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We present the reconstruction of palaeoenvironmental conditions in the Gdansk, Bornholm, and Arkona Basins of the Baltic Sea over the last millennium. A multiproxy study (including geochemical, XRF, grain size, AMS, and micropalaeontological analyses) of five short sediment cores was performed. The relative age of the sediments was determined based on the Pb distribution along the sediment sequences, as radiocarbon dating has resulted in an excessively old age. The retrieved cores cover two comparable warm periods, the Medieval Climate Anomaly and the Modern Warm Period, for which the increase in surface water productivity was reconstructed. Notably, the production of diatoms was higher during the colder periods (the Dark Ages and Little Ice Age), but this was also the case within the Modern Warm Period. In the Gdansk Basin, the initial salinity increase during the Littorina transgression started after 7.7 cal. a BP. The increased inflow activity was reconstructed during the Medieval Climate Anomaly, even in the Gdansk Basin, despite, in general, very low foraminiferal amounts and diversity. The strongly positive North Atlantic Oscillation Index during this period led to the prevalence of westerly winds over the Baltic region and stronger saltwater intrusions. In the recent sediments, the reconstructed inflow frequency demonstrates a variability against the reduction trend, and a general decline compared to the Medieval Climate Anomaly is seen. [ABSTRACT FROM AUTHOR]

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Over the last four decades, organic-walled dinoflagellate cysts have shown high potential as tracers of past sea-surface conditions during the Quaternary. These microfossils relate to the pelagic productivity of both phototrophic and heterotrophic protist organisms and are recovered in high numbers in almost all marine environment settings from the nearshore and estuarine systems to the distal continental margin. In polar environments, where other conventional proxies are rare or absent, dinoflagellate cysts showed a relatively high diversity of species and a close relationship with sea-ice cover duration, winter and summer temperature, and salinity, enabling quantitative reconstructions of several oceanic variables over time. From the temperate to the tropical latitudes of the Atlantic Ocean, their modern distribution highlights a response to primary productivity and seasonal contrasts in surface temperature. They also have proven that they could be used as tracers of eutrophication in stratified systems and can also highlight human impact on their distribution. In this paper, we present an overview of dinoflagellate cysts as ecological tracers in recent and past sediments of the Atlantic Ocean, from the Arctic to the Antarctic. We provide examples of their use as proxies in paleoclimatic-palaeoceanographic studies at glacial to interglacial time scales, with emphasis on the last ice age to recent (last 25 kyr), the northern North Atlantic and western-eastern tropic North Atlantic. We also discuss their potential as tracers of anthropogenic stress in coastal environments. [ABSTRACT FROM AUTHOR]

We present the reconstruction of palaeoenvironmental conditions in the Gdansk, Bornholm, and Arkona Basins of the Baltic Sea over the last millennium. A multiproxy study (including geochemical, XRF, grain size, AMS, and micropalaeontological analyses) of five short sediment cores was performed. The relative age of the sediments was determined based on the Pb distribution along the sediment sequences, as radiocarbon dating has resulted in an excessively old age. The retrieved cores cover two comparable warm periods, the Medieval Climate Anomaly and the Modern Warm Period, for which the increase in surface water productivity was reconstructed. Notably, the production of diatoms was higher during the colder periods (the Dark Ages and Little Ice Age), but this was also the case within the Modern Warm Period. In the Gdansk Basin, the initial salinity increase during the Littorina transgression started after 7.7 cal. a BP. The increased inflow activity was reconstructed during the Medieval Climate Anomaly, even in the Gdansk Basin, despite, in general, very low foraminiferal amounts and diversity. The strongly positive North Atlantic Oscillation Index during this period led to the prevalence of westerly winds over the Baltic region and stronger saltwater intrusions. In the recent sediments, the reconstructed inflow frequency demonstrates a variability against the reduction trend, and a general decline compared to the Medieval Climate Anomaly is seen.

Over the last four decades, organic-walled dinoflagellate cysts have shown high potential as tracers of past sea-surface conditions during the Quaternary. These microfossils relate to the pelagic productivity of both phototrophic and heterotrophic protist organisms and are recovered in high numbers in almost all marine environment settings from the nearshore and estuarine systems to the distal continental margin. In polar environments, where other conventional proxies are rare or absent, dinoflagellate cysts showed a relatively high diversity of species and a close relationship with sea-ice cover duration, winter and summer temperature, and salinity, enabling quantitative reconstructions of several oceanic variables over time. From the temperate to the tropical latitudes of the Atlantic Ocean, their modern distribution highlights a response to primary productivity and seasonal contrasts in surface temperature. They also have proven that they could be used as tracers of eutrophication in stratified systems and can also highlight human impact on their distribution. In this paper, we present an overview of dinoflagellate cysts as ecological tracers in recent and past sediments of the Atlantic Ocean, from the Arctic to the Antarctic. We provide examples of their use as proxies in paleoclimatic-palaeoceanographic studies at glacial to interglacial time scales, with emphasis on the last ice age to recent (last 25 kyr), the northern North Atlantic and western-eastern tropic North Atlantic. We also discuss their potential as tracers of anthropogenic stress in coastal environments.

Lacustrine rift basins are ideal continental settings for understanding organic matter (OM) accumulation mechanisms, because lacustrine deposits are most sensitive to variable climatic and palaeoenvironmental conditions. The Lunpola Basin is a Cenozoic lacustrine rift basin with widespread oil shale depositions that provide a valuable example of triggering factors that controlled OM accumulation. In the investigated interval of the basin, high Si, Ti, Zr, Th, Al and rare earth element concentrations suggest high clastic fluxes during the oil shale deposition. These high clastic fluxes could be attributed to warm and humid climates due to high values of ln(Al2O3/Na2O) and C‐value (Ʃ (Fe + Mn + Cr + Ni + V + Co)/Ʃ (Ca + Mg + Sr + Ba + K + Na)). The Lunpola shales and oil shales were deposited in saltwater environments under enhanced dysoxic to anoxic conditions with high palaeoproductivity. In the Lunpola Basin, climate warming can be subdivided into two different stages based on C‐value and ln(Al2O3/Na2O) variations. Each stage is consistent with an increase in the primary productivity of the palaeolake. Thus, a model for climate‐induced OM enrichment in lacustrine rift basins is proposed, which indicates that climate and primary productivity are the key factors controlling OM accumulation. [ABSTRACT FROM AUTHOR]

We characterised the organic matter content of marine deposits at the Oxfordian–Kimmeridgian transition in the Boulonnais (France). Organic rich deposits in platform environments are evidenced in the uppermost Cymodoce and lowermost Mutabilis Zone (early late Kimmeridgian), associated with enhanced planktonic palaeoproductivity and/or developing dysoxia/anoxia. Similar organic rich intervals in early late Kimmeridgian are also evidenced in platform deposits in Normandy and Charentes in France, and in basinal deposits from Yorkshire and Dorset in UK. This refined onset of the organic rich bands (ORB), as described in NW Europe during the late Jurassic, is coeval with seawater warming. We propose that this seawater warming was an important trigger of the onset of the late Jurassic ORB deposition system in NW Europe, which began at the Cymodoce–Mutabilis boundary during the early late Kimmeridgian and lasted until the middle part of the Tithonian, over a time span of 6.8 Myr.

The organic-rich shales found in the Wufeng–Longmaxi Formation are typically deposited in oxygen-deficient reducing environments. One of the primary sources of debate revolves around the question of whether the anoxic bottom water found in these shales is either euxinic or ferruginous, and this matter remains unresolved. Previous studies have mostly focused on the Wufeng–Longmaxi Formation as a whole in order to understand the key factors that control organic matter accumulation (OMA). However, research on OMA for each member, including the Wufeng Formation (WF), the lower Longmaxi Formation (LLM), and the upper Longmaxi Formation (ULM), has been insufficient. This paper aims to investigate the palaeoenvironmental conditions and OMA mechanisms of the Wufeng–Longmaxi shales in western Hubei by integrating data on total organic carbon (TOC) content, mineral compositions, major and trace elements, and iron speciation. The results indicate that the Wufeng–Longmaxi shales were deposited under highly restricted hydrographic conditions, except for relatively open and upwelling conditions in the upper WF. Silica in the upper WF was primarily biogenic origin and not hydrothermal. Ferruginous conditions were the primary redox conditions for organic-rich shales except for minor formations in the lower LLM that were deposited under euxinic conditions. Due to the tectonic uplift caused by the Kwangsian Orogeny in the upper LLM, the palaeoenvironment was characterized by a warmer and wetter climate, high terrigenous influx, oxic conditions, and low productivity as the result of the insufficient nutrients caused by the weak upwelling, leading to the turnover of graptolite biozones from LM5 to LM6. The factors influencing OMA changed vertically. TOC contents have a highly positive correlation with Al content, indicating that terrigenous influx was the main factor affecting OMA in the WF, which significantly differed from patterns found in other regions. This suggests that the sedimentation rate of organic matter was higher than the terrigenous dilution rate during the WF stage. The combination of redox conditions and productivity were the main factors affecting OMA in the LLM, while terrigenous influx was the key factor controlling OMA in the ULM, resulting in the dilution of organic matter. Regions in the eastern Yiling block, which are close to the Qinling Ocean, show better prospects for shale gas exploration. This research will further facilitate the development of shale gas in this area. [ABSTRACT FROM AUTHOR]

