Outline
Comptes Rendus

Extension in Alpine Western Europe and West Mediterranean
Comptes Rendus. Géoscience, Volume 338 (2006) no. 4, pp. 225-228.
Metadata
Published online:
DOI: 10.1016/j.crte.2006.02.005
André Michard 1

1 Laboratoire de géologie, École normale supérieure, 24, rue Lhomond, 75231 Paris cedex 05, France
@article{CRGEOS_2006__338_4_225_0,
     author = {Andr\'e Michard},
     title = {Extension in {Alpine} {Western} {Europe} and {West} {Mediterranean}},
     journal = {Comptes Rendus. G\'eoscience},
     pages = {225--228},
     publisher = {Elsevier},
     volume = {338},
     number = {4},
     year = {2006},
     doi = {10.1016/j.crte.2006.02.005},
     language = {en},
}
TY  - JOUR
AU  - André Michard
TI  - Extension in Alpine Western Europe and West Mediterranean
JO  - Comptes Rendus. Géoscience
PY  - 2006
SP  - 225
EP  - 228
VL  - 338
IS  - 4
PB  - Elsevier
DO  - 10.1016/j.crte.2006.02.005
LA  - en
ID  - CRGEOS_2006__338_4_225_0
ER  - 
%0 Journal Article
%A André Michard
%T Extension in Alpine Western Europe and West Mediterranean
%J Comptes Rendus. Géoscience
%D 2006
%P 225-228
%V 338
%N 4
%I Elsevier
%R 10.1016/j.crte.2006.02.005
%G en
%F CRGEOS_2006__338_4_225_0
André Michard. Extension in Alpine Western Europe and West Mediterranean. Comptes Rendus. Géoscience, Volume 338 (2006) no. 4, pp. 225-228. doi : 10.1016/j.crte.2006.02.005. https://comptes-rendus.academie-sciences.fr/geoscience/articles/10.1016/j.crte.2006.02.005/

Version originale du texte intégral

Quite recently, the geological description of a restricted zone of the Peloritani Mountains of northeastern Sicily appeared in Comptes rendus Geoscience [46]. Indeed, the cited paper documents the first evidence for synorogenic extension in this segment of the Alpine orogen, and thus ranks among the many recent works that deal with extensional tectonics in Alpine Western Europe and West-Mediterranean areas. Within this large domain, Tertiary extensional tectonics is evidenced in two different settings, i.e., on the one hand, the Pyrenean-Alpine foreland, and, on the other hand, the Alpine belts themselves.

First, Tertiary extension is responsible for the development of a major, NNE-trending rift system (Fig. 1), referred to as the European Cenozoic Rift System (ECRIS), with both onshore parts (Rhine graben, Limagnes, etc.) and offshore parts (Gulf of Lion, Valencia Trough, etc.). The onshore ECRIS extends in ‘stable Europe’, but its southern, offshore continuation affects large parts of the Pyrenean–Alpine belt itself (eastern Pyrenees, southwestern Alps, Betic Cordilleras, etc.). Remarkably, these extensional structures developed contemporaneously with the youngest stages of the Alpine orogenesis, and in the framework of ongoing Africa–Europe plate convergence. Some decades ago, there was a tendency to consider extensional tectonics as independent from the opposite, compressional one, and thus the model of abnormal mantle/plume-related active rifting was generally preferred [34]. Since then, the coupling of rifting and plate convergence was clearly recognized following different scenarios such as collisional foreland splitting (e.g., [10,11], with references therein), forebulge flexural bending [47], back-arc spreading and slab roll-back [15,21,24,38,44], or slab-pull [29,32].

Fig. 1

Early Miocene palaeotectonic sketch map of ECRIS and West-Mediterranean areas, after Michard et al. [31] and Dèzes et al. [11]. Legend: dark grey: orogens; light grey: areas of young oceanic or thinned continental crust; stippled: intracontinental rift system; large black arrow: Africa–Europe convergence; small facing black arrows: maximum horizontal stress direction; white arrows: Neogene extension in the Internal Alps [7,18]; light grey arrows: extensional stress in the northwestern Alpine foreland [40]. Al: Alboran; AB: Algerian-Balearic basin; Ca: Calabria; GL: Gulf of Lion; Ka: Kabylias; LPB: Ligurian–Provençal basin; Pe: Peloritani Mountains.

