Neo-Alpine evolution of the Southern Eastern Alps

Abstract The Eastern Southern Alps, located to the east of the N Giudicarie Line, have been originated by polyphase compressional evolution of Tertiary age. The oldest structural system corresponds to the Mesoalpine (Eocene) and early Neoalpine (Oligomiocene) compressional events, which originated the Dinaric system (NW–SE trending) present in the NE side of the Southern Alps. The subsequent tectonic belt is the Valsugana structural system, ENE–WSW trending, Serravallian– Tortonian in age. The intense activity of this compressional event is documented both by stratigraphic and structural data and by fission track studies which indicate uplifting of some 4 km in the hangingwall of the Valsugana overthrust between 12 and 8 Ma B.P. The more external structures NE–SW trending are located in the Montello–Friuli zone which were generated by the Messinian–Pliocene compressions (whose principal stress axis is SE–NW oriented). Structural and kinematic links between the Montello–Friuli belt and the Giudicarie zone have been recognized by new analytical data documenting that the Schio–Vicenza fault system transferred compressive deformations to the Giudicarie belt, where, the previous structures (belonging to the Valsugana system) were strongly enhanced by the subsequent compressions. Since the Montello–Friuli belt and the Schio–Vicenza system developed during the Messinian–Pliocene Adriatic compressional event, the out-of-sequence tectonic reactivations in the Giudicarie belt have to be considered mostly Messinian–Pliocene in age rather than Tortonian, as previously proposed. This compressional Adriatic event produced wide deformations in the Alps, both internally, like in the Montello–Friuli and Giudicarie, and, very likely, also externally, as in the Jura and the frontal external French Western Alps. The three structural systems here described are clearly represented in a N–S trending balanced profile crossing the Central Dolomites, close to the Italian trace of the Central European Profile (CEP) where a seismic reflexion acquisition campaign is presently in progress according to the German, Austrian and Italian joint program of the TRANSALP Project. The crustal and lithospheric interpretation using available data (revision of previous refraction profiles) assumes strong indentation of the Adriatic lithosphere to the N coupled by southward delamination of the Adriatic crust, coherent with the setting of the upper crust shown in the balanced cross section. Similar indentation processes were recognized up to date only in the Western and Central Alps (CROP–ECORS and NFP20 Profiles).

[1]  H. Laubscher.  Large-scale, thin-skinned thrusting in the southern Alps: Kinematic models , 1985 .

[2]  G. M. Bargossi,et al.  The evolution of a calc-alkaline basic to silicic magma system: Geochemical and Rb-Sr, Sm-Nd, and isotopic evidence from the Late Hercynian Atesina-Cima d'Asta volcano-plutonic complex, northern Italy , 1993 .

[3]  C. Doglioni.  Tectonics of the Dolomites (southern alps, northern Italy) , 1987 .

[4]  H. Laubscher.  Deep seismic data from the central Alps : mass distributions and their kinematics , 1990 .

[5]  H. Laubscher.  Some overall aspects of Jura dynamics , 1972 .

[6]  R. Lacassin.  Plate-scale kinematics and compatibility of crustal shear zones in the Alps , 1989, Geological Society, London, Special Publications.

[7]  Consiglio Nazionale delle Ricerche . Progetto Finalizzato Geodinamica.  Structural model of Italy and gravity map , 1990 .

[8]  D. Dietrich,et al.  Alpine tectonics — an overview , 1989, Geological Society, London, Special Publications.

[9]  Lothar Ratschbacher,et al.  Lateral extrusion in the eastern Alps, PArt 2: Structural analysis , 1991 .

[10]  P. R. Cobbold,et al.  Lateral extrusion in the eastern Alps, Part 1: Boundary conditions and experiments scaled for gravity , 1991 .

[11]  A. Castellarin,et al.  The Middle Triassic magmatic-tectonic arc development in the Southern Alps , 1988 .

[12]  A. Castellarin,et al.  Importance of Hercynian tectonics within the framework of the Southern Alps , 1981 .

[13]  C. Doglioni.  Triassic diapiric structures in the central Dolomites (northern Italy) , 1984 .

[14]  M. Weger,et al.  Footwall uplift in an orogenic wedge: the Tauern Window in the Eastern Alps of Europe , 1998 .

[15]  M. Parish,et al.  Kinematics of the Alpine arc and the motion history of Adria , 1989, Nature.

[16]  A. Bosellini,et al.  Eoalpine and mesoalpine tectonics in the Southern Alps , 1987 .

[17]  S. Scarascia,et al.  Crustal structures in the central-eastern Alpine sector: A revision of the available DSS data , 1997 .

[18]  James Jackson,et al.  Active tectonics of the Adriatic Region , 1987 .

[19]  D. Bernoulli,et al.  From rifting to drifting: tectonic evolution of the South-Alpine upper crust from the Triassic to the Early Cretaceous , 1993 .

[20]  F. Roure,et al.  Early Neogene deformation beneath the Po plain : constraints on the post-collisional Alpine evolution , 1990 .

[21]  D. Bernoulli,et al.  Mediterranean and Tethys , 1977 .

[22]  A. Rebez,et al.  Scismotectonics of the Northwest External Dinarides , 1990 .

[23]  M. Bott.  The origin of arcs , 1989 .

[24]  A. Castellarin,et al.  Southalpine Versus Po Plain Apenninic Arcs , 1986 .

[25]  H. Laubscher.  Shallow and deep rotations in the Miocene Alps , 1996 .