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The late Miocene was a period of declining CO2 levels and extensive environmental changes, which likely had a large impact on monsoon strength as well as on the weathering and erosion intensity in the South Asian Monsoon domain. To improve our understanding of these feedback systems, detrital clays from the southern Bay of Bengal (International Ocean Discovery Program Site U1443) were analyzed for the radiogenic isotope compositions of Sr, Nd, and Pb to reconstruct changes in sediment provenance and weathering regime related to South Asian Monsoon rainfall from 9 to 5 Ma. The 100 kyr resolution late Miocene to earliest Pliocene record suggests overall low variability in the provenance of clays deposited on the Ninetyeast Ridge. However, at 7.3 Ma, Nd and Pb isotope compositions indicate a switch to an increased relative contribution from the Irrawaddy River (by ∼10%). This shift occurred during the global benthic δ13C decline, and we suggest that global cooling and increasing aridity resulted in an eastward shift of precipitation patterns leading to a more focused erosion of the Indo‐Burman Ranges. Sr isotope compositions were decoupled from Nd and Pb isotope signatures and became more radiogenic between 6 and 5 Ma. Grassland expansion generating thick, easily weatherable soils may have led to an environment supporting intense chemical weathering, which is likely responsible for the elevated detrital clay 87Sr/86Sr ratios during this time. This change in Sr isotope signatures may also have contributed to the late Miocene increase of the global seawater Sr isotope composition., Plain Language Summary: The South Asian or Indian monsoon affects the lives of billions. Through the erosion and weathering of rocks, the monsoon also has the potential to remove carbon dioxide from the atmosphere through increased weathering in the region including the Himalaya Mountains. The late Miocene, between 9 and 5 million years ago, was a period of global cooling and proliferation of grasslands in different regions including South Asia. Here, we examine the composition of clays formed by rock weathering during the late Miocene to determine their source region around the Bay of Bengal. The results suggest a generally stable mixture of sources with the strongest sources being regions with the highest monsoon rainfall today. We identify slight changes in the mixture of sources, which accompany a global change in carbon cycling, highlighting the role monsoon climate likely played in these changes. Toward the end of the Miocene, we identify a change in the Sr isotopes, which was not caused by source changes but by the strength of the rock weathering. This change has been observed in global records and it seems likely that it was driven by rock weathering in the South Asian Monsoon region., Highlights: Radiogenic isotope compositions of detrital clays from the Bay of Bengal indicate a generally stable provenance from 9 to 5 Ma. A step change in Nd and Pb isotope compositions at ∼7.3 Ma reflects a climatically driven eastward shift in precipitation patterns resulting in enhanced erosion of the Indo‐Burman Ranges. Elevated 87Sr/86Sr between 6 and 5 Ma was likely related to increased chemical weathering caused by thicker soils and by C4 plant expansion., DFG, ANR, IODP

Oceanic anoxic events (OAEs) document major perturbations of the global carbon cycle with repercussions for the Earth's climate and ocean circulation that are relevant to understanding future climate trends. Here, we compare the onset and development of Cretaceous OAE1a and OAE2 in two drill cores with unusually high sedimentation rates from the Vocontian Basin (southern France) and Tarfaya Basin (southern Morocco). OAE1a and OAE2 exhibit remarkable similarities in the evolution of their carbon isotope (δ13C) records, with long-lasting negative excursions preceding the onset of the main positive excursions, supporting the view that both OAEs were triggered by massive emissions of volcanic CO2 into the atmosphere. However, there are substantial differences, notably in the durations of individual phases within the δ13C positive excursions of both OAEs. Based on analysis of cyclic sediment variations, we estimate the duration of individual phases within OAE1a and OAE2. We identify (1) a precursor phase (negative excursion) lasting ∼430 kyr for OAE1a and ∼130 kyr for OAE2, (2) an onset phase of ∼390 and ∼70 kyr, (3) a peak phase of ∼600 and ∼90 kyr, (4) a plateau phase of ∼1340 and ∼200 kyr, and (5) a recovery phase of ∼380 and ∼440 kyr. The total duration of the positive δ13C excursion is estimated at 2700 kyr for OAE1a and 790 kyr for OAE2, and that of the main carbon accumulation phase is estimated at 980 and 180 kyr. The long-lasting peak, plateau and recovery phases imply fundamental changes in global nutrient cycles either (1) by submarine basalt–seawater interactions, (2) through excess nutrient inputs to the oceans by increasing continental weathering and river discharge, or (3) through nutrient recycling from the marine sediment reservoir. We investigated the role of phosphorus in the development of carbon accumulation by analysing phosphorus speciation across OAE2 and the mid-Cenomanian Event (MCE) in the Tarfaya Basin. The ratios of organic carbon and total nitrogen to reactive phosphorus (Corg∕Preact and Ntotal∕Preact) prior to OAE2 and the MCE hover close to or below the Redfield ratio characteristic of marine organic matter. Decreases in reactive phosphorus resulting in Corg∕Preact and Ntotal∕Preact above the Redfield ratio during the later phase of OAE2 and the MCE indicate leakage from the sedimentary column into the water column under the influence of intensified and expanded oxygen minimum zones. These results suggest that a positive feedback loop, rooted in the benthic phosphorus cycle, contributed to increased marine productivity and carbon burial over an extended period of time during OAEs.

Tectonics and regional monsoon strength control weathering and erosion regimes of the watersheds feeding into the Bay of Bengal, which are important contributors to global climate evolution via carbon cycle feedbacks. The detailed mechanisms controlling the input of terrigenous clay to the Bay of Bengal on tectonic to orbital timescales are, however, not yet well understood. We produced orbital‐scale resolution geochemical records for International Ocean Discovery Program Site U1443 (southern Bay of Bengal) across five key climatic intervals of the middle to late Miocene (15.8–9.5 Ma). Our new radiogenic Sr, Nd, and Pb isotope time series of clays transported to the Ninetyeast Ridge suggest that the individual contributions from different erosional sources overall remained remarkably consistent during the Miocene despite major tectonic reorganizations in the Himalayas. On orbital timescales, however, high‐resolution data from the five investigated intervals show marked fluctuations of all three isotope systems. Interestingly, the variability was much higher within the Miocene Climatic Optimum (around 16–15 Ma) and across the major global cooling (~13.9–13.8 Ma) until ~13.5 Ma, than during younger time intervals. This change is attributed to a major restriction on the supply of High Himalayan erosion products due to migration of the peak precipitation area toward the frontal domains of the Himalayas and the Indo‐Burman Ranges. The transient excursions of the radiogenic isotope signals on orbital timescales most likely reflect climatically driven shifts in monsoon strength., Key Points: A consistent mix of clay sources contributed to the Bay of Bengal throughout the middle to late Miocene A marked change in detrital Sr, Nd, and Pb isotope variability at 13.5 Ma was related to Miocene global cooling Transient orbital‐scale fluctuations in clay source most likely reflect changes in monsoon intensity, Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659

Across the Miocene–Pliocene boundary (MPB; 5.3 million years ago, Ma), late Miocene cooling gave way to the early-to-middle Pliocene Warm Period. This transition, across which atmospheric CO2 concentrations increased to levels similar to present, holds potential for deciphering regional climate responses in Asia—currently home to more than half of the world’s population— to global climate change. Here we find that CO2-induced MPB warming both increased summer monsoon moisture transport over East Asia, and enhanced aridification over large parts of Central Asia by increasing evaporation, based on integration of our ~1–2-thousand-year (kyr) resolution summer monsoon records from the Chinese Loess Plateau aeolian red clay with existing terrestrial records, land-sea correlations, and climate model simulations. Our results offer palaeoclimate-based support for ‘wet-gets-wetter and dry-gets-drier’ projections of future regional hydroclimate responses to sustained anthropogenic forcing. Moreover, our high-resolution monsoon records reveal a dynamic response to eccentricity modulation of solar insolation, with predominant 405-kyr and ~100-kyr periodicities between 8.1 and 3.4 Ma., Global warming drove ‘wet gets wetter and dry gets drier’ climate shifts in Asia ~5.3 million years ago with monsoon pacing by ~400,000 and ~ 100,000 year cycles. This could be a template for future Asian climate response to anthropogenic warming.