Second, the close association of extension and shortening within the collisional belt itself during orogenesis was recognized in the Alps, particularly in the Tauern and Simplon culminations, and the western Alps [2,18,30,35,51], the Betic Cordilleras [20,25,36], and Calabria [43,49]. This was interpreted, either in relation with lateral escape of the compressed belt (orogen-parallel extension), or by gravity-driven collapse of the thickened orogenic prism (orogen-perpendicular extension). On the other hand, extensional structures may also accompany extrusion of buoyant metamorphic rocks in the subduction channel, resulting in ‘relative extension’ (ductile normal shear) with respect to the rigid hanging-wall [14,22]. Such varied synorogenic/late orogenic extensional processes are crucial for the exhumation of high-pressure, low-temperature (HP–LT) metamorphic rocks. Back-arc rifting may immediately follow, and take advantage of these intra-orogenic extensional processes, which is perfectly illustrated in the Alboran domain. There, the Alpujarride–Sebtide units of the Betic Rif orogen evolved through alternating compressional–extensional deformations during the Late Palaeogene [3,6,9] before being definitely exhumed during the Late Oligocene–Early Miocene Alboran rifting, and then folded and uplifted (up to 3000 m in the Sierra Nevada [19,26]) or drowned beneath the Alboran Sea [5,8,20] during the Neogene. The quoted paper by Somma et al. [46] illustrates a closely similar example from the Peloritan–Calabrian Arc, which is the eastern homologous of the Betic-Rif, or Gibraltar Arc.

The balance between extension and compression (shortening) during the late orogenic stages was repeatedly questioned in the western Alps, a belt where high-grade HP–LT (eclogite-facies) and ultra-high-pressure (UHP) rocks are widely exposed, and which, however, escaped such an intense rifting evolution as the West-Mediterranean domain. The role of early ‘relative extension’ in the subduction channel as a mechanism for the early exhumation of eclogite-facies/UHP rocks has been emphasized [1,22,30]. However, the widespread effects of late orogenic extension were clearly recognized through structural field studies of active and recent faults, seismic analysis of focal mechanisms, and geodesy, including GPS measurements (see [7], with references therein). At the base of the northwest-verging Dent-Blanche thrust nappe, late top-to-the-southeast deformation is coincident with (late) eclogite exhumation, and relevant to gravity-driven crustal extension [37]. Likewise, the Penninic Front has been inverted, i.e. this major thrust was changed into a normal fault [4,48]. In spite of the permanent Africa–Europe convergence, the internal Alps have undergone widespread extensional deformation during the Neogene, evolving from early, orogen-parallel extrusion to late and ongoing orogen-perpendicular spreading [7].

A warm controversy currently concerns the ECRIS development onshore [12,32]. Whereas Merle and Michon [29], Michon et al. [33] and Michon and Merle [32] advocate a slab-pull model, Dèzes et al. [11,12] come to the conclusion that the onshore parts of ECRIS evolved by passive rifting in response to collisional foreland splitting. The latter authors particularly argue that the Ligurian–Piemontese (Upper Penninic) oceanic slab was detached from the European lithosphere in the course of the Late Eocene, and then that slab-pull forces relaxed at the very moment when the onset of ECRIS evolution occurred. They also emphasize that volcanic activity in the ECRIS area started during the Palaeocene, reflecting the activation of a mantle upwelling system beneath the Alpine foreland. This mantle anomaly gave rise to discrete mantle plumes, imaged by seismic tomography, and caused thermal weakening of the foreland lithosphere, thus rendering it prone to deformation [52]. Additionally, flexural bending at the outer bulge of the Valaisan subduction likely played an important role in the ECRIS formation [47]. By contrast, evolution of the Gulf of Lion–Valencia Trough rift system, forming the offshore extension of ECRIS, was controlled by back-arc extension related to roll-back of the Ligurian slab [39,45]. The latter process was in fact responsible for the opening of all West-Mediterranean basins [15,21,27,28,41,50], as well as of the late orogenic evolution of the associated Alpine belts [4,13,16,17,23,43]. The mechanisms at work within the overthickened crust (e.g., in the Corsica–Ligurian transect) during extension evolve from ductile, with formation of core complexes, to brittle, with rigid block faulting, crustal separation, and formation of new oceanic crust [42].