We present a new high-resolution reconstruction of annual sea-surface temperatures (SSTa) and net primary productivity (NPP) using novel coccolithophore-based models developed for the Eastern Equatorial Pacific (EEP). We combined published coccolithophore census counts from core-tops in the Eastern Pacific with 32 new samples from the Equatorial region, to derive a new statistical model to reconstruct SSTa. Results show that the addition of the new EEP samples improves existing coccolithophore-based SST-calibrations, and allow reconstructing SSTa in the EEP with higher confidence. We also merged the relative abundance of deep-photic species Florisphaera profunda in the same surface sediment samples with existing calibration datasets for tropical regions, to reconstruct annual NPP. Both temperature and productivity calibrations were successfully applied to fossil coccolith data from Ocean Drilling Project Site 1240, in the EEP. The coccolith-based SSTa estimates show a cooling during the Last Glacial Maximum (LGM) and the Younger Dryas, and warming at the start of the Holocene. This pattern differs in the timing and magnitude of the temperature changes from other available SST-reconstructions based on biogeochemical and faunal proxies. We discuss these discrepancies to be the result of different proxy sensitivities to insolation forcing, seasonal bias, and/or preservation artifacts. Reconstructed annual NPP shows a general decreasing trend from the late last glacial period to recent times, which we relate to the weakening of wind-driven equatorial upwelling towards the Holocene. We also calculated carbon export using our SSTa and NPP reconstructions, and compared to other geochemical-based reconstructions for the same location. Our coupled SSTa-NPP reconstruction provides key data to more fully assess the evolution of primary and export productivity as well as organic carbon burial in the EEP, with implications for its role in global biogeochemical cycles across glacial terminations.

Deep‐sea sediments record palaeoenvironmental and oceanographic changes over time through variations in their magnetochemical and sedimentological properties. This study presents the Late Quaternary sedimentary reconstruction of three sediment cores extracted from a source‐to‐sink sedimentary system located in a high marginal platform of the north‐west Iberian Margin. The aim of this reconstruction is to explore the palaeoclimatic, palaeoproductivity and diagenetic changes over the last 172 cal ka bp attending to geochemical, magnetic and sedimentological variations. The record is comprised of four sedimentary units consisting of pelagic, hemipelagic and detrital facies, the latter associated with ice‐rafted debris events at Heinrich Stadials. These findings allowed the reconstruction of the lithostratigraphy attending to climatic changes, covering the last eleven Heinrich Stadials. These units and facies successions are controlled by the superposition of the Milankovitch and Dansgaard–Oeschger cycles. Low sedimentation rates have been reported, especially during cold periods. Palaeoproductivity was assessed using total organic carbon and calcium carbonate content, together with biogenic barium (Babio) and organic phosphorus (Porg), both calculated via total digestion analysis using standard calculations. Mass accumulation rates for total organic carbon, Babio and Porg were calculated. Furthermore, a sequential extraction was performed to explore the different phases of the barium within sediments: biogenic barite (Babar), barium associated with iron and manganese oxides (Baox) and Ba associated with aluminosilicates (Badet). Results display a limitation in the use of the biogenic barium and phosphorus and mass accumulation rates, suggesting detrital Ba (Badetr) contribution during Heinrich Stadials, which could mask the calculations. In contrast, only calcium carbonate fluctuates attending to glacial/interglacial cycles. Regarding some diagenetic proxies (i.e. Mn, Mn/Fe and Mn/Ti), they reveal oxidation fronts of different generations, suggesting that the early diagenesis has not reached steady‐state, because the redoxcline fluctuates. This fact suggests an erosional activity that causes the continuous oxygenation of the sediment and non‐steady‐state conditions. [ABSTRACT FROM AUTHOR]

Sequential extraction of core samples collected from Pulicat Lake, east coast of India, showed that on average, 59% of labile Cr and 28% of labile Al remain adsorbed onto Fe–Mn oxides. Similarly, 61% of labile Al and 36% of labile Cr are associated with organic matter. Cross‐correlation analysis revealed that in the Fe–Mn oxides phase, Cr primarily exists with Mn‐oxides, while Al remains mainly adsorbed onto Fe‐oxides. Factor analysis revealed four factors that could explain 82% of the variance in the data. Changes in water column ionic composition, salinity, dissolution of Fe–Mn oxides during microbial oxidation of organic matter, changes occurring to the organic matter and calcium carbonate during early diagenesis are the key factors influencing the Al and Cr concentrations in the labile fractions. The results of this study are useful to interpret palaeoenvironmental conditions. [ABSTRACT FROM AUTHOR]

Aeolian dust input exerts significant influence on oceanic biogeochemical cycles and further potentially controls atmospheric CO2 concentrations. However, the possible link between long-term aeolian dust supply and primary productivity in the western North Pacific remains poorly understood. Here, we present a comprehensive study of major and trace elements and total organic carbon (TOC) concentrations of sediments from Integrated Ocean Drilling Program (IODP) Site U1430 in the southern Japan Sea, in order to reconstruct oceanic palaeoproductivity evolution and test its possible link to Asian dust input since 4 Ma. Palaeoproductivity proxies indicate remarkable increases in productivity at ∼3–2 Ma followed by high-frequency oscillations in productivity since 1.2 Ma. We suggest that higher dust-derived iron supply from Central Asia at 3–2 Ma, which was likely driven by the growth of the Northern Hemisphere ice sheets, could account for enhanced primary productivity and export production in the Japan Sea. Such increased oceanic palaeoproductivity could enhance organic carbon burial, which might contribute to the decrease in atmospheric CO2 concentrations, and provide a positive feedback to the global cooling. However, the Tsushima Warm Current (TSWC) intrusion via the southern Tsushima Strait, which was controlled by glacioeustatic sea level changes, has been the principal cause of the rapid changes in primary productivity and benthic redox condition since 1.2 Ma, regardless of continuously increased Asian dust input. [ABSTRACT FROM AUTHOR]

The coevolution of the redox environment, productivity and Ediacaran fauna is crucial to understanding the trigger of Early Cambrian explosion of the Chengjiang Biota and Qingjiang Biota in the southwestern and northern margins of the South China Craton, respectively. Multiple element and isotope geochemical proxies are effective indicators for palaeo-ocean environment and productivity. In this study, our new combination of geochemical proxies of Fe T /Al, Th/U, V/(V + Ni), V/Sc, Ce anom , U anom, Cr EF , Al/Ti, Mo EF , (Al, P, Ba, Cu, Zn, Ni)xs, and δ13C and δ98Mo isotopic data from the Ediacaran Dengying Formation in the Gaojiashan section suggest multiple rapid short-term pulsed oxygenation and reduction events. An approximate correlation between the redox environments, palaeoproductivity and life events can be concluded as well. Based on the stratigraphic position, lithology, fossil records and geochemical characteristics, the entire profile of the Ediacaran Dengying Formation can be divided into five intervals. The redox environment of Interval I experienced fluctuations from predominantly anoxic to slightly suboxic environments, and then increased to a flexible dysoxic – oxic – anoxic environment during Interval II. Meanwhile, the productivity also frequently fluctuated at a relatively low level. The relatively unstable seawater and pulsing fluctuations of the redox conditions and palaeoproductivity can be correlated to the hydrothermal activities. From Interval III, the redox environments have been improved by several phases of oxygenation, from the relatively oxic – suboxic conditions at the beginning of Interval III to highly oxic conditions during Interval IV. Meanwhile, the palaeoproductivity soared after the early stage of Interval III and continuously increased to a high level until the later stage of Interval III and Interval IV. The highly oxic environment and continuously increasing palaeoproductivity resulted in the flourishing of the Ediacaran Gaojiashan fauna. From Interval V, both the redox conditions and the palaeoproductivity were at a low level, although they improved during the later stage, resulting in the previous Cloudina fauna disappearing. After comparing other contemporaneous profiles in South China and worldwide, we found that most profiles experienced similar variation of Ediacaran seawater redox environments that were under a chronically turbulent, with rapid short-term pulsed oxygenation and reduction events. This type of pulsed oxygenation did not deplete the local life community significantly. The regional depositional settings, redox environments and palaeoproductivity are the most important controlling factors of the life events. [ABSTRACT FROM AUTHOR]

