A record of continental collision and regional sediment flux for the Cretaceous and Palaeogene core of SE Asia: implications for early Cenozoic palaeogeography.

Palaeogene sedimentary rocks exposed in West Java were derived from local volcanic sources and central Sundaland, the continental core of SE Asia. Detrital zircons from seven sandstone samples contain U-Pb age populations with ages of 50-80 Ma, 74-145 Ma, 202-298 Ma, 480-653 Ma and 723-1290 Ma. Late Cretaceous and Palaeogene zircons in Middle Eocene forearc sandstones are interpreted as derived from two spatially and temporally discrete volcanic arcs located in Java and Sulawesi respectively. In contrast, all other populations have a Sundaland provenance. Most Permian-Triassic zircons were derived from granites of this age in the SE Asian Tin Belt. Mid-Cretaceous zircons in all Upper Eocene and Lower Oligocene formations were derived from the Schwaner Mountains of SW Borneo. The differences in zircon populations reflect changing Sundaland sources with time. In the Middle Eocene, sediment was derived mainly from the Tin Belt. From the Late Eocene onwards a Borneo source became more important. Older zircon ages are from SE Asia basement that once formed part of Gondwana. Zircons also record the timing of microcontinental collision at the Java margin (c. 80 Ma) that halted Cretaceous subduction and probably resulted in the elevation of large parts of continental SE Asia. [ABSTRACT FROM AUTHOR]