Abstract: The Early Tertiary Rift Basins of Offshore South Sulawesi, Indonesia

Maurice A. Cucci, Richard A. Garrard, Mark Golborne

Integration of seismic, petrophysical, and biostratigraphic data, indicates that the Paleogene strata offshore South Sulawesi are related to a complex rift system that was twice activated and in both cases subsequently failed. The initial rifting event occurred during the late Paleocene/early Eocene. Individual basins appear as a discontinuous series of "sags" oriented north-south on a Cretaceous platform. Initial deposits were subaerial and submarine volcanics of the Langi Formation and are coeval with paralic siliciclastics of the Salo Kalupang Formation. By the middle Eocene the rifting event had failed and these strata were uplifted and eroded forming a major unconformity.

The second rifting event began in the Middle Eocene, occurring close to but not always coincident with the sites of earlier "sags". These rifts have a north-south orientation, extending from offshore South Sulawesi to near Sabalana Island at the intersection with the east-west trending Kangean-Lombok rift system. The base of the middle Eocene sequence (Malawa/Toraja Formations) comprises terrestrial and lacustrine sediments and are overlain by widespread fluvio-deltaic deposits. In the late Eocene rifting ceased, having isolated extensive shelfal areas from the highland Sulawesi siliciclastic sediment supply. In the late Eocene a major marine transgression transformed these former sites of siliciclastic deposition into sites of carbonate deposition characterized by vast shallow water arbonate platform deposits (Tonasa/Makali Formation) with localized reefal buildups.

By the Late Miocene carbonates gave way to siliciclastic sediments (Camba Formation) derived from the establishment of a major magmatic belt. During the Late Tertiary, compressional tectonics inverted many of the Paleogene rift basins to form classic "Sunda" type folds.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994