References

[1] D. Avigad; Z. Garfunkel; L. Jolivet; J.M. Azañón Back-arc extension and denudation of Mediterranean eclogites, Tectonics, Volume 16 (1997), pp. 924-941

[2] D. Avigad; C. Chopin; R. Le Bayon Thrusting and extension in the southern Dora-Maira ultra-high-pressure massif (western Alps): view from below the coesite-bearing unit, J. Geol., Volume 111 (2003), pp. 57-70

[3] J.C. Balanyá; V. García-Dueñas; J.M. Azañón; M. Sánchez-Gómez Alternating contractional and extensional events in the Alpujarride nappes of the Alboran Domain (Betics, Gibraltar Arc), Tectonics, Volume 16 (1997), pp. 226-238

[4] S. Ceriani; B. Fügenschuh; S.M. Schmid Multi-stage thrusting at the ‘Penninic Front’ in the western Alps between Mont-Blanc and Pelvoux massifs, Int. J. Earth Sci., Volume 90 (2001), pp. 685-702

[5] A. Chalouan; R. Saji; A. Michard; A.W. Bally Neogene tectonic evolution of the southwestern Alboran basin as inferred from seismic data off Morocco, AAPG Bull., Volume 81 (1997), pp. 1161-1184

[6] A. Chalouan; A. Michard; H. Feinberg; R. Montigny; O. Saddiqi The Rif mountain building (Morocco): a new tectonic scenario, Bull. Soc. géol. France, Volume 172 (2001), pp. 603-616

[7] J.-D. Champagnac; C. Sue; B. Delacou; M. Burkhard Brittle deformation in the inner NW Alps: from early orogen-parallel extrusion to late orogen-perpendicular collapse, Terra Nova, Volume 16 (2004), pp. 232-242

[8] M.C. Comas; J.-P. Platt; J.I. Soto; A.B. Watts The origin and tectonic history of the Alboran basin: Insight from ODP leg161 results, Proc. Ocean Drill. Program Sci. Results, Volume 161 (1999), pp. 555-580

[9] A. Crespo-Blanc; J. Campos Structure and kinematics of the South-Iberian paleomargin and its relationship with the Flysch Trough units. Extensional tectonics within the Gibraltar Arc fold-and-thrust belt (western Betics), J. Struct. Geol., Volume 23 (2001), pp. 1615-1630

[10] J.F. Dewey; B.F. Windley Paleocene-Oligocene tectonics of NW Europe, Geol. Soc. Lond. Spec. Publ., Volume 39 (1988), pp. 25-31

[11] P. Dèzes; S.M. Schmid; P.A. Ziegler Evolution of the European Cenozoic Rift System: interaction of the Alpine and Pyrenean orogens with their foreland lithosphere, Tectonophysics, Volume 389 (2004), pp. 1-33

[12] P. Dèzes; S.M. Schmid; P.A. Ziegler Reply to comments by L. Michon and O. Merle on “Evolution of the European Cenozoic Rift System: interaction of the Alpine and Pyrenean orogens with their foreland lithosphere” by P. Dèzes, S.M. Schmid and P.A. Ziegler, Tectonophysics, Volume 389 (2004), pp. 1-33 (257–262)

[13] C. Doglioni; M. Fernandez; E. Gueguen; F. Sabat On the interference between the early Apennines-Maghrebides back-arc extension and the Alps–Betics orogen in the Neogene geodynamics of the Western Mediterranean, Bull. Soc. geol. It., Volume 118 (1999), pp. 75-89

[14] A. Escher; C. Beaumont Formation, burial and exhumation of basement nappes at crustal scale: a geometric model based on the Western Swiss-Italian Alps, J. Struct. Geol., Volume 19 (1997), pp. 955-974

[15] C. Faccenna; C. Piromallo; A. Crespo-Blanc; L. Jolivet; F. Rossetti Lateral slab deformation and the origin of the Mediterranean arcs, Tectonics, Volume 23 (2004) | DOI

[16] D. Frizon de Lamotte; B. Saint Bezar; R. Bracène; E. Mercier The two main steps of the Atlas building and geodynamics of the western Mediterranean, Tectonics, Volume 19 (2000), pp. 740-761

[17] D. Frizon de Lamotte; A. Crespo-Blanc; B. Saint-Bézar; M. Comas; M. Fernàndez; H. Zeyen; P. Ayarza; C. Robert-Charrue; A. Chalouan; M. Zizi; A. Teixell; M.-L. Arboleya; F. Alvarez-Lobato; M. Julivert; A. Michard TRANSMED-Transect I: Betics, Alboran Sea, Rif, Moroccan Meseta, High Atlas, Jbel Saghro, Tindouf basin (W. Cavazza; F. Roure; W. Spakman; G.M. Stampfli; P.A. Ziegler, eds.), The Transmed Atlas: The Mediterranean Region from Crust to Mantle, Springer-Verlag, Berlin, Heidelberg, 2004

