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See detailLate Holocene changes in cyanobacterial community structure in maritime Antarctic lakes
Fernandez-Carazo, Rafael; Verleyen, Elie; Hodgson, Dominic A et al

in Journal of Paleolimnology (2013), 50

Despite the dominance of cyanobacteria in polar freshwater aquatic ecosystems, little is known about their past biodiversity and response to climate and environmental changes. We explored the use of light ... [more ▼]

Despite the dominance of cyanobacteria in polar freshwater aquatic ecosystems, little is known about their past biodiversity and response to climate and environmental changes. We explored the use of light microscopy of microfossils, high performance liquid chromatography of the fossil pigment composition and denaturing gradient gel electrophoresis of fossil 16S rRNA genes to study past and present-day differences in cyanobacterial community structure in response to climate changes in two adjacent maritime Antarctic lakes with contrasting depths (4 and 26 m) and light climates. Light microscopy was of limited use because of degradation of cell structures. Fossil cyanobacterial pigment concentrations were below the detection limits of our method in several sediment samples in the deep lake, but abundant and diverse inthe sediment core from the shallow pond, probably as a consequence of increased light availability and/or a more diverse and abundant benthic cyanobacterial flora. Total carotenoid and chlorophyll concentrations were highest in both lakes between ca. 2,950 and 1,800 cal yr BP, which coincides with the late Holocene climate optimum recognised elsewhere in maritime Antarctica. Cyanobacterial molecular diversity was higher in the top few centimeters of the sediments in both lakes. In deeper sediments, the taxonomic turnover of cyanobacteria appeared to be relatively small in response to past climate anomalies in both lakes, underscoring the broad tolerance of cyanobacteria to environmental variability. This, however, may in part be explained by the low taxonomic resolution obtained with the relatively conserved 16S rRNA gene and/or the preferential preservation of particular taxa. Our results highlight the potential of fossil DNA in lake sediments to study colonization and succession dynamics of lacustrine cyanobacteria and warrant further investigation of the factors that affect preservation of cyanobacterial DNA. [less ▲]

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See detailLate Holocene environmental changes inferred from diatom, chironomid, and pollen assemblages in an Andean lake in Central Chile, Lake Laja (36°S)
Urrutia, Roberto; Araneda, Alberto; Torres, Laura et al

in Hydrobiologia (2010), 648

A sediment core encompassing the last 2000 years was extracted from Lake Laja, Chile, (36°54′S, 71°05′W) using an Uwitec drilling platform. The sediment was subsampled for loss on ignition, nutrients ... [more ▼]

A sediment core encompassing the last 2000 years was extracted from Lake Laja, Chile, (36°54′S, 71°05′W) using an Uwitec drilling platform. The sediment was subsampled for loss on ignition, nutrients, biogenic silica, and biological proxies (diatoms, chironomids, pollen). The sedimentary profile was characterized by several coarse volcanic layers. Loss on ignition, nutrients, and biogenic silica showed an increasing trend that suggests a recent shift to a higher trophic status. Diatom assemblages also suggested higher nutrient content with increased abundances of Aulacoseira granulata, A. distans, and Asterionella formosa. At the same time, a marked change in the benthic and facultative planktonic taxa may be associated with cooling. This period of change coincides with the European Little Ice Age (LIA). The chironomid profile showed four key zones distinguished largely by changes in the abundance of Tanytarsini, Parachironomus, and Macropelopia. Like diatoms, chironomids also seemed to reflect a shift to higher trophic conditions in the upper part reflected by increasing abundance of taxa such as Tribelos/Phaenopsectra, Cricotopus/Orthocladius, and Ablabesmyia. The most striking feature in the chironomid assemblage is the abundance of Podonominae, Parapsectrocladius, and Limnophyes/Compterosmittia, which could be associated with a cold-dry period between 1500 and 1900 AD in Lake Laja (the period of the European LIA). Pollen assemblages indicated fluctuations in humidity through changes in Nothofagus dombeyi-type, Poaceae, and Ephedra, and we inferred a strong human impact over the last 100 years from the appearance of Plantago and increased levels of Poaceae and Asteraceae subf. Cichorioidae. Finally, the three proxies showed the occurrence of a cold-dry event in Lake Laja (~1550–1900 AD), which roughly coincides with the European LIA. However the data from this research, does not prove neither rejects the existence of the occurrence of the MWP in the central Andes. [less ▲]

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See detailLate Holocene environmental changes recorded in the sediments of Lago Thompson, Northern Chilean Patagonia
Fagel, Nathalie ULg; Nuttin, L.; Bertrand, S. et al

Poster (2010)

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See detailLate Holocene history of the Fuji Five Lakes (Japan)
Lamair, Laura ULg; Hubert, Aurelia ULg; Boes, Evelien et al

