References of "Palaeogeography, Palaeoclimatology, Palaeoecology"
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See detailBiochemostratigraphy of the upper Frasnian in the Namur–Dinant Basin, Belgium: Implications for a global Frasnian–Famennian pre-event
Azmy, Karem; Poty, Edouard; Mottequin, Bernard ULg

in Palaeogeography, Palaeoclimatology, Palaeoecology (2012), 313-314

The Upper Frasnian sequence of the Namur–Dinant Basin in southern Belgium consists of mixed siliclastic–carbonate succession of a ramp setting, where the sequence spans the rhenana–linguiformis conodont ... [more ▼]

The Upper Frasnian sequence of the Namur–Dinant Basin in southern Belgium consists of mixed siliclastic–carbonate succession of a ramp setting, where the sequence spans the rhenana–linguiformis conodont zones. Earlier studies investigated the chemostratigraphic variations during the Frasnian-Famennian event, but little has been yet known about the nature of the counterpart variations that immediately preceded that time interval. Despite the scarcity of well-preserved brachiopods, sixty–one calcitic shells were collected mainly from beds of the Neuville and Les Valisettes formations (Lower and Upper rhenana zones), to investigate biochemostratigraphic profiles of oxygen-, carbon-isotope and rare earth element (REE) variations of the time interval immediately before the Frasnian-Famennian boundary. The δ18O and δ13 C values of the well-preserved shells range from − 9.5 to − 5.6 ‰ VPDB (− 7.7 ± 1.1, n = 33) and from − 1.8 to 3.8 ‰ VPDB (1.1 ± 1.7, n = 33), respectively, which are within the documented global values. The C- and O-isotope profiles exhibit parallel shifts, particularly at the top of the Neuville Formation (top of the Lower rhenana Zone), which are associated with a sea-level rise and shrinkage in the brachiopod community. Also, the Th/U (0.9 ± 0.6, n = 16) and Ce/Ce* (2.2 ± 0.5, n = 16) ratios suggest deposition under reducing conditions consistent with sea transgression. [less ▲]

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See detailDid a Katian Large Igneous Province trigger the Late Ordovician glaciation ? A hypothesis tested with a carbon cycle model
Lefebvre, Vincent; Servais, Thomas; François, Louis ULg et al

in Palaeogeography, Palaeoclimatology, Palaeoecology (2010), 296

The Ordovician is known as a period with high temperatures and high sea levels and a cooling event at the end of the period, leading to the Hirnantian glaciation and the !rst of the ‘big !ve’ mass ... [more ▼]

The Ordovician is known as a period with high temperatures and high sea levels and a cooling event at the end of the period, leading to the Hirnantian glaciation and the !rst of the ‘big !ve’ mass extinctions of marine life. The cause of this cooling event remains unclear. Several authors correlate it with a drop in atmospheric pCO2 to a threshold permitting the ice accumulation on the Gondwana supercontinent. However, what are the reasons of the atmospheric pCO2 decrease? Here, we follow the hypothesis initiated by Barnes (2004) that an Ordovician superplume event occurred during the Middle to Late Ordovician. Such an event would not only have a large impact on the Ordovician biodiversi!cation (Barnes, 2004) but it would also be responsible for the climatic upheaval during the Late Ordovician by the emplacement of a low latitudinal continental basaltic province that had an impact on the atmospheric pCO2. There is no direct evidence of a superplume event or of basaltic traps and the present study is therefore a hypothetical modelling approach where we demonstrate with a numerical box model, including carbon, alkalinity and phosphorus cycles coupled with a 1D climate model (energy balance model-EBM) (François and Walker,1992), that such a scenario allows to explain both the mid-Ashgill (Katian) global warming event, known as the Boda Event (Fortey and Cocks, 2005), and the subsequent Late Ordovician (Hirnantian) glaciation. Because silicate weathering is enhanced upon warm and wet climate, we try to constrain the size and the latitudinal emplacement of the basaltic province leading to a suf!cient consumption of atmospheric pCO2 to the threshold proposed by Herrmann et al. (2004 a, b) to initiate a glaciation on Gondwana. [less ▲]

