Crustal and lithospheric structure of the Western Alps: geodynamic significance

Marchant, Robin; Stampfli, Gérard M.

doi:10.1007/978-3-0348-9098-4_24

Cited by 13 publications

(20 citation statements)

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“…Slab break-off or partial slab break-off of the Tethyan lithosphere has been proposed as the driving force for thermal and extensional tectonic events in the Alps during Oligocene times (Von Blanckenburg and Davies 1995;Marchant and Stampfli 1997;Stampfli et al 1998). Tomography reveals a complex slab configuration below the Alps (Lippitsch et al 2003;Spakman and Wortel 2004).…”

Section: Slab Dynamicsmentioning

confidence: 99%

Extensional neotectonics around the bend of the Western/Central Alps: an overview

Sue

Delacou

Champagnac

et al. 2007

Int J Earth Sci (Geol Rundsch)

126

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The Western Alps' active tectonics is characterized by ongoing widespread extension in the highest parts of the belt and transpressive/compressive tectonics along its borders. We examine these contrasting tectonic regimes using a multidisciplinary approach including seismotectonics, numerical modeling, GPS, morphotectonics, fieldwork, and brittle deformation analysis. Extension appears to be the dominant process in the present-day tectonic activity in the Western Alps, affecting its internal areas all along the arc. Shortening, in contrast, is limited to small areas located along at the outer borders of the chain. Strike-slip is observed throughout the Alpine realm and in the foreland. The stress-orientation pattern is radial for r3 in the inner, extensional zones, and for r1 in the outer, transcurrent/tranpressional ones. Extensional areas can be correlated with the parts of the belt with the thickest crust. Quantification of seismic strain in tectonically homogeneous areas shows that only 10-20% of the geodesy-documented deformation can be explained by the Alpine seismicity. We propose that, Alpine active tectonics are ruled by isostasy/buoyancy forces rather than the ongoing shortening along the Alpine Europe/Adria collision zone. This interpretation is corroborated by numerical modeling. The Neogene extensional structures in the Alps formed under increasingly brittle conditions. A synthesis of paleostress tensors for the internal parts of the West-Alpine Arc documents major orogen-parallel extension with a continuous change in r3 directions from ENE-WSW in the Simplon area, to N-S in the Vanoise area and to NNW-SSE in the Briançon area. Minor orogen-perpendicular extension increases from N to S. This second signal correlates with the present-day geodynamics as revealed by focal-plane mechanisms analysis. The orogen-parallel extension could be related to the opening of the Ligurian Sea during the Early-Middle Miocene and to compression/ rotation of the Adriatic indenter inducing lateral extrusion.

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Section: Slab Dynamicsmentioning

confidence: 99%

Extensional neotectonics around the bend of the Western/Central Alps: an overview

Sue

Delacou

Champagnac

et al. 2007

Int J Earth Sci (Geol Rundsch)

126

150

View full text Add to dashboard Cite

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“…The reader can find more detailed descriptions and discussions of the various formations encountered in the Préalpes Médianes in: Stretching factor from Marchant and Stampfli (1997b), assuming original crustal thickness of 30 km. Baud (1972Baud ( , 1987 for the Triassic; Thury (1973), Mettraux (1989), Mettraux and Mosar (1989), and Borel (1998) for the Lower Jurassic (Lias); Furrer and Septfontaine (1977), Furrer (1979), and Septfontaine (1983) for the Middle Jurassic (Dogger); Weiss (1949), Isenschmid (1983), Heinz (1985), and Heinz and Isenschmid (1988) for the Upper Jurassic ('Malm'); Boller (1963) for the Lower Cretaceous (Neocomian); Caron and Dupasquier (1989), and Python-Dupasquier (1990) for the middle Cretaceous; Guillaume (1986) for the upper CretaceousTertiary.…”

Section: Sedimentology and Palaeotectonicsmentioning

confidence: 99%

“…16. Cross-section of the western Alps on a western Switzerland transect, and simplified palinspastic model, modified from Marchant (1993), Marchant and Stampfli (1997b). or its interpretation as evidence of a Cretaceous collision between Adria and the Briançonnais (e.g. Deville, 1993).…”

Section: Incorporation Of the Briançonnais Terrane In The Accretionarmentioning

confidence: 99%

“…These data sets have been analysed from a structural, petrological and sedimentological point of view. Structural models were constrained at depth by deep seismic data and lithospheric cross-sections (Stampfli, 1993;Marchant, 1993;Marchant and Stampfli, 1997b). Together with palaeontological and absolute age determinations, these data allowed the construction of subsidence curves and the elaboration of flexural models.…”

Section: Introductionmentioning

confidence: 99%

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Subduction and obduction processes in the Swiss Alps

et al. 1998

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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.

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“…The present structural framework of the western Alps is shown in figures 1 and 2 (modified from Marchant, 1993;Marchant and Stampfli, 1997a;Marchant and Stampfli, 1997b), and are based on a structural model developed mainly by the Lausanne school (e.g Escher et al, 1997;Escher et al, 1988;Steck et al, 1997;Steck et al, 1989). …”

Section: The Structural Framework Of the Western Alpsmentioning

confidence: 99%