The Southern Alps east of the Giudicarie Belt: Did they really act as an indenter?

According to Ratschbacher et al. (1991) the eastern part of the south directed fold and thrust belt of the Southern Alps located east of the Giudicarie Belt acted as a rigid indenter responsible for the exhumation of the Tauern Window and the eastward lateral extrusion of the Austroalpine nappe pile in the Miocene. However, there is an apparent contradiction in that the Dolomites indenter is itself part of the Southern Alps fold- and thrust belt and hence far from being rigid. Realizing that different parts of thus fold- and thrust belt became deformed during distinct deformation events during different time intervals helps to solve this dilemma. In the Lombardian Southern Alps to the west, and along the kinematically linked sinistrally transpressive Giudicarie fold- and thrust belt, most of the south-directed thrusting occurred twice. Important thrusting occurred before the oldest intrusions of the Adamello pluton (before 45Ma), in the innermost parts of the Lombardian Southern Alps, very probably during the Late Cretaceous (94-78 Ma) as is suggested by the occurrence of flysch deposits whose detritus had its source in the Austroalpine units: the Late Cretaceous Lombardian flysch found along the foothills adjacent to the Po Plain and the remnants of this same flysch belt also found along the northern segment of the Giudicarie line. A second event occurred during the Miocene that postdates 22 Ma (age of the youngest marine sediments affected by sinistral transpression within the Giudicarie Belt), kinematically linked to the frontal-most thrust sheets of the Lombardian Southern Alps (figure 1). Schönborn (1992) quantified the amount of this post-Adamello Miocene N-S shortening to some 56km increasing eastward to some 87 km. Much of this Miocene N-S convergence is accommodated by northward wedging and underthrusting of the crystalline underpinnings of the fold-and thrust belt below the Central Alps and shallower parts parts of the preexisting about 30 Ma old Tonale Line (Schmid et al. 1996). The Giudicarie fold-and thrust belt, however, sinistrally displaced the entire crustal section of the eastern Southern Alps by about the same amount, i.e. some 72km (68km N-S component) to the north (Pomella et al. 2012). This resulted a sinistral offset of the pre-existing Tonale line in respect to the Pustertal segment of the Periadriatic line, associated with suspected indentation and rapid exhumation of the Tauern Window. Deformation in the eastern part of the Southern Alps fold-and thrust belt (the Dolomites), however, occurred during entirely different time intervals. Parts of the Dolomites were affected by Dinaric SW-directed thrusting at 48-32Ma when the external Dinarides extended into the yet unfolded strata of the future Dolomites. After some 8 Ma of quiescence Miocene deformation in the Dolomites did initiate after the Langhian (i.e. after ca. 14 Ma) in the Dolomites as indicated by the youngest sediments involved along the Val Sugana thrust system (Castellarin et al. 1992, 1998). From a structural point of view the Val Sugana thrust system of the Dolomites ends westward before reaching the Giudicarie fold and thrust belt to which it is kinematically unrelated. The end of the suspected indentation of the Dolomites indenter, and hence sinistral transpression along the Giudicarie belt, can be estimated on the basis of the end of fast cooling in the Tauern window due to exhumation at around 14 Ma (Scharf et al. 2013). In conclusion, it appears that indentation occurred during the 22-14 Ma time interval when the Dolomites east of the Giudicarie Belt remained undeformed and indeed acted as an indenter

Dating Polygenetic Metamorphic Assemblages along a Transect across the Western Alps