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See detailBulk organic geochemistry of sediments from Puyehue Lake and its watershed (Chile, 40°S): Implications for paleoenvironmental reconstructions
Bertrand, Sébastien; Sterken, Mieke; Vargas-Ramirez, Lourdes et al

in Palaeogeography, Palaeoclimatology, Palaeoecology (2010), 294

Since the last deglaciation, the mid-latitudes of the southern Hemisphere have undergone considerable environmental changes. In order to better understand the response of continental ecosystems to ... [more ▼]

Since the last deglaciation, the mid-latitudes of the southern Hemisphere have undergone considerable environmental changes. In order to better understand the response of continental ecosystems to paleoclimate changes in southern South America, we investigated the sedimentary record of Puyehue Lake, located in the western piedmont of the Andes in South-Central Chile (40°S). We analyzed the elemental (C, N) and stable isotopic ([delta]13C, [delta]15N) composition of the sedimentary organic matter preserved in the lake and its watershed to estimate the relative changes in the sources of sedimentary organic carbon through space and time. The geochemical signature of the aquatic and terrestrial end-members was determined on samples of lake particulate organic matter (N/C: 0.130) and Holocene paleosols (N/C: 0.069), respectively. A simple mixing equation based on the N/C ratio of these end-members was then used to estimate the fraction of terrestrial carbon ([latin small letter f with hook]T) preserved in the lake sediments. Our approach was validated using surface sediment samples, which show a strong relation between [latin small letter f with hook]T and distance to the main rivers and to the shore. We further applied this equation to an 11.22 m long sediment core to reconstruct paleoenvironmental changes in Puyehue Lake and its watershed during the last 17.9 kyr. Our data provide evidence for a first warming pulse at 17.3 cal kyr BP, which triggered a rapid increase in lake diatom productivity, lagging the start of a similar increase in sea surface temperature (SST) off Chile by 1500 years. This delay is best explained by the presence of a large glacier in the lake watershed, which delayed the response time of the terrestrial proxies and limited the concomitant expansion of the vegetation in the lake watershed (low [latin small letter f with hook]T). A second warming pulse at 12.8 cal kyr BP is inferred from an increase in lake productivity and a major expansion of the vegetation in the lake watershed, demonstrating that the Puyehue glacier had considerably retreated from the watershed. This second warming pulse is synchronous with a 2 °C increase in SST off the coast of Chile, and its timing corresponds to the beginning of the Younger Dryas Chronozone. These results contribute to the mounting evidence that the climate in the mid-latitudes of the southern Hemisphere was warming during the Younger Dryas Chronozone, in agreement with the bipolar see-saw hypothesis. [less ▲]

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See detailFamennian charcoal of Belgium.
Prestianni, Cyrille ULg; Decombeix, Anne-laure; Thorez, Jacques ULg et al

in Palaeogeography, Palaeoclimatology, Palaeoecology (2010)

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See detailCarbon-isotope analysis of fossil wood and dispersed organic matter from the terrestrial Wealden facies of Hautrage (Mons Basin, Belgium).
Yans, Johan; Gerards, Thomas ULg; Gerrienne, Philippe ULg et al

in Palaeogeography, Palaeoclimatology, Palaeoecology (2010), 291

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See detailWeathering in the Lake Baikal watershed during the Kazantsevo (Eemian) interglacial: Evidence from the lacustrine clay record
Fagel, Nathalie ULg; Mackay, Anson W

in Palaeogeography, Palaeoclimatology, Palaeoecology (2008), 259(2-3), 244-257

The clay-mineralogical record of a piston core recovered on an elevated plateau in the northern basin of Lake Baikal has been investigated for the Kazantsevo interglacial period (i.e., Eemian s.s ... [more ▼]

