Abstract The Makassar Strait is an important oceanic gateway, through which the main branch of the Indonesian Throughflow (ITF) transports water from the Pacific to the Indian Ocean. This study identifies a number of moderate (>10 km 3 ) to giant (up to 650 km 3 ) mass transport deposits within the Makassar North Basin Pleistocene–Recent section. The majority of submarine landslides that formed these deposits originated from the Mahakam pro-delta, with the largest skewed to the south. We see clear evidence for ocean-current erosion, lateral transport and contourite deposition across the upper slope. This suggests that the ITF is acting as an along-slope conveyor belt, transporting sediment to the south of the delta, where rapid sedimentation rates and slope oversteepening results in recurring submarine landslides. A frequency for the >100 km 3 failures is tentatively proposed at 0.5 Ma, with smaller events occurring at least every 160 ka. This area is therefore potentially prone to tsunamis generated from these submarine landslides. We identify a disparity between historical fault rupture-triggered tsunamis (located along the Palu-Koro fault zone) and the distribution of mass transport deposits in the subsurface. If these newly identified mass failures are tsunamigenic, they may represent a previously overlooked hazard in the region.

Abstract The Indonesian Throughflow (ITF) transfers c . 15 Sv (1 Sv=10 6 m 3 s −1 ) of relatively cool, fresh water from the tropical Pacific Ocean to the tropical Indian Ocean. Additionally, the ITF is a key interocean component of the global ocean warm water route, which returns water from the Pacific Ocean to the Atlantic Ocean to close the loop of the thermohaline overturning circulation associated with North Atlantic Deep Water. That flow consequently freshens the Indian Ocean and transports heat between basins. The ITF can also be described by the island rule, which relates the winds over the entire South Pacific Ocean to the magnitude of the ITF. El Niño-Southern Oscillation (ENSO) dominates the regional variability in the Pacific Ocean and exerts a strong control over the variability of ITF transport. The Indian Ocean responds to the ENSO signal as well, but is also influenced by the Indian Ocean Dipole, a climate phenomenon that may act independently of ENSO to affect the ITF.

Abstract The transfer of surface and intermediate water from the Pacific to Indian Ocean through the Indonesian passages (Indonesian Throughflow: ITF) strongly influences the heat and freshwater budgets of tropical water masses, in turn affecting global climate. Here, we use combined δ 18 O and Mg/Ca analyses of surface and thermocline planktonic foraminifers to estimate variations in sea surface temperature, salinity and mixed layer thickness over the last 140 ka. Comparison of water mass properties reveals a steeper thermocline temperature gradient in the Timor Strait than in the eastern Indian Ocean during glacials, implying a decrease in ITF cool thermocline outflow. A major freshening and cooling of thermocline waters occurred at c . 9.5 ka, when sea level rose above a critical threshold, allowing establishment of a shallow marine connection from the South China Sea to the Java Sea. Comparison of benthic δ 13 C profiles ( c . 1800 to 3000 m water depth) suggests vigorous mixing of Indian Ocean and ITF outflow intermediate waters during interglacials. In contrast, deep and intermediate water masses became more stratified during glacials. Lower δ 13 C values at c . 3000 m water depth reflect a decrease in deepwater ventilation, probably related to slowdown of the global thermohaline circulation during glacials.

Abstract Collision between Australia and SE Asia began in the Early Miocene and reduced the former wide ocean between them to a complex passage which connects the Pacific and Indian Oceans. Today, the Indonesian Throughflow passes through this gateway and plays an important role in global thermohaline flow. The surrounding region contains the maximum global diversity for many marine and terrestrial organisms. Reconstruction of this geologically complex region is essential for understanding its role in oceanic and atmospheric circulation, climate impacts, and the origin of its biodiversity. The papers in this volume discuss the Palaeozoic to Cenozoic geological background to Australia and SE Asia collision. They provide the background for accounts of the modern Indonesian Throughflow and oceanographic changes since the Neogene, and consider aspects of the region’s climate history.

The Subis Platform is considered one of the very few outcrops in Malaysia which records remarkable changes in the growth history of a carbonate system. The Subis Platform is located near Batu Niah, Sarawak. Stratigraphically, the Subis Platform is named the Subis Limestone, a member of the Tangap Formation. This article discusses the older succession of the Subis Limestone at the Subis-2 well and the Hollystone Quarry. Both well and outcrop indicate a slightly older succession based on the occurrence of larger benthic foraminifera and calcareous nannofossils. The age of the Subis Limestone ranges from Oligocene to Miocene, based on the occurrence of the larger benthic foraminifera Miogypsinoides sp. (late Oligocene, Te4) and Miogypsina sp. (early Miocene, Te5), as well as on the calcareous nannofossils Sphenolithus capricornutus and Sphenolithus conicus (Te4). The boundary between the late Oligocene and the early Miocene coincides with a sharp change from foraminifera-dominated facies to coral-dominated facies, shown at the Hollystone Quarry. The Subis Limestone records a transgression event from mixed siliciclastic–carbonate (Subis-2 well) to clean biohermal carbonates as shown in the outcrops of the Subis quarries. Our findings on the Oligo–Miocene boundary were then compared with those from other carbonates around Southeast Asia. It is clear that coral reefs existed in Southeast Asia earlier than was first thought, by Oligocene times. The role of localized tectonic events, siliciclastic influx, oceanic mineralization, and Indonesian Throughflow are the main controls to determine the biota changes from foraminifera to coral-dominated facies.

