Rifting and collision in the Southern Alps

Schumacher, Markus E.; Schönborn, Gregor; Bernoulli, Daniel; Laubscher, H. P.

doi:10.1007/978-3-0348-9098-4_15

Cited by 34 publications

(51 citation statements)

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“…The first one is the petrographic and 394 F. Schlunegger et al Lombardic deformation (which resulted in deformation of the Southalpine nappes, see above) is constrained by cross-cutting relationships between dated strata and southern Alpine structures (Fig 8A) (Pieri & Groppi, 1981;Schumacher et al, 1996). At the same time, deformation and exhumation became focused in the region surrounding the Aar massif.…”

Section: The Alpine Drainage Networkmentioning

confidence: 99%

Possible environmental effects on the evolution of the Alps-Molasse Basin system

2007

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Environmental effects on the evolution of the Alps-Molasse 383 ABSTRACT We propose three partly unrelated stages in the geodynamic evolution of the Alps and the sedimentary response of the Molasse Basin. The first stage comprises the time interval between ca. 35 and 20 Ma and is characterized by a high ratio between rates of crustal accretion and surface erosion. The response of the Molasse Basin was a change from the stage of basin underfill (UMM) to overfill (USM). Because the response time of erosional processes to crustal accretion and surface uplift lasts several millions of years, the orogen first experienced a net growth until the end of the Oligocene. As a result, the Molasse basin subsided at high rates causing the topographic axis to shift to the proximal basin border and alluvial fans to establish at the thrust front. During the Aquitanian, however, ongoing erosion and downcutting in the hinterland caused sediment discharge to the basin to increase and the ratio between the rates of crustal accretion and surface erosion to decrease. The result was a progradation of the dispersal systems, and a shift of the topographic axis towards the distal basin border. The second stage started at ca. 20 Ma at a time when palaeoclimate became more continental, and when the crystalline core became exposed in the orogen. The effect was a decrease in the erosional efficiency of the Swiss Alps and hence a reduction of sediment discharge to the Molasse Basin. We propose that this decrease in sediment flux caused the Burdigalian transgression of the OMM. We also speculate that this reduction of surface erosion initiated the modification of Alpine deformation from vertically-to mainly horizontally directed extrusion (deformation of the Southern Alps, and the Jura Mountains some Ma later). The third stage in the geodynamic development was initiated at the Miocene/Pliocene boundary. At that time, palaeoclimate possibly became wetter, which, in turn, caused surface erosion to increase relative to crustal accretion. This change caused the Alps to enter a destructive stage and the locus of active deformation to shift towards to the orogenic core. It also resulted in a net unloading of the orogen and thus in a flexural rebound of the foreland plate.We conclude that the present chronological resolution is sufficient to propose possible feedback mechanisms between environmental effects and lithospheric processes. Further progress will result from a down-scaling in research. Specifically, we anticipate that climate-driven changes in sediment flux altered the channel geometries of USM and OSM deposits, the pattern of sediment transport and thus the stacking arrangement of architectural elements. This issue has not been sufficiently explored and awaits further detailed quantitative studies.

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Section: The Alpine Drainage Networkmentioning

confidence: 99%

Possible environmental effects on the evolution of the Alps-Molasse Basin system

2007

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“…Exposing classical fold-and-thrust architecture [Laubscher, 1985[Laubscher, , ' 1990Roeder, 1989Roeder, , 1992SctuSnborn, 1992] including thrust basement units, the Southern Alps lack Alpine metamorphism except for the spatially restricted area in the north deformed under anchimetamorphic to epimetamorphic conditions (see discussion by Schumacher et al [1997]) presumably during Late Cretaceous [Bersezio and Fornaciari;Bernoulli and Winkler, 1990]. South Alpine deformation is not coeval for the western and the eastern part [Doglioni and Bosellini, 1987;Massari, 1990].…”

Section: Settingmentioning

confidence: 99%

Balancing cross sections with kinematic constraints: The Dolomites (northern Italy)

Schönborn¹

1999

Tectonics

103

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Abstract. Balancing of structural cross sections is often hindered by a limited database or tectonic complications. In such cases, kinematic constraints may help to better constrain the construction of a cross section and its extrapolation to depth. The kinematic implications of a known structure (generally at the surface) have to be considered for the unknown structure and for the internal consistency of a cross section. A key point is the quantification of shortening of the known structure. The extrapolation of this parameter allows balancing in an approximate way, emphasizing major structures while minor structures are either neglected or treated in a simplified way. With this approach a quick overview can be achieved on how much leeway for interpretation exists, • critical points for testing various working hypotheses become more evident, and the trial-and-error effort during the construction of a balanced section is considerably shortened. Still the implications the observed structures have on the deeper crustal levels can be assessed. This concept is applied to a section across the Italian Dolomites, a brittle fold-and-thrust belt lacking reflection seismic data so far and thus with a poorly known deep structure. Still active south vergent Alpine thrusting is oriented approximately perpendicular to previous Dinaric thrusting. The ramp flat style is dominant due to rheological constrasts within the stratigraphic sequence. Thanks to kinematic balancing based on surface data, three Alpine thrust systems could be identified, each defining a thrust sheet with its particular basement unit and its sedimentary part. Superposition of the two more external basement units led to the presently observed high elevation of the Triassic sequence in the Dolomites. Shortening since late Miocene times amounts to more than 50 km. Retrodeformation of Alpine thrusting is a key for better understanding the previous Dinaric structures and kinematics.

