Tectonic evolution of the Bantimala Complex, South Sulawesi, Indonesia

Abstract

The Bantimala Complex of South Sulawesi, Indonesia is an assemblage of northeastdipping tectonically stacked slices. The slices consist mainly of high pressure metamorphic rocks, radiolarian chert, breccia, sandstone and shale, and melange. In order to understand the tectonic evolution of the Bantimala Complex, we have investigated the lithology, age, stratigraphy, structure and relationships of the components. The K-Ar ages of high P-low T metamorphic rocks suggest that an oceanic plate subducted beneath the Sundaland continent during the Late Jurassic or earliest Cretaceous. The subduction ceased during the Albian, and the high pressure schists were exhumed and eroded at the surface before and during the deposition of middle Cretaceous radiolarian chert. The exhumation of the schists was related to the collision of microcontinents derived from Gondwanaland. The Jurassic shallow marine sedimentary rocks in the Bantimala Complex are possibly remnant fragments of the collided microcontinent. Tectonic stacking of the Bantimala Complex was caused by Neogene subduction and collision of another continental fragment further to the east.

Prograde and retrograde evolution of eclogites from the Bantimala Complex in South Sulawesi, Indonesia

“…1a). The study area (South Sulawesi) predominantly comprises sandstone, shale, chert, basalt, dunite, lherzolite, serpentinite, and various metamorphic rocks ranging from low grade to eclogite-facies conditions (Sukamto, 1982;Wakita et al, 1994Wakita et al, , 1996Miyazaki et al, 1996;Parkinson et al, 1998) (Fig. 1b).…”

“…1b). The Bantimala Complex is a tectonic stack of slices mainly consisting of various sedimentary rocks, ultramafic rocks, metabasites, and metapelites with ages ranging from Jurassic to middle Cretaceous (Sukamto, 1982;Wakita et al, 1994Wakita et al, , 1996Miyazaki et al, 1996;Parkinson et al, 1998). The metamorphic rocks mainly occur within a mélange unit.…”

“…Hatched areas represent the inferred P-T conditions for the oceanic crust beneath present-day NE Japan (cold) and SW Japan (warm) subduction zones (Peacock and Wang, 1999). kinson et al, 1998) and Bantimala Complexes (113-137 Ma: Wakita et al, 1994Wakita et al, , 1996Parkinson et al, 1998). As a consequence, there are two possibilities for the subduction system in these complexes: (1) the Bantimala and Luk Ulo Complexes might be derived from different subduction complexes, similar to the NE and SW Japan subduction system, or (2) the Bantimala and Luk Ulo Complexes are derived from a single subduction system, as proposed by Hamilton (1979), Parkinson et al (1998), and Kadarusman et al (2007), and experienced metamorphic evolution as a result of increasing/decreasing geothermal gradients during continuous subduction.…”

Early Cretaceous Radiolarians in Manganese Carbonate Nodule From the Barru Area, South Sulawesi, Indonesia.

“…The complex is believed to be equivalent and has been named the Bantimala Tectonic Complex (Sukamto, 1982 Previously, Wakita et al (1994bWakita et al ( , 1996 reported middle Cretaceous (Albian to Cenomanian = 108 -92 Ma) radiolarians extracted from chert and siliceous shale of the Bantimala Complex. The two differences that related on radiolarian occurrence in the Barru Complex and the Bantimala Complex are radiolarians age and radiolarian-bearing rocks.…”

“…Of the two exposures, the larger (Bantimala Complex) is the better known. The detailed geology of the Bantimala Complex has been investigated by Sukamto (1975Sukamto ( , 1978Sukamto ( , 1982Sukamto ( , 1986, Hasan (1991) and Wakita et al (1994bWakita et al ( , 1996. Sukamto (1982) established that the older rocks, which unconformably overlain by Late Cretaceous Balangbaru Formation -flysch type sedimentary rocks, as a mass named the Bantimala Tectonic Complex.…”