Magmatism in western Indonesia, the trapping of the Sumba Block and the gateways to the east of Sundaland

Abstract

The western Sulawesi magmatic belt and the Sunda–Banda arc define the eastern and south-eastern margins of Sundaland, which is part of the relatively stable Eurasian plate. The eastern margin is bounded by the Makassar Strait which separates western Sulawesi from Kalimantan. The initial opening of the Makassar Strait took place in the late Cretaceous–Early Tertiary leading to the opening of the Pacific–Indian Ocean gateway during Neogene time. Recent studies indicate similarities in the late Cretaceous–Paleogene stratigraphic sequence and calc-alkali magmatism between Sumba, south Sulawesi and south-east Kalimantan, suggesting a Sundaland origin for all of these areas. The southward migration of Sumba to the present frontal arc position of the Sunda–Banda arc has occurred since Late Cretaceous–Paleocene time.