The Cretaceous black shales of Colombia are among the most important successions in the north of South America and have attracted the attention of many geoscientists and exploration companies over the last few decades, because of their high hydrocarbon potential and the presence of emerald deposits. However, many uncertainties still remain with regard to their tectonic setting, sequence stratigraphy, depositional environments, palaeoxygenation conditions, and organic matter preservation. In order to develop a more integrated picture of these different processes and conditions, we conducted a detailed sedimentological, inorganic geochemical (U, V, Ni, Zn, Mn, Fe, Ti, Mo, Cu, Cr, Cd, Ba) and sequence stratigraphic analysis of the Cretaceous black shales in the Magdalena-Tablazo Sub-Basin (Eastern Cordillera Basin) of Colombia. Eleven lithofacies and five lithofacies associations of a storm-dominated, siliciclastic-carbonate ramp were identified, which range from basin to shallow inner ramp environments. These facies were grouped into six third-order stratigraphic sequences showing high-order cycles of marine transgression with constrained regressive pulses during the late Valanginian to early Coniacian. The black shales succession represents deposition under anoxic bottom water with some intervals representing dysoxic-suboxic conditions. The evolution of the sedimentary environments and their palaeoxygenation history reflect tectonic and eustatic sea-level controls that 1) produced a variable orientation and position of the coastline throughout the Cretaceous; 2) conditioned the low-gradient ramp geometry (<0.3°) and 3) modified the oxygenation conditions in the Magdalena-Tablazo Sub-Basin. An improved understanding of the sedimentary setting during deposition of the Cretaceous black shales in the Magdalena-Tablazo Sub-Basin assists in highlighting the interplay between the mechanism of sedimentation and continuum anoxic conditions prevailing in a basin, as well the important role of nutrient input from continental runoff as a trigger of high productivity and extended anoxia conditions. [ABSTRACT FROM AUTHOR]

Posidonia oceanica is a marine phanerogam that buries a significant part of its belowground production forming an organic bioconstruction known as mat. Despite Posidonia seagrass mats have proven to be reliable archives of long-term environmental change, palaeoecological studies using seagrass archives are still scarce. Here we reconstruct four millennia of environmental dynamics in the NE coast of Spain by analysing the carbon and nitrogen stable isotopic composition of P. oceanica sheaths, the proportion of different seagrass organs throughout the seagrass mat and other sedimentological proxies. The palaeoenvironmental reconstruction informs on long-term ecosystem productivity and nutrient loading, which have been linked to global (e.g., solar radiation) and local (e.g., land-use changes) factors. The long-term environmental records obtained are compared with previous palaeoecological records obtained for the area, showing a common environmental history. First, a relative seagrass ecosystem stability at ~4000 and 2000 cal. yr BP. Then, after a productivity peak at ~1400–800 cal. yr BP, productivity shows an abrupt decline to unprecedented low values. The fluctuations in ecosystem productivity are likely explained by increases in nutrient inputs related to human activities – mostly in the bay watershed – concomitantly with changes in total solar radiation. Cumulative anthropogenic stressors after Roman times may have started to affect ecosystem resilience, dynamics and productivity, with more abrupt regime shifts during the last millennium. These results add into recent research showing the potential of seagrass archives in reconstructing environmental change and seagrass post-disturbance dynamics, hence providing unvaluable information for improving the efficiency in managing these key coastal ecosystems. [ABSTRACT FROM AUTHOR]

Limnological reconstructions of primary productivity have demonstrated its response over Quaternary timescales to drivers such as climate change, landscape evolution and lake ontogeny. In particular, sediments from Lake Baikal, Siberia, provide a valuable uninterrupted and continuous sequence of biogenic silica (BSi) records, which document orbital and sub-orbital frequencies of regional climate change. We here extend these records via the application of stable isotope analysis of silica in diatom opal (δ 30 Si diatom ) from sediments covering the Last Interglacial cycle (Marine Isotope Stage [MIS] 5e; c. 130 to 115 ka BP) as a means to test the hypothesis that it was more productive than the Holocene. δ 30 Si diatom data for the Last Interglacial range between +1.29 and +1.78‰, with highest values between c. 127 to 124 ka BP (+1.57 to +1.78‰). Results show that diatom dissolved silicon (DSi) utilisation, was significantly higher (p = 0.001) during MIS 5e than the current interglacial, which reflects increased diatom productivity over this time (concomitant with high diatom biovolume accumulation rates [BVAR] and warmer pollen-inferred vegetation reconstructions). Diatom BVAR are used, in tandem with δ 30 Si diatom data, to model DSi supply to Lake Baikal surface waters, which shows that highest delivery was between c. 123 to 120 ka BP (reaching peak supply at c. 120 ka BP). When constrained by sedimentary mineralogical archives of catchment weathering indices (e.g. the Hydrolysis Index), data highlight the small degree of weathering intensity and therefore representation that catchment-weathering DSi sources had, over the duration of MIS 5e. Changes to DSi supply are therefore attributed to variations in within-lake conditions (e.g. turbulent mixing) over the period, where periods of both high productivity and modelled-DSi supply (e.g. strong convective mixing) account for the decreasing trend in δ 30 Si diatom compositions (after c. 124 ka BP). [ABSTRACT FROM AUTHOR]

The lower 1st Member (Es1L) of the Oligocene Shahejie Formation is the most important source rock interval in the Raoyang Sag and the Baxian Sag. To reveal the controlling factors that affected the distribution of organic-rich source rocks, we analyzed the lower Es1 (Es1L) samples collected from the Raoyang Sag and the Baxian Sag using sedimentological and geochemical techniques to reconstruct the lacustrine palaeoenvironmental conditions. Most of the samples had chemical index of alteration (CIA ⁎ ) values between 70 and 75, which reflect a stable and moderately weathered source under a transitional climate. The distribution of depocenters and palaeo-water depths indicated that the main catchment area was concentrated in the Raoyang Sag, with a maximum palaeo-water depth of 14 m and a wave-base depth of 7.5 m. Stable isotope data from carbonates (δ 18 O carb and δ 13 C carb ) showed that the lakes with long residence times in the Raoyang Sag had a positive correlation and that the lakes with short residence times in the Baxian Sag had no isotopic covariance during the deposition of the lower Es1. The P/Al and P/Ti ratios, P total and carbon isotope values of the organic matter (δ 13 C org ) in the two sags illustrated stable palaeoproductivity without much fluctuation. The enrichments of Mo, U and ratios of (C:P) org , B/Ga and Sr/Ba further indicated saline and anoxic bottom water conditions associated with stable water-column stratification in Well Xi63 and brackish and less anoxic bottom water conditions in Well ND1 during the deposition of the main source rock of the lower Es1. Moreover, the plots of Mo and U enrichment versus TOC and hydrogen index values versus Δδ 13 C (i.e., the difference between the δ 13 C values of carbonates and organic matter) corroborated the inference that the preservation of organic matter was the main factor controlling the formation of organic-rich source rocks in the Raoyang Sag and the Baxian Sag during the deposition of the lower Es1. [ABSTRACT FROM AUTHOR]

New biostratigraphical, chemical and stable isotope (C, O) data are presented from the Lókút section (Transdanubian Range, Hungary) representing a ca. 13 m thick continuous succession of Lower Tithonian–Lower Berriasian pelagic limestones. The study is conducted to verify timing of nannofossil events and major palaeoenvironmental changes at the Jurassic/Cretaceous transition including lithogenic input, palaeoredox and palaeoproductivity variations. Nannofossil zones from NJT 16b to NKT have been identified in the Lókút section and correlated with magnetostratigraphy, covering an interval from polarity zone M21r to M18r. The nannofossil Zone NJT 16b spans the interval from the upper part of M21r to lowermost part of M19n2n but its lower limit is poorly defined due to large diachronism in first occurrence (FO) of Nannoconus infans in various Tethyan sections. FOs of N. kamptneri minor and N. steinmannii minor are situated in the topmost part of the M19n2n and lowermost part of M19n1r magnetozones, respectively. They are located ca. 2–2.5 m above the J/K boundary defined as Intermedia/Alpina subzonal boundary, which falls within the lower half of magnetozone M19n2n. The position of first occurrences of these taxa is similar to that from the Puerto Escaño section (southern Spain) and slightly lower than in Italian sections (Southern Alps). Concentrations of chemical element proxies of terrigenous transport (Al, K, Rb, Th) decrease towards the top of the Lókút section, which suggests a decrease in input of terrigenous material and increasing carbonate productivity during the Early Tithonian and the Berriasian. Slight oxygen depletion at the sea bottom (decrease of Th/U ratio), and large increase in concentrations of productive elements (P, Ba, Ni, Cu) is observed upsection. Nutrients supply via upwelling seems to be the most likely explanation. Increase in phosphorus accumulation rate and a microfacies change from Saccocoma to calpionellid dominated took place in the polarity chron M19r, which apparently coincided with the worldwide Nannofossil Calcification Event, related to a bloom of strongly calcified calcareous nannoplankton taxa. Deposition in the Lókút area was probably affected by long-term climatic trends: aridization and warming. Decreasing δ 13 C values of bulk carbonates throughout the Tithonian and the Berriasian are interpreted as a result of a global trend of accelerated carbonate productivity supported by local factors such as increased upwelling intensity, and a possible change in the composition of carbonate mud. [ABSTRACT FROM AUTHOR]

