Journal: Swiss Journal of Geosciences

Abbreviation

Swiss J Geosci

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Springer

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1661-8734
1661-8726

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Publications1 - 10 of 56
  • A marine pebbly mudstone from the Swiss Alps: palaeotectonic implications and some consequences for the interpretation of Precambrian diamictites
    Item type: Journal Article
    Letsch, Dominik; Kiefer, Lea (2017)
    Swiss Journal of Geosciences
    Pebbly mudstones are a conspicuous element of sedimentary sequences deposited in different tectonic settings and sedimentary environments. Whereas for many diamictites a glacial origin seems plausible, the problem to distinguish glacial from non-glacial diamictites is often difficult for Precambrian examples where palaeoclimatic constraints are generally lacking. This article documents an Eocene pebbly mudstone of the Southhelvetic nappes of eastern Central Switzerland (Blockmergel) for which a glacial origin can be firmly rejected and which may thus serve as an example for non-glacial marine diamictites and their sedimentary and palaeotectonic environment. The Blockmergel are interpreted as the product of gravitational deposition of single blocks across steep palaeo-slopes (subaqueous rockfall) into a basin otherwise dominated by suspension settling sedimentation. The Blockmergel occur within the basal part of the early fill of the North Alpine Foreland Basin, which constitutes a deepening upward sequence above basal shallow marine limestones. The Blockmergel demonstrate substantial Middle to Late Eocene sub-aerial erosion and fluvial transport (producing the rounded pebbles) and local extensional fault movements in the proximal part of the incipient North Alpine Foreland Basin. They are capped sharply by forced-regressive shoreface sandstones and the whole sequence thus demonstrates locally very shallow to subaerial conditions within an otherwise rather deep hemipelagic marine basin. This, and the extensional fault movements, are linked to a long-standing feature of Helvetic palaeogeography—the Southhelvetic swell zone. That this swell still operated during the Priabonian i.e. shortly before finally being overthrust by the orogenic wedge of the evolving Alpine orogen is a new element in Alpine palaeotectonics and seems to highlight the importance of the reactivation of inherited palaeotectonic faults. Finally, the example of the Blockmergel is suggested as a useful analogue to help distinguishing glacial-sourced from slope-derived diamictites in the Neoproterozoic sedimentary record and may thus help resolving the “diamictite dichotomy”.
  • Palynology of Triassic–Jurassic boundary sections in northern Switzerland
    Item type: Journal Article
    Schneebeli-Hermann, Elke; Looser, Nathan; Hochuli, Peter A.; et al. (2018)
    Swiss Journal of Geosciences
  • Preface: Special issue - The Alps as part of a larger system of Circum-Mediterranean orogens: papers presented at the 13th Alpine Workshop held in Zlatibor (Serbia)
    Item type: Other Journal Item
    Schmid, Stefan M.; Cvetković, Vladica; Šarić, Kristina; et al. (2019)
    Swiss Journal of Geosciences
  • Earthquakes in Switzerland and surrounding regions during 2017 and 2018
    Item type: Journal Article
    Diehl, Tobias; Clinton, John Francis; Cauzzi, Carlo Virgilio; et al. (2021)
    Swiss Journal of Geosciences
    This report summarizes the seismicity in Switzerland and surrounding regions in the years 2017 and 2018. In 2017 and 2018, the Swiss Seismological Service detected and located 1227 and 955 earthquakes in the region under consideration, respectively. The strongest event in the analysed period was the ML 4.6 Urnerboden earthquake, which occurred in the border region of cantons Uri, Glarus and Schwyz on March 6, 2017. The event was the strongest earthquake within Switzerland since the ML 5.0 Vaz earthquake of 1991. Associated ground motions indicating intensity IV were reported in a radius up to about 50 km and locally approached intensity VI in the region close to the epicentre. Derived focal mechanisms and relative hypocentre relocations of the immediate aftershocks image a NNW–SSE striking sinistral strike-slip fault. Together with other past events in this region, the Urnerboden earthquake suggests the existence of a system of sub-parallel strike-slip faults, likely within in the uppermost crystalline basement of the eastern Aar Massif. A vigorous earthquake sequence occurred close to Château-d'Oex in the Préalpes-Romandes region in western Switzerland. With a magnitude of ML 4.3, the strongest earthquake of the sequence occurred on July 1, 2017. Focal mechanism and relative relocations of fore- and aftershocks image a NNE dipping normal fault in about 4 km depth. Two similarly oriented shallow normal-fault events occurred between subalpine Molasse and Préalpes units close to Châtel-St-Denis and St. Silvester in 2017/18. Together, these events indicate a domain of NE–SW oriented extensional to transtensional deformation along the Alpine Front between Lake Geneva in the west and the Fribourg Fault in the east. The structural complexity of the Fribourg Fault is revealed by an ML 2.9 earthquake near Tafers in 2018. The event images a NW–SE striking fault segment within the crystalline basement, which might be related to the Fribourg Fault Zone. Finally, the ML 2.8 Grenchen earthquake of 2017 provides a rare example of shallow thrust faulting along the Jura fold-and-thrust belt, indicating contraction in the northwestern Alpine foreland of Switzerland.
