Crustal reflections beneath the Alps and the Alpine foreland: Geodynamic implications

Mugnier, Jean‐Louis; Marthelot, J. M.

doi:10.1029/gd022p0177

Cited by 7 publications

(6 citation statements)

References 15 publications

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“…More specifically, sub-surface data and surface data (field observations and geological maps at 1:50 000) were used to build cross-section A west of FZ1, while east of FZ1, the construction of the cross-section relies on the analysis of 1:50 000 scale geological maps and the ECORS-CROP profile (Le Roure et al, 1990;Mugnier and Marthelot, 1991) recently revised by Pfiffner (2014). The Cenozoic filling consists of Oligocene and Eocene deposits and is involved in https://doi.org/10.5194/se-2021-46 Preprint.…”

Section: The St Lattier Thrust or Fault Zone 5 (Fz5)mentioning

confidence: 99%

Chronology of thrust propagation from an updated tectono-sedimentary framework of the Miocene molasse (western Alps)

Kalifi

Leloup

Sorrel

et al. 2021

Preprint

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Abstract. After more than a century of research, the chronology of the deformation of the external part of the Alpine belt is still controversial for the Miocene epoch. In particular, the poor dating of the foreland basin sedimentary succession hampers a comprehensive understanding of the kinematics of the deformation. Here we focus on the Miocene Molasse deposits of the northern subalpine massifs, southern Jura, Royans, Bas-Dauphiné, Crest and La Bresse sedimentary basins through a multidisciplinary approach to build a basin-wide tectono-stratigraphic framework. Based on sequence stratigraphy constrained by biostratigraphical, chemostratigraphical (Sr-isotopes) and magnetostratigraphical data between the late Aquitanian (~21 Ma) and the Tortonian (~8.2 Ma), the Miocene Molasse chronostratigraphy is revised with a precision of ~0.5 Ma. The Miocene Molasse sediments encompass four different palaeogeographical domains: (i) the oriental domain, outlined by depositional sequences S1a to S3 (~21 to ~15 Ma), (ii) the median domain characterized by sequences S2 to S5 (~17.8 to ~12 Ma), (iii) the occidental domain, in which sequences S2a to S8 (~17.8 to ~8.2 Ma) were deposited and, (iv) the Bressan domain, where sedimentation is restricted to sequences S6 to S8 (~12 to ~8.2 Ma). A structural and tectono-sedimentary study is conducted based on new field observations and the reappraisal of regional seismic profiles, thereby allowing the identification of five major faults zones (FZ). The oriental, median and occidental paleogeographical domains are clearly separated by FZ1, FZ2 and FZ3, suggesting strong interactions between tectonics and sedimentation during the Miocene. The evolution in time and space of the paleogeographical domains within a well-constrained structural framework reveals syntectonic deposits and a westward migration of the depocenters, and allows to establish the following chronology of thrust propagation at the western alpine front: (i) A compressive phase (P1) corresponding to thrusting above the Chartreuse Orientale Thrust (FZ1), which was likely initiated during the Oligocene. This tectonic phase generated reliefs that limited the Miocene transgression to the east; (ii) the ~W-WNW/E-ESE-directed compressive phase (P2) involving the Belledonne basal thrust, which activated the Salève thrust (SAL) fault and successively FZ2 to FZ5 from east to west. Phase P2 deeply shaped the Miocene palaeogeographical evolution and most probably corresponded to a prominent compressive phase at the scale of the Alps during the early to middle Miocene (between 18.05 +/- 0.25 Ma and ~12 Ma). In those ~6 Myr, the Miocene sea was forced to regress rapidly westwards in response to westward migration of the active thrusts and exhumation of piggy-back basins atop the fault zones; (iii) the last phase (P3) of Tortonian age (~10 Ma), which likely implied a significant uplift (350 m minimum) of the Bas-Dauphiné basin, whereas horizontal motions prevailed within the Jura Mountains.

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Section: The St Lattier Thrust or Fault Zone 5 (Fz5)mentioning

confidence: 99%

Chronology of thrust propagation from an updated tectono-sedimentary framework of the Miocene molasse (western Alps)

Kalifi

Leloup

Sorrel

et al. 2021

Preprint

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“…Though this geological interpretation of the deep seismic profile is fascinating, it seems to us an over-interpretation of geophysical data. We maintain the rational interpretation of this zone proposed by Cannic et al [1999], and based on a coherency-weightedmigration procedure of the seismic sections [Mugnier and Marthelot, 1991]. The mean dip of the westernmost reflection band is smaller than the dip of the easternmost one, and the domain between the two reflection zone does not necessarly extend at depth along the flatter part of the suture.…”

