Possible environmental effects on the evolution of the Alps-Molasse Basin system

We propose three partly unrelated stages in the geodynamic evolution of the Alps and the sedimentary response of the Molasse Basin. The first stage comprises the time interval between ca. 35 and 20 Ma and is characterized by a high ratio between rates of crustal accretion and surface erosion. The response of the Molasse Basin was a change from the stage of basin underfill (UMM) to overfill (USM). Because the response time of erosional processes to crustal accretion and surface uplift lasts several millions of years, the orogen first experienced a net growth until the end of the Oligocene. As a result, the Molasse basin subsided at high rates causing the topographic axis to shift to the proximal basin border and alluvial fans to establish at the thrust front. During the Aquitanian, however, ongoing erosion and downcutting in the hinterland caused sediment discharge to the basin to increase and the ratio between the rates of crustal accretion and surface erosion to decrease. The result was a progradation of the dispersal systems, and a shift of the topographic axis towards the distal basin border. The second stage started at ca. 20 Ma at a time when palaeoclimate became more continental, and when the crystalline core became exposed in the orogen. The effect was a decrease in the erosional efficiency of the Swiss Alps and hence a reduction of sediment discharge to the Molasse Basin. We propose that this decrease in sediment flux caused the Burdigalian transgression of the OMM. We also speculate that this reduction of surface erosion initiated the modification of Alpine deformation from vertically- to mainly horizontally directed extrusion (deformation of the Southern Alps, and the Jura Mountains some Ma later). The third stage in the geodynamic development was initiated at the Miocene/Pliocene boundary. At that time, palaeoclimate possibly became wetter, which, in turn, caused surface erosion to increase relative to crustal accretion. This change caused the Alps to enter a destructive stage and the locus of active deformation to shift towards to the orogenic core. It also resulted in a net unloading of the orogen and thus in a flexural rebound of the foreland plate. We conclude that the present chronological resolution is sufficient to propose possible feedback mechanisms between environmental effects and lithospheric processes. Further progress will result from a down-scaling in research. Specifically, we anticipate that climate-driven changes in sediment flux altered the channel geometries of USM and OSM deposits, the pattern of sediment transport and thus the stacking arrangement of architectural elements. This issue has not been sufficiently explored and awaits further detailed quantitative studie

Sedimentological and palynological constraints on the basal Triassic sequence in Central Switzerland

In Central Switzerland, Mesozoic sedimentation began after erosion and peneplainisation of the Hercynian relief and late Paleozoic continental deposition in SW-NE striking pull-apart basins. The first Triassic sedimentary sequence overlaying a weathered crystalline basement consists of a relatively thin (<10 m), lithologically highly variable unit with coarse-grained siliciclastic deposits at the base, grading into a mixed sandstone/shale-dolomite sequence followed by well-bedded dolomites with chert nodules. Sedimentary texture analyses and petrological investigations revealed four different sedimentary units starting at the base with a regolith unit that represents the weathered crystalline basement. It is overlain by terrestrial plain deposits, followed by mixed siliciclastic-carbonaceous sediments and a sequence of dolomites, deposited between the supralittoral and eulittoral zones of a tidal flat (Mels-Formation), and the eulittoral to sublittoral zones of a carbonate tidal flat environment (Röti-Dolomit), respectively. Palynological data from four localities in Central Switzerland indicate a heterochronous early Anisian age (Aegean - Bithynian/Pelsonian) for the supra- to eulittoral mixed siliciclastic-carbonaceous sediments. These new biostratigraphic ages suggest that the first Triassic marine transgression in Central Switzerland is time equivalent with those of the basal Wellendolomit in Northern Switzerland but slightly older than in the Germanic Basin. Consequently, Central Switzerland was located at this time at the northern shoreline of the Tethys and not on the southern limit of the Germanic Basi

Cathodoluminescence Instrumentation for Analysis of Martian Sediments

International audienceThe morphologic study of the surface of Mars reveals that liquid water existed during the first few hundred millions of years of the planet's history (e.g. Smith et al. 1999). The flow of water produced extensive erosion in some place, but also large sedimentary basins. With a long enough duration of the presence of liquid water and the oxidation of basalts, the emergence of biological activity may have eventually occurred, as on Earth. The detection of biomarkers at the surface of Mars is one of the main challenges of current and planned planetary exploration missions (e.g. Westall et al. 2000). Looking for a fossil or present biological activity may be approached by the search for cells, but also by the study of the results of their activity and their interface with the sedimentary environment. Such bio-sedimentations are known among the oldest terrestrial fossils and testify to the earliest terrestrial bioactivity. A discovery of such bio-sedimentations on the Martian surface would be of prime interest for addressing some of the key goals in exobiology. Cathodoluminescence (CL) is a method relevant to the search for life, as it is in line with these analytical goals of detecting bio-sedimentations (Barbin et al. 1999), and it fits well with robotic facilities usable in modern space missions (Blanc et al. 1999, Thomas et al. 2002. 2005). An established technique, cathodoluminescence is a newcomer to Martian exploration, whereit is expected to contribute to the mineralogical characterisation of sedimentary rocks, to the search for biomarkers revealing past biological activity, and to identify past geochemical conditions (Melezhik et al. 1999; Denson et al. 2007). CL is one of the best methods when the growth dynamics, microstructure, and origin of minerals need to be determined, such as with Martian sediments. CL has become an important standard technique for studying geological materials, offering a wide spectrum of applications (Marshall 1988; Barker and Kopp 1991; Barbin and Schvoerer 1997; Pagel et al. 2000). However, it is in the field of sedimentology and petrography that CL has proved to be especially valuable

Archäometrische und archäologische Studien an antiken Skulpturen im Museum der Bildenden Künste, Budapest

Die über mehrere Jahre durchgeführten archäometrischen Untersuchungen der antiken Steindenkmäler in der Antikensammlung des Budapester Museums der Bildenden Künste, die im Zusammenhang einer neuen archäologischen Erforschung der Denkmäler stattfanden, werden hier bekannt gemacht. Dabei hat sich gezeigt, daß die echte Kooperation der beiden Forschungszweige mittels intensiver Diskussion und Schärfung der Methoden und Argumente zu neuen Erkenntnissen führen kann. Die Beachtung archäometrischer Informationen durch die Archäologie bringt einerseits Bestätigung kunsthistorischer Einordnungen; sie wirft andererseits aber auch neue Fragen auf, die bisweilen zu innovativen Interpretationen führen oder auch unerwartet zu derzeit nicht lösbaren Problemen, die daher zu einer wissenschaftlichen Debatte anregen. In mehreren Abschnitten werden für diese Potentiale und Schwierigkeiten charakteristische Beispiele antiker Skulpturen der Sammlung aufgezeigt.This article the long-term archaeometric research on the ancient marble sculptures in the Collection of Classical Antiquities of the Museum of Fine Arts in Budapest, conducted in relation to new archaeological research on those Greek and Roman works of art. The cooperation of these two disciplines applied to ancient sculptures by discussing and re-examining the methods and arguments resulted in new findings. Consideration of archaeometric information in archaeological research may support art-historical classification on the one hand; on the other it often raises new questions leading to innovative interpretations or unexpected and in some cases even currently unsolvable problems, thus stimulating scientific debate. Several sections of this article discussing characteristic examples try to show the potential and difficulties of combined archaeological and archaeometrical research related to ancient sculptures in the Budapest collection