Publications

Amalgamation and dispersion of terranes characterized the growth and slivering of Southeast Sundaland into the present configuration of central Indonesia. Amalgamation of the Paternoster-West Sulawesi terrane which docked, in mid-Cretaceous time, onto the Southwest Borneo terrane, thus closed the Meso-Tethys Ocean at the Meratus suture. This made Sundaland expand its area to the east and southeast. In the Late Cretaceous time, the Ceno-Tethys oceanic plate subducted beneath Southeast Sundaland, giving rise to coeval volcanism in the Meratus Mountains and the surrounding areas. Dispersion of some terranes in Southeast Sundaland occurred in the Paleogene through successive rifting and the opening of the Makassar Straits and the Flores Sea, with an eastern drift of South Sulawesi and Sumba away from Southeast Kalimantan to their present positions. Prior to the dispersion, the Meratus Mountains, South Sulawesi, and Sumba (called here the Trilogy of Southeast Sundaland) were united or adjacent to each other and underwent similar Late Cretaceous volcanism. The Late Cretaceous Volcanics and/or Volcanic-Clastics are therefore the common marker of their union. Our field studies in 2018-2019 at Sumba, South Sulawesi, and the Meratus Mountains (South Kalimantan) in the program, called the “Trilogy of Southeast Sundaland Terranes,” sampled the Late Cretaceous volcanics/ volcanic-clastics in these areas to prove that they were once united. Petrographic, petrochemical, isotopic, and geochronological data of the rock formations, based on the recent and previous analyses, show that these rocks, in the three terranes, are co-genetic spatially and temporally thus indicating their previous unity. The paired Paleogene dispersions of South Sulawesi from South Kalimantan, and successively Sumba from South Sulawesi, had resulted in rifted structures in the present Makassar Straits, the Flores Sea, and offshore Sumba. The rifted structures contain source rocks, reservoirs, seals, and structural-stratigraphic traps. Oil has been discovered therein, so further exploration is required since these objectives have not been sufficiently explored in the past and are thus still interesting.