Much of our understanding of Earth's past climate comes from the measurement of oxygen and carbon isotope variations in deep-sea benthic foraminifera. Yet, long intervals in existing records lack the temporal resolution and age control needed to thoroughly categorize climate states of the Cenozoic era and to study their dynamics. Here, we present a new, highly resolved, astronomically dated, continuous composite of benthic foraminifer isotope records developed in our laboratories. Four climate states-Hothouse, Warmhouse, Coolhouse, Icehouse-are identified on the basis of their distinctive response to astronomical forcing depending on greenhouse gas concentrations and polar ice sheet volume. Statistical analysis of the nonlinear behavior encoded in our record reveals the key role that polar ice volume plays in the predictability of Cenozoic climate dynamics.

Test geochemistry of planktonic foraminifera is an indispensable tool in reconstructing past ocean hydrological changes. It is essential to investigate region-specific implications of test geochemistry, although those established from other regions can be broadly applied. In this study, characteristics of δ18O and Mg/Ca from tests of four planktonic foraminiferal species, Globigerinoides ruber sensu stricto (s.s.), Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neogloboquadrina dutertrei, from 60 core-top sediment samples retrieved from the Indonesian Throughflow (ITF) region were studied. These geochemical data were compared with modern hydrographic profiles in order to assess their relations and to investigate potential implications of test geochemical parameters in reconstructing past oceanographic change in the ITF region. Calcification depths of these four species were first estimated based on comparison between measured test δ18O and predicted calcite δ18O that was calculated from modern temperature and salinity. The results indicate that G. ruber s.s. and G. sacculifer calcify within the mixed-layer at 0–50 m and 20–75 m, respectively, whereas P. obliquiloculata and N. dutertrei calcify within the thermocline at around 75 to 125 m. A combined study of excess Mg/Ca (difference between measured and predicted Mg/Ca) and salinity suggests that salinity exerts a negligible impact on test Mg/Ca of these foraminiferal species in the ITF region. Comparison of test Mg/Ca-derived temperatures with temperature profiles of the upper 200 m of the water column from the seas of the ITF region also indicate calcification depths of these species, which match well with the above estimations using test δ18O. It further indicates that G. sacculifer may be more sensitive in reflecting changes in the depth of the mixed-layer, highlighting a potential use of Mg/Ca temperature difference between G. ruber s.s. and G. sacculifer in reconstructing the depth of the mixed-layer in the ITF region. Keywords: Test geochemistry, Multi-species, Planktonic foraminifera, Core-top sediments, Indonesian Throughflow region

The Miocene epoch (23.03–5.33 Ma) was a time interval of global warmth, relative to today. Continental configurations and mountain topography transitioned toward modern conditions, and many flora and fauna evolved into the same taxa that exist today. Miocene climate was dynamic: long periods of early and late glaciation bracketed a ∼2 Myr greenhouse interval—the Miocene Climatic Optimum (MCO). Floras, faunas, ice sheets, precipitation, pCO2, and ocean and atmospheric circulation mostly (but not ubiquitously) covaried with these large changes in climate. With higher temperatures and moderately higher pCO2 (∼400–600 ppm), the MCO has been suggested as a particularly appropriate analog for future climate scenarios, and for assessing the predictive accuracy of numerical climate models—the same models that are used to simulate future climate. Yet, Miocene conditions have proved difficult to reconcile with models. This implies either missing positive feedbacks in the models, a lack of knowledge of past climate forcings, or the need for re-interpretation of proxies, which might mitigate the model-data discrepancy. Our understanding of Miocene climatic, biogeochemical, and oceanic changes on broad spatial and temporal scales is still developing. New records documenting the physical, chemical, and biotic aspects of the Earth system are emerging, and together provide a more comprehensive understanding of this important time interval. Here, we review the state-of-the-art in Miocene climate, ocean circulation, biogeochemical cycling, ice sheet dynamics, and biotic adaptation research as inferred through proxy observations and modeling studies. The initial workshops that catalyzed this project were supported by The Bolin Center for Climate Research, Stockholm University, and the Swedish Research Council (Conference Grant nr. 2018–06,618 to M. Steinthorsdottir). The authors acknowledge funding from: the Swedish Research Council (VR starting grant nr. NT7-2016 04,905 to M. Steinthorsdottir; VR grants nr. 2016–03,912 to A. M. de Boer and nr. 2016–04,434 to J. Henderiks); the United States National Science Foundation (NSF), through the P2C2 program grant nr. 1602905 to M. Huber, the Atmospheric and Geospace Sciences program grant nr. to N.J.B (who is also supported by the Alfred P. Sloan Foundation as a Research Fellow), and the Global Change, Sedimentary Geology & Paleobiology, and Geobiology and Low-temperature Geochemistry programs grant nrs. 1349749 and1561027 to M. J. Kohn; and the UK Natural Environment Research Council (grant NE/P019102) to C. H. Lear. E. Gasson acknowledges funding from a Royal Society fellowship. Clara Bolton, Peter Bijl, Daniel Breecker, Jeremy Caves Rugenstein, Florence Collioni, Mikael Fortelius, David Lazarus, Eelco Rohling, Francesca Sangiorgi, Maria Seton, Erik Skovbjerg Rasmussen, Appy Sluijs, Lars Werdelin, and Zhongshi Zhang are thanked for their useful comments with respect to Figure 1. M. Huber acknowledges assistance in Miocene work from Nick Herold and Ashley Dicks. No new data were created for this study, and all reviewed data sets are available through the cited original papers. The authors declare no conflict of interest.

The distribution of benthic foraminifera of the Uvigerinidae family, which are abundant in middle to upper Pleistocene samples from the Yamoto Basin in the Japan Sea, have been analyzed quantitatively and used for paleoceanographic interpretations. Twenty-three Uvigerinidae species are reported from IODP Site U1426, 6 of which are present in at least three or more samples with 10% or more abundance and considered as dominant species. The abundance and ecological preferences of dominant Uvigerinidae species, comprised of Uvigerina mediterranea, Uvigerina yabei, Uvigerina sp.1, Uvigerina peregrina suggest dysoxic conditions, with high influx of organic matter between 775 and 475 ka in response to the enhanced flow of the Tsushima Warm Current. The end of MIS 13 marked the onset of more extreme glacial interglacial climate cycles in the Japan Sea. Glacial interglacial alternations of Uvigerina peregrina and Trifarina angulosa from 475 ka to the Holocene indicate major fluctuations in circulation and productivity within this semi-enclosed basin. Both U. peregrina and T. angulosa respond to 100 kyr variability, reflecting the paleoclimatic shift and global ice volume changes associated with the Middle Pleistocene Transition.