We investigate the response of the central equatorial Indian Ocean (ODP Site 716, Maldives) upwelling system to orbital forcing between 3.64 and 4.19 Ma. This time interval in the early Pliocene was characterized by global average temperatures considerably warmer than present and reduced zonal and meridional sea surface temperature gradients across the major oceans. Chlorin, a degradation product of chlorophyll and a potential indicator of primary productivity, was previously shown to record orbital scale variations at this site. To confirm that chlorin records primary productivity and to understand the mechanism controlling the orbital variations, we compare changes in the planktic foraminiferal assemblages with the chlorin content of the sediment. Cross wavelet analysis demonstrates the in-phase relationship between the abundance of thermocline species and chlorin content, indicating that upwelling and a shallower thermocline drive the productivity changes. The aragonite content in periplatform carbonates is known to reflect variations in sea-level and/or climate, with high values generally indicating sea-level highstands. The aragonite content in the studied interval shows precession and eccentricity astronomical cycles, whereas the primary productivity proxies show only precessional cycles. The negative correlation between aragonite content and the relative abundance of thermocline species on the precessional band implies that the primary productivity increased during sea-level lowstands. This phase coupling is consistent with Quaternary productivity records from the central Indian Ocean that were proposed to be controlled by orbital induced variations of the El Niño-Southern Oscillation (ENSO). We therefore propose that a similar mechanism was active in the early Pliocene despite major changes in the global boundary conditions. [ABSTRACT FROM AUTHOR]

Two cores from 1200 m water depth from Vestnesa Ridge on the western Svalbard margin have been investigated for the distribution of benthic and planktic foraminiferal assemblages, oxygen and carbon isotopes, geochemical and sedimentological parameters including magnetic susceptibility, total organic carbon (TOC) and CaCO 3 content of the sediment. Vestnesa Ridge is known for the presence of numerous pockmarks, where methane gas is bubbling out from the seafloor. One core was taken from a pockmark with active seepage of methane, while the second core was taken just outside the seepage area for comparison. The purpose of the study is to reconstruct the palaeoceanography and compare to published palaeoceanographic records from the area and evaluate if seepage of methane have had any impact on the distribution patterns of benthic foraminiferal species and the sedimentary environments through time. The results indicate almost continuous presence of Atlantic water throughout the last 43,000 years. During the Heinrich H1 interval ca. 18,000–15,300 years Atlantic water flowed subsurface along the bottom and the period stands out with the highest bottom-water temperatures of the last 43,000 years. Settlement of a community of chemo-synthesizing bivalves indicates increase in the release of methane beginning during H1. However, in both records of seep versus non-seep environments, the distribution patterns of benthic foraminiferal species, diversity, and productivity of the specimens were the same, indicating that seepage of methane had no influence on the foraminiferal faunas. Our results show that the palaeoceanographic development at Vestnesa Ridge was similar to the development over the western Svalbard margin and the Fram Strait confirming previously published results. We conclude that the benthic foraminifera at the methane seep site were mainly controlled by palaeoceanographic changes and associated changes in the sedimentary environment and palaeoproductivity overprinting any eventual influence of seepage of methane. [ABSTRACT FROM AUTHOR]

The relationship between monsoon-induced productivity and ocean circulation over millennial timescales is crucial. However, a study regarding the circulation of the western Arabian Sea (WAS) needs to be conducted. Understanding the seasonal, surface, and thermocline ocean circulation throughout the glacial-Interglacial period in the WAS is also elusive and essential. The long distant Antarctic Intermediate Water (AAIW) flow, and Sub-antarctic Mode Water (SAMW) penetration to the north side of the equator in the Indian Ocean needs to be understood and underlined using the micropaleontological (planktonic foraminiferal assemblages) and geochemical analysis such as oxygen isotope of Globigerinoides ruber and Neogloboquadrina dutertrei (δ18O G.ruber and δ18O N.dutertrei) in this study. Furthermore, understanding the variations in paleoproductivity, upper oceanic water column stratification, surface mixing, and thermocline layer variability in the WAS is also helpful. According to the results, the variation in the upwelling intensity during Glacial-Interglacial and monsoon variation suggest the upper water stratification/vertical mixing in the WAS. Here, we provide new evidence of poorly ventilated water mass in our region. Our results indicate that enhanced northward expansion of AAIW coincides with the weakening of summer monsoon during glacial periods except mid-MIS4, reflected by isotopic study and assemblages. In this context, depleted δ18O N. dutertrei value and high concentration of Globorotalia menardii (G. menardii) were due to lack/absence of AAIW ventilation and SAMW; therefore, warming occurred in the mid-MIS4. [Display omitted] • Mid-MIS4 warming enhanced the upwelling in the WAS as evident by assemblages and oxygen isotope records. • The weak intermediate ocean current circulation of AAIW and SAMW to the WAS during mid-MIS4 was responsible for the poor ventilation towards upper thermocline. • The glacial period (MIS6) is showing highest degree of stratification as evident by dominance presence of mixed-layer oligotrophic species and decreased relative abundance of mixed-layer eutrophic species. • Moderate winter convective mixing occurred during MIS2 as compared to MIS6. • Deepening of thermocline under thickening of mixed layer during interglacial periods (MIS5 & 1) and vice-versa during glacial period (MIS6). [ABSTRACT FROM AUTHOR]

The sediment cores of 20 cm length collected from 31 to 83 m range of water depth from the inner shelf of Bay of Bengal west of 'Swatch of No Ground' were analyzed for grain size, organic carbon, total nitrogen, calcium carbonate and clay mineralogy. Grain size analysis revealed that the sediment size decreases from west to east within the study area indicating a possible direction of transport towards east parallel to the coast. The grain size also decreases with increasing water depth, i.e. north to south, indicating sediment contribution to the area of study from Hooghly and other local rivers. In the cores studied, illite was the dominant clay mineral which seems to be a product of glacial weathering under arid conditions with its source being the Himalayan region. The organic carbon content was low in the sediments and was attributed to low plankton production or intense oxidation processes. Low calcium carbonate percentage also supports the view of a low productivity in this region. Organic carbon increases gradually from west to east indicating its association with finer sediments and also indicates transport due to currents which drift the organic carbon away before it settles down within the sediments. Higher values relatively closer to the coast in the eastern side indicate additional contribution from Sunderban mangroves. The C/N ratio obtained indicates mixed source of terrestrial and marine for the organic matter in the sediments. Sedimentation rates available for deltaic plains and shelves off Bangladesh when adopted for the present area revealed that a 20 cm long sediment column was deposited in around 10 years. In most of the cores studied, a change in the trend of sediment components and organic carbon was observed at around 10 cm where grain size increases and organic carbon decreases towards the surface inferring that during the last 5 years, possible floods during NE monsoon or due to melting of ice in Himalaya are responsible for releasing additional water and material which brought a change in hydrodynamic conditions. The surface depletion of organic carbon indicates its dilution by the addition of coarser materials. [ABSTRACT FROM AUTHOR]

Upwelling intensity in the South China Sea has changed over glacial-interglacial cycles in response to orbital-scale changes in the East Asian Monsoon. Here, we evaluate new multi-proxy records of two sediment cores from the north-eastern South China Sea to uncover millennial-scale changes in winter monsoon-driven upwelling over glacial Terminations I and II. On the basis of U/Th-based speleothem chronology, we compare these changes with sediment records of summer monsoon-driven upwelling east of South Vietnam. Ocean upwelling is traced by reduced (UK'37-based) temperature and increased nutrient and productivity estimates of sea surface waters (δC on planktic foraminifera, accumulation rates of alkenones, chlorins, and total organic carbon). Accordingly, strong winter upwelling occurred north-west of Luzon (Philippines) during late Marine Isotope Stage 6.2, Heinrich (HS) and Greenland stadials (GS) HS-11, GS-26, GS-25, HS-1, and the Younger Dryas. During these stadials, summer upwelling decreased off South Vietnam and sea surface salinity reached a maximum suggesting a drop in monsoon rains, concurrent with speleothem records of aridity in China. In harmony with a stadial-to-interstadial see-saw pattern, winter upwelling off Luzon in turn was weak during interstadials, in particular those of glacial Terminations I and II, when summer upwelling culminated east of South Vietnam. Most likely, this upwelling terminated widespread deep-water stratification, coeval with the deglacial rise in atmospheric CO. Yet, a synchronous maximum in precipitation fostered estuarine overturning circulation in the South China Sea, in particular as long as the Borneo Strait was closed when sea level dropped below −40 m. [ABSTRACT FROM AUTHOR]