Conference (2015, July)

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See detailLate Lower and Middle Devonian Miospores from Saudi Arabia.
Loboziak, S; Streel, Maurice ULg

in Review of Palaeobotany and Palynology (1995), 89

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See detailLate middle Frasnian to early Famennian (Late Devonian) strophomenid, orthotetid and athyridid brachiopods from southern Belgium
Mottequin, Bernard ULg

in Journal of Paleontology (2008), (82), 1052-1073

Brachiopods of the orders Strophomenida, Orthotetida, and Athyridida from the late middle Frasnian–early Famennian interval (hassi to triangularis conodont zones) in the Namur-Dinant Basin (southeastern ... [more ▼]

Brachiopods of the orders Strophomenida, Orthotetida, and Athyridida from the late middle Frasnian–early Famennian interval (hassi to triangularis conodont zones) in the Namur-Dinant Basin (southeastern margin of Laurussia; southern Belgium) are described. Nine genera and subgenera represented by 12 species are recognized here. One new genus, Retrorstrophia, and one new species, Douvillina area, are erected. Crinisarina stainbrooki is proposed to solve the homonymy between C. reticulata (Gosselet, 1877) and Cleiothyridina reticulata Stainbrook, 1947, the type species of Crinisarina Cooper and Dutro, 1982. A lectotype is selected and illustrated for C. reticulata. A new name is also proposed for Athyris reticulata Chen and Xu, 2000, which is assigned here to Crinisarina: C. shashishanensis nom. nov. In southern Belgium, the last representatives of the families Douvillinidae and Leptostrophiidae (Strophomenida) are from the Upper rhenana Zone (late Frasnian). Athyridid brachiopods, especially the representatives of the subfamily Cleiothyridininae constituted a significant part of the early Famennian recovery faunas with spiriferids and rhynchonellids, just after the late Frasnian mass extinction. [less ▲]

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See detailLate Middle to Late Frasnian Atrypida, Pentamerida, and Terebratulida (Brachiopoda) from southern Belgium
Mottequin, Bernard ULg

in Geobios (2008), 41

In the Namur–Dinant Basin (Belgium), the last Atrypida and Pentamerida originate from the top of the Upper Palmatolepis rhenana Zone (Late Frasnian). Within this biozone, their representatives belong to ... [more ▼]

In the Namur–Dinant Basin (Belgium), the last Atrypida and Pentamerida originate from the top of the Upper Palmatolepis rhenana Zone (Late Frasnian). Within this biozone, their representatives belong to the genera Costatrypa, Desquamatia (Desquamatia), Radiatrypa, Spinatrypa (Spinatrypa), Spinatrypina (Spinatrypina?), Spinatrypina (Exatrypa), Waiotrypa, Iowatrypa and Metabolipa. No representative of these orders occurs within the Palmatolepis linguiformis Zone. The disappearance of the last pentamerids, mostly confined to reefal ecosystems, is clearly related to the end of the edification of the carbonate mounds; it precedes shortly the atrypid one. This event, resulting from a transgressive episode, which induces a progressive and dramatic deterioration of the oxygenation conditions, takes place firstly in the most distal zones of the Namur–Dinant Basin (southern border of the Dinant Synclinorium; Lower P. rhenana Zone). It is only recorded within the Upper P. rhenana Zone in the Philippeville Anticlinorium, the Vesdre area, and the northern flank of the Dinant Synclinorium. It would seem that the terebratulids were absent during the Famennian in this basin, probably due to inappropriate facies. Among the 13 species described or briefly discussed (Palmatolepis hassi to Upper P. rhenana zones), Pseudoatrypa godefroidi nov. sp. and Spinatrypina (Exatrypa) marmoris nov. sp. are proposed as new. [less ▲]

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See detailLate Miocene vegetation reconstruction with the CARAIB model
François, Louis ULg; Otto, Dominique; Fluteau, Frédéric et al

Conference (2001)

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See detailLate Miocene vegetation reconstruction with the CARAIB model
François, Louis ULg; Ghislain, Maxime; Otto, Dominique et al

in Palaeogeography, Palaeoclimatology, Palaeoecology (2006), 238(1-4), 302-320

Climatic outputs from the atmospheric general circulation model ECHAM4 coupled to a mixed layer ocean model are used as inputs to the CARAIB global vegetation model to reconstruct the distribution of ... [more ▼]

