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Malusa M.G.,University of Milan Bicocca | Villa I.M.,University of Milan Bicocca | Villa I.M.,Institute For Geologie | Vezzoli G.,University of Milan Bicocca | Garzanti E.,University of Milan Bicocca
Earth and Planetary Science Letters | Year: 2011

Tectonic reconstructions and quantitative models of landscape evolution are increasingly based on detailed analysis of detrital systems. Since the definition of closure temperature in the 1960s, mineral ages of low-temperature geochronometers are traditionally interpreted as the result of cooling induced by erosion, whose rate is a simple, unique function of age patterns. Such an approach can lead to infer paradoxically high erosion rates that conflict with compelling geological evidence from sediment thickness in basins. This indicates that tectonic and landscape models that solely interpret mineral ages as due to cooling during exhumation may not be valid.Here we propose a new approach that takes into account the effects of both crystallization and exhumational cooling on geochronometers, from U-Pb on zircon to fission tracks on apatite. We first model the mechanical erosion of an unroofing magmatic complex and the resulting accumulation and burial of the eroded units in reverse order in the basin. Detrital mineral ages follow a regular pattern downsection. Some mineral ages, such as e.g. U-Pb ages of zircons, cluster around the "magmatic age", i.e. the crystallization of the magma. Its value is constant along the stratigraphic column in the sedimentary basin; we refer to this behavior as "stationary age peak". Some other mineral ages, such as e.g. apatite fission-track ages, are often younger than the magmatic age. When they vary smoothly with depth, they define a "moving age peak", which is the only possible effect of undisturbed cooling during overburden removal, and can therefore be used to calculate an erosion rate.The predictions of our model were tested in detail on the extremely well-studied Bregaglia (Bergell) orogenic pluton in the Alps, and on the sedimentary succession derived from its erosion, the Gonfolite Group. The consistency between predicted and observed age patterns validates the model. Our results resolve a long-standing paradox in quantitative modelling of erosion-sedimentation, namely the scarcity of sediment during apparently fast erosion. Starved basins are the observational baseline, and modelling must be tuned to include a correct analysis of detrital mineral geochronology in order to reconcile perceived discrepancies between stratigraphical and geochronological information. In addition, our data demonstrate that volcanoes were active on top of the growing Oligocene Alps.This study illustrates rigorous criteria for detrital mineral geochronology that are applicable to any geological setting, including magmatic arcs and collision orogens, and provides fundamental interpretive keys to solve complex puzzles and apparent paradoxes in geological reconstructions. © 2010 Elsevier B.V.

Pagonis V.,McDaniel College | Chithambo M.L.,Rhodes University | Chen R.,Tel Aviv University | Chruscinska A.,Nicolaus Copernicus University | And 4 more authors.
Journal of Luminescence | Year: 2014

During time-resolved optical stimulation experiments (TR-OSL), one uses short light pulses to separate the stimulation and emission of luminescence in time. Experimental TR-OSL results show that the luminescence lifetime in quartz of sedimentary origin is independent of annealing temperature below 500 C, but decreases monotonically thereafter. These results have been interpreted previously empirically on the basis of the existence of two separate luminescence centers LH and LL in quartz, each with its own distinct luminescence lifetime. Additional experimental evidence also supports the presence of a non-luminescent hole reservoir R, which plays a critical role in the predose effect in this material. This paper extends a recently published analytical model for thermal quenching in quartz, to include the two luminescence centers LH and LL, as well as the hole reservoir R. The new extended model involves localized electronic transitions between energy states within the two luminescence centers, and is described by a system of differential equations based on the Mott-Seitz mechanism of thermal quenching. It is shown that by using simplifying physical assumptions, one can obtain analytical solutions for the intensity of the light during a TR-OSL experiment carried out with previously annealed samples. These analytical expressions are found to be in good agreement with the numerical solutions of the equations. The results from the model are shown to be in quantitative agreement with published experimental data for commercially available quartz samples. Specifically the model describes the variation of the luminescence lifetimes with (a) annealing temperatures between room temperature and 900 C, and (b) with stimulation temperatures between 20 and 200 C. This paper also reports new radioluminescence (RL) measurements carried out using the same commercially available quartz samples. Gaussian deconvolution of the RL emission spectra was carried out using a total of seven emission bands between 1.5 and 4.5 eV, and the behavior of these bands was examined as a function of the annealing temperature. An emission band at ∼3.44 eV (360 nm) was found to be strongly enhanced when the annealing temperature was increased to 500 C, and this band underwent a significant reduction in intensity with further increase in temperature. Furthermore, a new emission band at ∼3.73 eV (330 nm) became apparent for annealing temperatures in the range 600-700 C. These new experimental results are discussed within the context of the model presented in this paper. © 2013 Elsevier B.V.

