Magmato-sedimentary Carboniferous to Jurassic evolution of the western Tauern window,Eastern Alps (constraints from U-Pb zircon dating and geochemistry)     

Veselá Petra  Söllner Frank  Finger Friedrich  Gerdes Axel 《International Journal of Earth Sciences》2011,100(5):993-1027

New geochronological U-Pb (LA-ICP-MS) zircon data and geochemical analyses from the Variscan orthogneisses and metavolcanic rocks in the western Tauern window are presented and used to reconstruct the pre-Alpine evolution of this area. The late- and post-Variscan stage in the Tauern window was characterised by distinct magmatic pulses accompanied by the formation of volcano-sedimentary basins. The magmatic activity started in the Visean (335.4 ± 1.5 Ma) with the intrusion of a K-rich, durbachitic biotite-granite (protolith of the Ahorn gneiss). Following a period of exhumation and erosion, Westfalian–Stefanian volcanics were deposited (Grierkar meta-rhyodacite: 309.8 ± 1.5 Ma; Venntal meta-rhyolite: 304.0 ± 3.0 Ma). A renewed magmatic pulse occurred in the Early Permian, producing large volumes of tonalites and granodiorites (Tux meta-granodiorite: 292.1 ± 1.9 Ma). The youngest magmatism is characterised by pyroclastic and tuffitic deposits (Pfitsch meta-rhyolite: 280.5 ± 2.6 Ma; Schönach valley meta-andesite: 279.0 ± 4.8 Ma). This volcanism was probably related to crustal extensional faulting within an intra-continental graben and horst setting, asthenospheric upwelling and heat flow increase due to the onset of the Permian rifting. The Permo-Triassic peneplanation and subsidence is documented by shallow marine and evaporitic deposits. Probably in the Middle Jurassic times, the area was flooded and in the Late Jurassic the whole area was covered by limestones, representing post-rift sediments on the southern European continental margin.  相似文献   

Biorefining of Green Biomass – Technical and Energetic Considerations     

Birgit Kamm  Petra Schönicke  Michael Kamm 《洁净——土壤、空气、水》2009,37(1):27-30

The development of biorefineries is the key for access to an integrated production of food, feed, chemicals, materials, goods, fuels and energy of the future. This communication considers an integrated green biorefinery combined with today's production of feed in the green agriculture. Special attention is given to the combination of physical and biotechnological processes for the production of proteins as well as platform chemicals such as lactic acid and lysine. Mass and energy flows (steam and electricity) are given for the biorefining of green biomass to produce platform chemicals, proteins, feed and biogas from residues.  相似文献   

Devensian Late-glacial and early Flandrian environmental history of the Vale of Pickering,Yorkshire, England     

Petra Day 《第四纪科学杂志》1996,11(1):9-24

Pollen, sedimentological and charcoal particle analyses are presented from Devensian Late-glacial and early- to mid-Flandrian deposits from a former lake in the Vale of Pickering, Yorkshire. The combined analytical methods provide evidence for a short-lived climatic deterioration towards the end of the Late-glacial Interstadial, followed by a brief recovery prior to the Loch Lomond Stadial. This deterioration may be correlated with one of the ‘pre-Younger Dryas’ cooling periods identified not only in other pollen sequences from Britain and Europe, but from such diverse sources as Foraminifera from the Norwegian Sea and electrical conductivity measurements from the Greenland ice sheet. Loss-on-ignition and magnetic susceptibility data suggest that the Loch Lomond Stadial was characterised by an initial prolonged temperature decline, followed by a sudden more severe downturn resulting in particularly intense solifluction. Radiocarbon accelerator dating of the early Flandrian marl deposits illustrates the problem of age determination in calcareous lakes, and an estimate of the magnitude of ‘hard water error’ is obtained. The local population expansion of Alnus glutinosa is dated to 7640 ± 85 yr BP, but there is possible evidence for a Late-glacial presence of the tree, the significance of which is discussed in relation to other sites in east Yorkshire. © 1996 John Wiley & Sons, Ltd.  相似文献   

Durbachites–Vaugnerites – a geodynamic marker in the central European Variscan orogen     

Jürgen F. von Raumer  Fritz Finger  Petra Veselá  Gérard M. Stampfli 《地学学报》2014,26(2):85-95