The lower Garau Formation known as the Radiolaria Flood Zone (RFZ) is investigated for reconstructing palaeoceanography and controlling factors that resulted in the organic matter and radiolarian rich beds. A stratigraphic section named Tang-e-Haft located to the northwest of Zagros range with a thickness of 320 m mainly composed of argillaceous limestone, and limestone is used for this study. The RFZ is dated late Berriasian to earliest Aptian via using nannofossils, foraminifera, and palynology integrated. Semi-quantitative study of different microfossil groups and biofacies analaysis demonstrates deposition of this member in an intermediate depth under dys- to anaerobic marine condition with a shallowing upward trend. Richness of radiolarians with prevailed spumellaria assemblage and high organic matter content revealed presence of high palaeoproductivity during time of deposition. This productivity was induced by paleocurrents and upwelling systems. Values of total organic carbon (TOC), gamma ray, and amount of amorphous organic matter (AOM) in palynology slides in the lower parts of the section show a peak that indicates that palaeoproductivity was more intense in the lowermost part. Dominance of the radiolarians and consequently the RFZ unit ended up in the early Aptian. This time is coincided with Leupoldina cabri bloom and Oceanic Anoxic Event 1a (OAE1a). This event resulted in an extinction and significant reduction among radiolarians. Depopulation of radiolarians made new habitats for other organisms that planktonic foraminifera with elongated chambers were the first group to benefit the situation. [ABSTRACT FROM AUTHOR]

We present a high resolution, multiproxy study of the relationship between pelagic and benthic environments of a coastal upwelling system in the subtropical NE Atlantic Ocean. Marine sediments corresponding to late MIS3 to the Holocene in the radiocarbon dated core GeoB7926, retrieved off Mauritania (21°N) were analysed to reconstruct productivity in surface waters and its linkage to deep waters during the last 35 ka BP. High latitude cold events and changes in atmospheric and oceanographic dynamics influenced upwelling intensity over this time period. Subsequently, this caused changes in primary productivity off this low-latitude coastal upwelling locality. The benthic foraminiferal fauna displays four main community shifts corresponding to fundamental climatic events, first of all during late MIS3 (35–28 ka BP), secondly from 28 to 19 ka BP (including Heinrich event 2 and the LGM), thirdly within Heinrich event 1, the Bølling Allerød and the Younger Dryas (18–11.5 ka BP) and finally during the Holocene (11.5–0 ka BP). In particular, strong pelagic–benthic coupling is apparent in MIS 3, as demonstrated by increased primary productivity, indicated by moderate DAR and the dominance of benthic foraminiferal species which prefer fresh phytodetritus. A decline in upwelling intensity and nutrient availability follows, which resulted in a proportionately larger amount of older, degraded matter, provoking a shift in the benthic foraminifera fauna composition. This rapid response of the benthic environment continues with a progressive increase in upwelling intensity due to sea level and oceanographic changes and according high surface production during the LGM. During Heinrich event 1 and the Younger Dryas, extreme levels of primary production actually hindered benthic environment through the development of low oxygen conditions. After this period, a final change in benthic foraminiferal community composition occurs which indicates a return to more oxygenated conditions during the Holocene. [ABSTRACT FROM AUTHOR]

Abstract: The top 1m radiocarbon dated section of a 5.6m long sediment core retrieved from the Equatorial Indian Ocean is studied for productivity changes in response to climate variability that have taken place during the last ~33kyr. The robust indicators of marine productivity such as phytol and brassicasterol exhibit distinctly higher contents (av. 5.8ng/g and 4.8ng/g respectively) during the LGM (25–17kyBP) as compared to the succeeding period (16–5kyBP: av. 1.9ng/g each) and preceding period (33–25kyBP: av. 1.8 and 0.8ng/g respectively) which suggest increased productivity during the cold and dry climate of the LGM. The Corg content is also relatively higher during this period than the warmer Holocene. However, marginally higher C/N ratios (~7.8) and enrichment of δ13Corg (~−19.8‰) during the LGM than the Holocene (C/N ~6.4 and δ13Corg ~−21.5‰), and also the higher carbon preference index (CPI) of n-alkanes and n-alkanols together suggest the presence of terrestrial organic matter in the sediment. The increased equatorial productivity and terrestrial organic matter input together during the LGM may indicate intensified inter-monsoon equatorial Westerly Jets resulting in elevated productivity. [Copyright &y& Elsevier]

A geochemical analysis has been conducted in the Fuente de la Vidriera section of the External Subbetic (Betic Cordillera, southern Spain) in order to interpret the incidence of the Toarcian Oceanic Anoxic Event (T-OAE) in the western- most end of the Tethys. The obtained values of detrital, redox and palaeoproductivity proxies throughout the succession show minor fluctuations, but only punctual significant changes. Detrital input is nearly constant during the studied interval, except punctually in the lower part of serpentinum Zone, characterized by an increase in both fluvial and eolian detrital transport. Associated to this local higher fluvial and eolian activity, a comparatively higher concentration of organic matter is punctually registered, as revealed by the comparatively highest total organic carbon (TOC) value (0.99 wt.%). The remaining part of the section shows TOC values in the lower range of those registered in the Tethyan Toarcian sections (<0.4 wt.%). The obtained ratios of redox-sensitive trace metals lead to the interpretation of oxic to dysoxic bottom-waters, with a singular sharp decrease in oxygenation corresponding to a short interval within the serpentinum Zone (sample FV- 18) correlated to the T-OAE. The minor incidence of the T-OAE registered in this west- ernmost end of the Tethys, in which punctual dysoxic conditions are restricted only to a decimetre-scale interval reveals the importance of regional context and local oceanic-atmosphere dynamics on the local record of this phenomenon. [ABSTRACT FROM AUTHOR]

This study examines the dynamics of organic carbon contributions from different sources to the sediments of a ~39 m core from Ísafjarðardjúp Fjord, Northwest Iceland, throughout the Holocene. Furthermore, it shows that the variability of terrestrial organic carbon (OCterr) and marine organic carbon (OCmar) is linked to palaeoclimatic change throughout the Holocene. glycerol-dialkyl-glycerol-tetraether (GDGT), alkenone, n-alkane, total OC and total nitrogen analyses were conducted on 326 samples to yield high-resolution branched versus isoprenoid tetraether index (BIT-index), n-alkane/alkenone index and C/N ratio records from ~10,800 to ~300 cal. a BP. These records were used to estimate the OCterr and the OCmar contributions to the sediments. Three different approaches of estimating the OCterr contribution yield different relative amounts, but similar long-term trends. These results indicate that the combination of biomarker records is a good approach to reconstruct OCterr contributions but also highlight the strengths and weaknesses of the individual biomarkers. The OCterr contribution to the total OC inventory continually increases throughout much of the Holocene but does not rise above 30%. It seems to have been driven by changing climate rather than changing sedimentation rates, and during the late Holocene, anthropogenic activity may have been an influence. The reconstructed OCmar contribution to the sediment was used to model changes in palaeoproductivity throughout the Holocene. These changes were likely forced by changes in nutrients supplied both by the catchment area and the Irminger Current. [ABSTRACT FROM AUTHOR]

Sequential samples of a 7.82-m sediment core from Genggahai Lake in the central Gonghe Basin, controlled with 12 accelerator mass spectrometry (AMS) C dates, have been analysed for total organic carbon (TOC) and total nitrogen (TN) contents, carbon isotope of bulk organic matter ( δC), and carbonate content. Plant macrofossils and stem encrustations, derived mainly from the species of P. pectinatus, M. spicatum and Chara spp., were identified, and they dominated the aquatic plant community of the lake. Alternations of plant macrofossils of Chara spp. and the vascular species reflect the changing productivity of the lake over time. In such a shallow lake, the carbonate content is highly related to photosynthesis of aquatic macrophytes and thus indirectly indicates variations in productivity, consistent with a quantitative estimate of palaeoproductivity. Based on these results, the palaeoproductivity history was reconstructed over the past ca. 16 ka. The lake was formed or recharged at 15.3 cal ka BP, as indicated by aeolian sand deposits at the core base. A marked increase in palaeoproductivity occurred from 15.3 to 11.6 cal ka BP. Between 11.6 and 9.2 cal ka BP, a sharply increased water-level, modulated probably by the enhanced Asian summer monsoon, might have exceeded the optimum water depth for macrophyte vegetation, causing a marked decline in coverage of aquatic macrophytes and low palaeoproductivity. The palaeoproductivity appeared to be high in the early stage of the period from 9.2 to 7.4 cal ka BP, and then decreased at approximately 8.6 cal ka BP. The palaeoproductivity sustained an overall high level between 7.4 and 2.1 cal ka BP, and decreased gradually since 2.1 cal ka BP. Our results suggest that the variability of Genggahai Lake palaeoproductivity may be associated with fluctuations of the lake level controlled by the strength of the Asian summer monsoon, probably indicating changes in the Asian summer monsoon. [ABSTRACT FROM AUTHOR]