[18] B. Fügenschuh; D. Seward; N. Mancktelow Exhumation in a convergent orogen: the western Tauern window, Terra Nova, Volume 9 (1997), pp. 213-217

[19] J. Galindo-Zaldívar; A. Jabaloy; F. González-Lodeiro; F. Aldaya Crustal structure of the central sector of the Betic Cordilleras (SE Spain), Tectonics, Volume 16 (1997), pp. 18-37

[20] V. García-Dueñas; J.C. Balanyá; J.M. Martínez-Martínez Miocene extensional detachment in the outcropping basement of the northern Alboran Basin (Betics) and their tectonic implications, Geo-Mar. Lett., Volume 12 (1992), pp. 88-95

[21] L. Jolivet; C. Faccenna; N. D'Agostino; M. Fournier; D. Worall The kinematics of back-arc basins, examples from the Tyrrhenian, Aegean and Japan Seas, Geol. Soc. Lond. Spec. Publ., Volume 156 (1999), pp. 21-53

[22] L. Jolivet; C. Faccenna; B. Goffé; E. Burov; P. Agard Subduction tectonics and exhumation of high-pressure metamorphic rocks in the Mediterranean orogens, Am. J. Sci., Volume 303 (2003), pp. 353-409

[23] O. Lacombe; L. Jolivet Structural and kinematic relationships between Corsica and the Pyrenees-Provence domain at the time of the Pyrenean orogeny, Tectonics, Volume 24 (2005), p. TC1003 | DOI

[24] L. Lonergan; N. White Origin of the Betic-Rif mountain belt, Tectonics, Volume 16 (1997), pp. 504-522

[25] J.M. Martínez-Martínez; J.M. Azañón Mode of extensional tectonics in the southeastern Betics (SE Spain): Implications for the tectonic evolution of the peri-Alboran orogenic system, Tectonics, Volume 16 (1997), pp. 205-225

[26] J.M. Martínez-Martínez; J.I. Soto; J.C. Balanyá Orthogonal folding of extensional detachments: Structure and origin of the Sierra Nevada elongated dome (Betics, SE Spain), Tectonics, Volume 21 (2002) | DOI

[27] G. Mascle; P. Tricart; L. Torelli et al. Structure of the Sardinia Channel: crustal thinning and tardi-orogenic extension in the Apenninic-Maghrebian orogen; results of the Cyana submersible survey (SARCYA and SARTUCYA) in the Western Mediterranean, Bull. Soc. géol. France, Volume 175 (2004), pp. 607-627

[28] A. Mauffret; D. Frizon de Lamotte; S. Lallemant; C. Gorini; A. Maillard E-W opening of the Algerian basin (Western Mediterranean), Terra Nova, Volume 16 (2004), pp. 257-264

[29] O. Merle; L. Michon The formation of the West European Rift: a new model as examplified by the Massif Central area, Bull. Soc. géol. France, Volume 172 (2001), pp. 213-221

[30] A. Michard; C. Chopin; C. Henry Compression versus extension in the exhumation of the Dora-Maira coesite-bearing unit, western Alps, Italy, Tectonophysics, Volume 221 (1993), pp. 173-193

[31] A. Michard; A. Chalouan; H. Feinberg; B. Goffé; R. Montigny How does the Alpine belt end between Spain and Morocco?, Bull. Soc. géol. France, Volume 173 (2002), pp. 3-15

[32] L. Michon; R.T. van Balen; O. Merle; H. Panier The Cenozoic evolution of the Roer Valley rift system integrated at a European scale, Tectonophysics, Volume 367 (2003), pp. 101-126

[33] L. Michon; O. Merle Discussion on “Evolution of the European Cenozoic Rift System: interaction of the Alpine and Pyrenean orogens with their foreland lithosphere”, Tectonophysics, Volume 401 (2005), pp. 251-256

[34] H.J. Neugebauer Crustal doming and mechanisms of rifting. Part I: Rift formation, Tectonophysics, Volume 45 (1978), pp. 159-186

[35] J.P. Platt Dynamics of orogenic wedges and the uplift of high-pressure metamorphic rocks, Geol. Soc. Am. Bull., Volume 97 (1986), pp. 1037-1053

[36] J.P. Platt; R.L.M. Vissers Extensional collapse of thickened continental lithosphere: a working hypothesis for the Alboran Sea and Gibraltar Arc, Geology, Volume 17 (1989), pp. 540-543

