Neogene sediment provenance and paleogeography of SE Sulawesi, Indonesia

Neogene syn-and post-orogenic sedimentary rocks in Sulawesi are important to understand the history of collision of Australian continental crust with SE Asia. However, they have received relatively little attention, and have generally been considered to be molasse-type deposits of similar characteristics across Sulawesi—the Celebes Molasse. New field sedimentological observations, results from heavy mineral studies and detrital zircon U–Pb geochronology, together with conventional sandstone petrography identify three important provenance shifts, that can be correlated with significant tectonic events and enable the reconstruction of the Neogene palaeogeography of SE Sulawesi. The first provenance shift was related to the Early Miocene collision of Australian crust and the North Sulawesi volcanic arc, accompanied by ophiolite emplacement in East Sulawesi, marked by a change from pre-collision carbonates to ultramafic-rich clastics of the Bungku Formation. A second change in the Late Miocene was marked by input of abundant metamorphic detritus including blueschists into the Pandua Formation indicating exhumation of Oligo-Miocene subduction zone material. The third provenance change, of Mio-Pliocene age, was from the ophiolite- and blueschist-rich Pandua Formation to the quartz-rich Langkowala Formation, and records blocking of the ophiolite debris pathways by the rise and progressive unroofing of low- to high-grade metamorphic rocks. The Neogene sedimentary rocks of SE Sulawesi record Early Miocene collision and ophiolite emplacement, followed by extension which led to exhumation of Mesozoic and metamorphic rocks, driven by Banda subduction rollback.Nanyang Technological UniversityPublished versionThis project was funded by the SE Asia Research Group of Royal Holloway University of London, Earth Observatory of Singapore, Nanyang Technological University, which is supported by a consortium of oil companies

The Celebes Molasse: a revised Neogene stratigraphy for Sulawesi, Indonesia

Over the past century, a wide variety of poorly dated sediments that unconformably overlie pre-Neogene rocks in Sulawesi have been assigned to the Celebes Molasse and interpreted as post-orogenic rocks deposited after a major collision. New data from fieldwork and laboratory studies, including mineralogical, palaeontological and zircon geochronological analyses, provide the basis for a new Neogene stratigraphy and show that sediments assigned to the Celebes Molasse have significant variations in age, environment of deposition, composition and sedimentation history. Identified unconformities in the (1) Early Miocene (c. 23 Ma), (2) Middle Miocene (c. 15 Ma), (3) Mio-Pliocene (c. 6–5.3 Ma), and (4 and 5) Pleistocene (c. 1.8 and 0.1 Ma) separate Lower Miocene, Middle to Upper Miocene, Pliocene, Pleistocene and Holocene mega-sequences. These mega-sequences resulted from Early Miocene collision followed by extension, driven by subduction rollback, causing both uplift and subsidence, in contrast to previous interpretations of multiple collisions.Nanyang Technological UniversityPublished versionThis research was a project of the SE Asia Research Group (SEARG) supported by a consortium of oil companies who funded the PhD of the first author. This research was supported by the Earth Observatory of Singapore and comprises EOS contribution number 381

Plio-Pleistocene sedimentation and palaeogeographic reconstruction in the Poso Depression, Central Sulawesi, Indonesia: from a sea channel to a land bridge

The Poso Depression provides a record of Plio-Pleistocene environments and palaeogeography of Central Sulawesi. Outcrop-based sedimentological and provenance studies suggest that during the Pliocene the Poso Depression was a sea channel connecting Gorontalo and Bone bays formed in an asymmetric half-graben. The Pliocene history began with deposition of the Puna Formation with fan deltas at the eastern basin margin and channel complexes in the deep-water basin further east. Analyses of light and heavy minerals indicate the main sediment source was ultrabasic rocks in East Sulawesi with minor and intermittent magmatic and metamorphic input from West Sulawesi. Later, in the Middle to Late Pliocene, carbonates of the Poso Formation accumulated on the eastern basin margin. They are unconformably overlain by shallow marine glaucophane-rich siliciclastics of the Pleistocene Lage Formation that are associated with the rapid exhumation and uplift of the Pompangeo metamorphic complex. This uplift led to the development of a land bridge connecting western and eastern Sulawesi. The terrane evolution favoured increasing the area of exposed land due to rapid tectonic uplift, which when combined with the tropical climate, contributed to faunal speciation and dispersal in Sulawesi.Nanyang Technological UniversityPublished versionThis study was supported by the SE Asia Research Group of Royal Holloway University of London, United Kingdom, which is backed by a consortium of oil companies. This research was also supported by the Earth Observatory of Singapore (EOS), Singapore and comprises EOS contribution number 508

Neogene history of fluvial to shallow marine successions in the Kendari Basin, SE Sulawesi, Indonesia