Multichronometric analyses were performed on samples from a transect in the French-Italian Western Alps crossing nappes derived from the Briançonnais terrane and the Piemonte-Liguria Ocean, in an endeavour to date both high-pressure (HP) metamorphism and retrogression history. Twelve samples of white mica were analysed by 39Ar-40Ar stepwise heating, complemented by two samples from the Monte Rosa nappe 100 km to the NE and also attributed to the Briançonnais terrane. One Sm-Nd and three Lu-Hf garnet ages from eclogites were also obtained. White mica ages decrease from c. 300 Ma in the westernmost samples (Zone Houillère), reaching c. 300°C during Alpine metamorphism, to 6·45 atoms per formula unit increases eastward. Across the whole traverse, phengitic mica grown during HP metamorphism defines the D1 foliation. Syn-D2 mica is more Si-poor and associated with nappe stacking, exhumation, and hydrous retrogression under greenschist-facies conditions. Syn-D1 phengite is very often corroded, overgrown by, or intergrown with, syn-D2 muscovite. Most importantly, syn-D2 recrystallization is not limited to S2 schistosity domains; micrometre-scale chemical fingerprinting reveals muscovite pseudomorphs after phengite crystals, which could be mistaken for syn-D1 mica based on microstructural arguments alone. The Cl/K ratio in white mica is a useful discriminator, as D2 retrogression was associated with a less saline fluid than eclogitization. As petrology exerts the main control on the isotope record, constraining the petrological and microstructural framework is necessary to correctly interpret the geochronological data, described in both the present study and the literature. Our approach, which ties geochronology to detailed geochemical, petrological and microstructural investigations, identifies 47-48 Ma as the age of HP formation of syn-D1 mica along the studied transect and in the Monte Rosa area. Cretaceous apparent mica ages, which were proposed to date eclogitization by earlier studies based on conventional ‘thermochronology', are due to Ar inheritance in incompletely recrystallized detrital mica grains. The inferred age of the probably locally diachronous, greenschist-facies, low-Si, syn-D2 mica ranges from 39 to 43 Ma. Coexistence of D1 and D2 ages, and the constancy of non-reset D1 ages along the entire transect, provides strong evidence that the D1 white mica ages closely approximate formation ages. Volume diffusion of Ar in white mica (activation energy E = 250 kJ mol−1; pressure-adjusted diffusion coefficient D'0 < 0·03 cm2 s−1) has a subordinate effect on mineral ages compared with both prograde and retrograde recrystallization in most sample

Corporate Governance und Unternehmungsbewertung in der Schweiz

Die Diskussion über die Qualität guter Corporate Governance und deren Auswirkung auf den Unternehmenswert beschäftigt Wissenschaft und Praxis seit mehreren Jahren. Allerdings existiert noch keine umfassende empirische Studie zum Einfluss der Corporate Governance auf den Unternehmenswert schweizerischer Firmen. Diese Lücke soll durch die vorliegende Arbeit geschlossen werden. Neben einem breiten Corporate Governance Index umfasst die Studie fünf weitere Governance Mechanismen, von welchen sowohl theoretische als auch empirische Arbeiten vermuten lassen, dass sie das Potential haben, die aus der Prinzipal-Agenten Beziehung resultierenden Kosten zwischen dem Management und den Aktionären zu reduzieren. Die Resultate multivariater OLS Regressionen zeigen, dass eine gute Corporate Governance vom Kapitalmarkt durch eine höhere Bewertung entschädigt wird

Wang-Landau sampling for quantum systems: algorithms to overcome tunneling problems and calculate the free energy

We present a generalization of the classical Wang-Landau algorithm [Phys. Rev. Lett. 86, 2050 (2001)] to quantum systems. The algorithm proceeds by stochastically evaluating the coefficients of a high temperature series expansion or a finite temperature perturbation expansion to arbitrary order. Similar to their classical counterpart, the algorithms are efficient at thermal and quantum phase transitions, greatly reducing the tunneling problem at first order phase transitions, and allow the direct calculation of the free energy and entropy.Comment: Added a plot showing the efficiency at first order phase transition

Orogenic lithosphere and slabs in the greater Alpine area – interpretations based on teleseismic P-wave tomography

