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Projects / Fundamental Research / Regional Studies / Triassic Geodynamics, Tethys, Central Europe, Atlantic ... / Details 2
       
 

Triassic Geodynamic Development of the Tethyan, Central European and Atlantic Domains

Details 2
  
       
       
  Latest Triassic to earliest Jurassic (Rhaetian to Sinemurian)
With the accretion of the Cimmerian terranes to the East European platform, Pangea had reached its most complete configuration in the Norian to Rhaetian. Neotethys rifting and sea-floor spreading extended further to the west. In combination with sinistral transcurrent movements along the North Africa Line marine basins in the future Central Atlantic and the Tethys domain join for the first time to form an E-W trending seaway (Thierry 2000, Stampfli et al. 2001b). Cimmerian compression in the southeastern Central European basins and associated reduced subsidence and inversion continued into the Hettangian.
  
       
  Plate-tectonic reconstruction for the Early Jurassic, Hettangian, 200 Ma
Modified from Stampfli G.M., Borel G.D. (2004), see external link
    
       
  Plate Dynamics and Intra-Plate Forces
Since the Hercynian orogeny and the formation of Pangea in the Carboniferous mantle convection had slowed down (Ziegler et al. 2001). Possible reasons include:
(1) the insulating effect of the Pangean mega-continent on the mantle, and
(2) the accumulation of subducted cool Rheic and Paleotethyan oceanic lithosphere near the core mantle boudary, which resulted in cooling of the outer core and changed its convection.

In the late Permian to Triassic a bi-polar deep mantle convection system with upwelling cells benath Gondwana and the western Panthalassa was gradually established. The upwelling convection cell below Gondwana induced radial outflow of the asthenosphere and, by combined lithospheric drag and plate boudnary forces, the progressive breakup of Pangea. Mantle plumes started to develop under the future plate boundaries and progressively weakened the lithosphere during the early Mesozoic to Cenozoic.

However, the current models propose that interfering plate boundary forces and mantle drag forces, not mantle plume activity, were the main cause for the breakup of Pangea, which initiated in the Triassic. The change in mantle convection patterns, the interaction of the propagating Neotethys and central/northern Atlantic rift systems controlled the breakup of Pangea and the tensional regime of the central-western European domain during the Triassic. The Carnian Cimmerian collision was probably driven by combined ridge-push forces from the early Neotethyan spreading axis, slab-pull forces from the subducting Paleotethyan oceanic lithosphere and mantle drag forces.
 
Magmatic and Volcanic Events
In the Triassic, only subordinate volcanic and magmatic activity occured in the Central and Western European rift basins. Rift-related volcanism is restricted to the Middle-Late Triassic of the Central Graben (North Denmark, Ziegler et al. 1988). The subduction of the Paleotethys triggered early to late Triassic magmatic-volcanic activity which extends from Turkey to Northern Italy. In the southern Alps, volcanics and few intrusives feature a clear calc-alkaline, shoshonitic trend and spatial zonation between rhyolite-andesites and basalts (Castellarin et al. 1988). Geochecmical and isotope compositions possibly reflect an interaction of magmas from the upper mantle and lowermost crust, which may be explained by the break-off of the Paleo-Tethys subduction slab.

In any case, the calc-alkaline, shoshonitic trend, the spatial distribution and the Ladinian to Carnian age of volcaniclastics in the Southern Alps excludes a rift-related origin, e.g. from rifting of the future Meliata ocean, which took place already in the Permian. In the Pelagonian Zone, geochemical trends indicate an intra-plate origin (Stampfli et al. 2001b). Paleotethys subduction- and Cimmerian collision-related volcanic activity was widespread at the at the southern Eurasian margin east of the Moesian platform.

The conspicious low level of volcanic/magmatic activity in epicontinental Central Europe and the northwestern Tethys is in clear contrast to the the intensive magmatic/volcanic activity of Latest Triassic to earliest Jurassic age in the Central-North Atlantic and Bay of Biskay wrench and rift system (Deckart et al. 1997, Olsen 1997). The central Atlantic flood basalts form one of the largest magmatic provinces in Phanerozoic history. The strongly reduced volcanic/magmatic activity in the Triassic of Central and Western Europe indicate, that rifting occurred in response to crustal extension and slowly developing asthenospheric convection systems rather than by the development of multiple hot spots or mantle plumes.