The clay-mineralogical record of a piston core recovered on an elevated plateau in the northern basin of Lake Baikal has been investigated for the Kazantsevo interglacial period (i.e., Eemian s.s. equivalent in northern Europe). The age model (as inferred from palaeomagnetic intensity) suggests that this stage spans ca. 128 to 117 kyr BP. Relative clay mineral abundances and clay-mineral ratios are used to reconstruct the weathering conditions within the Baikal watershed at a sub-millennial resolution, and suggest that the clay record is highly variable. A bimodal clay-data distribution is in agreement with different clay sources and/or formation between the studied glacial and interglacial periods. High amounts of smectites in the Taz glacial samples (128.7-136.4 kyr BP) may be explained by an additional source of neoformed smectites during the glacial stage. In addition to the classically used smectite/illite ratio, the mineralogical results are integrated by the calculation of a hydrolysis index that takes into account the abundance of all clay species and their sensitivity to chemical weathering. A principal components analysis (PCA) of the Baikal clay minerals allows the comparison of the clay parameters with regard to weathering conditions. Clay data are further compared (i) with diatom and pollen profiles, (ii) with pollen-based quantitative reconstructions for the same core material, and (iii) with other climate reconstructions for the Lake Baikal region and Siberia. Several features of our record are highlighted here. During the early period of the Kazantsevo interglacial (128.4-125.2 kyr BP), weathering processes remain controlled by physical reworking for more than 2 kyr after the initial transition from cold to warm conditions. Inception of chemical weathering starts only after ca. 125 kyr BP, a period coincident with the warmest conditions according to both the pollen record and by the strongest chernozem development in Siberian soils. Within the interglacial interval, the hydrolysis index displays a two-step increase, punctuated by a minimum value ca. 122 kyr BP. The increasing but irregular trend persists after the transition from the Kazantsevo interglacial to the Zyryanka glacial (similar to 117 kyr BP). Peak chemical weathering, as inferred by clay changes, lags the interglacial/ glacial transition by at least 2 kyr. This suggests that pedogenesis remains active after the interval of surface stabilization. Lake Baikal clay minerals trace the nature of the main weathering conditions within the watershed. We note any increase in physical weathering is rapidly recorded in sedimentary clay assemblages but the mineral imprint to chemical weathering changes is more gradual, lagging reconstructed climate conditions over the lake by ca. 2 kyr. 0 2007 Elsevier B.V.. All rights reserved. [less ▲]

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See detailClay-mineral record in Lake Baikal sediments: The Holocene and Late Glacial transition
Fagel, Nathalie ULg; Boes, Xavier

in Palaeogeography, Palaeoclimatology, Palaeoecology (2008), 259(2-3), 230-243

We analyse the clay-mineralogical composition of two 1-m long cores from elevated plateaus in the southern and northern basins of Lake Baikal. Our aim is to test the limits of classically used clay ... [more ▼]

We analyse the clay-mineralogical composition of two 1-m long cores from elevated plateaus in the southern and northern basins of Lake Baikal. Our aim is to test the limits of classically used clay proxies for climate reconstructions. Mineralogical signature is determined by X-ray diffraction on oriented aggregates from Holocene and Late Glacial sediments. Mineralogical results are presented on a palaeomagnetic-derived time scale. Sampling at a centimeter resolution allows for a sub-millenial order reconstruction. The evolution of clay-derived climate proxies (smectite/illite peak intensity ratio, S/I) is compared between the two locations, with respect to other climate reconstructions for the Lake Baikal area and Siberia. During the Late Glacial punctual increases of S/I are related to changes of particle source rather than any climate change. At both sites the most intense chemical weathering conditions occured during the Subboreal, lagging the Eurasian middle Atlantic climate optimum. S/I follows a gradual but irregular increase through the Holocene, probably related to slow warming favourable to the development of the Siberian soils. The different sensitivity to hydrolysing conditions in northern and southern sites can be explained by a combination of local lithological and topographical parameters. (c) 2007 Elsevier B.V. All rights reserved. [less ▲]

