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The AAPG/Datapages Combined Publications Database

Indonesian Petroleum Association


IPA-AAPG Deepwater and Frontier Symposium, 2004
Pages 389-397

Exploration Significance of High Resolution Bathymetry in the Makassar Straits

Philip A. Teas, John Decker, Achmad Nurhono, Aliza Isnain


Over the period of 2000-2004 Unocal has compiled bathymetry data from multiple sources, synthesizing each of the datasets into a Makassar Strait regional bathymetric map. This work is continually updated, but is developed to a degree that it now has significant impact on understanding of the basins within the Makassar.

Modern bathymetry is a result of the combination of structural/tectonic and depositional processes. As such, examination of the bathymetry brings insight into active tectonics, delineation of structural domains, depositional systems from shelf to basin floor, and somewhat into dominance of deposition vs. structural deformation. Even at relatively low resolution, a bathymetric map of the Makassar Strait illustrates compression across the basin, dominant over approximately the past 15Ma and represented today by surface anticlines on both sides of the strait. At higher resolution, along the anticlines we can resolve slumping of the over-steepened forelimb and re-direction of depositional systems. The basin wide bathymetry also illustrates the dominance of the Mahakam River for delivery of clastics to the basin, as well as the northern and southern limits of the basin along remnant transform faults. The basin floor itself also reveals a major tectonic lineament expressed as a step from more shallow to deeper seafloor from south to north.

Greater exploration significance is gained from smaller scale views of bathymetry. With a more focused view we find areas of active extensional faulting as well as folds, and submarine mud-volcanoes defining areas of active fluid venting. Additional tectonic lineaments are expressed by changes in slope angle and degree of canyonization which clearly show a major boundary just northeast of the Mahakam delta. Looking at the style of canyons we find evidence for recent rapid uplift at the northern margin of the Makassar Strait vs. aggrading canyon systems on the western margin. In addition to structural details the modern bathymetry provides a wealth of depositional system analogs, from large low-relief fans in deep water to footwall carbonates in shallow water. Along the slope of the western basin margin channel levee systems reaching into the basin floor are clearly imaged. Some of these systems appear to coalesce into a bajada forming the lower slope in the southwestern area of the basin.

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