Timor–Tanimbar Trough: The Foreland Basin of the Evolving Banda Orogen

  1. P. A. Allen and
  2. P. Homewood
  1. M. G. Audley-Charles

Published Online: 5 MAY 2009

DOI: 10.1002/9781444303810.ch5

Foreland Basins

Foreland Basins

How to Cite

Audley-Charles, M. G. (1986) Timor–Tanimbar Trough: The Foreland Basin of the Evolving Banda Orogen, in Foreland Basins (eds P. A. Allen and P. Homewood), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303810.ch5

Author Information

  1. Department of Geological Sciences, University College London, London WC1E 6BT, UK

Publication History

  1. Published Online: 5 MAY 2009
  2. Published Print: 22 DEC 1986

ISBN Information

Print ISBN: 9780632017324

Online ISBN: 9781444303810

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Keywords:

  • Timor-Tanimbar Trough - foreland basin of evolving Banda orogenic deposits;
  • Timor-Tanimbar Trough - depression filled with sea water to depths ranging 2 and 3 km;
  • Timor-Tanimbar trough - forearc accretionary wedge or foredeep;
  • stratigraphy and structure bearing aspects on tectonic controversy;
  • wetar suture and wetar thrust;
  • stratigraphical-structural evolution of Timor-Tanimbar trough;
  • Timor-Tanimbar Trough - flooded by the sea

Summary

Seismic refraction surveys indicate the 2–3 km deep, 1200 km long and locally up to 70 km wide Timor–Tanimbar Trough is underlain by continental crust varying (west to east) between 31 and 40 km thick. Seismic reflection surveys indicate this Trough is underlain by downbowed Australian continental shelf overlain on the Banda Arc (northern) side by a series of reflectors that dip northwards away from the Australian margin. These reflectors appear to represent a pile of thrust sheets composed of Australian continental margin sedimentary rocks that have moved towards the Australian continent. Immediately south of the Outer Banda Arc islands these reflectors are overlain by seismically chaotic material which is itself overlain locally by a reflective, well bedded section interpreted as Plio–Pleistocene turbidites derived from the rising Banda orogen.

The stratigraphy and structure exposed in the islands of Timor and Tanimbar and the stratigraphy in wells on the Australian shelf are compared with the seismic survey data for the Trough separating these islands from the Australian shelf. These data, and the drilling results from DSDP site 262 are used as a basis for discussion of the Neogene–Quaternary evolution of this foredeep of the Banda collisional orogen. The usual tectonic interpretation is that this foreland basin evolved by the subduction trench migrating into the northward converging Australian continental margin. This concept regards the Outer Banda Arc islands as tectonic melange scraped from the downgoing Australian plate and the Trough, not as a foreland basin or foredeep but, as part of this forearc accretionary wedge melange. Another view considers this continental margin has in the Timor region overridden the trench and Benioff zone by about 240 km. This implies the foreland basin developed partly by the loading effect of the southward migrating pile of thrust sheets downbowing the continental margin after the continental margin had overridden the trench and Benioff zone.

The Timor Trough was initiated immediately after the nappes were emplaced in Timor in the mid-Pliocene. The subsidence history of DSDP site 262 indicates that the axis of the Trough, originally located close to the nappes and rising Banda orogen, migrated away from the collision zone towards the Australian craton at 7·5 cm yr−1 from mid- to Late Pliocene. The present axis of the Timor–Tanimbar Trough has subsided 2·3 km at 1 mm yr−1 while the nappes have been uplifted nearly 5 km initially at a rate of 3 mm yr−1 for about 700,000 yr then at 1 mm yr−1 for 2·7 Myr.