Miocene lateral extrusion in the inner western Alps revealed by dynamic fault analysis

Champagnac, Jean‐Daniel; Sue, Christian; Delacou, Bastien; Tricart, Pierre; Allanic, Cécile; Burkhard, Martin

doi:10.1029/2004tc001779

Cited by 40 publications

(57 citation statements)

References 65 publications

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“…Note also that the pattern of rock uplift rate is spatially disconnected to the location of the rotation pole, and rock uplift also occurs in the Western Alps (Stocchi et al, 2005), where largescale extension was clearly documented (Sue et al, 2000;Calais et al, 2002;Delacou et al, 2004;Champagnac et al, 2006). Therefore, the large discrepancy between the rate of shortening derived from the reversed model and the rate invoked from kinematic data either imply that the GPS data do not reflect ongoing (and hypothetical) long-term shortening, or that horizontal plate kinematics cannot be the main agent of rock uplift in the Central and Western Alps.…”

Section: Modern Crustal Convergencementioning

confidence: 99%

Erosion-driven uplift of the modern Central Alps

et al. 2009

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We present a compilation of data of modern tectono-geomorphic processes in the Central European Alps which suggest that observed rock uplift is a response to climate-driven denudation. This interpretation is predominantly based on the recent quantification of basinaveraged Late Holocene denudation rates that are so similar to the pattern and rates of rock uplift rates as determined by geodetic leveling. Furthermore, a GPS data-based synthesis of Adriatic microplate kinematics suggests that the Central Alps are currently not in a state of active convergence. Finally, we illustrate that the Central Alps have acted as a closed system for Holocene redistribution of sediment in which the peri-Alpine lakes have operated as a sink for the erosional products of the inner Central Alps.While various hypotheses have been put forward to explain Central Alpine rock uplift (e.g. lithospheric forcing by convergence, mantle processes, or ice melting) we show with an elastic model of lithospheric deformation, that the correlation between erosion and rock uplift rates reflects a positive feedback between denudation and the associated isostatic response to unloading. Thus, erosion does not passively respond to advection of crustal material as might be the case in actively converging orogens. Rather, we suggest that the geomorphic response of the Alpine topography to glacial and fluvial erosion and the resulting disequilibrium for modern channelized and associated hillslope processes explains much of the pattern of modern denudation and hence rock uplift. Therefore, in a non-convergent orogen such as the Central European Alps, the observed vertical rock uplift is primarily a consequence of passive unloading due to erosion.

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Section: Modern Crustal Convergencementioning

confidence: 99%

Erosion-driven uplift of the modern Central Alps

et al. 2009

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“…Very few and isolated field studies in the Western Alps have allowed to identify active faults (orange symbols on Fig. 5 a compiled after Lacassin et al 2001, andChampagnac et al 2006). Displaced Quaternary deposits provide circumstantial evidence for post-Würm offsets which have been correlated with regional seismicity in order to evaluate the coherency of the neotectonic indications.…”

Section: Neotectonic Synthesismentioning

confidence: 99%

“…A detailed analysis of this area reveals a first NNE-SSW extension, then a strike-slip regime with r3 oriented E-W. Such strike-slip movements are often observed together with typical normal fault geometries Fig. 14 Synthetic paleostress map covering the western internal Alpine belt (from Champagnac et al 2006). More than 300 paleostress tensors are represented, corresponding to about 6,000 fault measurements.…”

Section: Orogen-parallel Versus Orogen-perpendicular Extensionmentioning

confidence: 99%

“…We refer to Champagnac et al (2006) for the parameters of these paleostress tensors. Faulting systematically overprints ductile compressional structures (folds, nappe piles, schistosities).…”

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%

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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

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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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Miocene lateral extrusion in the inner western Alps revealed by dynamic fault analysis

Cited by 40 publications

References 65 publications

Erosion-driven uplift of the modern Central Alps

Erosion-driven uplift of the modern Central 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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