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See detailSeismically-triggered organic-rich layers in recent sediments from lake Gollukoy (North Anatolian Fault, Turkey
Avşar, Ulaş; Hubert, Aurelia ULg; De Batist, Marc et al

in Quaternary Science Reviews (2014), 103

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See detailLate Quaternary evolution of sediment provenances in the Central
Fagel, Nathalie ULg; Not, Christelle; Gueibe, Jonathan et al

in Quaternary Science Reviews (2014), 92

Mineral assemblage, trace element content and Nd and Pb isotope signatures were analysed on the fine fraction (<20 mm) of sedimentary records from the Northern Mendeleev Ridge in the Central Arctic Ocean ... [more ▼]

Mineral assemblage, trace element content and Nd and Pb isotope signatures were analysed on the fine fraction (<20 mm) of sedimentary records from the Northern Mendeleev Ridge in the Central Arctic Ocean. Our aimwas to identify the detrital particle provenance and to interpret the changes over the past w250 ka in the relative contribution of the different source-areas in relation to paleoenvironmental conditions. The clay mineral assemblage and the Nd and Pb isotope signatures depict systematic changes over the Late Quaternary. The bulk mineralogy exhibits increases in the relative contribution of carbonate minerals vs. silicates in interglacial/deglacial intervals. In glacial intervals, the mineral assemblage of the <20 mm fraction is characterised by an enrichment in kaolinite, counterbalanced by a decrease in illite. The Nd and Pb isotope signatures of <20 mm fraction are interpreted using a three end-member mixing model, involving crustal supplies from North America and Canada, from the Siberian margin and some from volcanic material. A compilation of geochemical signatures of geological terraines surrounding the Arctic Ocean allowed each end-member to be assigned a representative signature, averaging the signal of the eroded terraines. The Suspended Particulate Matter (SPM) of the MacKenzie River represents an average signature of the sedimentary supplies delivered from the North American platform and Canadian margin. The SPM of the Lena River reflects the mean sedimentary signature of the Siberian platform. The Okhotsh-Chukotka province from the Eastern border of Siberia is identified as the most probable volcanic source. Late Quaternary evolution of the estimated relative contribution of the three end-members confirms that the sediment provenances in the Central Arctic Ocean remain close to the current conditions during past interglacials/deglacials MIS1e3, MIS5/TII and MIS7/TIII. In contrast, glacial conditions (MIS4 and MIS6) record minimum supplies from the American margin, associated with increased volcanic contribution, to the Mendeleev Ridge core location suggesting a different sea-ice circulation associated with a low sea-level and reduced shelf area. [less ▲]

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See detailBiological nitrate utilization in south Siberian lakes (Baikal and Hovsgol) during the last glacial period: the influence of climate changes on primary productivity
Watanabe Nara, F.; Watanabe, T.; Kakegawa, T. et al

in Quaternary Science Reviews (2014), 90

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See detailRole of sea ice in global biogeochemical cycles: Emerging views and challenges
Vancoppenolle, M; Meiners, K.M.; Michel, C. et al

in Quaternary Science Reviews (2013), 79

Observations from the last decade suggest an important role of sea ice in the global biogeochemical cycles, promoted by (i) active biological and chemical processes within the sea ice; (ii) fluid and gas ... [more ▼]

