U/Pb dating of a terminal Pliocene coral from the Indonesian Seaway

Pristine detrital Platygyra corals were discovered in an exhumed package of syn-orogenic marine sediments on the island of Timor in the eastern Indonesian region and dated using U–Pb techniques. A single coral from the upper part of the sequence yields a 238U/206Pb–207Pb/206Pb concordia age of 2.66 ± 0.14 (2σ) Ma that is supported by coral 87Sr/86Sr chemostratigraphy and foraminiferal biostratigraphy from bounding strata. Minor U-series disequilibrium is best explained by U mobility within the last ~ 150 ka, as pore water chemistry was altered during exhumation, and is unlikely to have affected 238U/206Pb and the apparent sample age by more than 1–2%. The ability to date corals beyond the limits of 14C and U/Th techniques provides the opportunity to improve the temporal resolution of associated marine chronostratigraphic records. In this instance, we refine the timing of Timorʹs emergence from beneath the waters of the Indonesian Seaway (IS) and the initiation of turbiditic deposition at the study site to between ca. 3.35 and 2.66 Ma. These results have implications for the evolution of topography and IS oceanic pathways in the active orogenic belts along the northern fringes of the Australian Plate.