Makassar Strait Basins

Tectonic provinces in the Makassar Strait Region (Darman, 2014)
Makassar Strait is located between Borneo and Sulawesi Island. In general the region is separated into two parts by NW-SE Adang - Paternoster Lateral Fault. The northern part compose of Kutei Basin in the west, North Makassar Basin in the centre and two basins in the east called Lariang and Karama Basins. Palu-Koro Fault set the northern boundary of the northern part. Paternoster Platform and the South Makassar Basin is located in the southern part of this region.

Fig. 2. PGS-1 South-North Seismic section across across Makassar Strait (Source: PGS)
PGS has processed and published a NS seismic line which cross different tectonic unit in the Makassar Strait. PGS-1 line goes across Muara Sub-basin of Tarakan Basin in the north, Mangkalihat Platform, North Makassar Basin, South Makassar Basin, Paternoster Platform and Lombok Basin.
Fig. 3. Location map fo PGS-1 seismic line

1. Palu Koro Fault
Fig. 4. TGS seismic line which shows the Mangkalihat Platform 
and the Palu Koro Fault system (right; Baillie, 2005)
The NW-SE oriented Palu Koro Fault system developed in the north of Makassar Strait. This fault is still active and generated a number of significant earth quake in Sulawesi onshore. The seismic section offshore shows a rough seabottom. Figure 4 shows a seismic section across the Mangkalihat Platform on the left and rough sea-bottom topography on the right, which is caused by the Palu-Koro fault system. Figure 5 provide the zoom-in image of Figure 4 to show the detail of the Palu-Koro fault system.

Fig. 5. TGS Seismic line, showing the detail of the Palu Koro 
Fault in Fig. 4 (Baillie, 2005)

2. Offshore Kutei Basin
Fig. 6. TGS MDD99 Line 19, showing the eastern margin 
of offshore Kutei Basin. 
The majority of Kutei Basin covers the eastern part of Borneo onshore. The drainage basin supplied sediments to the paleo-Mahakam Delta which develop further as deepwater system in the Makassar Strait. TGS MDD99 Line 19 (Fig. 6) shows the margin between the offshore Kutei Basin and the Northern Makassar Strait. The seismic section shows minimum deformation in the Northern Makassar Strait (right of Fig. 6) and potential toe-thrust system developed in the outer margin of the offshore Kutei Basin (left of Fig. 6).

PGS 3D seismic reprocessing in the southern part of offshore Kutei Basin  (Fig. 7) provide some detail images of the deltaic - deepwater system.
Fig. 7. Location map of the 3D seismic reprocessed by PGS.
Fig. 8. Dip line of PGS 3D seismic

Fig. 9. Strike line of PGS 3D seismic

3. Lariang Basin
Fig. 10. Seismic expression of North Makassar Strait (left) and 
Majene thrust belt (right). After Baillie, 2005. 
Structural Styles of the West Sulawesi Deep-Water Fold and Thrust Belt, Makassar Straits, Indonesia

by Jose de Vera & Ken McClay Fault Dynamics Research Group, Royal Holloway, University of London, Egham, United Kingdom

Southeastern part of Makassar Basin, Deepwater fold
belts. Source: TGS
The offshore margin of West Sulawesi (eastern Makassar Straits) is characterized by an active, Late Miocene/Early Pliocene to present day, NE-SW-trending and NW-verging deepwater fold and thrust belt. The fold and thrust is approximately 250 km long and as much as 75 km wide and consists of an Oligocene to present day succession that was deposited on subsiding, thinned, rifted continental crust and is now deformed by SW-to NE-verging thrust fault-related folds deformed on multiple detachment layers. Based on the across strike variations in structural style and bathymetry changes, the West Sulawesi fold and thrust belt can be divided into five across-strike main structural domains. From northwest to southeast these are: the abyssal plain, the deformation front, the folded domain, the thrust domain and the inversion domain. The abyssal plain is solely deformed by Pliocene to Pleistocene, low-displacement, planar extensional faults, which are interpreted to be the result of flexural subsidence ahead of the advancing thrust front. The structural styles of the deformation front are strongly controlled by inversion of the Pliocene to Pleistocene extensional faults. Inversion of pre-existing faults controls fault localization and fold vergence, giving rise to complex wedge and triangle zone geometries.
Southeastern part of Makassar Basin, Deepwater fold
belts. Source: TGS
The structural styles of the folded and thrust domains are characterized by complex NW- to SE-trending detachment and fault-propagation folds, with multiple detachment levels developed in Oligocene and Miocene mudstones. The inversion domain is the innermost and oldest element of the thrust belt and consists of large anticlines that resulted from reactivation of Paleocene rift structures. The results presented in this work are based on the structural analysis of 3480 km of regional 2D seismic lines.
The structural patterns described here have implications for understanding fault-fold geometries and growth in other deepwater fold and thrust belts.

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009


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