Based on recent results of AlpArray, we propose a new model of Alpine collision that involves subduction and detachment of thick (∼ 180 km) European lithosphere. Our approach combines teleseismic P-wave tomography and existing local earthquake tomography (LET), allowing us to image the Alpine slabs and their connections with the overlying orogenic lithosphere at an unprecedented resolution. The images call into question the conventional notion that downward-moving lithosphere and slabs comprise only seismically fast lithosphere. We propose that the European lithosphere is heterogeneous, locally containing layered positive and negative Vp anomalies of up to 5 %–6 %. We attribute this layered heterogeneity to seismic anisotropy and/or compositional differences inherited from the Variscan and pre-Variscan orogenic cycles rather than to thermal anomalies. The lithosphere–asthenosphere boundary (LAB) of the European Plate therefore lies below the conventionally defined seismological LAB. In contrast, the lithosphere of the Adriatic Plate is thinner and has a lower boundary approximately at the base of strong positive Vp anomalies at 100–120 km. Horizontal and vertical tomographic slices reveal that beneath the central and western Alps, the European slab dips steeply to the south and southeast and is only locally still attached to the Alpine lithosphere. However, in the eastern Alps and Carpathians, this slab is completely detached from the orogenic crust and dips steeply to the north to northeast. This along-strike change in attachment coincides with an abrupt decrease in Moho depth below the Tauern Window, the Moho being underlain by a pronounced negative Vp anomaly that reaches eastward into the Pannonian Basin area. This negative Vp anomaly is interpreted as representing hot upwelling asthenosphere that heated the overlying crust, allowing it to accommodate Neogene orogen-parallel lateral extrusion and thinning of the ALCAPA tectonic unit (upper plate crustal edifice of Alps and Carpathians) to the east. A European origin of the northward-dipping, detached slab segment beneath the eastern Alps is likely since its down-dip length matches estimated Tertiary shortening in the eastern Alps accommodated by originally south-dipping subduction of European lithosphere. A slab anomaly beneath the Dinarides is of Adriatic origin and dips to the northeast. There is no evidence that this slab dips beneath the Alps. The slab anomaly beneath the Northern Apennines, also of Adriatic origin, hangs subvertically and is detached from the Apenninic orogenic crust and foreland. Except for its northernmost segment where it locally overlies the southern end of the European slab of the Alps, this slab is clearly separated from the latter by a broad zone of low Vp velocities located south of the Alpine slab beneath the Po Basin. Considered as a whole, the slabs of the Alpine chain are interpreted as highly attenuated, largely detached sheets of continental margin and Alpine Tethyan oceanic lithosphere that locally reach down to a slab graveyard in the mantle transition zone (MTZ)

The timing of polyphase Miocene tectonics in Northern Romania

This study addresses the polyphase Miocene tectonic evolution in the Maramures area (northern Romania) by combining field observations, stratigraphic arguments and fission-track analysis (Tischler et al. in press). Fission-track analysis has been carried out on basement samples from the Rodna horst, situated in the East Carpathians (Bucovinvian nappes). This area was affected by Cretaceous medium- to low-grade metamorphism, followed by post-collisional exhumation and renewed moderate thermal overprint due to the deposition of Eocene to Early Miocene sediments. Based on paleostress analyses of mesoscale structures, three main tectonic phases can be disdinguished in the study area, all of which are postdate the earliest Miocene (Aquitanian, 20.5 Ma). In late Early Miocene (Burdigalian) the Pienide nappes, nonmetamorphic flysch series, were emplaced onto the Paleogene to Early Miocene sedimentary cover of the Bucovinian nappes...conferenc

Imaging structure and geometry of slabs in the greater Alpine area – a P-wave travel-time tomography using AlpArray Seismic Network data