Durbachites–Vaugnerites are K–Mg‐rich magmatic rocks derived from an enriched mantle source. Observed throughout the European Variscan basement, their present‐day geographical distribution does not reveal any obvious plate‐tectonic context. Published geochronological data show that most durbachites–vaugnerites formed around 335–340 Ma. Plotted in a Visean plate‐tectonic reconstruction, the occurrences of durbachites–vaugnerites are concentrated in a hotspot like cluster in the Galatian superterrane, featuring a distinctive regional magmatic province. Reviewing the existing local studies on Variscan durbachite–vaugnerite rocks, we interpret their extensive appearance in the Visean in terms of two factors: (i) long‐term mantle enrichment above early Variscan subduction systems; and (ii) melting of this enriched subcontinental mantle source during the Variscan collision stage due to thermal anomalies below the Galatian superterrane, possibly created by slab windows and and/or the sinking of the subducted Rheic slab into the mantle. The tectonic reorganization of Europe in the Late Palaeozoic and during the Alpine orogeny has torn apart and blurred this marked domain of durbachites–vaugnerites.  相似文献   

Linkages Between Boundary-Layer Structure and the Development of Nocturnal Low-Level Jets in Central Oklahoma   总被引：1，自引：1，他引：0  

Petra M. Klein  Xiao-Ming Hu  Alan Shapiro  Ming Xue 《Boundary-Layer Meteorology》2016,158(3):383-408

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Fluid inclusions in granulite-facies metapelites of the Hercynian ancient lower crust of the Serre,Calabria, Southern Italy     

Petra Herms  Volker Schenk 《Contributions to Mineralogy and Petrology》1992,112(2-3):393-404

Investigations of fluid inclusions in granulitefacies metapelites of southern Calabria enable characterization of the fluid composition of these lower crustal rocks, and constrain the petrologically deduced retrograde P-T path characterized by isothermal uplift prior to isobaric cooling in middle crustal levels. Fluid inclusions in cordierite, garnet and sillimanite have a CO₂-rich composition. Inclusions in cordierite rarely contain minor amounts of N₂ and H₂O, and in garnets some CO₂–CH₄–N₂ inclusions have been analyzed by Raman microprobe. Quartz reveals the most complex fluid melusion compositions (1) CO₂-rich, (2) CO₂–CH₄–N₂, (3) CH₄–N₂, (4) H₂O–MgCl₂–CaCl₂–NaCl, (5) H₂O–NaCl and (6) H₂O–CO₂. The earliest fluid inclusions after peak metamorphism are rich in CO₂ with minor amounts of N₂ and H₂O. An early CO₂–(H₂O–N₂) fluid composition has been confirmed by detection of CO₂, H₂O and N₂ in the channels of the cordierite structure. Most of the early CO₂-rich fluid inclusions were modified during the uplift from the lower to the middle crustal level, resulting in a density decrease with CO₂ still dominant. The subsequent isobaric cooling led to further modifications of the fluid inclusions. High-density inclusions around implosion textures or scattered amongst lower-density ones must have formed during this cooling episode. Aqueous inclusions in quartz are mostly formed late and are consistent with trapping during retrograde rehydration.This project has been supported by the DFG as contribution to the special program Continental Lower Crust  相似文献   

Turbidite system architecture and sedimentary processes along topographically complex slopes: the Makran convergent margin     

JULIEN BOURGET  SEBASTIEN ZARAGOSI  NADINE ELLOUZ‐ZIMMERMANN  NICOLAS MOUCHOT  THIERRY GARLAN  JEAN‐LUC SCHNEIDER  VALENTINE LANFUMEY  SIGFRIED LALLEMANT 《Sedimentology》2011,58(2):376-406

This study investigates the morphology and Late Quaternary sediment distribution of the Makran turbidite system (Makran subduction zone, north‐west Indian Ocean) from a nearly complete subsurface mapping of the Oman basin, two‐dimensional seismic and a large set of coring data in order to characterize turbidite system architecture across an active (fold and thrust belt) margin. The Makran turbidite system is composed of a dense network of canyons, which cut into high relief accreted ridges and intra‐slope piggyback basins, forming at some locations connected and variably tortuous paths down complex slopes. Turbidite activity and trench filling rates are high even during the Holocene sea‐level highstand conditions. In particular, basin‐wide, sheet‐like thick mud turbidites, probably related to major mass wasting events of low recurrence time, drape the flat and unchannellized Oman abyssal plain. Longitudinal depth profiles show that the Makran canyons are highly disrupted by numerous thrust‐related large‐scale knickpoints (with gradients up to 20° and walls up to 500 m high). At the deformation front, the strong break of slope can lead to the formation of canyon‐mouth ‘plunge pools’ of variable shapes and sizes. The plunge pools observed in the western Makran are considerably larger than those previously described in sub‐surface successions; the first insights into their internal architecture and sedimentary processes are presented here. Large plunge pools in the western Makran are associated with large scoured areas at the slope break and enhanced sediment deposition downstream: high‐amplitude reflectors are observed inside the plunge pools, while their flanks are composed of thin‐bedded, fine‐grained turbidites deposited by the uppermost part of the turbidity flows. Thus, these architectural elements are associated with strong sediment segregation leading to specific trench‐fill mechanisms, as only the finer‐grained component of the flows is transferred to the abyssal plain. However, the Makran accretionary prism is characterized by strong along‐strike variability in tectonics and fluvial input distribution that might directly influence the turbidite system architecture (i.e. canyon entrenchment, plunge pool formation or channel development at canyon mouths), the sedimentary dynamics and the resulting sediment distribution. Channel formation in the abyssal plain and trench‐fill characteristics depend on the theoretical ‘equilibrium’ conditions of the feeder system, which is related closely to the balance between erosion rates and tectonic regime. Thus, the Makran turbidite system constitutes an excellent modern analogue for deep‐water sedimentary systems with structurally complex depocentres, in convergent margin settings.  相似文献   