The Indonesian Throughflow (ITF), the sole conduit between the Pacific and Indian Oceans, regulates the heat and fresh water budgets between these oceans and plays a key role as the ‘warm water pathway’ in the global thermohaline circulation. In this study, we reconstructed a 25-kyr history of the ITF thermocline, based on well-dated, high-resolution (~200 yrs) records of Pulleniatina obliquiloculata δ18O and Mg/Ca from Core SO217-18515 (3.63°S, 119.54°E; water depth: 688 m), retrieved from the southern Makassar Strait. We integrated these new records with data from offshore Luzon (MD98-2188; 14.82°N, 123.49°E; water depth: 730 m), from the center of the Western Pacific Warm Pool (WPWP) (3cBX; 8.02°N, 139.6°E; water depth: 2829 m) and from the Timor Sea (MD01-2378; 13.08°S, 121.79°E; water depth: 1783 m). Both sea surface and thermocline temperatures decreased and their difference (ΔT) increased in the southern Makassar Strait and Timor Sea between 11 and 2.5 ka, corresponding to enhanced El Nino activity and dominance of East Asian winter monsoon over summer monsoon. In contrast, sea surface and thermocline temperatures increased and ΔT decreased during the last ~2.5 kyrs concomitantly with declining El Nino activity and relative weakening of the East Asian winter monsoon. Our results additionally show that ice volume corrected seawater δ18O of both sea surface and thermocline in Cores SO217-18515 and MD01-2378 co-vary with Borneo stalagmite δ18O, a proxy of regional precipitation in the WPWP, thus indicating vertical mixing of upper ocean waters along the ITF pathway. We propose that changes in the state of the El Nino-Southern Oscillation and in East Asian monsoon related to regional precipitation exerted a major influence on the ITF thermocline profile during the Holocene and largely controlled changes in ITF thermocline temperature throughout the last 25 kyrs.

Integrated Ocean Drilling Program Expedition 346 “Asian Monsoon” obtained sediment successions at seven sites in the Japan Sea (Sites U1422–U1427 and U1430) and at two closely located sites in the northern East China Sea (Sites U1428 and U1429). The Quaternary sediments of the Japan Sea are characterized by centimeter- to decimeter-scale dark–light alternations at all sites deeper than 500 m water depth. The sedimentary records from these sites allow an investigation of the regional environmental response to global climate change, including changes in the Asian Monsoon and eustatic sea level. However, the discontinuous occurrence of calcareous microfossils in the deep-sea sediments and their distinct isotope signature that deviates from standard marine δ18O records do not permit the development of a detailed stable isotope stratigraphy for Japan Sea sediments. Here, we present the tephrostratigraphy for the two southernmost sites drilled in the Japan Sea (Sites U1426 and U1427) and for one site drilled in the East China Sea (Site U1429) along with the benthic δ18O isotope stratigraphy for the shallower Site U1427 and the East China Sea Site U1429. Eighteen tephra layers can be correlated between sites using the major-element composition and morphology of volcanic glass shards, and the compositions of grains and heavy minerals. Tephra correlations show that negative δ18O peaks in the Japan Sea correspond to positive glacial maxima peaks in the East China Sea. Using this integrated stratigraphic approach, we establish an orbital-scale age model at Site U1427 for the past 1.1 Myr. The correlation of tephra layers between the shallower Site U1427 (330 m below sea level: mbsl) and the deeper Site U1426 (903 mbsl) in the southern Japan Sea provides the opportunity for further age constraints. Our results show that alternations in sediment color at Sites U1426 and U1427 can be correlated for the past 1.1 Myr with minor exceptions. Thus, the stable isotope stratigraphy established at the shallower Site U1427 can be correlated to Site U1426, and in turn to all sites drilled during Expedition 346, based on correlations of dark–light layering.

We reconstructed the orbital-scale variability of deep-water mass properties in the equatorial Indian Ocean during the late early to late Miocene (17.9 to 8.2 Ma) using benthic foraminiferal oxygen (δ18O) and carbon (δ13C) isotope records, in combination with X-ray fluorescence scanner elemental records at International Ocean Discovery Program (IODP) Site U1443. These records suggest that hyperthermal-like features (negative excursions in δ18O and δ13C coupled to suboxic and acidic conditions in the deep ocean) developed at eccentricity maxima during the Miocene Climatic Optimum (MCO; 16.9 to 14.7 Ma) on an almost ice-free Earth. Elevated Mn and U concentrations indicate that bottom and pore waters in the Indian Ocean became progressively suboxic during the later phase of the MCO. A fundamental change in deep-water circulation occurred after the expansion of the East Antarctic Ice Sheet during the Middle Miocene Climatic Transition (MMCT; 14.7 to ~13.8 Ma). Stepwise increases in δ18O at ~13.8 and ~13.1 Ma concurred with dampening of deep-water δ18O and δ13C variability, as Antarctic ice cover expanded and became more stable. A marked improvement in deep-water oxygenation after ~13.5 Ma coincided with the end of the last δ13C maximum of the Monterey Excursion. Carbonate dissolution in the equatorial Indian Ocean intensified and prolonged episodes of reduced carbonate deposition during the Carbonate Crash interval (~12.6 to 8.6 Ma) were not restricted to eccentricity maxima as during the MCO. Rising Mn and U concentrations after ~9 Ma indicate decreased oxygenation of bottom and pore waters, associated with the onset of the Biogenic Bloom in the Indian Ocean.

We present a high-resolution (~20 to 100 years temporal resolution) reconstruction of hydrological changes in the Makassar Strait over the last 14 kyr from Core SO217-18517 retrieved off the Mahakam Delta (1°32.198′S, 117°33.756′E; 698 m water depth) during the SO217 Makassar-Java Cruise. Sea surface temperatures, based on Mg/Ca of Globigerinoides ruber and alkenone UK′37, and seawater δ18O reconstructions, based on G. ruber δ18O and Mg/Ca, in combination with sortable silt grain size measurements and X-ray fluorescence (XRF) core scanner derived elemental data provide evidence for increased precipitation during the Bolling-Allerod (BA) and early Holocene and for warmer and more saline surface waters and a decrease in the intensity of the Indonesian Throughflow (ITF) during the Younger Dryas (YD). XRF derived Log (Zr/Rb) records, sortable silt data and increased sedimentation rates indicate decreased winnowing, interpreted as a slowdown of the ITF thermocline flow during the YD. We attribute this decline in ITF intensity to slowdown of the Atlantic meridional overturning circulation during the YD. We suggest that changes in Makassar Strait surface hydrology during this interval of Northern Hemisphere cooling and Southern Hemisphere warming were related to a southward displacement of the Intertropical Convergence Zone.

We investigated the onset and development of Cretaceous Oceanic Anoxic Event 2 (OAE2) in a newly drilled core (SN degrees 4) from the Tarfaya Basin (southern Morocco), where this interval is unusually expanded. High-resolution (centimeter-scale equivalent to centennial) analysis of bulk organic and carbonate stable isotopes and of carbonate and organic carbon content in combination with XRF scanner derived elemental distribution reveal that the ocean-climate system behaved in a highly dynamic manner prior to and during the onset of OAE2. Correlation with the latest orbital solution indicates that the main carbon isotope shift occurred during an extended minimum in orbital eccentricity (similar to 400 kyr cycle). Shorter-term fluctuations in carbonate and organic carbon accumulation and in sea level related terrigenous discharge were predominantly driven by variations in orbital obliquity. Negative excursions in organic and carbonate delta C-13 preceded the global positive delta C-13 shift marking the onset of OAE2, suggesting injection of isotopically depleted carbon into the atmosphere. The main delta C-13 increase during the early phase of OAE2 in the late Cenomanian was punctuated by a transient plateau. Maximum organic carbon accumulation occurred during the later part of the main delta C-13 increase and was associated with climate cooling events, expressed as three consecutive maxima in bulk carbonate delta O-18. The extinctions of the thermocline dwelling keeled planktonic foraminifers Rotalipora greenhornensis and Rotalipora cushmani occurred during the first and last of these cooling events and were likely associated with obliquity paced, ocean-wide expansions, and intensifications of the oxygen minimum zone, affecting their habitat space on a global scale.

