Abstract: Combining Micropetrographic and Palynologic Methods to Improve Paleoecological Interpretations of Peat Deposits: Examples from a Carolina Bay in South Carolina and the Everglades of Florida

COHEN, ARTHUR D., CHRISTIAN P. GAGE, WILLARD S. MOORE, and ROBERT S. VANPELT

Peat deposits can be excellent archives of past changes in the depositional and ecological conditions under which they formed. Part of the story of these changes can be gleaned from analysis of the palynomorphs extracted from the peat. However, a much more meaningful reconstruction can be obtained by combining palynological techniques with micropetrographic-botanical analysis. This combined technique (supplemented by Cs-137, Pb-210, and C-14 dating) was found to be especially useful in distinguishing anthropogenically-derived changes in the ecosystem from natural changes.

Examples of this approach are presented from our studies of two peat deposits, one in the Everglades of Florida and the other at the Savannah River Site in South Carolina. The Everglades study is a transect of peat cores collected down-gradient from agricultural lands. The combined palyno-petrographic method was able to detect with some certainty the first appearance of contaminant-driven plant types into the region.

Paleo-hydrologic conditions can also be surmised by this method. For example, one of the Everglades sites was, until recently, in the center of a surface-water flow pathway, as indicated by the continuous presence in the core, prior to 1962/63, of deeper water aquatics and the reduction in oxidation and bioturbation indicators. An example of similar anthropogenically-induced changes in drainage conditions is illustrated at the SRS peat deposit, which is located down-gradient from a manmade cooling lake for a nuclear reactor. Significant recent changes in hydrology due to site development can readily be distinguished from pre-development ecological changes.

AAPG Search and Discovery Article #90939©1997 AAPG Eastern Section and TSOP, Lexington, Kentucky