The Tertiary structural and thermal evolution of the Central Alps—compressional and extensional structures in an orogenic belt

Steck, A.; Hunziker, Johannes C.

doi:10.1016/0040-1951(94)90058-2

Cited by 184 publications

(213 citation statements)

References 22 publications

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“…Further studies have confirmed this thermochronological jump in cooling ages for a range of minerals and isotopic systems (see synthesis in Steck and Hunziker [1994]). There is a consistent jump between older ages in the hanging wall (from circa 35 Ma with muscovite Rb/Sr to circa 5 Ma with apatite fission track) to younger ages in the footwall (from circa 20 Ma with muscovite Rb/Sr to circa 3 Ma with apatite fission track).…”

Section: Previous Thermochronological and Geochronological Workmentioning

confidence: 60%

“…[9] According to Steck and Hunziker [1994], the development of the Glishorn and Berisal back folds in the northern part of the footwall (Figure 1b) was associated with the young exhumation of the Aar Massif in the late Miocene, as established from fission track cooling ages [e.g., Michalski and Soom, 1990]. In turn, the brittle detachment (SL) was also considered to be late Miocene because it crosscuts these back folds (Figure 1b).…”

Section: Previous Thermochronological and Geochronological Workmentioning

confidence: 99%

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Geochronological evidence for continuous exhumation through the ductile‐brittle transition along a crustal‐scale low‐angle normal fault: Simplon Fault Zone, central Alps

et al. 2010

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[1] Major low-angle normal faults juxtapose different structural levels of the crust that record both brittle and ductile deformation. Field relationships alone cannot establish whether these different responses to deformation represent (1) parts of a single process of exhumation along the detachment or (2) two separate events, with the later, more discrete brittle detachment exhuming a fossil ductile shear zone from depth. These two general models are critically assessed for the lowangle normal Simplon Fault Zone (SFZ) in the central Alps. The SFZ shows a spatial transition from a broad ductile mylonitic shear zone to a discrete brittle detachment with identical kinematics. The age of the ductile shear zone and ductile-brittle transition is controversial. We present a detailed geochronological study based on fission track, 40 Ar/ 39 Ar, and Rb/Sr microsampling dating, coupled with structural, petrological, and chemical analyses that provides tight constraints on SFZ timing. Discontinuous mineral cooling ages over a broad range of temperatures across the fault zone argue for fault activity between 20 and 3 Ma. On the basis of synkinematic white mica in low-temperature shear zones and necks of foliation boudinage, the brittle-ductile transition in the footwall could be dated at ∼14.5-10 Ma. Overall, the data presented here are consistent with a continuous transition from ductile shearing to a more localized zone of brittle deformation within the same geological framework, over a period of ∼15 Ma. The SFZ is therefore an example of a telescoped crustal section within a single major lowangle fault, involving a continuous period of exhumation rather than a two-stage structure.

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Section: Previous Thermochronological and Geochronological Workmentioning

confidence: 60%

Section: Previous Thermochronological and Geochronological Workmentioning

confidence: 99%

Geochronological evidence for continuous exhumation through the ductile‐brittle transition along a crustal‐scale low‐angle normal fault: Simplon Fault Zone, central Alps

et al. 2010

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“…These 2D cases do not apply to the Western Alps, where extension is taking place at a high angle to shortening, subparallel to the belt. Given the strongly curved shape of the Western Alps, extension could be seen as a 3D effect of ''outer-arcstretching'' (Burg et al 2002), ''vertical indentation'', or a ''transtension in an overall compressional orogen'' (Hubbard and Mancktelow 1992;Steck and Hunziker 1994); however, the lateral consistency of arc-parallel extension observed within the entire belt remains difficult to explain in all these models.…”

Section: Orogen-parallel Extensionmentioning

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)

128

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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“…Boundaries between different lithological units (i.e., lines of outcrop), knowledge about possible correlations of these units (mainly from petrological examination) and recognition of geometric and kinematic constraints (from structural observations) are the principal inputs from field-based geological investigations. This information can be combined to develop a model of the geometry of the geology in three dimensions, often illustrated in a series of cross-sections or as a block diagram (e.g., see the description and instructive examples in Meyer, 1991;Hunziker, 1994 andSteck, 1998). Agreement with outcrop lines and internal consistency provide important visual cross-checks, but these are more readily and thoroughly controlled in truly threedimensional models.…”

Section: Introductionmentioning

confidence: 99%

A workflow to facilitate three-dimensional geometrical modelling of complex poly-deformed geological units

Maxelon

Renard

Courrioux

et al. 2009

Computers & Geosciences

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a b s t r a c tThe three-dimensional (3D) geometry of complexly deformed regions is often beyond the scope of simple 2D and 2.5D representation in cross-sections and block diagrams. Methods must be developed for fully three-dimensional representation. A workflow for such three-dimensional modelling of structurally complex areas is presented. Data requirements are tailored to typical results of structural field work in strongly deformed rocks from mid-crustal levels. The workflow is based on data evaluation and data export using standard geographical information system and database management systems. Three-dimensional modelling in polyphase deformed areas is highly dependent on the correct interpretation of variations in the orientation of the dominant planar fabrics. The computer-aided earth-modelling software 3D GeoModeller is well adapted for managing this problem. It calculates the geometry of geological interfaces taking into account simultaneously the foliation data and location of lithological contacts. The workflow is based on iterative model refinement based on interactive editing of the geometry in section and map views with data assessment and pre-processing using GIS software. This approach assures internal consistency of the resulting three-dimensional models. Modelling of the Lower Lepontine Nappes in the Central Alps is used as an illustrative example from a complexly deformed terrain.

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The Tertiary structural and thermal evolution of the Central Alps—compressional and extensional structures in an orogenic belt

Cited by 184 publications

References 22 publications

Geochronological evidence for continuous exhumation through the ductile‐brittle transition along a crustal‐scale low‐angle normal fault: Simplon Fault Zone, central Alps

Geochronological evidence for continuous exhumation through the ductile‐brittle transition along a crustal‐scale low‐angle normal fault: Simplon Fault Zone, central Alps

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

A workflow to facilitate three-dimensional geometrical modelling of complex poly-deformed geological units

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