Tectonics of the Dolomites
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Tectonics of the Dolomites Autor(en): Doglioni, Carlo Objekttyp: Article Zeitschrift: Bulletin für angewandte Geologie Band (Jahr): 12 (2007) Heft 2 PDF erstellt am: 26.09.2021 Persistenter Link: http://doi.org/10.5169/seals-226374 Nutzungsbedingungen Die ETH-Bibliothek ist Anbieterin der digitalisierten Zeitschriften. Sie besitzt keine Urheberrechte an den Inhalten der Zeitschriften. Die Rechte liegen in der Regel bei den Herausgebern. Die auf der Plattform e-periodica veröffentlichten Dokumente stehen für nicht-kommerzielle Zwecke in Lehre und Forschung sowie für die private Nutzung frei zur Verfügung. Einzelne Dateien oder Ausdrucke aus diesem Angebot können zusammen mit diesen Nutzungsbedingungen und den korrekten Herkunftsbezeichnungen weitergegeben werden. Das Veröffentlichen von Bildern in Print- und Online-Publikationen ist nur mit vorheriger Genehmigung der Rechteinhaber erlaubt. Die systematische Speicherung von Teilen des elektronischen Angebots auf anderen Servern bedarf ebenfalls des schriftlichen Einverständnisses der Rechteinhaber. Haftungsausschluss Alle Angaben erfolgen ohne Gewähr für Vollständigkeit oder Richtigkeit. Es wird keine Haftung übernommen für Schäden durch die Verwendung von Informationen aus diesem Online-Angebot oder durch das Fehlen von Informationen. Dies gilt auch für Inhalte Dritter, die über dieses Angebot zugänglich sind. Ein Dienst der ETH-Bibliothek ETH Zürich, Rämistrasse 101, 8092 Zürich, Schweiz, www.library.ethz.ch http://www.e-periodica.ch Bull, angew. Geol. Vol. 12/2 Dezember 2007 S.11-15 Tectonics of the Dolomites Carlo Doglioni1 Keywords: Southern Alps, thrust belt, Mesozoic tectonics, Alpine tectonics The Dolomites are a part of the Alps, and The Mesozoic extension is particularly therefore they recorded the subduction evident already from the general geologic map history of this orogeny (e. g. Kummerow et al. of the Dolomites located in the hangingwall 2004; Castellare et al. 2006). The Mesozoic of the Valsugana Thrust (Bosellini & Doglioni passive margin sequences deposited on top 1986). In fact the crystalline basement is of a hercynian basement were compressed much higher in the western side of the during the alpine evolution. The passive Dolomites with respect to the eastern part margin history is recorded particularly by (Fig. 1). Mesozoic extension generated mainly thickness variations of the sedimentary cover N-S trending normal faults, which separate (about 2 km above the Trento Horst, and the Trento Horst to the west and the about 4.5 km in the Belluno Graben, Fig. 1). Belluno Graben to the east. N70°-90° trending The thickness variations are spread-out strike-slip transfer faults accomodated over the entire late Permian, Triassic and undulations of the extension. Jurassic sequences, testifying an endless During the growth of the Alps, the Trento history of extensional-transtensional tectonics. Horst was probably the hardest lithospheric The Dolomites are located half on the segment of the Adriatic plate. For this Trento Horst and half on the Belluno reason, the Dolomites are relatively well Graben. preserved by alpine tectonics, and the original Late Permian to Early Cretaceous crustal Triassic platform-basin transitions are extension is well documented in the region spectacularly preserved. Acting as a stronger (Bertotti et al. 1993) and it is generally crustal block, the Dolomites are in fact a believed that extensional tectonics in the recess of the alpine thrust belt, in which the Southern Alps are a manifestation of sinistral Southern Alps (and the Dolomites) represent transtension during the Triassic to Early the retrobelt, i. e., that part of the double Cretaceous continental and subsequent verging orogen, where thrusts and folds are oceanic rifting between the Adriatic and the directed toward the upper plate (the Adriatic European plate. Inversion of extension to plate). The Giudicarle Belt, to the west of the compression in the Southern Alps is apparent Dolomites, is the left-lateral transpressive from middle Cretaceous time, coincident system bounding the Dolomites recess, and with the opening of the North Atlantic and transferring the deformation to the Milano- the general change of relative motion of Lombardy salient, formed within the Lom- Africa and Europe from sinistral transtension bardy Mesozoic basin. This structural to dextral transpression. undulation is one of the most prominent alpine features. ' Dipartimento di Scienze della Terra, Università Sapienza, The Dolomites are now geographically and Roma - Italy geologically located between the dextrally transpressive Pusteria Line to the north (a Summary of talks and contributions to the field trips given and at the VSP/ASP annual convention, Ortisei, Italy, June