Abstract: Data from agglutinated benthic foraminiferal assemblages and geochemical proxies make it possible to characterise different order sea-level dynamics —from a geological scale third-order transgressive–regressive cycle to a minor-scale, ecological range, maximum flooding-initial regressive phase—in part of the Valanginian from Spitsbergen. The transgressive–regressive cycle starts with abundance (foram/100g) of opportunist epifaunal forms related to deep waters and low productivity conditions on oxygenated sea-bed. The increase of these foraminifera, together with increased condensation and an impoverishment of trophic resources, is associated with the maximum flooding phase. The beginning of the subsequent regression shows a progressive diminution in foraminiferal abundance as a result of the greater sedimentation rate, the mounting proportions of deep infaunal forms, and the diminution of genera of deep-water environments. This initial regressive phase is associated with more arid climatic conditions (abrupt increase of eolian detrital proxies), and high palaeoproductivity (increase of Ba/Al, Sr/Al and P/Ti ratios and TOC), determining a diminution in the oxygenation (high values in Co/Al, Ni/Al and Mo/Al ratios and hydrogen index). After the initial productivity bloom, the foraminiferal abundance decreases, whereas diversity increases, favoured by the stability of environmental conditions (no fluctuations in palaeoproductivity, detrital and redox proxies), in turn related to deceleration of sea-level fall. The peaks of maximum foraminiferal abundance (optimum) of each morphogroup during the transition from maximum flooding to the beginning of regression allow us to identify an ecological replacement inter- and intra-microhabitats. In the different phases of ecological replacement, the dominant morphogroups are distributed in distinct microhabitats (epifaunal, shallow infaunal and deep infaunal) as a result of competition. [Copyright &y& Elsevier]

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Abstract: The Cenomanian/Turonian boundary interval (CTBI) is marked by an intense climatic warming presumably caused by large magmatic eruptions. This warming was characterised by one of the most prominent Mesozoic perturbations of the carbon cycle, the Oceanic Anoxic Event 2 (OAE2), which is marked by a well pronounced positive carbon isotope excursion (CIE). Sediments of the OAE2-interval often consist of organic rich black shales suggesting widespread bottom water anoxia during the CTBI. This study focuses on calcareous nannofossils from the CTBI of a European section (Wunstorf Core; northwest Germany). A total of 105 samples were examined for calcareous nannofossils using the settling technique. Eight bioevents (last occurrences: Corollithion kennedyi, Lithraphidites acutus; first occurrences: Rotelapillus biarcus, Corollithion exiguum, Eprolithus octopetalus, Eprolithus eptapetalus, Quadrum gartneri, Eiffellithus eximius) have been recognised throughout the middle Cenomanian to middle Turonian interval. With the exception of eleven samples preservation is moderate to good. Calcareous nannofossils are abundant (mean 2.0billion specimens/g sediment) and highly diverse (mean 58 species/sample). Assemblages are dominated by Watznaueria spp. (32.3%), Prediscosphaera spp. (13.4%), Zeugrhabdotus spp. (11.2%) and Biscutum spp. (10.5%). Pre-OAE2 and also post-OAE2 nannofossil assemblages show high abundances of Biscutum spp. (∼20%) indicative for stable mesotrophic conditions. The assemblages of the OAE2 itself are marked by high values for Watznaueria spp. and low frequencies of Biscutum spp. making oligotrophic conditions during the OAE2 likely. High absolute abundances of organic walled dinoflagellates and the occurrence of frequent stress tolerant nannofossil genera like Retecapsa spp. in the organic rich intervals suggest, however, a deposition of black shales enhanced by high primary productivity. Thus dinoflagellates and calcareous nannofossils are interpreted to reflect different seasonal signals during the time of black shale deposition. Short-term high fertile seasons allowed the blooming of the organic walled dinoflagellates whereas calcareous nannofossils dominated the longer oligotrophic seasons. The black shale deposition was supported by the formation of large amounts of organic matter during fertile seasons as well as by surface water stagnation during oligotrophic seasons. [Copyright &y& Elsevier]

Abstract: The palaeontological, geochemical and mineralogical records of core GNS84-C106 were analysed in order to reconstruct palaeohydrological changes and palaeoproductivity patterns in the Gulf of Salerno for the last 34 kyr. This approach, including compositional analysis of planktonic and benthic assemblages, gave an insight into the relationships between continental, sea surface and bottom environmental changes. The main source of variability of planktonic and benthic assemblages is related respectively to sea surface temperature and palaeobathymetry. Interrelated changes in surface salinity, nutrients, density gradient in the water column and organic fluxes at the bottom act as a secondary factor controlling the composition of both planktonic and benthic assemblages. The highest palaeoproductivity rates were reached during an interval spanning from late glacial to Middle Holocene, in conditions of enhanced continental run-off. During the Early and Middle Holocene, reduced surface salinity and density stratification were also coupled with the development of a deep chlorophyll maximum and enhanced flux or organic matter at the bottom. From about 6.5 kyr B.P. onward, a sharp reduction in palaeoproductivity took place, coupled with an increase in surface salinities. [Copyright &y& Elsevier]

The Holocene palaeoclimatic history of the Galician continental shelf has been investigated through the analyses of diatom remains, other siliceous compounds, biogenic silica (BSi) and metals content in a multiproxy approach to a gravity core recovered from the Galicia Mud Patch, NW Iberian Peninsula, covering the last 5000 years. Downcore changes in diatom assemblages composition and abundance reflect changes in diatom production related to long-/short-term variations in climate, regional oceanography, upwelling strength and river influx off the coast of NW Spain and Portugal. Palaeoclimatic variability was related to the relative strengths and position of the Azores High and Iceland Low pressure cells. Metals and microflora fluctuations are interpreted as changes in the riverine influence and upwelling intensity paced by oceanographic, atmospheric and climatic changes. Lack of diatoms between 4700-3300 and 1800-1200 cal. yr BP could be linked to early diagenetic processes taking place in the sediment after burial. Biogenic barium (Baexcess), metals and diatom assemblages, show a general increase of marine productivity for the last 1200 cal. yr BP. Between 800 and 500 cal. yr BP high production of the microflora is triggered by influx of river-derived nutrients under conditions of SW winds and storms resulting from a NAO negative-like phase. The biosiliceous and geochemical signatures of sediments from the last 500 cal. yr BP indicate conditions of enhanced upwelling and increased phytoplanktonic production associated with the intensification of northerly winds. Upwelling strengthening in this area, attributed to recent global warming, could provoke an increase in phytoplankton biomass with consequent biological, climatological and socioeconomical impacts. The imprint of anthropic activities has been recorded by the increasing Pb/Al ratios for the last 400 cal. yr BP. [ABSTRACT FROM AUTHOR]

Abstract: The sediments from the Congo deep-sea fan contain valuable information about past environmental conditions of the east equatorial Atlantic during the transition from the Last Glacial Maximum (LGM) to present-day climatic conditions. The high-resolution marine (organic-walled dinoflagellate cysts=dinocysts) and terrestrial (pollen) palynological records from two cores off equatorial West Africa, covering the last 30,000 years, document three major phases in surface productivity. (1) During the LGM relative sea level was low, nutrient enrichment due to seasonal coastal upwelling prevailed off the Congo mouth and high aridity prevailed in the catchment area. (2) At around 15.2 cal ka BP, monsoonal precipitation strengthened over the Congo Basin, generating high river discharges, river-induced upwelling, and increased nutrient flux to the ocean. In parallel, erosion of shelf sediments during shelf transgression further enhanced nutrient flux. (3) At around 9–8 cal ka BP, rainforest vegetation inhibited soil erosion, depleted nutrient supply, and restricted marine productivity to its modern levels. The study presents the application of modern analogues and a dinocyst transfer function to the reconstruction of primary palaeoproductivity (PP) in a region of freshwater influence. A database of recent dinocyst assemblages comprising of 208 sites in the equatorial Atlantic enabled the reconstruction of sea-surface annual PP 1.3 times higher during the LGM and also during the deglaciation, between 15.2 and 13.2 cal ka BP. The reconstruction is independent of, and thus provides corroboration for, other biological and geochemical proxies. [Copyright &y& Elsevier]