We investigate changes in benthic foraminiferal assemblages and estimate bottom water temperatures (BWT), based on Mg/Ca ratios of Oridorsalis umbonatus , over three selected intervals of major climate change during the late early to middle Miocene at Integrated Ocean Drilling Program (IODP) Sites U1337 (4463 m water depth) and U1338 (4200 m water depth), eastern equatorial Pacific Ocean. The targeted intervals are: (1) the onset of the Miocene Climatic Optimum (MCO; at ~ 16.9 Ma) and associated carbon cycle perturbation (Site U1337); (2) the episode of peak warmth within the MCO centered at 15.6 Ma (Site U1338); (3) the major cooling step at ~ 13.8 Ma related to east Antarctic ice-sheet expansion (Site U1338). Assemblages from these three intervals are mainly composed of cosmopolitan, long ranging (e.g., Paleogene to recent), lower bathyal to abyssal species, including calcareous elongated forms that became extinct during the middle Pleistocene. The onset of the MCO and interval of peak warmth had little impact on benthic foraminiferal accumulation rates (BFAR), abundances and assemblage composition. A transient BWT warming of 2.6 °C at the onset of the interval of peak warmth concurred with a benthic stable oxygen isotope (δ 18 O) decrease of 1‰, suggesting that the δ 18 O decrease was largely controlled by BWT changes. A substantial increase in BFAR and in the abundances of Epistominella exigua and epifaunal taxa after ~ 13.83 Ma coincides with increased opal accumulation rates, reflecting enhanced and seasonally pulsed organic carbon (C org ) flux to the seafloor during the global cooling step. During this interval, BWT decrease by 1.7 °C concurrent with a 1.0‰ increase in the stable oxygen isotope composition of seawater (δ 18 O sw ). Comparable trends at Ocean Drilling Program (ODP) Site 1146 in the South China Sea, with a 2.2 °C cooling and 0.9‰ increase in δ 18 O sw at ~ 13.8 Ma, further support that the benthic δ 18 O increase during the major cooling step was largely controlled by ice volume changes.

The stable isotope composition of planktonic foraminifera, Globigerinoides ruber (G. ruber), is a commonly used paleoenvironmental proxy. Globigerinoides ruber has two primary morphotypes, sensu stricto and sensu lato, which are differentiated by taxonomic criteria and, in some instances, stable isotopic values. Previous studies have reached differing conclusions surrounding the potential bias caused by the use of non-selective mixtures of morphotypes in paleoenvironmental reconstructions involving stable isotopes. Here, G. ruber s.s. and G. ruber s.l. from five time intervals within the last 85 ka, were analyzed from IODP Site U1429 sediments in the East China Sea. The oxygen isotopic compositions of these two morphotypes show statistically significant differences within all five intervals, with smaller s.s. values relative to s.l. values. The largest differences (0.77‰ to 0.82‰) are observed during interglacials (Holocene and Marine Isotopic Stage 5.1) with smaller differences during Marine Isotopic Stage 3 (0.45‰ to 0.56‰) and the Last Glacial Maximum (0.21‰). The isotopic offset between s.s. and s.l. is consistent with a deeper (colder) calcification depth of the s.l. morphotypes in the East China Sea. The decreased offset between the two morphotypes with increased glacial conditions may reflect decreased water column stratification during glacial intervals relative to interglacial intervals. According to these results, using a non-selective mixture of G. ruber morphotypes in paleoenvironmental reconstructions is inadvisable in this region.

Precipitation is the most important variable of Indonesian climate, yet there are substantial uncertainties about past and future hydroclimate dynamics over the region. This study explores vegetation and rainfall and associated changes in atmospheric circulation during the past 26,000 years in Wallacea, a biogeographical area in central Indonesia, wedged between the Sunda and Sahul shelves and known for its exceptionally high rainforest biodiversity. We use terrestrial plant biomarkers from sediment cores retrieved from Mandar Bay, off west Sulawesi, to reconstruct changes in Wallacean vegetation and climate since the Last Glacial Maximum (LGM). Enriched leaf wax carbon isotope (δ13Cwax) values recorded in Mandar Bay during the LGM, together with other regional vegetation records, document grassland expansion, implying a regionally dry, and possibly more seasonal, glacial climate. Depleted leaf wax deuterium isotope (δDwax) values in Mandar Bay during the LGM, and low reconstructed precipitation isotope compositions from nearby sites, reveal an intensified Austral-Asian summer monsoon circulation and a southward shift of the mean position of the Intertropical Convergence Zone, likely due to strong southern hemisphere summer insolation and the presence of large northern hemisphere ice sheets. Mandar Bay δ13Cwax was anti-correlated with δDwax during the LGM and the last deglaciation, but was positively correlated during most of the Holocene, indicating time-varying controls on the isotopic composition of rainfall in this region. The inundation event of the Sunda Shelf and in particular the opening of the Java Sea and Karimata Strait between 9.4 and 11.1 thousand years ago might have provided new moisture sources for regional convection and/or influenced moisture source trajectories, providing the trigger for shifts in atmospheric circulation and the controls on precipitation isotope compositions from the LGM to the Holocene.

We present centennial-scale records of sea surface temperature and oxygen isotopes in a sediment core from Mandar Bay, offshore Sulawesi in the southern Makassar Strait, which provide new insights into the variability of Indonesian climate over the past 26 kyr. The age model for the core is constrained by 17 AMS radiocarbon ages, with a surface ocean reservoir age correction based on paired wood and foraminiferal samples. Small Holocene reservoir ages of 105 180 years point to intense surface ocean atmosphere interchange linked to increased monsoonal precipitation, whereas Last Glacial Maximum and deglacial reservoir ages are significantly higher. Mg/Ca derived sea surface temperature reconstructions based on Globigerinoides ruber (s. s., white) exhibit an extended plateau during the Antarctic Cold Reversal, suggesting an atmospheric connection to high-latitude Southern Hemisphere climate and a seasonal bias on G. ruber. This is in agreement with southern hemisphere sites along the track of the Indonesian Throughflow and in contrast to Northern Hemisphere records from the South China Sea, Sulu Sea and Western Pacific (off Mindanao), which exhibit warming during the Bolling-Allerod. Ice-volume corrected delta O-18 seawater delta O-18(sw) increased during Heinrich Stadial 1 and the Younger Dryas, whereas the Bolling-Allerod is characterized by low delta O-18(sw). We attribute delta O-18(sw) variability in the southern Makassar Strait during the Last Glacial Maximum and glacial termination to changes in provenance and seasonality of precipitation rather than to variability in the amount of local precipitation and runoff. (C) 2016 Elsevier Ltd. All rights reserved.

