Geology of Coral Terraces, Huon Peninsula, New Guinea: A Study of Quaternary Tectonic Movements and Sea-Level Changes

A spectacular flight of terraces occurs on the northeast seaboard of Huon Peninsula, New Guinea. The terraces are clearly developed for more than 80 km and rise to over 600 m. They are built dominantly of coral reefs but include subordinate deltaic gravel formations. Interpretation of the reef succession depends on analysis of facies changes across a number of sections, and this is developed after prior analysis of reefs, lagoons, deltas, and submarine terraces on the modern coast. A record of sea-level changes relative to the rising land is determined for each section. Radiometric dating of the terrace reefs indicates Pleistocene sea-level maxima at the following times (yr B.P.): 30,000, 40,000 to 50,000, 60,000, 80,000, 105,000, 120,000, 140,000, 185,000, 220,000. Good agreement with dated reefs elsewhere reinforces these age estimates. Tectonic uplift has varied along the terraced area, because heights of terraces diminish from southeast to northwest, parallel to the coast; and yet records of relative sea-level changes are similar between sections. By assuming that upper Pleistocene interglacial sea levels were little different from the present level, tectonic and sea-level changes can in principle be separated. Using least-squares search, a “best estimate” sea-level curve and corresponding tectonic uplift pattern are derived on the basis of 11 sections. The sea-level curve compares well with Emiliani's generalized paleotemperature curve for the upper Quaternary.