Huck S.,Institute For Geologie | Heimhofer U.,Institute For Geologie
Geochemistry, Geophysics, Geosystems | Year: 2015

Deep-time shallow-marine carbonate platforms record distinct biotic responses to climatic and environmental stressors. Unfortunately, precise temporal assignment of these biotic responses is often problematical due to poor biostratigraphic control and/or a significant diagenetic overprint of the neritic bulk carbonate chemostratigraphic inventory. An accurate stratigraphic framework is essential to better understand the causal relation between biotic events recorded by carbonate platforms and environmental changes that, for instance, culminated in mass extinction events or prolonged episodes of oceanic anoxia. Here we provide an integrated carbon and strontium-isotope stratigraphy of the Early Cretaceous subtropical Provence carbonate platform in SE France that is based solely on pristine low-Mg calcite from rudist bivalves. Carbon-isotope data of geochemically screened rudist fragments enabled reconstruction of a characteristic Barremian pattern including the Mid-Barremian Event (MBE) that allowed for a precise correlation with stratigraphically well-constrained Tethyan shallow-water and hemipelagic reference sections. In order to evaluate ontogenetic carbon-isotope changes and the overall variability of the shell-derived carbon-isotope data, numerous sclerochronological carbon-isotope profiles of individual large rudist shells are presented. Strontium-isotope stratigraphy supports the carbon-isotope-based age of the studied sections, but also provides unequivocal evidence for a major hiatus in the depositional record covering large parts of the Late Barremian. In contrast to biostratigraphic and bulk carbonate chemostratigraphic archives, the here established chronostratigraphy of carbonate platform evolution in the southern Provence region demonstrates a twofold resurgence of rudist-rich carbonate platform production during the Early Aptian and arguably the latest Early Aptian. © 2015. American Geophysical Union. All Rights Reserved.

Figueiral I.,French National Center for Scientific Research | Mosbrugger V.,Institute For Geologie Und Palaontologie | Rowe N.P.,UMR 5120 | Utescher T.,Institute For Geologie | And 2 more authors.
Palaios | Year: 2014

The potential of fossilwood and charcoal frombrowncoaldeposits as sources of reliable paleoenvironmental information is explored with material fromthe Lower Rhine Embayment (Germany). The presence of charcoalified material demonstrates proof of natural wildfires in Tertiary mire environments, most probably during, or after periods of increased drainage and drying of surface vegetation and litter. The results presented suggest that sampling from charcoal layers may provide a more statistically reliable data set for study of such environments. Inclusion of taxa recovered from charcoal layers might compensate for the taphonomic and preservational bias of Tertiary lignitic floras based solely on the collection of lignitic wood. These data confirm the hypothesis that, during certain intervals of the Miocene, both monocotyledonous and dicotyledonous angiosperms might have dominated or represented significant portions of the peat-forming vegetation. The importance of palms and shrubby woody taxa, such as 'Cyrilla', is particularly striking from new evidence of charcoalified remains. In addition, certainwood anatomical features observed fromwell preserved lignitic wood and charcoal may be used as indicators of environmentally modulated growth: (1) clear growth rings testify to the existence of a seasonal climate; (2) wide variations in growth ring characters indicate variable environmental conditions; and (3) high incidence of dicotyledonous taxa, with abundant small vessels and scalariform perforation plates, is interpreted as evidence of a mesic environment.

Steck A.,University of Lausanne | Masson H.,University of Lausanne | Robyr M.,Institute For Geologie
Swiss Journal of Geosciences | Year: 2015

The Monte Rosa basement fold nappe, surrounded by other continental units of the Briançonnais s.l. domain and ophiolites of the Piemont Ocean, represents a major structure of the Pennine Alps situated at the border of the Canton Valais (Switzerland) and Italy. The Central Alps were formed during the collision and SE-directed underthrusting of the European below the Adriatic plate by successive underthrusting, detachment and accretion of the Austroalpine Sesia continental crust, the Piemont oceanic crust and the continental Briançonnais–Europe plate border. The 90–60 Ma Sesia high-pressure metamorphism, followed by the 50–38 Ma Zermatt-Saas Fee and Monte Rosa high-pressure metamorphism, and since 40 Ma by the Barrovian regional metamorphism, reveal a long-lasting Alpine evolution during convergence of both plates. The superposition of the ultra-high pressure Zermatt-Saas Fee ophiolites by the continental Cimes Blanche unit of the Briançonnais domain and the medium pressure ophiolitic Tsaté nappe is explained by delamination and tectonic flake detachment of the Cimes Blanches from the Briançonnais crust and its south directed thrust over the Zermatt-Saas Fee and Tsaté ophiolites. The main ductile deformational structures, related to the NW-directed nappe emplacement, were generated after 40 Ma under greenschist to amphibolite facies Barrovian orogenic metamorphism. Early extrusional structures have been transposed by the younger thrust structures. The NW-directed thrust of the Alps was accompanied since about 35 Ma by ductile dextral shear and backfolding in the zone of dextral transpression between the converging European and Adriatic plates. © 2015, Swiss Geological Society.