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See detailCarbon isotope lateral variability in a Middle Frasnian carbonate platform (Belgium): significance of facies, diagenesis and sea-level history
Da Silva, Anne-Christine ULg; Boulvain, Frédéric ULg

in Palaeogeography, Palaeoclimatology, Palaeoecology (2008), 269

Carbon isotopic variations of Frasnian shallow-water carbonates from Belgium are related to facies and major sea-level trends. The influence of the diagenetic overprint was assessed in order to determine ... [more ▼]

Carbon isotopic variations of Frasnian shallow-water carbonates from Belgium are related to facies and major sea-level trends. The influence of the diagenetic overprint was assessed in order to determine the primary signal of the Frasnian carbonates. Shallow-water microfacies are characterized by biostromes with stromatoporoids and lagoonal deposits dominated by carbonate mud and calcareous algae with subaerial exposure surfaces. The diagenetic history was controlled by three main events: early meteoric diagenesis (short-term subaerial exposure during deposition), late meteoric diagenesis (major Famennian regression) and burial diagenesis. The oxygen isotopic values are almost constant with respect to facies, original material (carbonate mud and cement) and sedimentological units (no differences before or after the main regression). This homogeneity is related to resetting during late meteoric diagenesis. The carbon isotopic values are related to facies (with the more negative values for the shallowest facies) and to major sea-level variations (most negative values after the main regression). This pattern is interpreted as being related to primary signals. This trend was enhanced by early meteoric diagenesis and the influence of more negative values from paleosols. The carbon isotope patterns reflect the influence of sea-level and water circulation on shallow water deposits and this influence implies that shallow-water carbonates are not necessarily good material for assessing the primary isotopic values of the ocean because of the influence of long residence time (“aging”) of the platform-top water and because of early diagenesis. [less ▲]

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See detailPalaeophytogeographical and palaeoecological implications of a miospore assemblage of earliest Devonian (Lochkovian) age from Saudi Arabia
Steemans, Philippe ULg; Wellman, C. H.; Filatoff, J.

in Palaeogeography, Palaeoclimatology, Palaeoecology (2007), 250(1-4), 237-254

Palynological samples from two boreholes drilled in the eastern part of Saudi Arabia contain a rich assemblage of cryptospores and trilete spores. They are dated as most probably Lochkovian in age ... [more ▼]

Palynological samples from two boreholes drilled in the eastern part of Saudi Arabia contain a rich assemblage of cryptospores and trilete spores. They are dated as most probably Lochkovian in age. Intriguingly, the cryptospores are very similar to those from a coeval continental palynomorph assemblage from the Old Red Sandstone Continent, whereas the trilete spores show a strong affinity with miospore assemblages from Western Gondwana. It is suggested that cryptospore-producing plants inhabited confined, damp biotopes and had a wide range of climatic tolerance. On the otherhand, trilete spore-producing plants inhabited a wider variety of biotopes but were more sensitive to climatic variations. The high degree of similarity between Old Red Sandstone and Saudi Arabian cryptospore assemblages favours palaeogeographic reconstructions where there is close proximity between Western Gondwana and Euramerica and/or a land connection between these palaeoplates. Climatic differences between the Old Red Sandstone Continent and the northern part of Western Gondwana can be invoked to explain the variations in the trilete spore assemblages. (c) 2007 Elsevier B.V. All rights reserved. [less ▲]

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See detailTree diversity in the Miocene forests of western Eurasia
Utescher, T.; Erdei, B.; François, Louis ULg et al

in Palaeogeography, Palaeoclimatology, Palaeoecology (2007), 253(1-2), 226-250

In the present study, published Miocene mega- and microfloral records compiled from a total of 92 localities in Western Eurasia are analysed with respect to diversity of different plant functional types ... [more ▼]

