INDONEISAN GEODYNAMICS AND PALEOOCEANOGRAPHY REVEALED IN AN EXHUMED PLIOCENE FOREARC BASIN, TIMOR LESTE

The Pliocene, synorogenic Viqueque Megasequence (VM) of East Timor accumulated in a forearc basin that developed during the transition from subduction to collision of the Australian continental margin with the Banda Arc. We use new approaches to investigate the exhumation history of the emerging archipelago, the dynamics of arc-continent collision, the chronology of large Indonesian earthquakes, and the paleooceanographic evolution of the Indonesian Throughflow from ca. 5.5 to < 2.5 Myr ago. The VM records an up-sequence progression of seafloor shoaling, from quiet pelagic carbonate deposition to marl deposition to interbedded marls and turbidites. The latter record the emergence of the proto-Timor archipelago in the form of progressive stratigraphic changes within the turbidites, from reworked marine clasts to volcanic clasts to corals shed from developing reefs to fossilized wood fragments shed from the biologically colonized islands. Foraminiferal studies and new U-Pb ages from detrital corals place temporal constraints on these events and permit us to tie geodynamic (changes in deformation style, earthquake-triggered turbidites) and paleooceanographic (changes in temperature and salinity) to robust chronologies. These, in turn, provide insight into the interplay between topography, tectonics and oceanography during forearc basin evolution in an active collision zone.