Section: Structural Reactivation At the Boundary Between Internal Andmentioning

confidence: 53%

“…Variscan initiation of an oceanic domain, Mesozoic extension at the margin of the Neo-Tethys, initial alpine thrusting that lead to a burying at more than 60 km before 35Ma [Bousquet et al, 2002] and probably before 45 Ma [Freeman et al, 1998;Fugenschuh and Schmid, 2003], ductile normal shearing at the foot-wall of the Briançonnais [Cannic et al, 1996;Bousquet et al, 2002] that lead to a rapid exhumation to a depth of ~40 km before 27 Ma, and presumably between 31 and 27 Ma [Bousquet et al, 2002;Fugenschuh and Schmid, 2003], break-back-reactivation of the Basal Briançonnais thrust [Mugnier et al, 1993;Freeman et al, 1998] that possibly occurred around 12 Ma [Cannic et al, 1999] and less than 3 km normal fault displacement [Cannic et al, 1999] that is occurring after 5 Ma [Fugenschuch and Schmid, 2003]. Due to this complex story, we use the term "Pennine suture" [Mugnier and Marthelot, 1991] for the boundary between the Internal Alps and the external Alps.…”

Section: Structural Reactivation At the Boundary Between Internal Andmentioning

confidence: 99%

“…Fig. 10: an interpretation of the deep seismic ECORS seismic line based on a coherency-weightedmigration procedure of the seismic sections [Mugnier and Marthelot, 1991] (Vertical scale in s. TWT). Fig.…”

Section: Remerciementsmentioning

confidence: 99%

“…Fig. 10: Une interprétation du profil sismique grande profondeur ECORS, basée sur une migration automatique avec pondération sur la cohérence du signal [Mugnier et Marthelot, 1991] (Echelle verticale en secondes-temps-double).…”

Section: Remerciementsunclassified

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The tholeiites of the Valaisan domain (Versoyen, western Alps): a Carboniferous magma emplaced in a small oceanic basin

Mugnier

Cannic

Lapierre³

2008

Bulletin De La Société Géologique De France

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International audienceThe mafic-ultramafic assemblages of the Versoyen complex exposed in the Valaisan domain is close to the boundary between the Internal and the External domains of the western Alps. Zircons extracted from the Versoyen complex suggest an emplacement during Paleozoic times, and probably during the Visean (~337 Ma). The base of the Versoyen complex is formed of laccoliths and sills associated with black shales, while pillow basalts and tuffs predominate at the uppermost levels. Locally, basaltic dikelets intruded leucocratic gneiss. Ultramafic-mafic cumulates form the bottom of the thickest intrusions while diabases are present along the chilled margins. All these rocks have been affected by a polyphased metamorphism under eclogitic to blueschist and greenschist facies conditions. Magmatic textures have been destroyed and the igneous mineralogy is seldom preserved. The mafic rocks of the Versoyen complex show tholeiitic to alkali-transitional affinities. The pillow basalts and the sill cores have flat REE patterns characteristic of N-MORB and T-MORB. Their {varepsilon}Nd (assuming an age of 337 Ma) ratios range from + 5.7 to + 9 which suggest a mixing of N-MORB and OIB sources. The sill margins show Th, U and LREE-enrichments and negative {varepsilon}Nd ratios. These features are likely related to contamination when hot mafic magmas intruded unconsolidated sediments rich in water. The high Th, U, LREE abundances and low {varepsilon}Nd ratio of the basaltic dikelet are probably related to crustal contamination occurring during magma ascent. The geochemical characteristics of the Versoyen rocks are compatible with a tholeiitic magma emplaced into a small oceanic basin in the vicinity of a continent. The importance of pre-Mesozoic crustal thinning evidenced in one segment of the boundary between the Internal and External zones of the Alps suggests that the Pennine Front is an Alpine mega-thrust inherited from a Variscan suture

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Characteristic reflection patterns in the Southeast Canadian Cordillera, Northern Appalachians and Swiss Alps

et al. 1993

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Crustal reflections beneath the Alps and the Alpine foreland: Geodynamic implications

Cited by 7 publications

References 15 publications

Chronology of thrust propagation from an updated tectono-sedimentary framework of the Miocene molasse (western Alps)

Chronology of thrust propagation from an updated tectono-sedimentary framework of the Miocene molasse (western Alps)

The tholeiites of the Valaisan domain (Versoyen, western Alps): a Carboniferous magma emplaced in a small oceanic basin

Characteristic reflection patterns in the Southeast Canadian Cordillera, Northern Appalachians and Swiss Alps

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