Abstract

It is generally considered that the Outer Banda Arc islands are composed in part of strongly deformed sediments that accumulated at the north Australian continental margin. The onset and completion of folding, nappe emplacement, imbrication and uplift that produced the islands of the Outer Banda Arc have been dated by means of planktonic foraminifera. The dating of the onset of uplift of Timor, from a deep submarine position at the end of the Neogene nappe emplacement, to mountains now reaching nearly 3 km high, indicates the rate of post-collision uplift to have been initially 3 mm/yr, then it slowed to about 1.5mm/yr. Where the Australian continental margin meets the eastern end of the present Java Trench there are indications that the Australian margin has overridden the Trench in the Timor region by 240 km. Micropalaeontological dating of the Neogene collision between the Australian continental slope–proximal rise and the trench provides constraints for checking the overriding hypothesis by calculating rates of convergence derived from plate motions (7.5cm/yr) against the rates based on the tectonic model (7.4cm/yr). After nappe emplacement (possibly faster than 6.25 cm/yr) shortening of the continental crust appears to have migrated towards the Australian continent so that the shelf itself has become involved in the imbrication with shortening of the cover rocks between the nappes and the present shelf edge amounting to about 40 km during the last 2 Ma

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