Zhang H.,Jilin University | Xie B.,Jilin University | Meng X.,Zhejiang University | Muller U.,BASF | And 9 more authors.
Microporous and Mesoporous Materials | Year: 2013

Beta zeolite as efficient catalyst has been widely used in industrial processes, and its synthesis is normally performed in the presence of tetraethylammonium hydroxide as organic template. Recent works show successful organotemplate-free and seed-directed synthesis of Beta zeolite (Beta-SDS) in the presence of Beta seeds at 140 C, providing a novel route for synthesizing low-cost zeolite catalysts. Notably, in the case for synthesizing Beta-SDS at 140 C (Beta-SDS140), the use of seeds is still very high (8-10% in silica source) and impurity of MOR zeolite easily appears due to the fast crystallization rate. We demonstrate here a rational synthesis of Beta-SDS at 120 C (Beta-SDS120) with pure BEA structure and improved zeolite quality in the presence of a very small amount of Beta seeds (as low as 1.4%) by decreasing zeolite crystallization rate. X-ray diffraction patterns show that calcination at 550 C for 4 h results in the loss of crystallinity at 8.0% and 15.8% for Beta-SDS120 and Beta-SDS140, respectively, suggesting that Beta-SDS120 has higher thermal stability than Beta-SDS140. N2 adsorption isotherms show that Beta-SDS120 has much higher surface area (655 m2/g) and micropore volume (0.25 cm3/g) than Beta-SDS140 (450 m 2/g, 0.18 cm3/g). These phenomena are reasonably assigned to that Beta-SDS120 samples have much less framework defects such as terminal Si-OH groups than Beta-SDS140. The Beta-SDS120 samples with good crystallinity, high thermal stability, large surface area and pore volume offer a good opportunity for their industrial applications as efficient and low-cost catalytic and adsorptive materials.© 2013 Elsevier Inc. All rights reserved.

Cenki-Tok B.,Montpellier University | Berger A.,Institute For Geologie | Gueydan F.,Montpellier University
International Journal of Earth Sciences | Year: 2015

Highly restitic rocks from the Antananarivo Block in northern Madagascar are investigated in this study in order to unravel processes of H2O-rich biotite formation in HT rocks. Polyphase metamorphism and melt migration occurred at 0.6 GPa and 850 °C. Biotite remains stable together with orthopyroxene and makes up to 45 vol% of the rock. In addition, three well-characterised and delimited microdomains having different textural, chemical and petrological characteristics are preserved. Thermodynamic models using the specific bulk compositions of the domains are in agreement with petrological observations. These rocks provide evidence that the lower crust may be strongly heterogeneous, locally associated to the formation of hydrous restites controlled by episodes of melt production and melt escape. This has significant consequences for understanding of the lower crust. © 2015 Springer-Verlag Berlin Heidelberg

Akkiraz M.S.,Dumlupinar University | Akgun F.,Dokuz Eylül University | Utescher T.,Institute For Geologie | Bruch A.A.,Senckenberg Institute | Mosbrugger V.,Senckenberg Institute
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2011