Abstract Collision between Australia and SE Asia began in Sulawesi, the world's eleventh‐largest island, in the Early Miocene and subsequently Neogene sediments were deposited largely in coastal to shelf environments throughout the island. These sediments have been assigned to the Celebes Molasse, previously considered as a single post‐orogenic unit deposited unconformably on pre‐Neogene sedimentary, metamorphic and ophiolitic rocks. The most complete and extensive sequences of Neogene sediments are in the Kendari Basin, situated at the southern end of the SE Arm of Sulawesi, where an outcrop‐based sedimentological study was undertaken to interpret depositional environments, palaeogeography and stratigraphy. The oldest Neogene sediments are shallow marine carbonates and deltaic siliciclastics of the Bungku Formation. They are unconformably overlain by the Upper Miocene Pandua Formation which consists of sediments deposited in a variety of environments including braided river channels, fluvio‐tidal channels, tidal flats, mouth bar complex and shoreface deposits. A Mio‐Pliocene subaerial unconformity separates the marginal marine serpentinite‐rich sediments of the Pandua Formation from the overlying fluviatile quartz‐rich Langkowala Formation. The sediments of the lower part of the Langkowala Formation include conglomeratic channel fill, while the sediments of the upper part are transgressive deposits decreasing in maximum grain‐size, marked by a reduction in channel/overbank ratio and increasing tidal influence. The transgressive Pliocene Eemoiko Formation is characterised by transgressive lags or onlap shell beds and deposits of a landwards‐backstepping carbonate platform. The improved understanding of the Kendari Basin will aid the interpretation of the sedimentation history of frontier basins surrounding SE Sulawesi, many of which have not yet been drilled

Detrital zircon and heavy mineral provenance from the Palu Formation, Sulawesi, Indonesia: constraints on exhumation of the Palu Metamorphic Complex and drainage evolution

Supplementary File 1. Observation locations

Detrital zircon and heavy mineral provenance from the Palu Formation, Sulawesi, Indonesia: constraints on exhumation of the Palu Metamorphic Complex and drainage evolution

Supplementary File 3. Data table for LA-ICP-MS U-Pb zircon analysis and zircon morphology observation of sample ES13-255 (Palu Formation)

Detrital zircon and heavy mineral provenance from the Palu Formation, Sulawesi, Indonesia: constraints on exhumation of the Palu Metamorphic Complex and drainage evolution

Supplementary File 2. Heavy mineral point counting

Data from: Synchronous diversification of Sulawesi's iconic artiodactyls driven by recent geological events

The high degree of endemism on Sulawesi has previously been suggested to have vicariant origins, dating back 40 Myr ago. Recent studies, however, suggest that much of Sulawesi’s fauna assembled over the last 15 Myr. Here, we test the hypothesis that more recent uplift of previously submerged portions of land on Sulawesi promoted diversification, and that much of its faunal assemblage is much younger than the island itself. To do so, we combined palaeogeographical reconstructions with genetic and morphometric data sets derived from Sulawesi’s three largest mammals: the Babirusa, Anoa, and Sulawesi warty pig. Our results indicate that although these species most likely colonized the area that is now Sulawesi at different times (14 Myr ago to 2-3 Myr ago), they experienced an almost synchronous expansion from the central part of the island. Geological reconstructions indicate that this area was above sea level for most of the last 4 Myr, unlike most parts of the island. We conclude that emergence of land on Sulawesi (~1–2 Myr) may have allowed species to expand synchronously. Altogether, our results indicate that the establishment of the highly endemic faunal assemblage on Sulawesi was driven by geological events over the last few million years

Materials and Methods, Supplementary Tables and Supplementary Figures from Synchronous diversification of Sulawesi's iconic artiodactyls driven by recent geological events

The high degree of endemism on Sulawesi has previously been suggested to have vicariant origins, dating back 40 Ma. Recent studies, however, suggest that much of Sulawesi's fauna assembled over the last 15 Myr. Here, we test the hypothesis that more recent uplift of previously submerged portions of land on Sulawesi promoted diversification and that much of its faunal assemblage is much younger than the island itself. To do so, we combined palaeogeographical reconstructions with genetic and morphometric datasets derived from Sulawesi's three largest mammals: the Babirusa, Anoa and Sulawesi warty pig. Our results indicate that although these species most likely colonized the area that is now Sulawesi at different times (14 Ma to 2–3 Ma), they experienced an almost synchronous expansion from the central part of the island. Geological reconstructions indicate that this area was above sea level for most of the last 4 Myr, unlike most parts of the island. We conclude that emergence of land on Sulawesi (approx. 1–2 Myr) may have allowed species to expand synchronously. Altogether, our results indicate that the establishment of the highly endemic faunal assemblage on Sulawesi was driven by geological events over the last few million years