Subduction and obduction processes in the Swiss Alps

Subduction and obduction processes in the Swiss Alps The significance of the Briançonnais domain in the Alpine orogen is reviewed in the light of data concerning its collision with the active Adriatic margin and the passive Helvetic margin. The Briançonnais which formerly belonged to the Iberian plate, was located on the northern margin of the Alpine Tethys (Liguro-Piémont ocean) since its opening in the early-Middle Jurassic. Together with the Iberian plate the Briançonnais terrane was separated from the European plate in the Late Jurassic–Early Cretaceous, following the northern Atlantic, Bay of Biscay, Valais ocean opening. This was accompanied by the onset of subduction along the northern margin of Adria and the closure of the Alpine Tethys. Stratigraphic and metamorphic data regarding this subduction and the geohistory of the Briançonnais allows the scenario of subduction–obduction processes during the Late Cretaceous–early Tertiary in the eastern and western Alps to be specified. HP–LT metamorphism record a long-lasting history of oceanic subduction-accretion, followed in the Middle Eocene by the incorporation of the Briançonnais as an exotic terrane into the accretionary prism. Middle to Late Eocene cooling ages of the Briançonnais basement and the presence of pelagic, anorogenic sedimentation lasting until the Middle Eocene on the Briançonnais preclude any sort of collision before that time between this domain and the active Adria margin or the Helvetic margin. This is confirmed by plate reconstructions constrained by magnetic anomalies in the Atlantic domain. Only a small percentage of the former Briançonnais domain was obducted, most of the crust and lithospheric roots were subducted. This applies also to domains formerly belonging to the southern Alpine Tethys margin (Austroalpine–inner Carpathian domain). It is proposed that there was a single Palaeogene subduction zone responsible for the Alpine orogen formation (from northern Spain to the East Carpathians), with the exception of a short-lived Late Cretaceous partial closure of the Valais ocean. Subduction in the western Tethyan domain originated during the closure of the Meliata ocean during the Jurassic incorporating the Austroalpine–Carpathian domain as terranes during the Cretaceous. The subduction zone propagated into the northern margin of Adria and then to the northern margin of the Iberian plate, where it gave birth to the Pyrenean–Provençal orogenic belt. This implies the absence of a separated Cretaceous subduction zone within the Austro-Carpathian Penninic ocean. Collision of Iberia with Europe forced the subduction to jump to the SE margin of Iberia in the Eocene, creating the Apenninic orogenic wedge and inverting the vergence of subduction from south- to north-directed. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Tectonophysics Elsevier

Subduction and obduction processes in the Swiss Alps

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Publisher
Elsevier
Copyright
Copyright © 1998 Elsevier Science B.V.
ISSN
0040-1951
eISSN
1879-3266
DOI
10.1016/S0040-1951(98)00142-5
Publisher site
See Article on Publisher Site

Abstract

The significance of the Briançonnais domain in the Alpine orogen is reviewed in the light of data concerning its collision with the active Adriatic margin and the passive Helvetic margin. The Briançonnais which formerly belonged to the Iberian plate, was located on the northern margin of the Alpine Tethys (Liguro-Piémont ocean) since its opening in the early-Middle Jurassic. Together with the Iberian plate the Briançonnais terrane was separated from the European plate in the Late Jurassic–Early Cretaceous, following the northern Atlantic, Bay of Biscay, Valais ocean opening. This was accompanied by the onset of subduction along the northern margin of Adria and the closure of the Alpine Tethys. Stratigraphic and metamorphic data regarding this subduction and the geohistory of the Briançonnais allows the scenario of subduction–obduction processes during the Late Cretaceous–early Tertiary in the eastern and western Alps to be specified. HP–LT metamorphism record a long-lasting history of oceanic subduction-accretion, followed in the Middle Eocene by the incorporation of the Briançonnais as an exotic terrane into the accretionary prism. Middle to Late Eocene cooling ages of the Briançonnais basement and the presence of pelagic, anorogenic sedimentation lasting until the Middle Eocene on the Briançonnais preclude any sort of collision before that time between this domain and the active Adria margin or the Helvetic margin. This is confirmed by plate reconstructions constrained by magnetic anomalies in the Atlantic domain. Only a small percentage of the former Briançonnais domain was obducted, most of the crust and lithospheric roots were subducted. This applies also to domains formerly belonging to the southern Alpine Tethys margin (Austroalpine–inner Carpathian domain). It is proposed that there was a single Palaeogene subduction zone responsible for the Alpine orogen formation (from northern Spain to the East Carpathians), with the exception of a short-lived Late Cretaceous partial closure of the Valais ocean. Subduction in the western Tethyan domain originated during the closure of the Meliata ocean during the Jurassic incorporating the Austroalpine–Carpathian domain as terranes during the Cretaceous. The subduction zone propagated into the northern margin of Adria and then to the northern margin of the Iberian plate, where it gave birth to the Pyrenean–Provençal orogenic belt. This implies the absence of a separated Cretaceous subduction zone within the Austro-Carpathian Penninic ocean. Collision of Iberia with Europe forced the subduction to jump to the SE margin of Iberia in the Eocene, creating the Apenninic orogenic wedge and inverting the vergence of subduction from south- to north-directed.

Journal

TectonophysicsElsevier

Published: Oct 30, 1998

References

  • The inception and early evolution of the North Alpine Foreland Basin, Switzerland
    Allen, P.A; Crampton, S.L; Sinclair, H.D
  • Alpine and Pre-Alpine subduction events in polycyclic basements of the Swiss Alps
    Biino, G; Marquer, D; Nussbaum, Ch
  • Sm–Nd isotopic evidence on the age of eclogitization in the Zermatt-Saas ophiolite
    Bowtell, S.A; Cliff, R.A; Barnicoat, A.C
  • The Lepontine Alps as an evolving metamorphic core complex during A-Type subduction. Evidence from heat flow, mineral cooling ages, and tectonic modeling
    Bradbury, H.J; Nolen-Hoeksema, R.C
  • Early Triassic paleomagnetic data from the Dolomites (Italy)
    Channell, J.E.T; Doglioni, C
  • Jurassic and Cretaceous paleomagnetic data from the Southern Alps (Italy)
    Channell, J.E.T; Doglioni, C; Stoner, J.S
  • Slab breakoff: a model of lithosphere detachment and its test in the magmatism and deformation of collisional orogens
    Davies, J.H; von Blanckenburg, F
  • Late Cretaceous, synorogenic low-angle normal faulting along the Schlinig fault (Switzerland, Italy, Austria) and its significance for the tectonics of the eastern Alps
    Froitzheim, N; Conti, P; van Daalen, M
  • Importance of inherited rift margin structures in the early north Alpine foreland basin, Switzerland
    Lihou, J.C; Allen, P.A
  • Subduction of continental crust in the Western Alps
    Marchant, R.H; Stampfli, G.M
  • Early to mid Tertiary crustal extension in the Central Alps. the Turba mylonite zone (Eastern Switzerland)
    Nievergelt, P; Liniger, M; Froitzheim, N; Mählmann, R.F
  • Exhumation of high-pressure rocks. A review of concepts and processes
    Platt, J.P
  • Dynamics of intra-plate compressional deformation. The Alpine foreland and other examples
    Ziegler, P.A; Cloetingh, S; van Wees, J.-D

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