Observations from the last decade suggest an important role of sea ice in the global biogeochemical cycles, promoted by (i) active biological and chemical processes within the sea ice; (ii) fluid and gas exchanges at the sea ice interface through an often permeable sea ice cover; and (iii) tight physical, biological and chemical interactions between the sea ice, the ocean and the atmosphere. Photosynthetic micro-organisms in sea ice thrive in liquid brine inclusions encased in a pure ice matrix, where they find suitable light and nutrient levels. They extend the production season, provide a winter and early spring food source, and contribute to organic carbon export to depth. Under-ice and ice edge phytoplankton blooms occur when ice retreats, favoured by increasing light, stratification, and by the release of material into the water column. In particular, the release of iron – highly concentrated in sea ice – could have large effects in the iron-limited Southern Ocean. The export of inorganic carbon transport by brine sinking below the mixed layer, calcium carbonate precipitation in sea ice, as well as active iceatmosphere carbon dioxide (CO2) fluxes, could play a central role in the marine carbon cycle. Sea ice processes could also significantly contribute to the sulphur cycle through the large production by ice algae of dimethylsulfoniopropionate (DMSP), the precursor of sulfate aerosols, which as cloud condensation nuclei have a potential cooling effect on the planet. Finally, the sea ice zone supports significant ocean-atmosphere methane (CH4) fluxes, while saline ice surfaces activate springtime atmospheric bromine chemistry, setting ground for tropospheric ozone depletion events observed near both poles. All these mechanisms are generally known, but neither precisely understood nor quantified at large scales. As polar regions are rapidly changing, understanding the large-scale polar marine biogeochemical processes and their future evolution is of high priority. Earth system models should in this context prove essential, but they currently represent sea ice as biologically and chemically inert. Paleoclimatic proxies are also relevant, in particular the sea ice proxies, inferring past sea ice conditions from glacial and marine sediment core records and providing analogs for future changes. Being highly constrained by marine biogeochemistry, sea ice proxies would not only contribute to but also benefit from a better understanding of polar marine biogeochemical cycles. [less ▲]

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See detailHydrological instability during the Last Interglacial in central Asia: a new diatom oxygen isotope record from Lake Baikal
Mackay, Anson; Swann, Georges; Fagel, Nathalie ULg et al

in Quaternary Science Reviews (2013), 66

Last Interglacial variability is commonly used as an analogue for variability in a future, warmer world. Pervasive cycles are increasingly apparent in Last Interglacial archives, although studies in ... [more ▼]

Last Interglacial variability is commonly used as an analogue for variability in a future, warmer world. Pervasive cycles are increasingly apparent in Last Interglacial archives, although studies in continental regions are under-represented. Here we provide a new isotopic record of diatom silica (d18Odiatom) spanning c. 127.5e115 ka BP from Lake Baikal in central Asia. Peak rain-fed discharge occurred c. 125.4 ka BP, shortly after July insolation maximum and initiation of Siberian soil development. Between 127 and 119.7 ka BP there are six marked fluctuations in d18Odiatom values, with a pacing of approximately 1.26 0.3 ka, similar to fluctuations of within lake productivity. Fluctuations in d18Odiatom values show good agreement with patterns in Atlantic meridional overturning circulation (AMOC), supporting hypothesis of strong teleconnections via theWesterlies between the North Atlantic and central Asia. Two periods of low d18Odiatom values are especially notable. The earliest between c. 126.5 and 126 ka BP is concurrent with the final stages of the Heinrich 11. The second between 120.5 and 119.7 ka BP is also concurrent with an increase in ice-rafted debris in the North Atlantic. Aquatic productivity in Lake Baikal increased between 119.7 and 117.4 ka BP before declining to the top of the record (115 ka BP) concomitant with a shift to predominately cool steppe catchment vegetation. However, isotopic composition of discharge into Lake Baikal provides evidence for strong penetration of Westerlies into central Asia during the latter stages of the Last Interglacial. Variability in d18Odiatom values was compared between the Last Interglacial and the Holocene. Millennial-scale variability was significantly more stable during the Last Interglacial, possibly linked to diminished influence of freshwater discharge on AMOC during periods of higher, global mean temperatures. [less ▲]

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See detailHydrological instability during the Last Interglacial in central Asia: a new diatom oxygen isotope record from Lake Baikal
Mackay, Anson; Swann, Georges; Fagel, Nathalie ULg et al

in Quaternary Science Reviews (2013), 66

Last Interglacial variability is commonly used as an analogue for variability in a future, warmer world. Pervasive cycles are increasingly apparent in Last Interglacial archives, although studies in ... [more ▼]