Geodynamic Development and Sea-Level Changes
On the large scale, Triassic Central European basins considerably overstepped the Permian basin margins. Combined with changes in far-field intra-plate forces (see above), resulting subsidence/uplift trends, changes in sediment input/production eustatic sea-level changes controlled the creation and destruction of accommodation space and its infill, e.g. major transgressive/regressive trends and unconformities. In the case of the epicontinental Central European basin, plate-tecontic reconfigurations and fa-fiedl intra-plate stresses also controlled the opening and closure of seaways to the Neotethys, e.g. during Upper Muschelkalk times (long-term sea-level highstand, pre-Cimmerian collision, open East Carpathian and Burgundy seaways) and Keuper times (long-term sea-level fall, Cimmerian collision the eastern segment of the southern Eurasian margin, closed East Carpathian and Moravian seaways). A conspicious feature of the Triassic geodynamic and paleogeographic development is the lack of marine connections between the Arctic and Paleo-/Neotethys basins across the western and central European domain (cf. late Permian, Jurassic). Any connections were blocked by regional updoming in the Faroer-Shetland and North-Sea area which led to the rapidly subsiding Central/Viking Graben with Triassic continental deposits of more than 4000 m thickness.

Long-term, 2nd order  (3-10 My) eustatic sea-level rises potentially develop in response to (Pitman 1978, discussion in Heller et al. 1996):
(1) by the swelling/shrinking of mid-ocean ridges (MOR), increased volcanic output and sea-floor spreading rates which reduces the volume of oceanic basins;
(2) large-scale basalt eruptions into ocean basins, the controversial “megaplumes”, related to triggering events in the D” region of the core-mantel boundary;
(3) by the onset of supercontinent breakup, destruction of old, dense oceanic lithosphere and the creation of young less dense lithosphere.

An all-time Phanerozoic sea-level lowstand occurred in the late Permian (Tatarian). During the Induan to early Anisian and the late Ladinian to Carnian two long-term eustatic sea-level rises for together approx. 100-120 m took place. They were followed by an intemittent eustatic sea-level fall for approx. 70-80 m during the Norian to Hettangian and a eustatic rise for 50 m until the early Pliensbachian.

The long-term Late Permian to early Jurassic eustatic sea-level rise may have been controlled by:
(1) the initial breakup of Pangea since the Triassic;
(2) the subduction of old, post-Late Silurian oceanic lithosphere of the Paleotethys until the Late Triassic;
(3) the creation of young oceanic lithosphere of the Neotethys since the early Permian. No quantitative approximations of sea-floor spreading rates are possible.

The timing, amplitude and origin of  short-term Triassic transgressive/regressive trends and 3rd order (1-3 My) eustatic sea-level changes are a matter of debate. Anisian, Late Ladinian and Rhaetian sequences appear to be correlative within current biostratigraphic uncertainties between the western Neotethys, epicontinental European basins and the Arctic (Rüffer & Zühlke 1995, Hardenbol et al. 1998). Time constraints in the Induan-Olenekian and late Carnian-Norian are insufficent for high-resolution sequence stratigraphic correlations. The majority of currently available high-resolution accommodation data come from a single plate, the Eurasian margin and intra-plate domains, including the Central European Basin. It is therefore questionable, if transgressive/regressive trends and 3rd order accommodation sequences reflect true eustatic sea-level changes, or if they were primarily influenced to controlled by geodynamic changes, e.g. in far-field intra-Eurasian plate stresses.
  
 
   
  Publications
cf. Scheck-Wenderoth, M., Krzywiec, P., Zühlke, R., Maystrenko, Y. and Froitzheim, N., 2008, Permian to Cretaceous tectonics, in: T. McCann, ed., The Geology of Central Europe: Mesozoic and Cenozoic, Volume 2, Geol. Soc. London, p. 999-1030.		  
 