Abstract: The high-resolution quantitative study of benthic foraminifera from the Elles section (NW Tunisia) that contains one of the most complete Cretaceous–Paleogene (K–Pg) boundary transition and spans about 357 kyr provides detailed data on the palaeoenvironmental turnover across the K–Pg boundary. Benthic foraminifera indicate outer neritic-uppermost bathyal depths without perceivable bathymetrical changes throughout. Uppermost Maastrichtian assemblages are well preserved and highly diversified, indicating stable environment and mesotrophic to weakly eutrophic conditions during the latest Cretaceous. Benthic foraminifera underwent a major faunal turnover in coincidence with the K–Pg boundary, where a dramatic and sudden decrease in the percentage of both infaunal morphogroups and buliminids, as well as in diversity, heterogeneity, and genus and species richness of the assemblages, are recorded indicating overall oligotrophic conditions. Benthic foraminifera do not show significant extinction at the end of the Cretaceous, with only about 3% of the species clearly becoming extinct together with the temporary disappearance of some taxa. A stepped pattern of faunal recovery and restructuring is recognizable during the lowermost Danian reflecting the gradual restabilization of the environmental conditions after the K–Pg boundary event. The nature and the abundance of food supply to the sea floor conditioned the faunal turnover in the earliest Paleogene which reflects not only a sudden collapse of the food web due to the extinction of calcareous primary producers, but also a major, rapid change in composition and abundance of food supply just after the K–Pg boundary. Short-term blooms of some opportunistic species within the G. cretacea Zone and the lowermost part of the Ps. pseudobulloides Zone would reflect instability in the benthic assemblages that might be related to the transfer to the sea floor of food supply not easily used by the benthos through short-term, large blooms or changes in abundance of opportunistic, various phytoplankton groups. The major environmental instability at the sea floor that just follows the K–Pg boundary event may have been thus related to changes in the phytoplankton composition and abundance and would have taken place over a period of about 25 kyr. Benthic foraminiferal assemblages appear to stabilize in the lowermost part of Zone Ps. pseudobulloides (∼65 kyr after the K–Pg boundary event). The sea floor ecosystem, at least at outer neritic-uppermost bathyal depths, may have recovered over a considerably shorter period than commonly suggested, even if the food delivery to the sea floor had not fully recovered the pre-K–Pg levels as indicated by the lower percentages of infaunal morphogroups and buliminids. This would be also in agreement with the rapid recovery of terrestrial ecosystems following the biotic crisis at the K–Pg boundary. The drastic change of benthic foraminiferal assemblages coincident with the K–Pg boundary at Elles and their staggered reorganization during the lowermost Paleogene are largely compatible with the catastrophic effects of a huge asteroid impact on Earth at the K–Pg boundary that severely destabilized the oceanic phytoplankton-based food web. [Copyright &y& Elsevier]

We review controls on extensional growth rate and shell thickness in the extant oyster Crassostrea. Data on these shell parameters for the ecologically similar Bathonian oyster Praeexogyra hebridica, sampled at carefully selected sites, are then used to test a hypothesis that small size in contemporaneous marine bivalves of north-west Europe was the product of reduced salinity. The hypothesis is refuted, at least to the extent that some additional factor must be involved. The relatively low extensional growth rate and shell thickness at the highest-salinity site, together with the elongate (‘etiolated’) shape there and the low extensional growth rate at all sites in comparison with Crassostrea, suggests that this factor is reduced primary productivity. Other faunal, sedimentological and diagenetic evidence is consistent with low productivity. We point to other possible instances of reduced productivity during the Middle Jurassic and discuss the possible role of this factor in encouraging the widespread colonization of brackish-water environments by bivalves in the Bathonian Stage. [ABSTRACT FROM AUTHOR]

Abstract: Oceanic stratification represents an effective mechanism to reduce vertical mixing of the water column, thereby locking up carbon dioxide (CO2) in the deep sea and preventing air–sea exchange of CO2. It has been proposed that enhanced stratification of the upper water column in polar oceans during late Cenozoic cooling episodes limited the upwelling of CO2-rich deep waters and thus CO2-release to the atmosphere, resulting in a net global drawdown of atmospheric CO2. Increased stratification in the Subarctic Northwest Pacific, during both the onset of Northern Hemisphere glaciation at 2.73 Ma and late Quaternary glacial periods, has been recently linked to enhanced ocean stratification south of the Antarctic Polar Front (APF) in the Pacific and Atlantic sectors of the Southern Ocean. Increased stratification of Southern Ocean surface waters was mainly deduced from a reduction of biological production during these cooling episodes, manifested by the decrease of geochemical proxies for productivity, such as biogenic opal and barium, in the marine sediment records. However, the records chosen from the Southern Ocean do not provide evidence for a more stratified upper water column, rather the observed decrease in biological productivity is likely to have resulted from an expansion of annual sea-ice coverage. The sediment records suggest that south of the APF in the Pacific and Atlantic sectors of the Southern Ocean, extensive sea ice may have contributed to the global CO2-drawdown during glacial periods, with hypothetical glacial increase of stratification in today''s permanent open-ocean zone merely being an “add on“ caused by this expansion. [Copyright &y& Elsevier]

The article presents abstracts of several studies on environmental geochemistry. Some of the abstracts presented include "Biogeochemical Cycling of Nutrients in Karstic Catchments, Southwestern China: Linkages to Changes of Eco-Environments," by Congqiang Liu and "Emerging Organic Contamination in China," by Guibin Jiang and colleagues.

Abstract: Two sediment cores from the Murray Canyons area, south of Kangaroo Island, South Australia, were investigated for proxy-records to reconstruct past productivity of the surface waters in the area over the last 175 ka. The proxies used included concentrations of aragonite, low- and high-Mg calcite, total carbonate, total organic carbon, sulfur and δ13C of Globigerina bulloides. Cyclic increases in palaeoproductivity were observed to be in tune with insolation minima at 30°S. The atmospheric conditions during insolation minima were comparable to present winter patterns, when strong westerly winds dominate over the area and bring dust from the central desert areas. During the last insolation minimum (last glacial maximum: LGM), the Murray Canyons laid directly under the “Eastern Australian Dust Plume”. Dust could have fertilized surface waters and initiated the observed productivity “increases” on a precessional time scale. The core from the more westerly canyons is richer in organic matter; this could be attributed to the influx of organic matter from shallower water, which is carried by an overflow of hypersaline water from the Spencer Gulf to the deep ocean, using the western canyons as conduits. There is no evidence that the “Palaeo-Murray River”, which debouches close to the core sites during sealevel lowstands, was a major source of nutrients for surface waters. Although total carbonate concentrations remained high, planktonic foraminifers were fewer in numbers during these periods, possibly due to reduced light penetration caused by suspended river material. A deglacial minimum in δ13C of Globigerina bulloides, observed in other cores from the southern hemisphere and attributed to a major hydrographic change south of the Polar Front, is also visible in our two cores, thus attesting to the global significance of the event. [Copyright &y& Elsevier]

Abstract: Changes in benthic foraminiferal and mollusk assemblages from the lower part of the Upper Pliocene of the Atsipades Section (Iraklion Basin, central Crete) were studied. The Atsipades Section represents a shallowing-upward sequence from outer shelf blue–gray clays at the bottom of the sequence, deposited below the storm wave base, to shallow inner shelf deposits affected by storm waves at the top. The foraminiferal assemblage at the bottom of the sequence is dominated by Bolivina spathulata, Bolivina dilatata and Uvigerinidae, a microfossil assemblage corresponding to the deepest deposits formed under dysoxic sea-floor conditions. Foraminiferal assemblages of the middle part of the section are highly diversified, predominantly Haynesina depressula, Cassidulina carinata and Reusella spinulosa. The top of the section is mainly characterised by Asterigerinata planorbis, Bolivina pseudoplicata, Cibicides lobatulus and Elphidium sp., a typically epiphytic foraminiferal assemblage which can be correlated with the presence of an algal covered sea-bottom. Within this general environmental trend, a minor shallowing cycle can be differentiated. The boundaries of this cycle can be inferred, based on a substantial microfossil assemblage change and on the coincidence of species diversity maximum and a planktonic/benthic (P/P + B) ratio peak. Nonetheless, upwelling currents and/or over-abundance of nutrients due to continental outflow could also contribute to increased diversity and P/P + B ratio. The character of the mollusk assemblages is in accordance with these trends. Moreover, the increase in diversity and in sculpture constitutes a clear indication of an increase in hydrodynamic energy related to a shallowing-upward trend. [Copyright &y& Elsevier]

Abstract: Palaeotemperatures during the Albian–Coniacian in the northernmost Pacific have been determined on the basis of oxygen isotopic analysis of well-preserved brachiopod and molluscan shells from the Koryak Upland, Far East Russia. Those obtained from the calcitic brachiopod shells from the Albian range from 12.5 to 22.7°C. The lower temperature level corresponds to winter seasons and the higher reflects summer temperatures. Probable winter isotopic palaeotemperatures, fluctuating from 10.9 to about 14.1°C, were obtained from Coniacian bivalve shells. Presumed spring and autumn isotopic palaeotemperatures for the Coniacian, fluctuating from 14.1 to 17.7°C, were obtained from rhynchonellid brachiopods and bivalves, all with calcitic shells, and ammonoids with aragonitic shells. Presumed summer isotopic palaeotemperatures varied between 18.5°C to 22.4°C. The new and previously published data suggest a short-term presence of polar ice during the Cretaceous (early Maastrichtian) only in the Southern Hemisphere on the Antarctic continent. Evidence pertaining to the Northern Hemisphere seems to suggest only occasional short-lived subfreezing conditions. These most probably occurred during polar winters in the early Valanginian, late Coniacian–early Santonian and early Maastrichtian. Temperatures in northern high latitudes during the course of even these winter seasons were probably not low enough for the formation of permanent sea ice. This may be a result of the lack of a continental massif in the North Pole area and a significant ameliorating effect of oceanic heat-transport poleward through the straits of Turgai and the Western Interior of North America. [Copyright &y& Elsevier]