[37] S.M. Reddy; J. Wheeler; R.W.H. Butler; R.A. Cliff; S. Freeman; S. Inger; C. Pickles; S.P. Kelley Kinematic reworking and exhumation within the convergent Alpine orogen, Tectonophysics, Volume 365 (2003), pp. 77-102

[38] J.-P. Rehault; G. Boillot; A. Mauffret The Western Mediterranean basin geological evolution, Mar. Geol., Volume 55 (1984), pp. 447-477

[39] E. Roca The Northwest Mediterranean basin (Valencia Trough, Gulf of Lion and Ligurian-Provençal basin): structure and geodynamic evolution, Mém. Mus. Hist. Nat. Paris, Volume 186 (2001), pp. 617-706

[40] M. Rocher; M. Cushing; F. Lemeille; S. Baize Stress induced by the Mio-Pliocene Alpine collision in northern France, Bull. Soc. géol. France, Volume 176 (2005), pp. 319-328

[41] N. Rollet; J. Deverchère; M.-O. Beslier; P. Gnoc; J.-P. Rehault; M. Sosson Back-arc extension, tectonic inheritance, and volcanism in the Ligurian Sea, West Mediterranean, Tectonics, Volume 21 (2002), p. TC1015 | DOI

[42] G. Rosenbaum; K. Regenauer-Lieb; R. Weinberg Continental extension: from core complexes to rigid block faulting, Geology, Volume 33 (2005), pp. 609-612

[43] F. Rossetti; B. Goffé; P. Monié; C. Faccenna; G. Vignaroli Alpine orogenic PTt-deformation history of the Catena Costiera area and surrounding regions (Calabrian Arc, southern Italy): The nappe edifice of North Calabria revised with insights on the Tyrrhenian-Apennine system formation, Tectonics, Volume 23 (2004), p. TC6011 | DOI

[44] L.H. Royden Evolution of retreating subduction boundaries formed during continental collision, Tectonics, Volume 12 (1993), pp. 629-638

[45] M. Séranne The Guf of Lion continental margin (NW Mediterranean) revisited by IBS: an overview, Geol. Soc. Lond. Spec. Publ., Volume 156 (1999), pp. 15-36

[46] R. Somma; A. Messina; S. Mazzoli Syn-orogenic extension in the Peloritani Alpine thrust belt (NE Sicily, Italy): evidence from the Ali unit, C. R. Geoscience, Volume 337 (2005), pp. 861-871

[47] G.M. Stampfli; J. Mosar; D. Marquer; R. Marchant; T. Baudin; G. Borel Subduction and obduction processes in the Swiss Alps, Tectonophysics, Volume 296 (1998), pp. 159-204

[48] C. Sue; P. Tricart Neogene to current normal faulting in the inner western Alps: a major evolution of the late Alpine tectonics, Tectonics, Volume 5 (2003), p. TC1050 | DOI

[49] S.N. Thomson Fission track analysis of the crystalline basement rocks of the Calabrian Arc, southern Italy: evidence of Oligo-Miocene late-orogenic extension and erosion, Tectonophysics, Volume 238 (1994), pp. 331-352

[50] J. Vergès; F. Sàbat Constraints on the Neogene Mediterranean kinematic evolution along a 1000-km transect from Iberia to Africa, Geol. Soc. Lond. Spec. Publ., Volume 156 (1999), pp. 63-80

[51] J. Wheeler; R.W.H. Butler Evidence for extension in western Alpine orogen: the contact between the oceanic Piemonte and overlying continental Sesia units, Earth Planet. Sci. Lett., Volume 117 (1993), pp. 457-474

[52] P.A. Ziegler; S. Cloetingh; J.-D. Van Wees Dynamics of intra-plate compressional deformation: the Alpine foreland and other examples, Tectonophysics, Volume 252 (1995), pp. 7-59


Comments - Policy


Articles of potential interest

Pressure–temperature–time constraints on the Maghrebide mountain building: evidence from the Rif–Betic transect (Morocco, Spain), Algerian correlations, and geodynamic implications

André Michard; François Negro; Omar Saddiqi; ...

C. R. Géos (2006)


The Western Alpine arc: a review and new kinematic model

Quentin Brunsmann; Claudio Luca Rosenberg; Nicolas Bellahsen

C. R. Géos (2024)


Alpine, Variscan, eo-Variscan belts: comparison between hot and cold orogens from the examples of French segments

Michel Faure

C. R. Géos (2024)