Climatic outputs from the atmospheric general circulation model ECHAM4 coupled to a mixed layer ocean model are used as inputs to the CARAIB global vegetation model to reconstruct the distribution of vegetation and the biosphere carbon stocks over the continents during the Late Miocene (Tortonian). The results show significant changes in the geographical distribution of vegetation during the Late Miocene compared to the present with a reduction of desert areas and an expansion of tropical seasonal forests, which reached temperate latitudes. These changes in vegetation distribution are accompanied by a moderate increase of the total biosphere carbon stock by 159Gt. Sensitivity tests to atmospheric CO2 have also been performed with the vegetation model only, i.e., while keeping constant all climatic variables to their reference Tortonian state. These tests point out the potential importance Of CO2 fertilization both regarding vegetation distribution and biosphere carbon storage. The impact of an atmospheric CO2 decrease (from 280 to 200ppmv) or increase (from 280 to 560ppmv) on the vegetation distribution appears to be at least as large as that of the climate change between the Tortonian and the present, while in terms of carbon storage the impact of atmospheric CO2 is far much larger than the climatic one. Although the actual response of vegetation to CO2 fertilization may be much smaller than its theoretical response in the model, these results emphasize the need to consider atmospheric CO2 as an important parameter for palaeovegetation reconstructions. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailLate Mousterian red pigment proceeding in Les Bossats, Seine-et-Marne (France)
Salomon, Hélène ULg; Bodu, Pierre; Geurten, Stéphanie

Conference (2012, June 01)

Les Bossats, near Ormesson, is a newly discovered late mousterian site dated around 47.000 B.P. by thermoluminescence. The archaeological level, fossilized by loess, revealed a rich industry based on the ... [more ▼]

Les Bossats, near Ormesson, is a newly discovered late mousterian site dated around 47.000 B.P. by thermoluminescence. The archaeological level, fossilized by loess, revealed a rich industry based on the discoide mode, associated with numerous fragments of red pigment rocks. The geological sources were identified by means of SEM-EDX, XRD, FT-IR, PIXE and by petrographical observation of thin sections. The past mechanical and morphological modifications of the pigment blocks were characterized by macro-photography, microscopy and topographical micro-measures of the used surfaces. It was thus possible to demonstrate that the colouring materials were brought to the site by the Neanderthals and the supply in raw material was local. Eleven blocks show different use marks such as facets, grooves and scars. The colouring materials employed by the Neanderthals on the camp site were used by different process (scraping, rubbing, crushing and grinding) in order to obtain red powder. The archaeological remains reveal an organized proceeding sequence of red pigment. During the late Mousterian a great phenomenon in expansion in western Europe is remarkable by the much wider exploitation of mineral red and black pigments corresponding to technical modifications and divers utilizations under development. As such, it questions our perception of the humanity of Neanderthal. Did he produced symbol by using pigments or were these minerals part of the economy of subsistence? [less ▲]

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See detailLate Night, la danse de la déperdition
Delhalle, Nancy ULg

in Alternatives Théâtrales (2014), (120),

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See detailLate Ordovician-earliest Silurian palynomorphs from northern Chad and correlation with contemporaneous deposits of southeastern Libya
Le Hérissé, A.; Paris, F.; Steemans, Philippe ULg

in Bulletin of Geosciences (2013), 83(3), 483-504

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See detailLate Pleistocene molecular dating of past population fragmentation and demographic changes in African rain forest tree species supports the forest refuge hypothesis
Duminil, Jérôme; Mona, Stefano; Mardulyn, Patrick et al

in Journal of Biogeography (in press)

Aim : Phylogeographical signatures of past population fragmentation and demographic change have been reported in several African rain forest trees. These signatures have usually been interpreted in the ... [more ▼]

Aim : Phylogeographical signatures of past population fragmentation and demographic change have been reported in several African rain forest trees. These signatures have usually been interpreted in the light of the Pleistocene forest refuge hypothesis, although dating these events has remained impracticable because of inadequate genetic markers. We assess the timing of interspecific and intraspecific genetic differentiation and demographic changes within two rain forest Erythrophleum tree species (Fabaceae: Caesalpinioideae). Location : Tropical forests of Upper Guinea (West Africa) and Lower Guinea (Atlantic Central Africa). Methods : Six single-copy nuclear genes were used to characterize the phylogeographical patterns of the parapatric sister species Erythrophleum suaveolens (characteristic of semi-deciduous or gallery forests) and Erythrophleum ivorense (characteristic of evergreen forests). The number of gene pools within each species was determined and the timings of their divergence and past demographic changes were estimated using Bayesian-based coalescent approaches. Results : Three geographically separated gene pools were identified within E. suaveolens, and a single gene pool was inferred in E. ivorense. All gene pools show signatures of demographic bottlenecks concomitant with the last glacial period (c. 120–12 ka). Species-tree inferences show that the two species diverged c. 600 ka, whereas the divergence between E. suaveolens gene pools was dated to the late Pleistocene (first divergence c. 120 ka, second c. 60 ka). Main conclusions : (1) Molecular dating of demographic changes of two African tropical forest tree species is consistent with the Pleistocene forest refuge hypothesis. (2) Tree species from Guinean evergreen tropical forests might have been less affected by past climate change than semi-deciduous species. (3) Our phylogeographical data support a recent date (Holocene) of the last opening of the Dahomey Gap. [less ▲]