In the present study, published Miocene mega- and microfloral records compiled from a total of 92 localities in Western Eurasia are analysed with respect to diversity of different plant functional types (PFTs). To study spatial diversity patterns and their evolution three time-intervals are selected corresponding to the Langhian (16.3-13.6 Ma), the Serravallian (13.6-11.6), and the earlier part of the Tortonian (11.6-8.5 Ma). First all arboreal species occurring in the floras are classified using a total of 13 different PFTs (functional types of trees and climatically defined subtypes). In a next step, diversity spectra with respect to these PFTs are generated for each site. Cluster analysis is then performed in order to obtain groups of floras with similar spectra that are interpreted in terms of vegetation type. Their spatial distribution in each time-interval is shown in maps. According to these results, zonally arranged patterns are obtained. Broadleaved Deciduous Forests are most important in the higher latitudes while Mixed Mesophytic Forests dominate the mid-latitudes in Western Eurasia. Broadleaved Evergreen Forests are of minor importance in the area of interest. The observed diversity patterns and their changes in time are correlated with spatial climate patterns and the continental palaeoclimate evolution. During the late Miocene cooling, Broadleaved Evergreen Forests completely disappear from the mid-latitudes of Western Eurasia, and Mixed Mesophytic Forests of the mid-latitudes are mostly replaced by broadleaved deciduous vegetation types. In the context of this cooling, a drier season became established in Western Europe during the Tortonian, as is evident from reconstructed arboreal diversity data and precipitation data. In Central Europe, vegetation types indicating permanently humid conditions persisted throughout all the three time-intervals analysed. (C) 2007 Elsevier B.V. All rights reserved. [less ▲]

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See detailUpper Devonian carbonate platform correlations and sea level variations recorded in magnetic susceptibility
Da Silva, Anne-Christine ULg; Boulvain, Frédéric ULg

in Palaeogeography, Palaeoclimatology, Palaeoecology (2006), 240(3-4), 373-388

This paper: concerns the analysis of four outcrops in the Frasnian (Upper Devonian) of Belgium. We compare the results of a precise sedimentological analysis with magnetic susceptibility (MS) data. This ... [more ▼]

This paper: concerns the analysis of four outcrops in the Frasnian (Upper Devonian) of Belgium. We compare the results of a precise sedimentological analysis with magnetic susceptibility (MS) data. This comparison allows us to improve stratigraphic correlations and to test the relationship between magnetic susceptibility and sea level changes. Considering the sedimentological study, different microfacies have been identified, from the external belt dominated by relatively argillaceous open marine facies with crinoids, to the biostromal and the lagoonal belt dominated by algae-rich muddy facies. Fourth- and third-order sequences have also been identified and are probably related to sea level variations. Magnetic susceptibility data provides us very good fourth-order correlations and the link between magnetic susceptibility and different sedimentological parameters is obvious. More precisely, MS appears to be related to fourth- and third-order sequences and to microfacies. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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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 detailThe Moesian Terrane during the Lochkovian - a new palaeogeographic and phytogeographic hypothesis based on miospore assemblages
Steemans, Philippe ULg; Lakova, I.

in Palaeogeography, Palaeoclimatology, Palaeoecology (2004), 208(3-4), 225-233

The relative position of terranes during the Palaeozoic can be indicated by a combination of palaeomagnetic and floral/faunal evaluation. Palaeomagnetic data are absent from the Moesian Terrane, South ... [more ▼]