Highlights • We present a 5 myr record of biogeochemical cycling in a Cretaceous upwelling area. • A novel quantitative approach for the evaluation of Fe speciation proxies was applied. • Ferruginous proxy signature reflects intense chemical weathering rather than anoxia. • Water column redox conditions evolved from oxic to nitrogenous to euxinic before OAE2. • Smaller seawater nitrate inventory facilitated sedimentary H2S release and euxinia. Abstract Oceanic Anoxic Events (OAEs) in Earth's history are regarded as analogues for current and future ocean deoxygenation, potentially providing information on its pacing and internal dynamics. In order to predict the Earth system's response to changes in greenhouse gas concentrations and radiative forcing, a sound understanding of how biogeochemical cycling differs in modern and ancient marine environments is required. Here, we report proxy records for iron (Fe), sulfur and nitrogen cycling in the Tarfaya upwelling system in the Cretaceous Proto-North Atlantic before, during and after OAE2 (∼93 Ma). We apply a novel quantitative approach to sedimentary Fe speciation, which takes into account the influence of terrigenous weathering and sedimentation as well as authigenic Fe (non-terrigenous, precipitated onsite) rain rates on Fe-based paleo-redox proxies. Generally elevated ratios of reactive Fe (i.e., bound to oxide, carbonate and sulfide minerals) to total Fe (FeHR/FeT) throughout the 5 million year record are attributed to transport-limited chemical weathering under greenhouse climate conditions. Trace metal and nitrogen isotope systematics indicate a step-wise transition from oxic to nitrogenous to euxinic conditions over several million years prior to OAE2. Taking into consideration the low terrigenous sedimentation rates in the Tarfaya Basin, we demonstrate that highly elevated FeHR/FeT from the mid-Cenomanian through OAE2 were generated with a relatively small flux of additional authigenic Fe. Evaluation of mass accumulation rates of reactive Fe in conjunction with the extent of pyritization of reactive Fe reveals that authigenic Fe and sulfide precipitation rates in the Tarfaya Basin were similar to those in modern upwelling systems. Because of a smaller seawater nitrate inventory, however, chemolithoautotrophic sulfide oxidation with nitrate was less efficient in preventing hydrogen sulfide release into the water column. As terrigenous weathering and sediment flux determine how much authigenic Fe is required to generate an anoxic euxinic or ferruginous proxy signature, we emphasize that both have to be taken into account when interpreting Fe-based paleo-redox proxies.

金沢大学理工研究域地球社会基盤学系, We integrate benthic foraminiferal stable isotopes, X-ray fluorescence elemental ratios, and carbonate accumulation estimates in a continuous sedimentary archive recovered at International Ocean Discovery Program Site U1443 (Ninetyeast Ridge, Indian Ocean) to reconstruct changes in carbonate deposition and climate evolution over the interval 13.5 to 8.2million years ago. Declining carbonate percentages together with a marked decrease in carbonate accumulation rates after ~13.2Ma signal the onset of a prolonged episode of reduced carbonate deposition. This extended phase, which lasted until ~8.7Ma, coincides with the middle to late Miocene carbonate crash, originally identified in the eastern equatorial Pacific Ocean and the Caribbean Sea. Interocean comparison reveals that intense carbonate impoverishment at Site U1443 (~11.5 to ~10Ma) coincides with prolonged episodes of reduced carbonate deposition in all major tropical ocean basins. This implies that global changes in the intensity of chemical weathering and riverine input of calcium and carbonate ions into the ocean reservoir were instrumental in driving the carbonate crash. An increase in U1443 Log (Ba/Ti) together with a change in sediment color from red to green indicate a rise in organic export flux to the sea floor after ~11.2Ma, which predates the global onset of the biogenic bloom. This early rise in export flux from biological production may have been linked to increased advection of nutrients and intensification of upper ocean mixing, associated with changes in the seasonality and intensity of the Indian Monsoon. ©2019. American Geophysical Union. All Rights Reserved., Embargo Period 6 months

We reconstructed the paleoceanographic evolution of the Japan Sea over the Pleistocene using benthic foraminiferal and organic geochemical records from sediment cores recovered at IODP Site U1426, which was drilled at a water depth of 900 m on the Oki Ridge in the southern Japan Sea. The dominant benthic foraminiferal biofacies and the assemblage composition, total organic and inorganic carbon, coarse fraction percentages indicate a notable reduction in primary productivity between 2150 and 1700 ka, due to the restricted supply of nutrients from the northern Pacific Ocean through the northern connecting strait. The inflow of the Tsushima Warm Current via the southern strait began after 1700 ka and marked a major change in the productivity regime of the Japan Sea, as shown by the increased abundance of calcareous foraminifera and enhanced CaCO3 (%). A marked shift in productivity occurred during the Middle Pleistocene Transition, as indicated by the dominance of low-oxygen tolerant species, and a higher influx of total organic carbon (%). The onset of more extreme glaciation at ~490–470 ka coincident with the Mid-Brunhes Event was linked to marked changes in foraminiferal assemblage composition, reflecting major changes in sea-level, oxygen availability at the seafloor, and carbonate compensation depth during intense glacial-interglacial cycles. Productivity changes were also modulated by 23 kyr variability, related to precessional insolation forcing at low latitudes, and superimposed on the 41 and 100 kyr variability, linked to high-latitude climate fluctuations.

The Miocene Climatic Optimum (MCO; similar to 16.9 to 14.7Ma) provides an outstanding opportunity to investigate climate-carbon cycle dynamics during a geologically recent interval of global warmth. We present benthic stable oxygen (O-18) and carbon (C-13) isotope records (5-12kyr time resolution) spanning the late early to middle Miocene interval (18 to 13Ma) at Integrated Ocean Drilling Program (IODP) Site U1335 (eastern equatorial Pacific Ocean). The U1335 stable isotope series track the onset and development of the MCO as well as the transitional climatic phase culminating with global cooling and expansion of the East Antarctic Ice Sheet at similar to 13.8Ma. We integrate these new data with published stable isotope, geomagnetic polarity, and X-ray fluorescence (XRF) scanner-derived carbonate records from IODP Sites U1335, U1336, U1337, and U1338 on a consistent, astronomically tuned timescale. Benthic isotope and XRF scanner-derived CaCO3 records depict prominent 100kyr variability with 400kyr cyclicity additionally imprinted on C-13 and CaCO3 records, pointing to a tight coupling between the marine carbon cycle and climate variations. Our intersite comparison further indicates that the lysocline behaved in highly dynamic manner throughout the MCO, with >75% carbonate loss occurring at paleodepths ranging from similar to 3.4 to similar to 4km in the eastern equatorial Pacific Ocean. Carbonate dissolution maxima coincide with warm phases (O-18 minima) and C-13 decreases, implying that climate-carbon cycle feedbacks fundamentally differed from the late Pleistocene glacial-interglacial pattern, where dissolution maxima correspond to C-13 maxima and O-18 minima. Carbonate dissolution cycles during the MCO were, thus, more similar to Paleogene hyperthermal patterns.

An expanded succession of organic-rich marlstones and limestones deposited in the Tarfaya Basin provides an outstanding opportunity to closely retrace climate evolution and sea-level changes during the Cretaceous greenhouse period. We present high-resolution X-ray fluorescence (XRF) scanning and bulk carbon- and oxygen-isotope records from two newly drilled sediment cores in the Tarfaya Atlantic coastal basin, which recovered a continuous Upper Turonian to Campanian succession of ∼290 m thickness. The XRF core scanning records reveal three long-term oscillations in the abundance of terrigenous elements (increase of Al, Ti, K, Si, and Fe normalized against Ca), which correspond to progressive transgressive phases followed by rapid regressions during the Coniacian and early Santonian. Sea-level highstands during this interval corresponding to the Coniacian−Santonian oceanic anoxic event 3 (OAE 3) are characterized by overall oxygen-depleted to anoxic conditions at the seafloor (indicated by the high organic carbon content, the presence of laminations, and low log[Mn/S], high log[V/Ca], and high log[Br/Ca]). The upper Santonian interval marks the transition from anoxic to oxic bottom-water conditions, prevalent through the early Campanian. The composite bulk carbonate δ 13 C curve exhibits strong similarities to the global stacked δ 13 C reference curve, characterized by negative excursions in the early Coniacian (Navigation and East Cliff events) and late Santonian (bracketed by the Haven Brow and Buckle events) and by positive excursions in the latest Turonian (Hitchwood event), middle Coniacian (Wight Fall event), and at the Santonian-Campanian boundary. During the early Campanian, enhanced accumulation of fine-grained carbonate and clay-rich hemipelagic sediments, increasing bulk carbonate δ 18 O, and low log(Br/Ca) and log(V/Ca) values indicate climate cooling, associated with a substantial improvement in bottom-water ventilation. Two long-term δ 13 C cycles of ∼2 m.y. duration, probably related to variations in Earth’s orbital eccentricity, are associated with the long-term cooling trend initiating the Campanian−Maastrichtian climate transition toward a cool greenhouse state.