Last Interglacial variability is commonly used as an analogue for variability in a future, warmer world. Pervasive cycles are increasingly apparent in Last Interglacial archives, although studies in continental regions are under-represented. Here we provide a new isotopic record of diatom silica (d18Odiatom) spanning c. 127.5e115 ka BP from Lake Baikal in central Asia. Peak rain-fed discharge occurred c. 125.4 ka BP, shortly after July insolation maximum and initiation of Siberian soil development. Between 127 and 119.7 ka BP there are six marked fluctuations in d18Odiatom values, with a pacing of approximately 1.26 0.3 ka, similar to fluctuations of within lake productivity. Fluctuations in d18Odiatom values show good agreement with patterns in Atlantic meridional overturning circulation (AMOC), supporting hypothesis of strong teleconnections via theWesterlies between the North Atlantic and central Asia. Two periods of low d18Odiatom values are especially notable. The earliest between c. 126.5 and 126 ka BP is concurrent with the final stages of the Heinrich 11. The second between 120.5 and 119.7 ka BP is also concurrent with an increase in ice-rafted debris in the North Atlantic. Aquatic productivity in Lake Baikal increased between 119.7 and 117.4 ka BP before declining to the top of the record (115 ka BP) concomitant with a shift to predominately cool steppe catchment vegetation. However, isotopic composition of discharge into Lake Baikal provides evidence for strong penetration of Westerlies into central Asia during the latter stages of the Last Interglacial. Variability in d18Odiatom values was compared between the Last Interglacial and the Holocene. Millennial-scale variability was significantly more stable during the Last Interglacial, possibly linked to diminished influence of freshwater discharge on AMOC during periods of higher, global mean temperatures. [less ▲]

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See detailDeconstructing the Last Glacial Termination: the role of millennial and orbital-scale forcings
Menviel, L.; Timmermann, A.; Timm, O. et al

in Quaternary Science Reviews (2011), 30

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See detailBiotically constrained palaeoenvironmental conditions of a mid-Holocene intertidal lagoon on the southern shore of the Arabian Gulf: evidence associated with a whale skeleton at Musaffah, Abu Dhabi, UAE
Stewart, John; Aspinall, S; Beech, M et al

in Quaternary Science Reviews (2011), 30

Whale remains (a left and right mandible, scapula, humerus and fragmentary radius and ulna as well as parts of the cranium and rostrum) belonging to a probable humpback whale (Megaptera cf. novaeangliae ... [more ▼]

Whale remains (a left and right mandible, scapula, humerus and fragmentary radius and ulna as well as parts of the cranium and rostrum) belonging to a probable humpback whale (Megaptera cf. novaeangliae) were found in the well-described sabkha sequence exposed in the Musaffah Industrial Channel, Abu Dhabi, United Arab Emirates. More precisely, the whale remains were found in a series of sediments representing a range of lagoonal facies. The sediments surrounding the whale bones were age-dated at approximately 5200 14C yrs BP and are herefore interpreted to correspond to the previously documented late Flandrian sea-level peak, receding a fall in sea-level which culminated in the supratidal sabkha overprint of the carbonates. associated with the whale remains is an assemblage of molluscs, foraminifera and ostracods. together with the inferred presence of sea grass and algae, these facies are interpreted to indicate a very shallow subtidal to intertidal lagoonal environment. Cirripede remains found associated with the skeleton were identified as those of the whale barnacle Coronula diadema and hence had their origins with the whale. Significantly, the low species diversity of microfossils suggests that higher salinities existed in the mid-Holocene lagoon than are present in modern counterparts. This is here inferred to be related to the onset of continental aridity in Arabia during the mid-Holocene. [less ▲]

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See detailForaminifera in elevated Bermudian caves provide further evidence for +21 m eustatic sea level during Marine Isotope Stage 11
van hengstum, P. J.; Scott, David; Javaux, Emmanuelle ULg

in Quaternary Science Reviews (2009), 28(19-20), 1850-1860

Two hypotheses have been proposed to explain the origin of marine isotope stage (MIS) 11 deposits in small Bermudian caves at þ21 m above modern sea level: (1) a þ21 m MIS 11 eustatic sea-level highstand ... [more ▼]