The relative position of terranes during the Palaeozoic can be indicated by a combination of palaeomagnetic and floral/faunal evaluation. Palaeomagnetic data are absent from the Moesian Terrane, South-Eastern Europe, and its position is here estimated thanks to palaeophytogeographic considerations based on miospore assemblages. Miospore assemblages have been studied in two boreholes from northern Bulgaria. Preliminary analyses of chitinozoans, acritarchs and phytodebris have already been published. The oldest samples were considered to be of Pridoli age based on chitinozoan data, but here we provide new miospore evidence suggesting a Lochkovian age. This age determination is in accordance with the new interpretations based on previously published acritarch data. It is likely that the previous Pridoli age determination was influenced by Pridoli chitinozoans being reworked into the Lochkovian. The miospores are typical of assemblages only present in a small area of Avalonia and the western part of the Baltica Plate, and belong to the sinuosus-zavallatus (S-Z) Phytogeographic Province, defined here. On the contrary to the miospores, marine palynomorphs have affinity with Gondwanan assemblages. The different palaeogeographic affinities of the different palynomorph groups are not necessarily in contradiction, as it has recently been suggested that the Rheic Ocean did not act, around the Silurian-Devonian boundary, as a hermetic barrier for transoceanic chitinozoan and acritarch exchange. Therefore, the results are tentatively interpreted as indicating that the Moesian Terrane, belonging to the S-Z Province, was close to southern Laurussia during the Lower Devonian. This northern position of the Moesian Terrane during the Lower Devonian conflicts with most current palaeogeographic reconstructions, but partially supports the hypothesis of a migration of this terrane from Gondwana to Laurussia during the Palaeozoic. The possible presence of reworked palynomorphs in the Lochkovian may reflect early tectonic events associated with the close proximity of the Moesian Terrane and the Dobrudgea periphery of Palaeo-Europe. (C) 2004 Elsevier B.V. All rights reserved. [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 detailAge model estimation in paleoclimatic research : fuzzy regression and radiocarbon uncertainties
Boreux, Jean-Jacques ULg; Pesti, G.; Duckstein, L. et al

in Palaeogeography, Palaeoclimatology, Palaeoecology (1997), 128(1), 29-37

A fuzzy linear regression-based method to relate the depth and age of sediment layers is described. Because algae, moss or local plants respond to climatic change, the age and depth of sediment layers are ... [more ▼]

A fuzzy linear regression-based method to relate the depth and age of sediment layers is described. Because algae, moss or local plants respond to climatic change, the age and depth of sediment layers are interrelated variables but the link between them is often imprecise. In most cases, due to the limited number of layers in a core (i.e., small number of data points), estimation of the slope and uncertainties in classical regression analysis does not take into account the uncertainties in radiocarbon dating. Here, fuzzy linear regression, which may be applied even to a very small data set, is utilized. The method, illustrated through a practical example, with eight data points, appears to be a promising tool in stratigraphic studies to link sediment age to layer depth and takes into account uncertainties from radiocarbon dating. [less ▲]

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See detailDiagenetic and paleogeographic significance of clay and other sedimentary components in the middle Devonian limestones of Western Ardennes, France
Chamley, H.; Proust, J. N.; Mansy, J. L. et al

in Palaeogeography, Palaeoclimatology, Palaeoecology (1997), 129

Givetian deposits accumulated in a more than 300-m-thick succession on a carbonate platform developed on the passive margin of the so-called Rheic ocean. These rocks crop out in the Ardenne massif at ... [more ▼]

Givetian deposits accumulated in a more than 300-m-thick succession on a carbonate platform developed on the passive margin of the so-called Rheic ocean. These rocks crop out in the Ardenne massif at Glageon in a structural context marked by small fault-controlled basins subjected to moderate overburden, tectonic and metamorphic constraints. Data on the clay mineral distribution, associated with detailed information on limestone facies/microfacies, as well as data on the depositional profile and sequence stratigraphic evolution of these rocks indicate strong carbonate diagenesis and moderate clay diagenesis, the latter being favoured by the early occurrence of the former, which prevented further fluid-rock interaction. The clay assemblage distribution, which roughly parallels the palaeomorphologic and palaeobathymetric shape of the Givetian continental margin, is organized in five successive zones indicating large-scale sequence stratigraphic evolution and the control of regional sea-level fluctuations. The clay and other sedimentary components provide additional information on the warm and variably humid climate, northern, relative to southern, terrigenous sources, the open sea relative to restricted depositional environments, the temporary tectonic rejuvenation of the continental hinterland and the chemical conditions allowing early diagenetic modifications. [less ▲]

