QUATERNARY UPLIFTED CORAL-REEF TERRACES ON ALOR-ISLAND, EAST INDONESIA

A flight of six major coral reef terraces, up to 700 m in altitude, oc curs along the eastern and northern sides of Kabola Peninsula, Alor Is land, Indonesia. Some radiometric dates have been obtained from unrecr ystallized coral samples collected in growth position by three differe nt methods (C-14, Th-230/U-234, ESR). This enabled the identification of the terraces corresponding to the Holocene and to oxygen-isotope st ages 5c, 5e and 7. According to the present elevation of the dated ter races, a 1.0-1.2 mm/y mean rate of uplift can be discerned. Extrapolat ion of this trend to the whole sequence of terraces reveals a good cor relation between the development of major terraces and interglacial or interstadial stages corresponding to astronomically calibrated oxygen isotope records, up to stage 13. The relatively rapid uplift rate in this region minimized the possibility of polycyclic sea-level stands a t the same levels and contributed to the good preservation of some mor phological reef features. Two superimposed marine notches are visible near the present shoreline, with retreat points at about 5.0 m and 8.6 m respectively above the present MLWST level. They can be interpreted as corresponding to a glacial interstadial (the upper notch) and to t he Holocene sea-level peak (the lower one). As Holocene emergence has been less than what could be expected from a 1 mm/y rate of uplift, a major coseismic vertical displacement may occur in the future.