Late Cenozoic geohistory of NW Buru, Indonesia and plate tectonic implications

Abstract

Mio-Pliocene deposits of Buru have been investigated in order to provide additional data concerning the timing, rate and magnitude of vertical movements in the northwestern end of the outer Banda Arc structure. Geohistory analysis of field and laboratory data of two sections recorded in NW Buru provide broad age-depth constraints only. Four episodes in the history of uplift and subsidence are distinguished and discussed in the light of present plate tectonic concepts. Deposition of the Early Miocene Hotong Formation, bathyal sandy clays and marls with intercalated turbidites, followed after a mid Tertiary period of open folding, uplift, erosion and, finally, partial resubmergence. These changes may be related to plate tectonic interaction with southeast Asia and not necessarily with the Australian continent - from which Buru initialy derived - which is now colliding with the Banda Arc. The Middle - Late Miocene (and possibly the Early Pliocene) left no sediments in Buru; it was a time of differential uplift (up to 20cm/ka), related to reorganisation of the regional deformation pattern, i.e. evolution of the Banda Arc system. During a poorly dated Pliocene depositional episode shallow marine fan-delta clastics were laid down in giant prograding sets, up to 50 m high and dipping up to 20 degrees, thus witnessing continuing differential movements in NW Buru. The same pattern of deformation exists to the present day.