LATE HOLOCENE CLIMATIC CYCLICITY PRESERVED IN THE PEATS OF DEVONSHIRE MARSH, BERMUDA

Analysis of pollen and spores preserved in a core extracted from the freshwater peats of Devonshire Marsh, Bermuda (32^o 18.538’ N; 64^o 45.306’ W) provides insight to the natural and anthropogenic changes in vegetation on the island. Sampling intervals of 5 cm in the upper 200 cm and 10 cm intervals from 200 cm to 765 cm depth in the core, where pollen preservation is poor, allows the development of a high-resolution regional climatic history in the Late Holocene. A ¹⁴C date of 4730±100 at 747 cm depth, in conjunction with 11 other radiocarbon dates, place pollen data derived from this core within a tight stratigraphic framework during this interval.

Changes in pollen spectra in the core indicate two cycles of wet and dry conditions during the past approximately 5000 years. These paleoclimatic changes are similar to those preserved in lake records in the Caribbean region and in marine sediments of the nearby Bermuda Rise, suggesting region climatic forcing. Climatic reconstructions presented herein are based primarily on proportional changes in the marsh vegetation, reflecting wetter versus drier environments. Wetter and cooler conditions, indicated by increased abundance of Myrica pollen and Pteridophytes spores occurred between ca. 4700 and 3800 yBP and 1210 and 60 yBP, while drier and warmer conditions, as evidenced by the increase in Sabal and Juniperus pollen, occurred between 3800 and 1750 yBP and the last 60 years. The interval between 1750 and 1210 yBP was extremely wet as evidenced by the presence of Typha and Cyperaceae pollen. Results also indicate that over the past 400 years since the colonization of Bermuda, the vegetation in and adjacent to Devonshire Marsh has been altered due to the introduction of non-indigenous plant species to the island and other anthropogenic factors including fire.