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Mark W. Andreason1, Alan F. Chatfield1, Joseph A. Curiale1, Mark V. Filewicz1, Edo D. Lumadyo2, Timothy P. Seeley1, Sigit Sutiyono1
(1) Unocal Corporation, Surar Land, TX
(2) Unocal Corporation, Sugar Land, TX

Abstract: Exploration in the gravity collapse rifts of the Salayar Basin, Indonesia

The Salayar Basin, located offshore southwest Sulawesi, is one of a series of gravity collapse rifts formed during the Mid-Cretaceous along the southeastern Sunda shield margin. These rifts opened due to plate roll-back as the Australian plate collided with the southeastern portion of the Sunda plate. The tectonic and thermal histories of the Salayar basin and the surrounding basins of the SE Sunda margin differ from the typical Indonesian back-arc basins of Sumatra and Java due to an early main rift event (Cretaceous) and significant crustal thickening prior to source bed deposition (Paleocene-Eocene). The geologic sequences of events in the Salayar basin are as follows: 1) Early Cretaceous accretion, thrusting, and uplift; granitic intrusion emplacement; low-angle subduction. 2) Mid-Cretaceous gravity collapse (rifting) due to Australian plate roll-back, deposition of deepwater flysch and turbidites. 3) Late Cretaceous isostatic adjustment of rift blocks. 4) Paleocene-Middle Eocene continuation of rifting, deposition of alluvial, lacustrine, and fluvio-deltaic environments. 5) Upper Eocene to Late Oligocene post-rift quiescence, carbonate platform development of basin margins, deepwater marls and shales in basin center. 6) Late Oligocene through Middle Miocene inversion. 7) Middle Miocene to present relative tectonic quiescence, sediment starved conditions, infill of lows. The Salayar basin has only been lightly explored in comparison to the Barito, East Java, and Sengkang basins, which share similar tectonic and thermal histories with the Salayar basin. Previous exploration efforts have targeted large inversion structures. Current understanding of the Paleocene-Eocene petroleum system points to hydrocarbon migration toward pre-inversion structures formed during the Cretaceous rift event.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana