Brittle deformation in the inner NW Alps: from early orogen‐parallel extrusion to late orogen‐perpendicular collapse

Champagnac, Jean‐Daniel; Sue, Christian; Delacou, Bastien; Burkhard, Martin

doi:10.1111/j.1365-3121.2004.00555.x

Cited by 42 publications

(41 citation statements)

References 51 publications

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“…1) faults. Champagnac et al (2004Champagnac et al ( , 2006, on the basis of the paleostress analysis of several meso-structural data, showed a more complex post-collisional tectonic evolution for this sector characterised by the occurrence of a further extension direction, roughly perpendicular to the trend of the belt, that follows the orogen-parallel extension.…”

Section: Figmentioning

confidence: 95%

“…By contrast, in the Jura Mountains, a NW-vergent fold and thrust belt developed since the Miocene (Mugnier and Vialon 1986). In the inner part of the chain, bordered by the Penninic Frontal Thrust and the Canavese Line, a number of papers (Cannic et al 1999;Bistacchi et al 2000;Rolland et al 2000;Collombet et al 2002;Calais et al 2002;Agard et al 2003;Delacou et al 2004Delacou et al , 2008Champagnac et al 2004Champagnac et al , 2006Selverstone, 2005;Tricart et al 2001Tricart et al , 2004Tricart et al , 2007Sue et al 2007a;Schwartz et al 2008) based on structural, fission track, paleomagnetic, seismological and geodetic data showed an extensionaltranstensive regime at least since the Miocene. In the central part of the Western Alps, two regional brittle fault systems, the Longitudinal and Transversal Fault systems (LF and TF in Fig.…”

Section: Figmentioning

confidence: 99%

“…Different models have been proposed to explain this complex structural setting, such as westward extrusion (Coward and Dietrich 1989), dextral transcurrence at the scale of the chain induced by the counterclockwise rotation of the Adria plate since Oligocene (Vanossi et al 1994;Castellarin 2001;Collombet et al 2002;Agard et al 2003;Sue and Tricart 2003;Malusà et al 2005Malusà et al , 2009, and polyphasic models that associate south-westward extrusion (Sue et al 2007a;Champagnac et al 2004Champagnac et al , 2006 or dextral transcurrence Perello et al 2004b) with buoyancy forces.…”

Section: Figmentioning

confidence: 99%

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Post-collisional tectonics in the Northern Cottian Alps (Italian Western Alps)

Perrone

Cadoppi

Tallone

et al. 2010

Int J Earth Sci (Geol Rundsch)

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Field mapping and structural analysis have allowed us to characterise the fault geometry and the postmetamorphic tectonics of an area located in the Northern Cottian Alps (inner Western Alps). Two main faulting stages were distinguished here. The first (Oligocene?-Early Miocene) is related to the development of an E-W-striking left-normal shear zone. This shear zone is interpreted as an antithetical of two regional, N-S right-lateral structures: the Col del Lis-Trana Deformation Zone (LTZ) and the Colle delle Finestre Deformation Zone (CFZ). The second faulting stage (post-Early Miocene) is related mainly to the development of N-S normal faults, coeval with the extensional reactivation of the LTZ and the CFZ. We discuss this kinematic evolution in the framework of the geodynamic evolution of the Western Alps.

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Section: Figmentioning

confidence: 95%

Section: Figmentioning

confidence: 99%

Section: Figmentioning

confidence: 99%

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Post-collisional tectonics in the Northern Cottian Alps (Italian Western Alps)

Perrone

Cadoppi

Tallone

et al. 2010

Int J Earth Sci (Geol Rundsch)

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“…Figure 13 presents examples of such normal faults, and related meso-scale and large-scale structures. Numerous other examples of such extensional and transcurrent late Alpine structures have been published in the Western and Central Alps (e.g., Tricart 2002, 2003;Champagnac et al 2003Champagnac et al , 2004Grosjean et al 2004). At first sight, the overall pattern of the r3 axes (Fig.…”

Section: Orogen-parallel Versus Orogen-perpendicular Extensionmentioning

confidence: 99%

“…The Neogene to present evolution of the Western Alpine Arc is characterized by the change from collision to postcollisional extension (e.g., Tricart 2002, 2003;Champagnac et al 2004Champagnac et al , 2006Selverstone 2005). In the Piedmont zone, ductile extension was replaced rapidly by brittle deformation, but in the Briançonnais zone it could have initiated directly in the brittle field.…”

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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)

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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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Subglacial extensional fracture development and implications for Alpine Valley evolution

Leith

Moore

Amann³

et al. 2014

JGR Earth Surface

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[1] Bedrock stresses induced through exhumation and tectonic processes play a key role in the topographic evolution of alpine valleys. Using a finite difference model combining the effects of tectonics, erosion, and long-term bedrock strength, we assess the development of near-surface in situ stresses and predict bedrock behavior in response to glacial erosion in an Alpine Valley (the Matter Valley, southern Switzerland). Initial stresses are derived from the regional tectonic history, which is characterized by ongoing transtensional or extensional strain throughout exhumation of the brittle crust. We find that bedrock stresses beneath glacial ice in an initial V-shaped topography are sufficient to induce localized extensional fracturing in a zone extending laterally 600 m from the valley axis. The limit of this zone is reflected in the landscape today by a valley "shoulder," separating linear upper mountain slopes from the deep U-shaped inner valley. We propose that this extensional fracture development enhanced glacial quarrying between the valley shoulder and axis and identify a positive feedback where enhanced quarrying promoted valley incision, which in turn increased in situ stress concentrations near the valley floor, assisting erosion and further driving rapid U-shaped valley development. During interglacial periods, these stresses were relieved through brittle strain or topographic modification, and without significant erosion to reach more highly stressed bedrock, subsequent glaciation caused a reduction in differential stress and suppressed extensional fracturing. A combination of stress relief during interglacial periods, and increased ice accumulation rates in highly incised valleys, will reduce the likelihood of repeat enhanced erosion events.

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Brittle deformation in the inner NW Alps: from early orogen‐parallel extrusion to late orogen‐perpendicular collapse

Cited by 42 publications

References 51 publications

Post-collisional tectonics in the Northern Cottian Alps (Italian Western Alps)

Post-collisional tectonics in the Northern Cottian Alps (Italian Western Alps)

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

Subglacial extensional fracture development and implications for Alpine Valley evolution

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