Studies on Peat in the Coastal Pains of Sumatra and Borneo : Part IV : A Study of the Floral Composition of Peat in Coastal Plain of Brunei, Borneo

Abstract

The coastal plain of the Baram-Belait river basin, Brunei can be divided into two stratified sequences; peat and mineral deposits. The mineral deposits consist of sand terrace, mangrove deposits and tidal flat deposits. Peat deposits derived from many kinds of the former vegetation cover started to accumulate on these mineral deposits during the Holocene period. Tidal flat and mangrove deposits are characterized by the abundant fossil pollen of mangrove vegetation, while fossil pollen in sand terrace are mostly derived from the former freshwater-swamp forest. Two kinds of peat deposits were found in the Baram-Belait river basin; (1) freshwater peat swamp, and (2) brackish-water peat swamp. Brackish-water peat swamp is mostly deposited in the bottom layer, and characterized by the dominance of mangrove pollen, except for peat deposits taken from Profile BRNI 86-28. All peat layers of this profile are mostly dominated by pollen derived from freshwater-swamp forest. Freshwater peat swamp taken from Profiles BRNI 86-14 and BRNI 86-18 is characterized by the former mixed dipterocarp forest. Between the upper and bottom layers, the mixed swamp forest occur, and they are characterized by the dominance of many kinds of fossil pollen types.