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“…As to the timing of tectonic events, a major provenance shift started at Langhian times, consistent with a climax in tectonic activity (early "Lombardic phase" of Schumacher et al 1996). Continuing convergence would have accreted the foredeep turbidites themselves to the frontal, buried thrust of the South-alpine range, mostly during the Tortonian (late "Lombardic phase" of Schumacher et al 1996).…”

Section: Discussionmentioning

confidence: 99%

“…Thus, a largely Tortonian age (late "Lombardic phase" of Schumacher et al 1996) seems to best fit the time constraints.…”

Section: Discussionmentioning

confidence: 99%

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The Lombardian Gonfolite Group in central Brianza (Como and Milano Provinces, Italy): Calcareous nannofossil biostratigraphy and sedimentary record of neo-alpine tectonics

Sciunnach

Tremolada

2004

Eclogae geol. Helv.

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The sedimentary succession cropping out in central Brianza, in an area embracing the territories of Besana Brianza, Briosco (Milan Province), Arosio and Inverigo (Como Province), is properly ascribed to the Lombardian Gonfolite Group. It consists of prevailing turbidite sandstones and marls, with conglomerate beds occurring in the central part of the section.A precise biostratigraphic dating of the succession was obtained through the analysis of calcareous nannofossils. The occurrence of reliable index species allowed us to recognise the NN3 to NN6 nannoplankton zones (Burdigalian to Serravallian). Since in the type-areas between Varese and Como the youngest dated units of the Gonfolite Group are Burdigalian in age, the studied succession documents a more recent part in the history of the south-alpine foredeep, that might have been recorded in outcrop elsewhere in Lombardy only by the ill-dated Gurone Sandstone and Bizzozzero Mudstone (Varese area). The deformation of the studied succession seemingly requires a single event of tectonic buckling, that is reliably constrained as late Serravallian to Tortonian (late "Lombardic Phase").Provenance signals point to roughly contemporaneous exhumation of the Pennidic nappes and active stacking of thrust sheets in the uprising Southern Alps. This phase of tectonic activity took place around the Langhian/Serravallian boundary (early "Lombardic Phase"). RIASSUNTOLa successione sedimentaria affiorante in un piccolo settore della Brianza centrale, che abbraccia il territorio dei Comuni di Besana Brianza, Briosco (Provincia di Milano), Arosio and Inverigo (Provincia di Como), mostra una chiara appartenenza al Gruppo della Gonfolite Lombarda. Essa è rappresentata da prevalenti arenarie e marne in facies torbiditica, con strati conglomeratici limitati alla parte centrale della colonna stratigrafica.Una datazione biostratigrafica precisa della successione è stata possibile grazie all'analisi dei nannofossili calcarei. La presenza di specie-indice affidabili ci ha consentito di riconoscere le zone a nannoplancton dalla NN3 alla NN6 (Burdigaliano-Serravalliano). Poiché nelle località-tipo tra Varese e Como le unità più recenti riconosciute all'interno della Gonfolite sono burdigaliane, la successione studiata documenta uno stadio più recente nell'evoluzione dell'avanfossa sudalpina, che potrebbe essere stata registrata in altri affioramenti in Lombardia solo dalle Arenarie di Gurone e dalle Peliti di Bizzozzero (Varese), unità la cui datazione rimane tuttavia poco precisa. La deformazione della successione in esame sembra compatibile con un singolo evento di piegamento, che si può ricondurre in modo convincente al Serravalliano superiore-Tortoniano (tarda "Fase Lombarda").I segnali di provenienza indicano una sostanziale contemporaneità tra l'esumazione delle falde Pennidiche e l'impilamento attivo dei sovrascorrimenti nelle Alpi Meridionali in via di sollevamento. Questa fase di attività tettonica ebbe luogo attorno al limite Langhiano/Serravalliano ("Fase Lombarda" iniziale).

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Rifting and collision in the Southern Alps

Cited by 34 publications

References 0 publications

Possible environmental effects on the evolution of the Alps-Molasse Basin system

Possible environmental effects on the evolution of the Alps-Molasse Basin system

Balancing cross sections with kinematic constraints: The Dolomites (northern Italy)

The Lombardian Gonfolite Group in central Brianza (Como and Milano Provinces, Italy): Calcareous nannofossil biostratigraphy and sedimentary record of neo-alpine tectonics

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