 
  References
Deckart, K., Feraud, G. & Bertrand, H. 1997. Age of Jurassic continental tholeiites of French Guyana, Surinam and Guinea: implications for the initial opening of the Central Atlantic Ocean. Earth and Planetary Science Letters, 150, 205-220.
Dercourt, J., Gaetani, M., Vrielynck, B., Barrier, E., Biju-Duval, B., Brunet, M.F., Cadet, J.P., Crasquin, S. &  Sandulescu, M. 2000. Atlas Peri-Tethys, palaeogeographical maps. Commission de la Carte Géologique du Monde/Commission for the Geologic Map of the World, Paris, Explanatory Notes, 269 p.
Fisher, M.J. & Mudge, D.C. 1998. Triassic. In: Glennie, K.W. (ed) Petroleum geology of the North Sea. Blackwell Scientific Publications, Oxford, 212-244.
Gaetani, M. 2000a. Olenekian (245-243 Ma). In: Dercourt, J., Gaetani, M., Vrielynck, E., Barrier, B., Biju-Duval, B., Brunet, M.F. Cadet, J.P., Crasquin, S. & Sandulescu, M. (eds), Atlas Peri-Tethys, paleogeographical maps. Commission de la Carte Géologique du Monde/Commission for the Geologic Map of the World, Paris, Explanatory Notes, 27-32.
Gaetani, M. 2000b. Early Ladinian (238-235 Ma). In: Dercourt, J., Gaetani, M., Vrielynck, E., Barrier, B., Biju-Duval, B., Brunet, M.F. Cadet, J.P., Crasquin, S. & Sandulescu, M. (eds), Atlas Peri-Tethys, paleogeographical maps. Commission de la Carte Géologique du Monde/Commission for the Geologic Map of the World, Paris, Explanatory Notes, 33-40.
Gaetani, M. 2000c. Late Norian (215-212 Ma). In: Dercourt, J., Gaetani, M., Vrielynck, E., Barrier, B., Biju-Duval, B., Brunet, M.F. Cadet, J.P., Crasquin, S. & Sandulescu, M. (eds), Atlas Peri-Tethys, paleogeographical maps. Commission de la Carte Géologique du Monde/Commission for the Geologic Map of the World, Paris, Explanatory Notes, 41-48.
Heller, P.L. Anderson, D.L. & Angevine, C.L. 1996. Is the middle Cretaceous pulso of rapid sea-floor spreading real or necessary. Geology, 24, 491-494.
Olivet, J.-L. 1996. La cinématique de la plaque Iberique. Bulletin des Centres de Rechérches Éxploration-Production Elf Aquitaine, 20/1, 131-195.
Olsen, P.E. 1997. Stratigraphic record of th early mesozoic breakup of Pangea in the Laurasia-Gondwana rift system. Annual Review of Earth and Planetary Sciences, 25, 337-401.
Pitman, W.C. 1978. Relationship between eustasy and stratigraphic sequences of passive margins. Bulletin of the Geological Society of America, 89, 1389-1403.
Stampfli, G.M. & Borel, G.D. 2004. The TRANSMED transect in spave and time: constraints on the paleotectonic evolution of the Mediterranean domain. In: Cavazza, W., Roure, F.M., Spakman, W., Stampfli, G.M. and Ziegler, P.A. (eds), The TRANSMED atlas, the Mediterranean region from crust to mantle. Springer/Heidelberg, p. 53-80.
Stampfli, G.M., Borel, G.D., Cavazza, W., Mosar, J. & Ziegler, P.A. 2001a. The paleotectonic atlas of the Peri-Tethyan domain. CD-ROM, European Geophysical Society.
Stampfli, G.M., Mosar, J., Favre, P., Pillevuit, A. & Vannay, J.-C. 2001b. Permo-Mesozoic evolution of the western tethys realm: the Neo-Tethys East Mediterranean basin connection. In: Ziegler, P.A., Cavazza, W., Robertson, A.H.F. and Crasquin-Soleau, S. (eds), Peri-Tethys Memoir 6: Peri-Tethyan Rift/wrench basins and passive margins. Mémoires du Muséum National D´Histoire Naturelle, 186, 51-108.
Thierry, J. 2000. Late Sinemutrian (193-191 Ma). In: Dercourt, J., Gaetani, M., Vrielynck, E., Barrier, B., Biju-Duval, B., Brunet, M.F. Cadet, J.P., Crasquin, S. & Sandulescu, M. (eds), Atlas Peri-Tethys, paleogeographical maps. Commission de la Carte Géologique du Monde/Commission for the Geologic Map of the World, Paris, Explanatory Notes, 49-60.
Ziegler, P.A. 1988. Evolution of the Arctic-North Atlantic and the western Tethys. American Association of Petroleum Geologists, Memoir, 43, 198 p.
Ziegler, P.A., Cloetingh, S., Guiraud, R. & Stampfli, G.M. 2001. Peri-tethyan platforms: constraints on dynamics of rifting and basin inversion. In: Ziegler, P.A., Cavazza, W., Robertson, A.H.F. and Crasquin-Soleau, S. (eds), Peri-Tethys Memoir 6: Peri-Tethyan Rift/wrench basins and passive margins. Mémoires du Muséum National D´Histoire Naturelle, 186, 9-49.
  
     
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