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New Insight of Fold-Thrust Belt Evolution as Implication of Hydrocarbon Prospect in the West Timor Island, Indonesia

Abstract

Fold-thrust belt plays becoming one of the main exploration targets in the Eastern Indonesia region including in the West Timor Island. Numerous evidence of oil and gas seeps has been found within the island particularly in the eastern part. Field evidence indicated that most seeps are observed along strike of fold-thrust belt. However, the relationship between fold-thrust belt evolution and source rock maturity as well as migration is unclear due to limited field data. This paper presented new interpretation of fold-thrust belt evolution using integrated field data, 2D seismic interpretation, geochemistry, palinspatic reconstructions and analogue sandbox modeling. Timor island is known as type locality of arc-continent collision characterized by fold-thrust belt deformation involving Paleozoic-Mesozoic Australian continental margin sediments. Several 2D palinspastic model, seismic section, and evidence from bathymetry around Timor Basin showing indication of loading of thrust system in the distal margin of Australian margin outer shelf slope generating the development of Timor Trough, followed by the same time occurance of reactivation of the older normal faults system at the NW Australian shelf. The evidence of petroleum system from oil seeps in Timor shows biomarker similarity with Jurassic source rock and Triassic source rock. Moreover, gas compositions of thermogenic gas seeps in Kolbano area shows indication of deep marine Triassic sourced-gas. Integrated 2D seismic and surface geological cross-section along Timor Sea and Timor Island suggests possibility of inversion anticline structure beneath Timor thrust-fold belt, as the primary structure target for future hydrocarbon exploration in West Timor Basinal area.