Date of Award

1992

Document Type

Senior Scholars Paper (Colby Access Only)

Department

Colby College. Geology Dept.

Advisor(s)

Robert E. Nelson

Second Advisor

Russell Cole

Third Advisor

Peter Harris

Abstract

Devonshire Marsh is a peatland on Bermuda. A 3cm diameter core was taken for palynologic, stratigraphic and radiometric analysis to determine the vegetational history of the marsh, and paleoenvironmental indications toward the island. Nine meters of core was obtained; samples from 20cm intervals were treated with a modified acetolysis procedure to extract fossil pollen and spores. On each slide the first 300 pollen grains and spores viewed were identified and counted. It was seen that Devonshire Marsh has undergone alternations of dry and moist periods in the time represented by this core; and that at least one, and perhaps two species in the marsh has suffered from anthropogenic impact. The stratigraphy of the marsh is predominantly woody, hydrous peat. One compact peat unit occurs at 5.5-6.0m. A radiocarbon date of 3520 +/- 100 B.P. was obtained at the base of this horizon. This correlates the unit to the very end of the Hypsithermal interval, and the end of a proposed North Atlantic thermal maximum. The pollen spectra from this unit are indicative of a substrate drier than present. A significant drop in Juniperus at the top of the core is believed to be the result of anthropogenic impact. Sabal also declines at the top. This decrease could be indicative of dropping mean annual temperatures or could be due to anthropogenic impact. In the absence of Juniperus and Sabal, Myrica is seen to dominate the pollen record of the marsh. A cyclical rise and fall of the Cyperaceae profile is concomitantly observed with a rise and fall of Poaceae profiles. The reason for this is unknown.

Keywords

Paleofloristic Trends, Devonshire Marsh, Bermuda, peatland

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