The Geometry and Origin of Gravity-Controlled Structures – Mass Transport Complex (Giant Slump) in South Makassar Strait Basin



2D and 3D seismic data set in South Makassar Strait identify the relatively coherent Mass Transport Complex that interpreted caused by gravitational movement or not caused by lateral tectonic movement. The South Makassar Strait Basin Mass Transport Complex (SMSB MTC) covers an area of at least 9000 km2 and with a total volume of 2438 km3. It is composed of a shale dominated sedimentary unit with high water content. The SMSB MTC differs from other very large MTC’s in displaying relatively coherent internal sedimentary stratigraphy, and is probably the largest know coherent MTC or slump. It has a central region up to 1.7 kms thick which forms a bowl-shape confined by two NW-SE trending steep lateral ramps in the upper slope area and a NE-SW trending frontal ramp area. The MTC anatomy can be divided into an extension headwall, translational, toe, flank, lateral apron and frontal apron domains. It is interpreted to be triggered by SMSB accelerated subsidence in the Pliocene and slid along a weak basal detachment that lies at the interface between two sedimentary units of different lithologies which was probably overpressured due to fluid migration events. The internal fault patterns of the MTC show that its movement in the upper slope to the middle part of the bowl area is extensional which changes to compressional in the toe domain and apron. Later extensional collapse of parts of the compressional toe area occurred with negative inversion on some faults. The coherent internal stratigraphy suggests the MTC deformed at a slow strain rate, perhaps in the order of cms/yr over thousands of years. Hence this type of MTC does not have the potential to generate tsunamis but could affect deepwater facilities built on the active MTC.


Author : Cipi Armandita