Stable carbon and oxygen isotopes (δ13C and δ18O) of foraminiferal tests are amongst the most important tools in paleoceanography, but the extent to which recrystallization can alter the isotopic composition of the tests is not well known. Here we compare three middle Miocene (16–13 Ma) benthic foraminiferal stable isotope records from eastern equatorial Pacific sites with different diagenetic histories to investigate the effect of recrystallization. To test an extreme case, we analyzed stable isotope compositions of benthic foraminifera from Integrated Ocean Drilling Program Site U1336, for which the geochemistry of bulk carbonates and associated pore waters indicates continued diagenetic alteration in sediments > 14.7 Ma. Despite this diagenetic overprinting, the amplitudes and absolute values of the analyzed U1336 stable isotopes agree well with high-resolution records from better preserved Sites U1337 and U1338 nearby. Our results suggest that although benthic foraminiferal tests of all three sites show some degree of textural changes due to recrystallization, they have retained their original stable isotope signatures. The good agreement of the benthic foraminiferal stable isotope records demonstrates that recrystallization occurred extremely rapidly (< 100 kyr) after deposition. This is confirmed by the preservation of orbital cyclicities in U1336 stable isotope data and δ18O values being different to inorganic calcite that would precipitate from U1336 pore waters during late recrystallization. The close similarity of the benthic foraminiferal stable isotope records between the sites allows the well-resolved paleomagnetic results of Site U1336 to be transferred to Sites U1337 and U1338 improving the global geological timescale.

A relatively low diversity, bathyal benthic foraminiferal assemblage was recovered from the Lower Cretaceous Rilang and Gyabula formations at Chuangde near Gyangze, southern Xizang (Tibet). The assemblage contains 16 taxa belonging to 14 genera, including epifaunal forms dominated by detritus feeders, such as Ammodiscus tenuissimus, Glomospira charoides and Glomospirella gaultina, and rare tubular forms considered to be suspension-feeders such as Rhizammina indivisa and Nothia excelsa. The infaunal component is dominated by Textulariopsis sp. and Pseudobolivina sp., with rare Psammosphaera sp., Haplophragmoides sp. and Reophax sp., previously assigned to a “Biofacies B” indicative of a mildly oxygen-deficient deep water environment and increased surface water productivity. However, the rare occurrence of robust calcareous forms indicates that taphonomic processes considerably altered the original assemblage. The occurrence of the age diagnostic small morphotype of Lenticulina ouachensis in the upper Rilang Formation indicates a late Valanginian–early Hauterivian age, allowing correlation with coeval sections from the Vocontian Trough, northern Tethys (Bavarian Alps) and eastern Indian Ocean (Ocean Drilling Program Site 766 off northwestern Australia).

Speleothem CaCO3 δ18O is a commonly employed paleomonsoon proxy. However, inferring local rainfall amount from speleothem δ18O can be complicated due to changing source water δ18O, temperature effects, and rainout over the moisture transport path. These complications are addressed using δ18O of planktonic foraminiferal CaCO3, offshore from the Yangtze River Valley (YRV). The advantage is that the effects of global seawater δ18O and local temperature changes can be quantitatively removed, yielding a record of local seawater δ18O, a proxy that responds primarily to dilution by local precipitation and runoff. Whereas YRV speleothem δ18O is dominated by precession-band (23 ky) cyclicity, local seawater δ18O is dominated by eccentricity (100 ky) and obliquity (41 ky) cycles, with almost no precession-scale variance. These results, consistent with records outside the YRV, suggest that East Asian monsoon rainfall is more sensitive to greenhouse gas and high-latitude ice sheet forcing than to direct insolation forcing., The underlying mechanisms driving the variability of the East Asia Monsoon during the late Pleistocene remain unclear. Here, the authors present a record of local precipitation and runoff from the East Chain Sea, which indicates strong sensitivity to greenhouse gases and high latitude ice sheet forcing.

The late Miocene offers the opportunity to assess the sensitivity of the Earth’s climate to orbital forcing and to changing boundary conditions, such as ice volume and greenhouse gas concentrations, on a warmer-than-modern Earth. Here we investigate the relationships between low- and high-latitude climate variability in an extended succession from the subtropical northwestern Pacific Ocean. Our high-resolution benthic isotope record in combination with paired mixed layer isotope and Mg/Ca-derived temperature data reveal that a long-term cooling trend was synchronous with intensification of the Asian winter monsoon and strengthening of the biological pump from ~7 Ma until ~5.5 Ma. The climate shift occurred at the end of a global δ13C decrease, suggesting that changes in the carbon cycle involving the terrestrial and deep ocean carbon reservoirs were instrumental in driving late Miocene climate cooling. The inception of cooler climate conditions culminated with ephemeral Northern Hemisphere glaciations between 6.0 and 5.5 Ma., The late Miocene period allows investigation of climate-carbon cycle dynamics on a warmer-than-modern Earth. Here, the authors show that changes in the global carbon cycle drove climate cooling, culminating in ephemeral Northern Hemisphere glaciations and intensification of the Asian winter monsoon from 7 to 5.5 Ma.

Highlights • Complete upper Albian to early Turonian climate archive in drilled core from Tarfaya Basin. • Eccentricity pacing of mid Cretaceous OAE isotope excursions. • MCE and OAE2 associated with climate cooling and sea level fall. Abstract A 325 m long continuous succession of uppermost Albian to lower Turonian pelagic (outer shelf) deposits was recovered from a new drill site in the central part of the Tarfaya Basin (southern Morocco). Natural gamma ray wireline logging, carbonate and organic carbon content, bulk carbonate and organic carbon stable isotopes and X-ray fluorescence (XRF)-scanner derived elemental distribution data in combination with planktonic foraminiferal biostratigraphy indicate complete recovery of the Cenomanian Stage. This exceptional sediment archive allows to identify orbitally driven cyclic sedimentation patterns and to evaluate the pacing of climatic events and regional environmental change across the Albian-Cenomanian boundary (ACB), the mid-Cenomanian Event (MCE) and Oceanic Anoxic Event 2 (OAE2) in the latest Cenomanian. The deposition of organic-rich sediments in the Tarfaya Basin, likely driven by upwelling of nutrient-rich water masses, started during the latest Albian and intensified in two major steps following the MCE and the onset of OAE2. The duration and structure of the MCE and OAE2 carbon isotope excursions exhibit striking similarities, suggesting common driving mechanisms and climate-carbon cycle feedbacks. Both events were also associated with eustatic sea level falls, expressed as prominent sequence boundaries in the Tarfaya Basin. Based on the 405 kyr signal imprinted on the Natural Gamma Ray (NGR) and XRF-scanner derived Log(Zr/Rb) records, we estimate the duration of the Cenomanian Stage to be 4.8 ± 0.2 Myr.

