Carboniferous high‐ P metamorphism and deformation in the Belledonne Massif (Western Alps)

2021 ◽  
Author(s):  
Jean‐Baptiste Jacob ◽  
Stéphane Guillot ◽  
Daniela Rubatto ◽  
Emilie Janots ◽  
Jérémie Melleton ◽  
...  
Keyword(s):  
Western Alps

scholarly journals Direct dating reveals the early history of opium poppy in western Europe

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Aurélie Salavert ◽  
Antoine Zazzo ◽  
Lucie Martin ◽  
Ferran Antolín ◽  
Caroline Gauthier ◽  
...  
Keyword(s):  
Western Europe ◽  
Western Alps ◽  
Western Mediterranean ◽  
Opium Poppy ◽  
Radiocarbon Dates ◽  
Macrobotanical Remains ◽  
History Of ◽  
Temperate Europe ◽  
Radiocarbon Chronology ◽  
Botanical Remains

AbstractThis paper aims to define the first chrono-cultural framework on the domestication and early diffusion of the opium poppy using small-sized botanical remains from archaeological sites, opening the way to directly date minute short-lived botanical samples. We produced the initial set of radiocarbon dates directly from the opium poppy remains of eleven Neolithic sites (5900–3500 cal BCE) in the central and western Mediterranean, northwestern temperate Europe, and the western Alps. When possible, we also dated the macrobotanical remains originating from the same sediment sample. In total, 22 samples were taken into account, including 12 dates directly obtained from opium poppy remains. The radiocarbon chronology ranges from 5622 to 4050 cal BCE. The results show that opium poppy is present from at least the middle of the sixth millennium in the Mediterranean, where it possibly grew naturally and was cultivated by pioneer Neolithic communities. Its dispersal outside of its native area was early, being found west of the Rhine in 5300–5200 cal BCE. It was introduced to the western Alps around 5000–4800 cal BCE, becoming widespread from the second half of the fifth millennium. This research evidences different rhythms in the introduction of opium poppy in western Europe.

scholarly journals Metasediments Covering Ophiolites in the HP Internal Belt of the Western Alps: Review of Tectono-Stratigraphic Successions and Constraints for the Alpine Evolution

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 411
Author(s):  
Paola Tartarotti ◽  
Silvana Martin ◽  
Andrea Festa ◽  
Gianni Balestro
Keyword(s):  
High Pressure ◽  
Western Alps ◽  
Metamorphic Evolution ◽  
Alpine Orogeny ◽  
Sedimentary Evolution ◽  
Hp Metamorphism ◽  
Tethys Ocean ◽  
Depositional Setting ◽  
Oceanic Rocks ◽  
Outer Band

Ophiolites of the Alpine belt derive from the closure of the Mesozoic Tethys Ocean that was interposed between the palaeo-Europe and palaeo-Adria continental plates. The Alpine orogeny has intensely reworked the oceanic rocks into metaophiolites with various metamorphic imprints. In the Western Alps, metaophiolites and continental-derived units are distributed within two paired bands: An inner band where Alpine subduction-related high-pressure (HP) metamorphism is preserved, and an outer band where blueschist to greenschist facies recrystallisation due to the decompression path prevails. The metaophiolites of the inner band are hugely important not just because they provide records of the prograde tectonic and metamorphic evolution of the Western Alps, but also because they retain the signature of the intra-oceanic tectono-sedimentary evolution. Lithostratigraphic and petrographic criteria applied to metasediments associated with HP metaophiolites reveal the occurrence of distinct tectono-stratigraphic successions including quartzites with marbles, chaotic rock units, and layered calc schists. These successions, although sliced, deformed, and superposed in complex ways during the orogenic stage, preserve remnants of their primary depositional setting constraining the pre-orogenic evolution of the Jurassic Tethys Ocean.

scholarly journals Pervasive fluid-rock interaction in subducted oceanic crust revealed by oxygen isotope zoning in garnet

2021 ◽  
Vol 176 (7) ◽  
Author(s):  
Thomas Bovay ◽  
Daniela Rubatto ◽  
Pierre Lanari
Keyword(s):  
Oxygen Isotope ◽  
Western Alps ◽  
Large Contribution ◽  
Chemical Mapping ◽  
Rock Interaction ◽  
Rock Density ◽  
Chemical Zoning ◽  
Dehydration Reactions ◽  
Subducted Oceanic Crust ◽  
Eclogite Facies

AbstractDehydration reactions in the subducting slab liberate fluids causing major changes in rock density, volume and permeability. Although it is well known that the fluids can migrate and interact with the surrounding rocks, fluid pathways remain challenging to track and the consequences of fluid-rock interaction processes are often overlooked. In this study, we investigate pervasive fluid-rock interaction in a sequence of schists and mafic felses exposed in the Theodul Glacier Unit (TGU), Western Alps. This unit is embedded within metaophiolites of the Zermatt-Saas Zone and reached eclogite-facies conditions during Alpine convergence. Chemical mapping and in situ oxygen isotope analyses of garnet from the schists reveal a sharp chemical zoning between a xenomorphic core and a euhedral rim, associated to a drop of ~ 8‰ in δ18O. Thermodynamic and δ18O models show that the large amount of low δ18O H2O required to change the reactive bulk δ18O composition cannot be produced by dehydration of the mafic fels from the TGU only, and requires a large contribution of the surrounding serpentinites. The calculated time-integrated fluid flux across the TGU rocks is 1.1 × 105 cm3/cm2, which is above the open-system behaviour threshold and argues for pervasive fluid flow at kilometre-scale under high-pressure conditions. The transient rock volume variations caused by lawsonite breakdown is identified as a possible trigger for the pervasive fluid influx. The calculated schist permeability at eclogite-facies conditions (~ 2 × 10–20 m2) is comparable to the permeability determined experimentally for blueschist and serpentinites.

Detection and source parameterization of small-energy fireball events in Western Alps with ground-based infrasonic arrays

2021 ◽  
Author(s):  
Giacomo Belli ◽  
Emanuele Pace ◽  
Emanuele Marchetti
Keyword(s):  
Western Alps ◽  
Apparent Velocity ◽  
Array Analysis ◽  
Small Energy ◽  
Small Aperture ◽  
Energy Estimation ◽  
Trajectory Reconstruction ◽  
Tnt Equivalent ◽  
Back Azimuth ◽  
Aperture Arrays

Summary We present infrasound signals generated by four fireball events occurred in Western Alps between 2016 and 2019 and that were recorded by small aperture arrays at source-to receiver distances < 300 km. Signals consist in a series of short-lived infrasonic arrivals that are closely spaced in time. Each arrival is identified as a cluster of detections with constant wave parameters (back-azimuth and apparent velocity), that change however from cluster to cluster. These arrivals are likely generated by multiple infrasonic sources (fragmentations or hypersonic flow) along the entry trajectory. We developed a method, based on 2D ray-tracing and on the independent optically determined time of the event, to locate the source position of the multiple arrivals from a single infrasonic array data and to reconstruct the 3D trajectory of a meteoroid in the Earth's atmosphere. The trajectories derived from infrasound array analysis are in excellent agreement with trajectories reconstructed from eyewitnesses reports for the four fireballs. Results suggest that the trajectory reconstruction is possible for meteoroid entries located up to ∼300 km from the array, with an accuracy that depends on the source-to-receiver distance and on the signal-to-noise level. We also estimate the energy of the four fireballs using three different empirical laws, based both on period and amplitude of recorded infrasonic signals, and discuss their applicability for the energy estimation of small energy fireball events ($\le 1{\rm{kt\,\,TNT\,\,equivalent}}$).

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