Stratigraphy and tectonic setting of the Cretaceous and Paleogene volcanic-sedimentary successions in northwest Sulawesi, Indonesia: implications for the Cenozoic evolution of Western and Northern Sulawesi

Abstract

New field and laboratory data from NW Sulawesi, Indonesia, integrated with existing information, provide a tectonostratigraphic framework for the Cretaceous and Paleogene of this region. The study area straddles two distinct provinces, referred to as ‘Western’ and ‘Northern Sulawesi’. Western Sulawesi forms the (rifted) continental margin of eastern Sundaland. It consists of a metamorphic basement, partly of Australian origin, overlain by Late Cretaceous turbidites that were deposited in a fore-arc setting (Latimojong Formation). These are in turn covered by volcanic-sedimentary successions that were deposited during the early Middle Eocene to earliest Miocene. They represent a transgressive cycle from syn-rift siliciclastics, through nummulitic limestone and associated shelf sediments, to deeper marine mudstones and turbidites (Budungbudung and Tinombo Formations). During the same period Northern Sulawesi developed as an oceanic island arc, characterized by bimodal volcanism (Papayato Volcanics), founded on (back arc?) oceanic crust. The Cretaceous and Paleogene volcanic and sedimentary suites show lithological and geochemical characteristics that reflect the contrasting tectonic setting of the two provinces. The tectonic relationship between the two domains is not clear. They probably formed a more or less continuous belt throughout the Cenozoic, but were definitely connected not later than the early Miocene. Strong deformation in the Paleogene formations in the northern part of NW Sulawesi and their unconformable relationship with the overlying formations may be the result of the collision of the north arm of Sulawesi with a continental fragment, of Australian derivation, during the early Miocene, or it may be related to the formation of a metamorphic core complex in a mid-Miocene extensional tectonic setting. A second major tectonic event, which commenced in the Pliocene and is still ongoing, affected the entire region.