Two-phase orogenic convergence in the external and internal SW Alps

Ford, Mary; Duchêne, Stéphanie; Gasquet, Dominique; Vanderhaeghe, Olivier

doi:10.1144/0016-76492005-034

Cited by 139 publications

(150 citation statements)

References 76 publications

(118 reference statements)

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“…All these features are consistent with the orientation of Africa-Europe convergence during Paleogene after Rosenbaum et al (2002). Considering the palinspastic reconstruction of Schmid & Kissling (2000), the propagation rate of the foreland basin after Ford et al (2006), and the subduction rate of the distal parts of the European margin , the rate of propagation of the orogen would have been of the same order of magnitude than the Africa-Europe convergence rate (~1 cm/yr). However this estimation is poorly constrained and it assumes that Adria was not moving independantly from Africa during Eocene times, which is still debated because of the possible occurrence of spreading of the Ionian sea between Africa and Adria before 35 Ma (Michard et al, 2002;Handy et al, 2010).…”

Section: Crustal Record Of Continental Subduction During the Eocenesupporting

confidence: 76%

“…A complete renewal of the tectonic setting ocurred close to the Eocene-Oligocene boundary, initiating a mature stage of collision with westward escape of the Internal Nappes stack. According to many authors (Ziegler, 1989;Stampfli et al, 2002;Collombet et al, 2002;Rosenbaum & Lister, 2005;Ford et al, 2006;Molli, 2008), the formation of the western Alpine arc occurred mainly after Eocene times, that is during this mature stage of collision with lateral extrusion. The deep part of the paleo-accretionnary wedge, having migrated northwards during the previous, continental subduction stage, was then cross-cut and thrust westwards over the emerged proximal part of the flexural basin, allowing a metamorphic rocks provenance for the synorogenic sediments during the Early Oligocene, a scenario which is summarized in fig.…”

Section: Discussionmentioning

confidence: 99%

“…Sediment supply from the south and northward or NW-ward sedimentary transport directions of the distal deltaic fans (Ravenne et al, 1987;Callec, 2001) are in agreement with this N to NW direction of propagation of the lithospheric flexure. However, as pointed by Ford et al (2006), the geometry of the Eocene flexural basin has been heavily distorted by the younger development of the Alpine arc. The starved infill of the Paleogene flexural basin bears evidence of synsedimentary deformation preceeding the emplacement of the first gravity-driven nappes and of the accretionnary wedge having caused the N to NW-directed deformation D2.…”

Section: Foreland Basin Propagation and Orogen Migration During The Ementioning

confidence: 99%

“…6, left). This Eocene propagation and coastal migration occurred towards the N-to NW in the southern Subalpine domain (Kerckhove, 1969;Guardia & Ivaldi, 1987) and in the Helvetic realm (Kempf & Pfiffner, 2004;Ford et al, 2006), apart from a SW-ward lateral propagation and confinement at the western termination of the basin (Maritime-Alps to Haute-Provence; Sztrakos & Du Fornel, 2003;Puigdefabregas et al, 2004;Campredon & Giannerini, 1982). Sediment supply from the south and northward or NW-ward sedimentary transport directions of the distal deltaic fans (Ravenne et al, 1987;Callec, 2001) are in agreement with this N to NW direction of propagation of the lithospheric flexure.…”

Section: Foreland Basin Propagation and Orogen Migration During The Ementioning

confidence: 99%

“…The distribution of the foreland basins in the southern Subalpine domain (External Zone of the Western Alps) changed completely during Early Oligocene times (Ford et al, 2006): The formation of the Digne nappe ( fig. 2; fig.…”

Section: Renewed Distribution Of Foreland Basins During Early Oligocenementioning

confidence: 99%

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Structural and sedimentary records of the Oligocene revolution in the Western Alpine arc

Dumont

Schwartz

Guillot

et al. 2012

Journal of Geodynamics

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Section: Crustal Record Of Continental Subduction During the Eocenesupporting

confidence: 76%

Section: Discussionmentioning

confidence: 99%

Section: Foreland Basin Propagation and Orogen Migration During The Ementioning

confidence: 99%

Section: Foreland Basin Propagation and Orogen Migration During The Ementioning

confidence: 99%

Section: Renewed Distribution Of Foreland Basins During Early Oligocenementioning

confidence: 99%

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Structural and sedimentary records of the Oligocene revolution in the Western Alpine arc

Dumont

Schwartz

Guillot

et al. 2012

Journal of Geodynamics

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Basement shear zones development and shortening kinematics in the Ecrins Massif, Western Alps

et al. 2014

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In the Western Alps, Oligocene shortening affected a highly heterogeneous European crust with Liassic half-grabens inherited from the rifting stage and the finite deformation was strongly partitioned between the rigid basement and the weak Jurassic sediments. In the Ecrins Massif (Oisans, external crystalline massifs), where the half-grabens are best exposed and preserved, compressional structures within the basement have to date never been described in details. This massif was shortened under moderate metamorphic conditions (250-350°C and 0.1-0.5 GPa), and the rheological contrast between the basement and the cover is strong. While the sediments are intensely folded, the cover-basement interface presents apparent open folds underlined by the Lower Triassic layers. The basement itself shows a more localized deformation along several brittle-ductile shear zones. We here report new evidences of such brittle-ductile shear zones characterized by anastomosed phyllonitic shear bands rich in phengite and quartz, a low-strength material where strain has localized. New detailed maps of reverse shear zones, faults, schistosity, and stretching lineations in both the cover and the basement are provided. We show that the Oligocene crustal shortening was mainly E-W to ENE-WSW. Local N-S to NW-SE shortening occurred and was limited to the eastern border of the Ecrins Massif, around the Penninic Frontal Thrust, which likely was a sinistral transpressive structure in this area. Finally, new balanced cross sections show that these basement shear zones have accommodated more than 50% of the Oligocene crustal shortening.

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A purely structural restoration of the NFP20‐East cross section and potential tectonic overpressure in the Adula nappe (central Alps)

Pleuger

Podladchikov

2014

Tectonics

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Common extrusion-type models for the high-to ultrahigh-pressure Adula nappe require a major normal fault along the top of this unit which is not conveyed in the structural record. This implies that such a normal fault existed but was completely erased during later deformational stages. However, there is evidence that decompression occurred during top-to-the-foreland thrusting. We performed a new, purely structural kinematic restoration of the central part of the NFP20-East cross section in order to estimate the burial depths of individual units without converting petrological pressure data into depth under the assumption that pressures were lithostatic. The results show that pressures within most of the units were close to but somewhat higher than lithostatic for several stages of the tectono-metamorphic history. Only for the maximum burial stage of the Adula nappe, we estimate local tectonic overpressures of 40 to 80% of the lithostatic pressures. Accepting such an amount of overpressure, which is moderate compared to values theoretically possible, the Adula nappe was probably not subducted to subcrustal depth. We propose that the structural record of the Penninic nappe stack is quite complete and suggest that the decay of tectonic overpressure is a feasible explanation for decompression from eclogite-to amphibolite-facies conditions during thrusting. Consequently, exhumation and convergence rates of the Eocene to Oligocene Alps may be smaller than previously assumed.

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Two-phase orogenic convergence in the external and internal SW Alps

Cited by 139 publications

References 76 publications

Structural and sedimentary records of the Oligocene revolution in the Western Alpine arc

Structural and sedimentary records of the Oligocene revolution in the Western Alpine arc

Basement shear zones development and shortening kinematics in the Ecrins Massif, Western Alps

A purely structural restoration of the NFP20‐East cross section and potential tectonic overpressure in the Adula nappe (central Alps)

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