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See detailSequence stratigraphy of the Frasnian-Famennian transitional strata: a comparison between South China and Southern Belgium
Muchez, P.; Boulvain, Frédéric ULg; Dreesen, R. et al

in Palaeogeography, Palaeoclimatology, Palaeoecology (1996), 123

The sedimentological evolution of the Frasnian-Famennian transitional strata in South China and southern Belgium has been investigated. A similar trend in the deepening and shallowing of the sedimentation ... [more ▼]

The sedimentological evolution of the Frasnian-Famennian transitional strata in South China and southern Belgium has been investigated. A similar trend in the deepening and shallowing of the sedimentation environment occurs in the two palaeogeographically distinct areas. The stratigraphic succession has been subdivided into depositional sequences. A general deepening occurs in the Palmatolepis rhenana conodont zone. During the most rapid rise in sea level, a transgressive systems tract formed. This transgressive systems tract is followed by a highstand systems tract in the late P. rhenana zone. A major sequence boundary within the latter zone is indicated by an unconformity in intraplatform and platform areas and by a conformity in the basinal area. The uppermost sediments within the late rhenana zone correspond to a lowstand systems tract. A rapid flooding took place near the base of the Palmatolepis linguiformis zone and dark shales and limestones formed. A second sequence boundary coincides with or is very close to the Frasnian-Famennian boundary (base P. triangularis zone). The global extinction event at the Frasnian- Famennian boundary coincides with an important eustatic fall in sea level. The proposed stratigraphic subdivision should allow worldwide correlations of shallow and deep water deposits. [less ▲]

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See detailNEOGENE TO QUATERNARY CLAY MINERAL FLUXES IN THE CENTRAL INDIAN BASIN
DEBRABANT, P.; Fagel, Nathalie ULg; CHAMLEY, H. et al

in Palaeogeography, Palaeoclimatology, Palaeoecology (1993), 103(3-4), 117-131

The late Cenozoic clay sedimentation in the Central Indian Basin was investigated by mineralogical analyses of five very long cores (33-49 m long), which were recovered between 1-degrees and 10-degrees-S ... [more ▼]

The late Cenozoic clay sedimentation in the Central Indian Basin was investigated by mineralogical analyses of five very long cores (33-49 m long), which were recovered between 1-degrees and 10-degrees-S along a transect at about 80-degrees-E and compared with data from adjacent ODP and piston cores. Progressive changes occur from North to South, and are especially marked by a decrease of illite and chlorite amounts balanced by increased contents of smectite and kaolinite. These changes arc attributed to a southwards reduction of Himalaya-derived detrital fluxes, and to a correlative augmentation both of smectite reworked from coastal Indian, Indonesian and volcanic submarine sources, and of kaolinite supplied from Australia and blocked by the equatorial divergence. The stratigraphic changes are more diversified than the geographic changes and develop discontinuously. High fluxes of illitic and chloritic materials during the middle-late Miocene reflect major activity of the Himalayan Main Central Thrust. A tectonic relaxation developed during the latest Miocene-early Pliocene, allowing alternating supply of illite-rich and smectite-rich sediments, which suggests periodical changes from distant to more local supply partly controlled by climate and by Indian intraplate deformations. The more abundant and constant amounts of smectite in late Pliocene-early Pleistocene sediments are chiefly attributed to erosion of Indian coastal zones favored by a worldwide sea-level drop. The middle to late Quaternary increase of the illite group resulted from the resumption of the tectonic activity in the Himalaya-Tibet range associated with a general climatic cooling. [less ▲]

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