Origin and contrasting succession pathways of the Western Carpathian calcareous fens revealed by plant and mollusc macrofossils     

Petra Hájková  Michal Horsák  Michal Hájek  Adam Lacina  Hana Buchtová  Barbora Pelánková 《Boreas: An International Journal of Quaternary Research》2012,41(4):690-706

Calcareous fens are unique environments whose history is almost unexplored. The radiocarbon dates of the basal layers of 49 undisturbed calcareous fens showed that in the Western Carpathians (central Europe) many of the extant fen sites originated fairly recently, with two peaks in the High Middle and Roman Ages, the former corresponding to human‐induced changes of the landscape. Conspicuous number of fens also appeared in the Lateglacial and later in the Bronze Age owing to suitable environmental conditions. The Lateglacial calcareous fens were of semi‐open character with coniferous trees, a heliophilous understorey, and mollusc communities composed of several snail species typical of glacial landscapes. We found wood of Taxus baccata in six localities between 7390 and 600 cal. a BP, suggesting that calcareous fens could have represented a refugial habitat for this red‐listed species during the middle Holocene. Using plant macrofossil and mollusc analyses of three representative profiles we illustrate the most common developmental types: (i) fens originating in the Lateglacial, having an open or semi‐open character during the whole Holocene; (ii) open fens originating as wooded wetlands; and (iii) open fens starting their development de novo in the late Holocene. Human activities were responsible for the formation of a high number of calcareous fens, especially in the Outer Western Carpathians, and became important drivers of fen biodiversity development. Only a few recently existing calcareous fens contain old sequences of calcareous deposits. They represent unique natural archives and harbour highly endangered relic populations of fen specialists, making their strict protection urgent.  相似文献   

BRACKEN FERN INVASION IN SOUTHERN YUCATÁN: A CASE FOR LAND‐CHANGE SCIENCE*     

LAURA C. SCHNEIDER 《Geographical review》2004,94(2):229-241

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Seasonality and time scales in the relationship between global SST and African rainfall   总被引：1，自引：0，他引：1  

Heiko Paeth  Petra Friederichs 《Climate Dynamics》2004,23(7-8):815-837

The main goal of this study is to determine the oceanic regions corresponding to variability in African rainfall and seasonal differences in the atmospheric teleconnections. Canonical correlation analysis (CCA) has been applied in order to extract the dominant patterns of linear covariability. An ensemble of six simulations with the global atmospheric general circulation model ECHAM4, forced with observed sea surface temperatures (SSTs) and sea ice boundary variability, is used in order to focus on the SST-related part of African rainfall variability. Our main finding is that the boreal summer rainfall (June–September mean) over Africa is more affected by SST changes than in boreal winter (December–March mean). In winter, there is a highly significant link between tropical African rainfall and Indian Ocean and eastern tropical Pacific SST anomalies, which is closely related to El Niño-Southern Oscillation (ENSO). However, long-term changes are found to be associated with SST changes in the Indian and tropical Atlantic Oceans, thus, showing that the tropical Atlantic plays a critical role in determining the position of the intertropical convergence zone (ITCZ). Since ENSO is less in summer, the tropical Pacific and the Indian Oceans are less important for African rainfall. The African summer monsoon is strongly influenced by SST variations in the Gulf of Guinea, with a response of opposite sign over the Sahelian zone and the Guinean coast region. SST changes in the subtropical and extratropical oceans mostly take place on decadal time scales and are responsible for low-frequency rainfall fluctuations over West Africa. The modelled teleconnections are highly consistent with the observations. The agreement for most of the teleconnection patterns is remarkable and suggests that the modelled rainfall anomalies serve as suitable predictors for the observed changes.  相似文献