Abstract The opening and constriction of oceanic gateways played an essential role in shaping the global climate throughout Earth's history. In this review, we provide an overview of the best-documented feedbacks between gateway dynamics and climate change throughout the Cenozoic. The discussed tectonically induced events comprise: (i) the opening of the Tasmanian Gateway and the glaciation of Antarctica during the Eocene–Oligocene; (ii) the water-mass exchange between the Atlantic and the Mediterranean via the Strait of Gibraltar that has occurred since the Miocene; and (iii) the closure of the American Seaway and (iv) the constriction of the Indonesian Throughflow, both argued to have been instrumental in the intensification of Northern Hemisphere Glaciation during the late Pliocene and early Pleistocene. Lastly, we look at (v) the climatic impact of the flooding and submergence of the Bering Strait during the Plio-Pleistocene and its influence on the Atlantic Meridional Overturning Circulation. While different in their underlying mechanisms, geographical scale and temporal evolution, these case studies demonstrate that even seemingly small-scale changes in the configuration of ocean seaways fundamentally altered the global climate system via their impact on oceanic currents, global heat transfer and carbon storage.

Abstract The SE Asian gateway is the connection from the Pacific to the Indian Ocean and it has diminished from a wide ocean to a complex narrow passage with deep barriers ( Gordon et al. 2003 ) as plate movements caused Australia to collide with SE Asia. It is one of several major ocean passages that existed during the Cenozoic but has received much less attention than others that opened, such as the Drake Passage, Tasman Gateway, Arctic Gateway or Bering Straits, or that closed, such as the Panama Gateway or Tethyan Gateway (e.g. von der Heydt & Dijkstra 2006 ; Lyle et al. 2007 , 2008 ). It is not entirely clear why there has been this comparative neglect, but it may reflect the relative limited knowledge of the large and remote areas of Indonesia and the western Pacific, in particular their geological history, and the relatively small number of active researchers in this large region. Unlike the Panama Gateway and Tethyan Gateway the SE Asian gateway is still partly open and the ocean currents that flow between the Pacific and Indian Oceans have been the subject of much recent work by oceanographers (e.g. Gordon 2005 ). We now know that the Indonesian Throughflow, the name given to the waters that pass through the only remaining low latitude oceanic passage on the Earth, plays an important role in Indo-Pacific and global thermohaline flow ( Gordon 1986 ; Godfrey 1996 ), and it is therefore probable

Abstract The fundamental processes and controls on carbonate deposition are well established. These include: water depth, temperature, salinity, clarity, and an abundance of sunlight, all of which control rates of growth among the biota while wave and current energy ensure a steady supply of nutrients. The aragonite-dominated systems of the tropical latitudes gave way to calcite dominance in higher latitudes. Mud-rich tidal-flat sequences characterize the Bahamian and Persian Gulf settings, while mud-free systems dominate the higher-energy settings of the Great Barrier Reef and cooler-water environments. With the inclusion of recently documented Lophelia “reef mounds” in deep arctic waters, together with studies of deep-water pelagic limestones, the globalization of carbonates was nearly complete - almost. One part of the global distribution pattern remains understudied and underappreciated, namely the equatorial belt. In old mariner terminology this latitudinal belt is known as the doldrums, notorious for its unpredictable calms and seasonal monsoon shifts in the wind and surface currents. In recent years, the Indonesia - Philippines archipelago has received particular attention from oceanographers and climatologists in recognition and growing awareness of the role of El Nino Southern Oscillation (ENSO) and the Indonesian Throughflow (ITF) and its relation to upwelling and changes in sea-surface temperature (SST), resulting in widespread reef death throughout the region. The archipelago straddles the equator and lies squarely within this equatorial belt. Average sea-water temperatures are ∼ 28–30°C, and salinities are much lower than normal, ∼< 32–34%. These values test the tolerance limits of many reef community members, hence their susceptibility to El Niño events. Collision tectonics has defined the structural style, geography, and hydrography of the archipelago since the earliest Tertiary and has profoundly influenced modern and Cenozoic depositional systems. Shifts in relative sea level are frequent and often dramatic, affecting not only depositional patterns but also diagenesis, with repeated subaerial and flooding events. The symmetry of the seasonal shifts introduces a bimodal pattern while the energy of the system reduces mud accumulation on the shallow platforms. Nearshore fringing reefs are limited by the high clastic discharge associated with high rainfall and landform topography. Coastal plains are clastic dominated, with mangrove swamp peats replacing the microbial mats that typify large tracts of the Bahamian and Persian Gulf platform settings. Thus, the region offers an excellent opportunity to study modern and ancient carbonate systems under this particular climatic and, perhaps just as importantly, tectonic setting. That almost half of Indonesia’s hydrocarbon reserves and production derive from these same Cenozoic carbonates provides additional reason for further study.