Preliminary investigation of the formation age and chemical characterization of the tropical peat in the middle Sepik Plain, northern Papua New Guinea

Abstract

Seven gouge cores in the middle Sepik Plain (northern Papua New Guinea) were bored to clarify the depositional age and the chemical characteristics of the tropical peat. The weakly-acidic peat layer (3–4 m thick) is distributed around the south bank of the Blackwater Lakes. The peat layer consists mainly of sago palm and grass remains within a mineral matrix of very fine sand and clay. Radiocarbon dating indicates that the peat’s formation had commenced by 3,710–3,560 cal BP. Nitrogen and exchangeable potassium reach their highest values in the upper 60 cm of the peat column. Conversely, exchangeable sodium, calcium and magnesium, as well as carbon, increase their values with depth in the peat. These differences in the exchangeable cations’ contribution suggest changes in the plant species, which were decomposed during the peat’s formation.