of the region. Emphasis is also given to identifying the timing of Holocene eustatic fluctuations and their impact on the coastal and inland hydrology and wetland assemblages. Methods employed include analysis of sediment composition (organic matter and carbonate), pollen, and other microfossil remains. Modern analog statistical techniques are used to compare the fossil pollen assemblages to over 189 modern surface samples from peninsular Florida, the southeast US and the Caribbean. Close analogs in the paleorecord are assumed to be similar to the modern vegetation types and by proxy to the environmental conditions such as hydroperiod, salinity and edaphic factors, that govern their distribution.; Results indicate that both coastal and inland Everglades plant communities have responded to large-scale climate and sea-level fluctuations over the last 5000 years. At 5000 yr BP precipitation was greater than today but gave way to and spells ca. 3000 yr BP. Reduced effective precipitation also occurs about 1000 yr BP, contemporaneous with the onset of the Medieval Warm Period. Sedimentological evidence suggests that sea levels rose more quickly or were higher than modern levels circa 1000 yr BP. At 400 yr BP changes in plant community structure reflect another reduced precipitation regime and possible evidence of freezing temperatures. Overall, the late Holocene in southern Florida is characterized by gradually decreasing moisture availability punctuated with century-scale fluctuations. Likewise the eustatic history is that of a gradually rising sea level with superimposed minor oscillations.