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See detailLate Quaternary clay mineral record in Central Lake Baikal (Academician Ridge, Siberia)
Fagel, Nathalie ULg; Boski, T.; Likhoshway, L. et al

in Palaeogeography, Palaeoclimatology, Palaeoecology (2003), 193(1), 159-179

We investigated the mineralogical composition of two cores recovered on the Academician Ridge (Central Lake Baikal, Siberia). Sedimentological features show that the cores are unaffected by turbidity ... [more ▼]

We investigated the mineralogical composition of two cores recovered on the Academician Ridge (Central Lake Baikal, Siberia). Sedimentological features show that the cores are unaffected by turbidity currents. However, hemipelagic deposition is not continuous, but intermittently disturbed by syn- or post-sediment reworking (e.g., bioturbation, slumps, faulting). Such modes of deposition are consistent with the complex uplift history of the ridge. Bulk mineralogy suggests that terrigenous sediment supplies are constant through glacial/interglacial stages, and diluted by diatom-rich intervals related to warmer interglacial stages. The core stratigraphy is based on the correlation of the diatom zonation and opal abundance with the marine oxygen isotope reference curve SPECMAP. The similar to 8-m cores partly recover the last four interglacial/glacial cycles, i.e., since oxygen isotope stage 8. We test the use of clay minerals as a proxy for paleoclimatic reconstruction. The clays are more weathered during the diatom-rich intervals in agreement with warmer climate conditions. However, the mean clay composition does not change significantly through glacial/interglacial stages. This observation implies that, in the Academician Ridge sediments, a simple smectite/illite ratio (S/I) does not alone provide a reliable indicator of climatic variation. It reflects the complex clay assemblages, especially the smectite group, delivered to Central Lake Baikal. Smectites include primarily illite-smectite mixed layers, made of a mixture of montmorillonite and beidellite. According to their behavior after cation saturation, the illite-smectite mixed layers are primarily transformed smectites, with some neoformed smectites intermittently observed. In addition, Al-smectites occur in minor proportions. We conclude that the S/I ratio has a climatic significance only if it evolves in parallel with the weathering stage of the clays and is confirmed by a change in the composition of the smectites. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailLate Quaternary climatic changes in southern Chile, as recorded in a diatom sequence of Lago Puyehue (40 degrees 40 ' S)
Sterken, Mieke; Verleyen, Elie; Sabbe, Koen et al

in Journal of Paleolimnology (2008), 39(2), 219-235

A late Quaternary diatom stratigraphy of Lago Puyehue (40 degrees 40'S, 72 degrees 28'W) was examined in order to infer past limnological and climatic changes in the South-Chilean Lake District. The ... [more ▼]

A late Quaternary diatom stratigraphy of Lago Puyehue (40 degrees 40'S, 72 degrees 28'W) was examined in order to infer past limnological and climatic changes in the South-Chilean Lake District. The diatom assemblages were well preserved in a 1,122 cm long, C-14-dated sediment core spanning the last 17,900 years, and were in support of an early deglaciation of Lago Puyehue. The presence of a short cold spell in South Chile, equivalent to the Younger Dryas event in the Northern Hemisphere, the Antarctic Cold Reversal in Antarctica, or the Huelmo-Mascardi event in southern South America, was not clearly evidenced in the diatom data, although some climate instability may have occurred between 13,400 and 11,700 cal. yr. BP, and a relatively long period (between 16,850 and 12,810 cal. yr. BP) with low absolute abundances and biovolumes could be tentatively interpreted as a period of low rainfall and/or temperatures. An increase in the moisture supply to the lake was tentatively inferred at 12,810 cal. yr. BP. After 9,550 cal. yr. BP, inferred stronger and longer persisting summer stratification, may have been the result of the higher temperatures associated with an early-Holocene thermal optimum. The mid-Holocene appeared to be characterized by a decrease in precipitation, culminating around 5,000 cal. yr. BP, and rising again after 3,000 cal. yr. BP, likely associated with a previously documented lowered frequency and amplitude of El Nino events. An increase in precipitation during the late Holocene (3,000 cal. yr. BP-present) might have marked subsequent increased frequency of El Nino occurrences, leading to drier summers and slightly moister winters in the area. [less ▲]

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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 detailThe Late Quaternary History of Biogeochemical Cycling of carbon
Pedersen; François, R.; François, Louis ULg et al

in Alverson, K. D.; Bradley, R. S.; Pedersen, T. F. (Eds.) Paleoclimate, Global Change and the Future (2003)

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