Tectonic post-collision processes in Timor
Indian Ocean crust subducted northwards at the Banda Trench from about 12 to 4 Ma. The Australian continental margin collided with the Asian fore-arc at about 4 Ma. Gradually the Banda Trench was transformed into the fold and thrust mountains of Timor Island. Tectonic collision processes developed when all ocean crust had been subducted and Australian continental crust was refused entry to the subduction path below the Asian fore-arc. The Banda Trench was then gradually converted into a Tectonic Collision Zone (TCZ) progressively filled by two highly deformed Australian continental upper crust mega-sequences. Slowing subduction of Australian sub-crustal lithosphere after c. 2.5 Ma led to uplift of the TCZ that raised Timor 3 km above sea level. Asian Banda fore-arc deformation is linked to c. 30 km southeastwards rollback of the subducting Australian mantle lithosphere. Two Asian fore-arc nappes were thrust southwards from the Banda fore-arc onto the older of two highly deformed Australian continental margin upper crust mega-sequences. The Wetar Suture was created as a thrust at the base of Australian partially detached continental lower crust propagated into the Asian fore-arc. Re-interpretation of BIRPS seismic and gravity data for the Timor region supports this collision model.