In the present paper, we have analyzed thirty-five palynofloras covering the time span from the Early Miocene (Aquitanian) to the Late Miocene (middle Tortonian) in Turkey. The results obtained are presented in tables and maps showing temporal palaeoprecipitation values.The mean annual precipitation (MAP) exceeds 1200. mm during the Aquitanian and early-middle Serravallian. It is suggested to have bŞen ŞetwŞen Ş000 and 1300. mm in the latest Serravallian-earliest Tortonian in Western and Central Turkey. In the early-middle Tortonian, the lower boundary of MAP decreases to below 1000. mm in Central and Eastern Turkey. Today, MAPs are represented by lower values around 600-1000. mm in Western and 400-600. mm in Central Turkey.For the driest month (LMP), the rainfall was not distributed homogeneously. In the Aquitanian, the calculations are betwŞen Ş6 and 48. mm with humid conditions in Western and Eastern Turkey. During the Burdigalian and Middle Miocene, the driest month precipitation varied with respect to locations. However, it is clear that there was a reduction in precipitation during the early-middle Tortonian, with values around 26-27. mm in Central and Eastern Turkey.The same pattern is observed for the wettest month precipitation (HMP), with estimates higher than 200. mm during the Aquitanian and earliest Tortonian, although some areas received low rainfall. HMP was reduced betwŞen Ş30 and 140. mm in the early-middle Tortonian.The warmest month precipitation (WMP) varied from 96 to 140. mm except for Konya-Ilgin, Kirşehir-HacIşiktaş and Manisa-Soma that received 88. mm during the Early-Middle Miocene. In the early-middle Tortonian, the amount of summer rainfall lay betwŞen Ş8 and 88. mm. The reason of the decrease in all rainfall parameters during the early-middle Tortonian could be related to several factors such as climatic cooling, altitude, aridification, palaeotopograhy or continentality. However, it is necessary to indicate that the Tortonian cooling had previously bŞen Şroposed by Akgün et al. (2007) as the explanation, using a large number of palynological assemblages in Turkey. We also observe a decrease in precipitation parameters during the Middle Miocene. This could be related to fact that either low species diversity can result in wide coexistence intervals or the Monterey cooling event was related to a cooling during the Langhian and Serravallian. © 2010 Elsevier B.V.

Lower-Middle Miocene successions from Kütahya province (Seyitömer and Tunçbilek sub-basins) were analyzed to reconstruct the palaeoclimate and vegetation of the period. A rich coniferous forest formed the dominant components among sporomorphs and consisted mainly of undeterminable Pinaceae, Pinus haploxylon type, Pinus diploxylon type, Picea, Cedrus, Cathaya, Keteleeria and Podocarpus. Pollen data also indicate the presence of some fern taxa (Osmunda, Polypodiaceae, Schizeaceae) Selaginella and Lycopodium. Cupressaceae frequently occur in all samples from both subbasins, and form part of the mixed forest assemblage. Two woody plants Castanea-Castanopsis and evergreen Quercus predominate in the assemblages as well. The reconstruction of palaeoclimate is based on the Coexistence Approach (CA) method and documents subtropical climate with cyclic variation in the sediment sequence. The vegetation does not show a clear change through the sequences studied. Small changes in the quantity of pollen taxa (e.g., thermophilous and arctotertiary) indicate small-scale cyclic temperature and precipitation oscillations during the deposition of the sediments. Using CA, seven palaeoclimate parameters were estimated. Quantitative palaeoclimate data indicate mean annual temperatures of 17-18°C, with winter temperatures of 8-10°C and summer temperatures of 27-28°C. Mean annual precipitation exceeded 1200 mm. The driest month precipitation was between 20 and 25 mm, the wettest month precipitation most frequently ranged between 200 and 250 mm and the summer precipitation was 100-150 mm. These values imply that the Kütahya area was warm and received more precipitation during the Early-Middle Miocene than in modern times. © TÜBİTAK.

Gies H.,Institute For Geologie | Muller U.,BASF | Yilmaz B.,BASF | Feyen M.,BASF | And 10 more authors.
Chemistry of Materials | Year: 2012

The hydrous layer silicate RUB-36, (C 6H 16N) 4 [H 4Si 36O 76], has been used for an interlayer expansion reaction with dichlorodimethylsilane to interconnect neighboring ferrierite-type layers to a three-dimensional framework silicate. The linker group (-O-Si(CH 3) 2-O-) still has the two methyl groups in the as-synthesized form (material name COE-3 [Si 20O 38(CH 3) 4] for the silicate framework) rendering hydrophobic properties. The interlayer expanded zeolite, IEZ, is thermally stable and can be calcined at 550 °C to yield a hydrophilic material COE-4 [Si 20O 38(OH) 4]. 29Si solid state MAS NMR experiments confirm the insertion of the linker group and the methyl and hydroxyl substitution in the as-made and calcined form, respectively. The BET surface area is 238 m 2/g for COE-3 and 350 m 2/g for COE-4. COE-3 and COE-4 crystallize in space group Pm with a = 12.2503(3) Å b = 13.9752(2) Å c = 7.3850(1) Å and β = 107.33(1)° and a = 12.16985(4) Ã?, b = 13.95066(3) Å c = 7.37058(2) Å, and β = 107.30(1)°, respectively. Rietveld crystal structure refinement of the PXRD pattern of COE-3 and COE-4 reveal the expanded, two-dimensional 10-ring pore system including the linker group as homogeneous structural property of the materials. © 2012 American Chemical Society.

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