We perform a teleseismic P-wave travel-time tomography to examine the geometry and structure of subducted lithosphere in the upper mantle beneath the Alpine orogen. The tomography is based on waveforms recorded at over 600 temporary and permanent broadband stations of the dense AlpArray Seismic Network deployed by 24 different European institutions in the greater Alpine region, reaching from the Massif Central to the Pannonian Basin and from the Po Plain to the river Main. Teleseismic travel times and travel-time residuals of direct teleseismic P waves from 331 teleseismic events of magnitude 5.5 and higher recorded between 2015 and 2019 by the AlpArray Seismic Network are extracted from the recorded waveforms using a combination of automatic picking, beamforming and cross-correlation. The resulting database contains over 162 000 highly accurate absolute P-wave travel times and travel-time residuals. For tomographic inversion, we define a model domain encompassing the entire Alpine region down to a depth of 600 km. Predictions of travel times are computed in a hybrid way applying a fast TauP method outside the model domain and continuing the wave fronts into the model domain using a fast marching method. We iteratively invert demeaned travel-time residuals for P-wave velocities in the model domain using a regular discretization with an average lateral spacing of about 25 km and a vertical spacing of 15 km. The inversion is regularized towards an initial model constructed from a 3D a priori model of the crust and uppermost mantle and a 1D standard earth model beneath. The resulting model provides a detailed image of slab configuration beneath the Alpine and Apenninic orogens. Major features are a partly overturned Adriatic slab beneath the Apennines reaching down to 400 km depth still attached in its northern part to the crust but exhibiting detachment towards the southeast. A fast anomaly beneath the western Alps indicates a short western Alpine slab whose easternmost end is located at about 100 km depth beneath the Penninic front. Further to the east and following the arcuate shape of the western Periadriatic Fault System, a deep-reaching coherent fast anomaly with complex internal structure generally dipping to the SE down to about 400 km suggests a slab of European origin limited to the east by the Giudicarie fault in the upper 200 km but extending beyond this fault at greater depths. In its eastern part it is detached from overlying lithosphere. Further to the east, well-separated in the upper 200 km from the slab beneath the central Alps but merging with it below, another deep-reaching, nearly vertically dipping high-velocity anomaly suggests the existence of a slab beneath the eastern Alps of presumably the same origin which is completely detached from the orogenic root. Our image of this slab does not require a polarity switch because of its nearly vertical dip and full detachment from the overlying lithosphere. Fast anomalies beneath the Dinarides are weak and concentrated to the northernmost part and shallow depths. Low-velocity regions surrounding the fast anomalies beneath the Alps to the west and northwest follow the same dipping trend as the overlying fast ones, indicating a kinematically coherent thick subducting lithosphere in this region. Alternatively, these regions may signify the presence of seismic anisotropy with a horizontal fast axis parallel to the Alpine belt due to asthenospheric flow around the Alpine slabs. In contrast, low-velocity anomalies to the east suggest asthenospheric upwelling presumably driven by retreat of the Carpathian slab and extrusion of eastern Alpine lithosphere towards the east while low velocities to the south are presumably evidence of asthenospheric upwelling and mantle hydration due to their position above the European slab

Corporate Governance, Unternehmensbewertung und Wettbewerb - eine Untersuchung für die Schweiz

Corporate governance; Ownership structure; Competition; Firm valuation; Endogeneity

Sp converted waves reveal the structure of the lithosphere below the Alps and their northern foreland

The structure of the lithosphere is reflecting its evolution. The Moho of the European lithosphere has already been studied intensively. This is, however, not yet the case for the lower boundary of the lithosphere, i.e., the lithosphere-asthenosphere boundary (LAB). We are using S-to-P converted seismic waves to study the structures of the Moho and the LAB beneath Europe including the greater Alpine Area with data from the AlpArray project and the European networks of permanent seismic stations. We use plain waveform stacking of converted waves without deconvolution and compare the results with stacking of deconvolved traces. We also compare Moho depths determinations using S-to-P converted waves with those obtained by other seismic methods. We present more detailed information about negative velocity gradients (NVG) below the Moho. Its lower bound may be interpreted as representing the LAB. We found that the thickness of the European mantle lithosphere is increasing from about 50°N towards the Alps along the entire east-west extension of the Alps. The NVG has also an east dipping component towards the Pannonian Basin and the Bohemian Massif. The Alps and their northern foreland north of about 50°N are surrounded in the east, west and north by a north dipping mantle lithosphere. Along 50°N, where the NVG is reversing its dip direction towards the north, is also the area along which the volcanoes of the European Cenozoic Rift System are located. Our results possibly indicate that the Alpine collision has deformed the entire lithosphere of the Alpine foreland as far north as about 50°N