segment of the Insubric Lineament) the 2007. SSE-vergent Valsugana Thrust to the south 11 (Fig. 2). These two main features have been fer zone bounding to the east to the active during Tertiary times. The Valsugana Dolomites recess, and transferring the Line is the SSE vergent overthrust which deformation to the Belluno salient. The marks the boundary between the Dolomites sedimentary cover in the Dolomites was shortened and the Venetian Prealps. Paleomagnetic by at least 10-15 km during this data from the Venetian Prealps have indicated deformation phase (mainly thin-skinned tectonics no significant rotation among thrust in this area). Ramps occurred at the margins sheets and a generally concordance of Late of Triassic carbonate platforms and at the Jurassic and Cretaceous data with the hinge zone between the Trento Horst and African apparent polar wander path (Chan- the Belluno Graben. nell et al. 1992). These low relative rotations From Late Oligocene to Recent, the between the Southalpine thrust sheets may Dolomites and the Venetian Alps have been be related to the deep roots in the basement affected by deeper SSE-vergent thrusting of of the thrust planes. the «Southalpine» deformation phase, which The Dolomites are located within an about deeply involved the basement (thick- 60 km wide pop-up, generated by the S-verg- skinned tectonics). The minimum total ing Valsugana thrust, and its conjugate N- shortening in the Dolomites and Venetian verging thrusts (the Funes Line). The pop-up Alps during this deformation phase is 40-50 is confining a crustal-scale syncline where km (Doglioni 1987). The Dolomites during most of the Dolomites are situated (Fig. 2). this latest Neo-Alpine phase assumed the Particularly during Middle Triassic times, pop-up geometry due to the Valsugana the Dolomites underwent a sinistral Thrust and its conjugate back-thrust. The transpressive tectonic phase, concentrated along push-up is responsible for the wide syncline the N70° alignment of the Stava Line - northern containing the sedimentary cover of the limb of the Cima Bocche Anticline. Along Dolomites, which adapted itself through this trend outcrop flower structures and flexural slip and flexural shear to the folding high angle strike slip faults, cutting the of the underlying basement. The inherited entire basement and sedimentary cover up Mesozoic architecture (normal faults and to Early Ladinian rocks. These features are strike-slip zones, carbonate platforms to cross-cut by the Late Ladinian - Early Carnian basins transitions) acted as inhomogenities intrusions of Predazzo and Monzoni, to the folding and controlled transfer zones supporting with other stratigraphie and and undulations of the Tertiary shortening. structural data the Middle Triassic age of Some Mesozoic features might also have this deformation (Doglioni 1987). Minor similar been reactivated or inverted (Doglioni & alignments occur more to the north in Carminati 2007). The previous NW-trending the Dolomites along the Fedaia Pass and the thrusts and folds have been folded and Val Gardena Pass. The Middle Triassic cross-cut by the deeper deformation (Fig. 4). volcanism occurring along the alignment is shoshonitic in character (Lucchini et al. 1982). Acknowledgments The first Alpine phase of shortening in the This short contribution has been motivated by Dolomites is Paleogene in age and is Peter Burri and is a brief summary of the result of represented by WSW-vergent thrusts of the years of discussions and cooperation with a number B<Dinaric» phase (Doglioni 1987). The front of of outstanding friends to which I want to of the Swiss this thrust belt runs from NW to SE across express my deepest gratitude: part «mafia», Albert W. Bally, Daniel Bernoulli, Hans throughout all the Dolomites (Fig. 3), but is Peter Laubscher and Rudolph Trümpy, plus Alberto rather the right-lateral transpressive trans¬ Castellarin, Giorgio Vittorio Dal Piaz, etc. 12 Western Dolomites Eastern Dolomites TRENTO HORST BELLUNO GRABEN Puez Marls M. Parei Congl. L.Cretaceous pelapic 3 U.-Oligocene ¦ '44 Dolomia Ammonitico Principale Rosso Dogger-Malm Norian lagoon Calcari Grigi Ma Lias 206 Dachstein Lms tìgoon 209 Rhaetian i/olcaniclastics IMJUWULIIUHW Pillow lavas Dolomia Principale 500 m tidal flat Nonan 220 Raibl Beds Durrenstein Ignimbri CO tidal flat Upper Carnian Permian Dolomite Cassian Dolomite BUU S. Cassiano Fm U. Ladinian-Carnian 227 Marmolada ACCELERATED Conglomerate aaoon"I SUBSIDENCE Latemar Lms Monzonites Granodiorites Fernazza Fm I tes Sciliar Dolomite Granites 270-290 Caotico eterogeneo 220-235 debris-flows U. Anisian-Ladinian Fm 234 h""1*«11 Livinallongo 241 Contrin Fm Richthofen Congl. Seria Dol mixed platform Fm ,M,,; Werfen r^K Scythian ZS1 - lagoon Bellerophon Fm rtr. sabkha Upper Permian #"> Gardena