Sediment Deposition and Late Holocene Environmental Change in a Tropical Lowland Basin: Waigani Lake, Papua New Guinea

Waigani Lake occupies a small basin adjacent to the Laloki River floodplain in lowland Papua New Guinea. The oring of the deposits and environmental history of this lake has been interpreted through an investigation of plant macrofossils, diatoms, geochemistry and mineralogy. Between c. 4400 and 2500 BP peat accumulated, probably under a swamp forest. During this period the site was isolated from the Laloki River. From 2500 to c. 1200 BP the site was inundated with their from the Laloki River with peak flooding after 1700 BP. Herbaceous swamp conditions then returned and continued until c. 1965 AD when massive nutrient enrichment of the swamp from sewage disposal resulted in a return to open water conditions. This sequence is matched, in part, by the late Holocene record of four fluvially-influenced lakes in Ecuador. Sediments in such lake systems may contain a sensitive record of environmental change and of past fluvial activity. This late Holocene record from Waigani Lake is the first account from the lowlands of New Guinea. It provides a potentially important palaeoenvironmental link betwen northern Australia and upland New Guinea.