Two hypotheses have been proposed to explain the origin of marine isotope stage (MIS) 11 deposits in small Bermudian caves at þ21 m above modern sea level: (1) a þ21 m MIS 11 eustatic sea-level highstand, and (2) a MIS 11 mega-tsunami event. Importantly, the foraminifera reported in these caves have yet to be critically evaluated within a framework of coastal cave environments. After statistically comparing foraminifera in modern Bermudian littoral caves and the MIS 11 Calonectris Pocket A (þ21 m cave) to the largest available database of Bermudian coastal foraminifera, the assemblages found in modern littoral caves – and Calonectris Pocket A – cannot be statistically differentiated from lagoons. This observation is expected considering littoral caves are simply sheltered extensions of a lagoon environment in the littoral zone, where typical coastal processes (waves, storms) homogenize and rework lagoonal, reefal, and occasional planktic taxa. Fossil protoconchs of the Bermudian cave stygobite Caecum caverna were also associated with the foraminifera. These results indicate that the MIS 11 Bermudian caves are fossil littoral caves (breached flank margin caves), where the total MIS 11 microfossil assemblage is preserving a signature of coeval sea level at þ21 m. Brackish foraminifera (Polysaccammina, Pseudothurammina) and anchialine gastropods (w95%, >300 individuals) indicate a brackish anchialine habitat developed in the elevated caves after the prolonged littoral environmental phase. The onset of sea-level regression following the þ21 m highstand would first lower the ancient brackish Ghyben-Herzberg lens (<0.5 m) and flood the cave with brackish water, followed by drainage of the cave to create a permanent vadose environment. These interpretations of the MIS 11 microfossils (considering both taphonomy and paleoecology) are congruent with the micropaleontological, hydrogeological and physical mechanisms influencing modern Bermudian coastal cave environments. In conclusion, we reject the mega-tsunami hypothesis, concur with the þ21 m MIS 11 eustatic sea-level hypothesis, and reiterate the need to resolve the disparity between global marine isotopic records and the physical geologic evidence for sea level during MIS 11. [less ▲]

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See detailC4 plants decline in the Himalayan basin since the Last Glacial Maximum
Galy, Valier; François, Louis ULg; France-Lanord, Christian et al

in Quaternary Science Reviews (2008), 27(13-14), 1396-1409

The Bengal Fan turbiditic system, supplied by the Ganga-Brahmaputra river system, provides an integrated record of Himalayan system erosion. Thanks to minor inputs of marine organic matter and almost ... [more ▼]

The Bengal Fan turbiditic system, supplied by the Ganga-Brahmaputra river system, provides an integrated record of Himalayan system erosion. Thanks to minor inputs of marine organic matter and almost complete preservation of riverine organic carbon, organic matter buried in Bengal Fan sediments is a proxy of Himalayan basin paleo-vegetation. The active channel-levee system of the middle fan documents the last 19 ka and allows the reconstruction of vegetation change in the Himalayan basin since the Last Glacial Maximum (LGM). We measured delta C-13 of organic carbon (C-org) in order to track changes in the proportions of C3 and C4 plants in the Himalayan basin. From LGM to mid-Holocene, delta C-13 of bulk C-org shifts of 3-4%. towards more negative values. Relative abundance of individual n-alkanes reveals that terrestrial higher plant inputs represent a dominant fraction of C-org buried in Bengal Fan sediments. delta C-13 of higher plants biomarkers mimic that of bulk C-org showing that the later can be used as continental paleo-vegetation proxy. delta C-13 negative shift from LGM to mid-Holocene, mostly indicates the transition from a dominant input of C4 plants to a dominant input of C3 plants and therefore reveals that C4 plants were more abundant in the basin under glacial conditions. Vegetation repartition in the basin simulated using the CARAIB dynamic vegetation model is consistent with C-org data. The model indicates a dominance of C4 plants in the Gangetic plain during the LGM while eastern part of the basin remains dominated by C3 plants. The comparison between our data and proxies of regional paleo-climate suggests that the large decline of C4 plants after the LGM was due to combined increase of atmospheric CO2 and humidity levels. Integrated record of Himalayan basin paleo-vegetation suggests more and conditions during the LGM than during the mid-Holocene and agrees with reconstructions of the monsoon indicating stronger SW monsoon during interglacial and stronger NE monsoon during glacial periods. (C) 2008 Elsevier Ltd. All rights reserved. [less ▲]

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See detailLichenometric application to recent dynamics and sediment transport of a Corsican stream (Figarella River– France).
Gob, Frédéric ULg; Petit, François ULg; Bravard, J. P. et al

in Quaternary Science Reviews (2003)

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