Pollen and diatom stratigraphy of a dendritic fluviaI/lacustrine mire system at Tasik Bera, Malaysia: Preliminary results

Abstract

The Tasik Bera mire system represents deposition of peat and peaty sediments within a dendritic fluvial drainage basin in the humid tropics. Peaty sediments have been accumulating for at least 4,500 years in the lowest part of the basin, but accumulation rates and hence the thickness and lateral extent of the mire underwent a rapid increase and expansion beginning at about 660 years BP. In this preliminary study, pollen and diatom stratigraphy of two cores is related to some physical and chemical characteristics of the organic rich sediments. The sediments are highly variable, both vertically and laterally, the variations principally controlled by the type of vegetation dominant. Vegetation in turn is related to the degree of wetness of the site. Three environments of deposition contribute peat with distinctive palynological and physical characteristics. The limnetic environment, dominated by algae and easily degraded aquatic macrophytes, contributes very fine hemic peaty sediment with high fine silt content and a large algal component. The littoral environment is dominated by sedges and the woody shrub Pandanus, both of which have a large sub-aqueous biomass, and are quite resistant to degradation. Sediment from this environment is woody, hemic to coarse hemic, with a moderate to high very fine silt content and a much smaller algal element. Forest swamps, which occupy most of the mire area, contribute woody, fibric to hemic peaty sediments with low to moderate mineral matter content in the form of clays and very fine silt. Succession from both limnetic to forest swamp, and the reverse, is recorded in cores from different sites. No part of the mire yet studied is approaching oligotrophic conditions.