  • New radiolarian data from the Jurassic ophiolitic mélange of Avala Mountain (Serbia, Belgrade Region)
    Item type: Journal Article
    Bragin, Nikita; Bragina, Liubov; Spajic, Nataša G.; et al. (2019)
    Swiss Journal of Geosciences
  • Origin of high Zn contents in Jurassic limestone of the Jura mountain range and the Burgundy
    Item type: Journal Article
    Jacquat, Olivier; Rambeau, Claire; Voegelin, Andreas; et al. (2011)
    Swiss Journal of Geosciences
  • Modern methods in Structural Geology and Tectonics:
    Item type: Journal Article
    Schmid, Stefan M.; Mancktelow, Neil; Mosar, Jon; et al. (2008)
    Swiss Journal of Geosciences
  • Tectonic significance of Triassic mafic rocks in the June Complex, Sanandaj–Sirjan zone, Iran
    Item type: Journal Article
    Shakerardakani, Farzaneh; Neubauer, Franz; Liu, Xiaoming; et al. (2018)
    Swiss Journal of Geosciences
    This study concentrates on the petrological and geochemical investigation of mafic rocks embedded within the voluminous Triassic June Complex of the central Sanandaj–Sirjan zone (Iran), which are crucial to reconstruct the geodynamics of the Neotethyan passive margin. The Triassic mafic rocks are alkaline to sub-alkaline basalts, containing 43.36–49.09 wt% SiO2, 5.19–20.61 wt% MgO and 0.66–4.59 wt% total alkalis. Based on MgO concentrations, the mafic rocks fall into two groups: cumulates (Mg# = 51.61–58.94) and isotropic basaltic liquids (Mg# = 24.54–42.66). In all samples, the chondrite-normalized REE patterns show enrichment of light REEs with variable (La/Yb)N ratios ranging from 2.48 to 9.00, which confirm their amalgamated OIB-like and E-MORB-like signatures. Enrichment in large-ion lithophile elements and depletion in high field strength elements (HFSE) relative to the primitive mantle further support this interpretation. No samples point to crustal contamination, all having undergone fractionation of olivine + clinopyroxene + plagioclase. Nevertheless, elemental data suggest that the substantial variations in (La/Sm)PM and Zr/Nb ratios can be explained by variable degrees of partial melting rather than fractional crystallization from a common parental magma. The high (Nb/Yb)PM ratio in the alkaline mafic rocks points to the mixing of magmas from enriched and depleted mantle sources. Abundant OIB alkaline basalts and rare E-MORB appear to be linked to the drifting stage on the northern passive margin of the Neotethys Ocean.
  • Tectonometamorphic history of the Gruf complex (Central Alps): exhumation of a granulite–migmatite complex with the Bergell pluton
    Item type: Journal Article
    Galli, Andrea; Le Bayon, Benjamin; Schmidt, Max W.; et al. (2013)
    Swiss Journal of Geosciences
  • Continental weathering as the source of iron in Jurassic iron oolites from Switzerland
    Item type: Journal Article
    Schunck, Stefan; Rickli, Jörg; Wohlwend, Stephan; et al. (2023)
    Swiss Journal of Geosciences
    Iron is extremely insoluble in oxic seawater. The lack of a large aqueous reservoir means that sediments rich in authigenic iron are rare in the modern ocean. In the Middle Jurassic, however, condensed iron-rich sedimentary rocks are widely distributed. Their formation coincides with increased volcanic activity and continental weathering related to the breakup of Pangea, suggesting iron supply through one of these processes. We studied three Swiss shallow-marine iron oolites from Herznach, Windgällen and Erzegg, all from condensed sedimentary sequences of Middle to early Late Jurassic age, to constrain the source of iron to these rocks, combining radiogenic neodymium, strontium and stable iron isotope analyses. Leached authigenic neodymium isotope compositions, which appear to preserve the primary signature, serve as a tracer for the potential involvement of hydrothermal fluids in the formation of the iron oolites. The three iron oolite successions yield crustal Nd isotope compositions (εNd between − 9 and − 7), providing no evidence for the involvement of such fluids. It is, thus, more likely that iron in the sediments derived from detrital fluvial inputs. Strontium isotope compositions, which could potentially support these findings, point to metamorphic overprinting associated with Alpine thrusting. The light iron isotope signatures associated with Middle to early Late Jurassic condensed sequences, δ56Fe between − 1.49 and − 0.57‰, suggest that microbially-mediated iron reduction was also involved in generating these sediments.
Publications1 - 10 of 56