The Quaternary hemipelagic sediments of the Japan Sea are characterized by centimeter- to decimeter-scale alternation of dark and light clay to silty clay, which are bio-siliceous and/or bio-calcareous to a various degree. Each of the dark and light layers are considered as deposited synchronously throughout the deeper (> 500 m) part of the sea. However, attempts for correlation and age estimation of individual layers are limited to the upper few tens of meters. In addition, the exact timing of the depositional onset of these dark and light layers and its synchronicity throughout the deeper part of the sea have not been explored previously, although the onset timing was roughly estimated as ~ 1.5 Ma based on the result of Ocean Drilling Program legs 127/128. Consequently, it is not certain exactly when their deposition started, whether deposition of dark and light layers was synchronous and whether they are correlatable also in the earlier part of their depositional history. The Quaternary hemipelagic sediments of the Japan Sea were drilled at seven sites during Integrated Ocean Drilling Program Expedition 346 in 2013. Alternation of dark and light layers was recovered at six sites whose water depths are > ~ 900 m, and continuous composite columns were constructed at each site. Here, we report our effort to correlate individual dark layers and estimate their ages based on a newly constructed age model at Site U1424 using the best available paleomagnetic datum and marker tephras. The age model is further tuned to LR04 δ18O curve using gamma ray attenuation density (GRA) since it reflects diatom contents that are higher during interglacial high-stands. The constructed age model for Site U1424 is projected to other sites using correlation of dark layers to form a high-resolution and high-precision paleo-observatory network that allows to reconstruct changes in material fluxes with high spatio-temporal resolutions. [Figure not available: see fulltext.].

Present day oceans are well ventilated, with the exception of mid-depth oxygen minimum zones (OMZs) under high surface water productivity, regions of sluggish circulation, and restricted marginal basins. In the Mesozoic, however, entire oceanic basins transiently became dysoxic or anoxic. The Cretaceous ocean anoxic events (OAEs) were characterised by laminated organic-carbon rich shales and low-oxygen indicating trace fossils preserved in the sedimentary record. Yet assessments of the intensity and extent of Cretaceous near-bottom water oxygenation have been hampered by deep or long-term diagenesis and the evolution of marine biota serving as oxygen indicators in today's ocean. Sedimentary features similar to those found in Cretaceous strata were observed in deposits underlying Recent OMZs, where bottom-water oxygen levels, the flux of organic matter, and benthic life have been studied thoroughly. Their implications for constraining past bottom-water oxygenation are addressed in this review. We compared OMZ sediments from the Peruvian upwelling with deposits of the late Cenomanian OAE 2 from the north-west African shelf. Holocene laminated sediments are encountered at bottom-water oxygen levels of < 7 μmol kg−1 under the Peruvian upwelling and < 5 μmol kg−1 in California Borderland basins and the Pakistan Margin. Seasonal to decadal changes of sediment input are necessary to create laminae of different composition. However, bottom currents may shape similar textures that are difficult to discern from primary seasonal laminae. The millimetre-sized trace fossil Chondrites was commonly found in Cretaceous strata and Recent oxygen-depleted environments where its diameter increased with oxygen levels from 5 to 45 μmol kg−1. Chondrites has not been reported in Peruvian sediments but centimetre-sized crab burrows appeared around 10 μmol kg−1, which may indicate a minimum oxygen value for bioturbated Cretaceous strata. Organic carbon accumulation rates ranged from 0.7 and 2.8 g C cm−2 kyr−1 in laminated OAE 2 sections in Tarfaya Basin, Morocco, matching late Holocene accumulation rates of laminated Peruvian sediments under Recent oxygen levels below 5 μmol kg−1. Sediments deposited at > 10 μmol kg−1 showed an inverse exponential relationship of bottom-water oxygen levels and organic carbon accumulation depicting enhanced bioirrigation and decomposition of organic matter with increased oxygen supply. In the absence of seasonal laminations and under conditions of low burial diagenesis, this relationship may facilitate quantitative estimates of palaeo-oxygenation. Similarities and differences between Cretaceous OAEs and late Quaternary OMZs have to be further explored to improve our understanding of sedimentary systems under hypoxic conditions.

An important tool for deep-sea temperature reconstruction is Mg/Ca paleothermometry applied to benthic foraminifera. Foraminifera of the genus Melonis appear to be promising candidates for temperature reconstructions due to their wide geographical and bathymetric distribution, and their infaunal habitat, which was suggested to reduce secondary effects from carbonate ion saturation (Δ[CO3 2−]). Here, we make substantial advances to previous calibration efforts and present new multi-lab Mg/Ca data for Melonis barleeanum and Melonis pompilioides from more than one hundred core top samples spanning in situ bottom temperatures from −1 to 16 °C, coupled with morphometric analyses of the foraminifer tests. Both species and their morphotypes seem to have a similar response of Mg/Ca to growth temperature. Compilation of new and previously published data reveals a linear dependence of temperature on Mg/Ca, with a best fit of Mg/Ca (mmol/mol) = 0.113 ± 0.005 ∗ BWT (°C) + 0.792 ± 0.036 (r2 = 0.81; n = 120; 1σ SD). Salinity, bottom water Δ[CO3 2−], and varying morphotypes have no apparent effect on the Mg/Ca-temperature relationship, but pore water Δ[CO3 2−] might have had an influence on some of the samples from the tropical Atlantic.

Amongst the rivers draining the mountainous islands of the Indonesian Archipelago, the Sepik River of Papua New Guinea is the largest contributor of solute and particulate material to the world ocean. Sites U1484 and U1485, drilled during International Ocean Discovery Program (IODP) Expedition 363 provide a continuous, ~555 kyr long, high-resolution record of mainly siliciclastic slope sedimentation on the northern continental margin of PNG, just offshore the mouth of the Sepik River. Sedimentological analysis, based on a combination of smear slide petrography, particle size analysis, high-resolution physical properties track data and visual core description, offers an unprecedented opportunity to investigate the evolution of this major tropical river throughout changing climate and sea-level conditions during the mid- to late Pleistocene. The Sites U1484 and U1485 sediment records exhibit a dramatic lithologic change at ~ 370 ka: the oldest deposits are dominated by pelagic mud, suggesting that the coarser-grained terrigenous discharge from rivers draining the New Guinea Highlands (including a “proto” Sepik River) was captured before reaching the ocean, when the Sepik River basin was an epicontinental sea. The occurrence of coarser-grained, mass-gravity (mainly hybrid) flows after ~370 ka suggests that the epicontinental sea became a more restricted, shallow-water to nonmarine basin, probably due to both basin infilling and the uplift of local coastal ranges. During the last three glacial-interglacial cycles (~300 kyr), this shallow inland basin was strongly affected by global variations in sea level: during sea level lowstands, the Sepik River cut into older sediments and discharged further offshore onto the shallow continental margins, promoting mass-gravity flows. Pelagic mud deposition on the continental margin during the most extreme highstands following deglaciations suggests a return to shallow marine conditions in the Sepik Basin and repositioning of the river mouth further inland, away from the shelf and from the location of the IODP sites. This also indicates that variations in terrigenous fluxes during these extreme highstands were not solely controlled by the intensity of the hydrological cycle and that global sea level variations also influenced sediment deposition. The sequence is interrupted by several massive grain flow deposits, occurring diachronously at Sites U1484 and U1485 and related to a period of intensified tectonic activity between ~280 ka and ~140 ka. The sedimentologic characteristics of these mass-gravity deposits and their lack of correlation between sites are interpreted as resulting from channelized flows along margin-parallel, fault-controlled channels caused by local and regional failures of the continental margins including the area of the Yalingi Canyon, ~50 km north of the sites, where large tsunamigenic events have also occurred in recent years. Time series analyses of magnetic susceptibility and natural gamma radiation (proxies for %sand and %clay content, respectively) indicate that river discharge fluxes were modulated at orbital frequencies (including obliquity-scale cycles), which suggests that precipitation and river discharge were not only linked to precessionally driven shifts in the mean position of the Intertropical Convergence Zone, but also to high-latitude climate change.

