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Evolution and Plays of the Banda Arc

Abstract

The horseshoe-shaped Banda Arc situated north of Australia and including parts of eastern Indonesia and Timor Leste, one of the most geologically-complex areas on Earth, is the product of complex Neogene and Quaternary collision between the Indo-Australian, Pacific and Eurasian tectonic plates. The Banda Arc (“arc” in the geometric sense” comprises the Banda Sea enclosed by a largely continental outer larger islands (the largest are Timor and Seram)and an inner, active volcanic arc (Banda or Spice Islands) with typically medium-K calcalkaline compositions related to (now ceased) subduction.Until the mid-19th century the Banda Islands were the world's only source of the spices nutmeg and mace. The area has long been of interest to petroleum explorers because of abundant onshore and offshore oil and gas seeps and similarities with geologically contiguous Mesozoic and Cenozoic successions in Australia where numerous petroleum systems exist and have been exploited. Exploration of the offshore Banda Arc has previously been limited because of water depths, remoteness, and seismic imaging problems associated with a zone of deformation occurring between a series of fore-deeps (Timor, Tanimbar and Seram ‘troughs”) and the Banda Sea. South of the Timor Trough, exploration drilling has shown that much of the Mesozoic section (and in particular, the Jurassic) is immature for hydrocarbon generation. The formation of a fold-and-thrust between 5.0 and 3.0 million years ago over relatively undeformed Mesozoic section has pushed Jurassic (and older) source rocks into the oil window and explains the presence of oil seeps such as found in the deepwater Raksasa mud-volcano, east of Timor. Potential traps north of the Timor Trough include horsts and fault-related features in the Mesozoic section beneath the fold-and-thrust belt and structural highs associated with large normal faults observed to present within the deformed zone. Mapping of multiclient 2D datasets has revealed several large fault dependent anticlinal leads up to 250 km2in areal extent with Jurassic Plover Formation and Triassic reservoir targets.