Biogenic records of the marine palaeoproductivity (carbonates, organic carbon, and C37 alkenones) and the molecular stratigraphy of past sea surface temperatures (SSTs; U37K′) were studied at high resolution in two cores of the Iberian Margin. The comparison of these records indicates that the oceanographic conditions switched abruptly during the past 160 kyr between three kinds of regimes. A first regime with high (17–22°C) SST and low productivity typifies the interglacial periods, marine isotopic stages (MIS) 5 and 1. Several periods during MIS 6, 2, and the terminations II and I are characterised by about 4–5°C colder SST and a higher organic matter accumulation, both of which define the second regime. This anticorrelation between SST and marine productivity suggests that these variations are related to the intensity of the coastal upwelling. By contrast with this upwelling behaviour, extremely low biological productivity and very cold SST (6–12°C) occurred during short phases of glacial MIS 6, 4, and 2, and as abrupt events (&ap;1 kyr or less) during MIS 3. The three oceanographic regimes are consistent with micropalaeontological changes in the same cores based on foraminifera and diatoms.The general trend of these hydrologic changes follows the long-term glacial/interglacial cycle, but the millennium scale variability is clearly related to Heinrich events and Dansgaard–Oeschger cycles. Strengthening of the upwelling corresponds probably to an intensification of the subtropical atmospheric circulation over the North Atlantic which was influenced by the presence of continental ice sheets. However, extreme glacial conditions due to massive discharges of icebergs interrupted the upwelling. Interestingly, both terminations II and I coincided with strong but transient intensification of the upwelling. [Copyright &y& Elsevier]

Environmental conditions and productivity changes in the southeastern Okhotsk Sea have been reconstructed for the last 20 ka using planktonic and benthic foraminiferal oxygen isotope records and calcium carbonate, organic carbon and opal content data from two sediment cores. Species variability in benthic foraminiferal and diatom assemblages provides additional palaeoceanographic evidence. AMS radiocarbon dating of the sediments and oxygen isotope stratigraphy serve as the basis for the age models of the cores for the last 20 14C kyr and for correlation between environmental variations in the Okhotsk Sea, and regional and global climate changes. Benthic foraminiferal assemblages in the two cores (depth 1590 and 1175 m) varied with time, so that we could recognise seven zones with different species composition. Changes in the benthic foraminiferal assemblages parallel major environmental and productivity variations. During the last glaciation, fluxes of organic matter to the sea floor showed strong seasonal variations, indicated by the presence of abundant A. weddellensis and infaunal Uvigerina spp. Benthic foraminiferal assemblages changed with warming at 12.5–11 and 10–8 14C kyr BP, when productivity blooms and high organic fluxes were coeval with global meltwater pulses 1A and 1B. Younger Dryas cooling caused a decline in productivity (11–10 kyr BP) affecting the benthic faunal community. Subsequent warming triggered intensive diatom production, opal accumulation and a strong oxygen deficiency, causing significant changes in benthic fauna assemblages from 5.26–4.4 kyr BP to present time. [Copyright &y& Elsevier]

Lacustrine organic-rich shales are well developed in the Dameigou Formation within the Yuka Depression of the Qaidam Basin. These fine-grained sediments have been proven to have good hydrocarbon generation potential; therefore, understanding the sedimentary palaeoenvironment of these shales and organic matter enrichment mechanism is essential to increase prospects for shale oil and gas resources. The mineralogy, elemental geochemistry, and organic geochemical data combined with lithology of ZK23-1 well from the Yuka Depression, Qaidam Basin have been comprehensively analyzed to determine the hydrocarbon potential, palaeoenvironmental changes, and tectonic setting of the lacustrine organic-rich shales in the seventh member of Middle Jurassic Dameigou Formation (J 2 d7). The profile of the ZK23-1 well is composed of three stages (Stages I to III) based on variations in bulk geochemical parameters and lithological observations. Mineral compositions of studied samples are dominated by clay minerals and quartz, with small amount of pyrite, calcite, dolomite, and plagioclase. Interestingly, all samples contain siderite, which is closely related to palaeoenvironment changes. Total organic carbon (TOC) content and hydrogen index (HI) vary significantly in the various lithologies, suggesting that oil shale holds the best hydrocarbon potential, followed by shales and mudstones. A warm-humid palaeoclimate prevailed in the Qaidam Basin during the Middle Jurassic; however, significant palaeoclimatic fluctuations occurred from Stages I to III in the J 2 d7, especially in Stage II. The climate varies from hot-arid to warm-humid in Stage II, likely resulting in changes in palaeowater column, chemical weathering intensity, as well as palaeoproductivity. The results of this study suggest that the Yuka Depression in the Middle Jurassic could be located at an active continental margin. Warm and humid conditions, as well as the tectonically quiescent setting with stable subsidence rate, are considered as two primary drivers for the enrichment and preservation of OM in the sediments of the J 2 d7. Ultimately, a comprehensive depositional model is proposed to interpret the evolution of deposition of the J 2 d7, providing new insights into the deposition of lacustrine organic-rich sediments linked to palaeoenvironment conditions and tectonic setting. • Three stages have been identified from ZK23-1 in the J 2 d7. • An obviously environmental fluctuation occurred from stage I to III of the J 2 d7. • Depositional models have been proposed to interpret the enrichment of OM. • The warm and humid condition and tectonically quiescent setting are popular. • Palaeoclimate and tectonic setting are primary drivers for OM enrichment. [ABSTRACT FROM AUTHOR]

During the last retreat of the Laurentide Ice Sheet in North America, many proglacial lakes formed as continental drainage was impounded against the southern and western ice margin. Lake Agassiz was the largest of these lakes. The bathymetry of Lake Agassiz at the Herman and Upper Campbell beach levels – formed at about 11.5–11.0 ka and 9.9–9.5 ka, respectively – was computer modelled in this study by first collecting data for the isostatically-deformed paleowater planes of the two lake levels (derived from isobase lines constructed from beach elevations), and then subtracting these from the modern topography of the former lake floor. Pixels with dimensions of 1/30 × 1/30 of a degree were used in the model. Using these data, the area and volume of the lake were also calculated: at the Herman level these were ∼152 500 km2 and ∼13 100 km3 respectively; at the Upper Campbell level these were ∼350 400 km2 and ∼38 700 km3. Contour maps showing the paleobathymetry of both periods in the lake's history were also constructed. Determining the paleobathymetry and volume of Lake Agassiz is an important step in understanding the impact that the lake had on its surrounding environment and on the rivers, lakes, and oceans into which it flowed. [ABSTRACT FROM AUTHOR]

Five Holocene sediment cores from the northwestern Baltic proper were analysed for lithology, siliceous microfossil assemblages and geochemical parameters. The data indicate that surface water salinity and redox conditions below the halocline have changed drastically at least four times since the Baltic Sea changed from a fresh water lake (the Ancylus Lake) to a semi-enclosed brackish water sea (the Litorina Sea) c. 8500 yrs BP. These variations appear to be mainly effects of changes in water depth at the thresholds of inlet areas. Based on these changes, and earlier studies of the shoreline displacement in the inlet areas, we propose a tentative model for changes of large scale water circulation in the Baltic Sea during the last c. 8500 yrs. At the transition from fresh to brackish water 8500 14C yrs BP, upwelling of nutrient rich bottom water started to occur, causing a slight increase in primary production. Diatom assemblages in sediments indicate a slow rise in surface water salinity during this period. At 7000-6500 14C yrs BP, surface water salinity and primary production simultaneously increased, as anoxic bottom conditions were established at depth below the halocline. We suggest that high primary production was caused by increased input of oceanic water, leading to increased upwelling of nutrient rich bottom water. At the anoxic bottoms laminated sediments formed until 5000-4500 14C yrs BP. This period (c. 7000-4500 14C BP) was contemporaneous with the post-glacial transgression maximum in Öresund, and we suggest it represents the most saline phase of the Baltic Sea post-glacial history. Due to a regression in Öresund starting 4500 14C yrs BP, upwelling decreased and the halocline was lowered, resulting in decreased primary productivity and hence oxic deep water conditions. The diatom assemblages of the sediments indicate a lowering of salinity at the beginning of this period. We suggest that the second period of anoxic bottom conditions c. 2000-1500 14C yrs BP was caused by a change of dominating inflows from the Öresund to the Belt Sea. This resulted in decreased salinity of the inflowing water which did not penetrate to the deepest parts of the basin as frequently as before. The diatom record indicates both a second lowering of salinity and a change in the large scale water circulation at the beginning of this period. [ABSTRACT FROM AUTHOR]