Funding for this research was provided by the Marie Curie Action Plan, Seventh Framework Program (Grant no. 237922) and BMBF Grant 03G0185A (VITAL). Paleostudies of the Indonesian Throughflow (ITF) are largely based on temperature and salinity reconstructions of its near surface component, whereas the variability of its lower thermocline flow has rarely been investigated. We present a multi-proxy record of planktonic and benthic foraminiferal δ18O, Mg/Ca-derived surface and lower thermocline temperatures, X-ray fluorescence (XRF)-derived runoff and sediment winnowing for the past 130 ka in marine sediment core SO18471. Core SO18471, retrieved from a water depth of 485 m at the southern edge of the Timor Strait close to the Sahul Shelf, sits in a strategic position to reconstruct variations in both the ITF surface and lower thermocline flow as well as to investigate hydrological changes related to monsoon variability and shelf dynamics over time. Sediment winnowing demonstrates that the ITF thermocline flow intensified during MIS 5d-a and MIS 1. In contrast during MIS 5e, winnowing was reduced and terrigenous input increased suggesting intensification of the local wet monsoon and a weaker ITF. Lower thermocline warming during globally cold periods (MIS 4 – MIS 2) appears to be related to a weaker and contracted thermocline ITF and advection of warm and salty Indian Ocean waters. Postprint

The evolution of the Australian monsoon in relation to high-latitude temperature fluctuations over the last termination remains highly enigmatic. Here we integrate high-resolution riverine runoff and dust proxy data from X-ray fluorescence scanner measurements in four well-dated sediment cores, forming a NE-SW transect across the Timor Sea. Our records reveal that the development of the Australian monsoon closely followed the deglacial warming history of Antarctica. A minimum in riverine runoff documents dry conditions throughout the region during the Antarctic Cold Reversal (15-12.9 ka). Massive intensification of the monsoon coincided with Southern Hemisphere warming and intensified greenhouse forcing over Australia during the atmospheric CO2 rise at 12.9-10 ka. We relate the earlier onset of the monsoon in the Timor Strait (13.4 ka) to regional changes in landmass exposure during deglacial sea-level rise. A return to dryer conditions occurred between 8.1 and 7.3 ka following the early Holocene runoff maximum.

International audience; Atmospheric carbon dioxide concentrations and climate are regulated on geological timescales by the balance between carbon input from volcanic and metamorphic outgassing and its removal by weathering feedbacks; these feedbacks involve the erosion of silicate rocks and organic-carbon-bearing rocks. The integrated effect of these processes is reflected in the calcium carbonate compensation depth, which is the oceanic depth at which calcium carbonate is dissolved. Here we present a carbonate accumulation record that covers the past 53 million years from a depth transect in the equatorial Pacific Ocean. The carbonate compensation depth tracks long-term ocean cooling, deepening from 3.0-3.5 kilometres during the early Cenozoic (approximately 55 million years ago) to 4.6 kilometres at present, consistent with an overall Cenozoic increase in weathering. We find large superimposed fluctuations in carbonate compensation depth during the middle and late Eocene. Using Earth system models, we identify changes in weathering and the mode of organic-carbon delivery as two key processes to explain these large-scale Eocene fluctuations of the carbonate compensation depth.

International audience; We present sea surface, upper thermocline, and benthic delta O-18 data, as well as temperature and paleoproductivity proxy data, from the International Marine Global Change Study Program (IMAGES) Core MD06-3067 (6 degrees 31' N, 126 degrees 30' E, 1575 m water depth), located in the western equatorial Pacific Ocean within the flow path of the Mindanao Current. Our records reveal considerable glacial-interglacial and suborbital variability in the Mindanao Dome upwelling over the last 160 kyr. Dome activity generally intensified during glacial intervals resulting in cooler thermocline waters, whereas it substantially declined during interglacials, in particular in the early Holocene and early marine oxygen isotope stage (MIS) 5e, when upwelling waters did not reach the thermocline. During MIS 3 and MIS 2, enhanced surface productivity together with remarkably low SST and low upper ocean thermal contrast provide evidence for episodic glacial upwelling to the surface, whereas transient surface warming marks periodic collapses of the Mindanao Dome upwelling during Heinrich events. We attribute the high variability during MIS 3 and MIS 2 to changes in the El Nino-Southern Oscillation state that affected boreal winter monsoonal winds and upper ocean circulation. Glacial upwelling intensified when a strong cyclonic gyre became established, whereas El Nino-like conditions during Heinrich events tended to suppress the cyclonic circulation, reducing Ekman transport. Thus, our findings demonstrate that variations in the Mindanao Dome upwelling are closely linked to the position and intensity of the tropical convection and also reflect far-field influences from the high latitudes.

We measured oxygen isotopes and Mg/Ca ratios in the surface-dwelling planktonic foraminifer Globigerinoides ruber (white s.s.) and the thermocline dweller Pulleniatina obliquiloculata to investigate upper ocean spatial variability in the Indo-Pacific Warm Pool (IPWP). We focused on three critical time intervals: the Last Glacial Maximum (LGM; 18-21.5 ka), the early Holocene (8-9 ka), and the late Holocene (0-2 ka). Our records from 24 stations in the South China Sea, Timor Sea, Indonesian seas, and western Pacific indicate overall dry and cool conditions in the IPWP during the LGM with a low thermal gradient between surface and thermocline waters. During the early Holocene, sea surface temperatures increased by similar to 3 degrees C over the entire region, indicating intensification of the IPWP. However, in the eastern Indian Ocean (Timor Sea), the thermocline gradually shoaled from the LGM to early Holocene, reflecting intensification of the subsurface Indonesian Throughflow (ITF). Increased surface salinity in the South China Sea during the Holocene appears related to northward displacement of the monsoonal rain belt over the Asian continent together with enhanced influx of saltier Pacific surface water through the Luzon Strait and freshwater export through the Java Sea. Opening of the freshwater portal through the Java Sea in the early Holocene led to a change in the vertical structure of the ITF from surface- to thermocline-dominated flow and to substantial freshening of Timor Sea thermocline waters.

Magnetic and grain size properties of a sediment core located in the western equatorial Pacific, off the southeastern tip of the Philippine island of Mindanao, are presented in an effort to reconstruct past changes in the East Asian Monsoon and deep ocean circulation during the last 160 kyrs. The sedimentary concentration of magnetic particles, interpreted to reflect past changes in runoff from Mindanao, varies almost in antiphase with Northern Hemisphere insolation. This suggests that precipitation was lower in the western equatorial Pacific region during boreal insolation maxima and thus corroborates model results showing opposing trends in precipitation between land and the marine realm there. Variations in the grain size distribution of the inorganic sediment fraction, as recorded by both the sortable silt mean size and the magnetic grain size, provide a monitor of changes in sediment reworking by bottom currents. The close correlation of this proxy of bottom current strength and the benthic delta(18)O record from the same site implies a tight coupling between deep water flow, most likely Antarctic Intermediate Water (AAIW), and global climate.