The Variscides, Uralides and Pangea assembly: Insights from plate reconstructions and numerical modelling
|Location||International Geological Congress,oslo 2008|
|Author||Torsvik, Trond۱; Cocks, L. Robin M.۲; Buiter, Susanne J.H.۱|
|Holding Date||08 October 2008|
During the Palaeozoic the geography of the Earth evolved greatly. At the beginning of this period there was only one superterrane, Gondwana, undoubtedly the largest terrane during the Lower Palaeozoic. However, surrounding it were numerous small terranes, many of which originally formed part of the Gondwanan superterrane, including Avalonia, Perunica and Armorica. Avalonia separated from Gondwana during the Early Ordovician and subsequently collided with Baltica (Late Ordovician) and Laurentia to form Laurussia during Silurian times. From the Late Carboniferous onwards Gondwana collided with Laurussia and intervening terranes, and the Variscan belt of Europe became part of an approximately 8000 km long collisional belt. At the same time, the Kazakhstan terranes collided along the eastern margin of Baltica forming the Uralides. By the end of the Permian, most terranes coalesced to form Pangea, the largest superterrane in Phanerozoic history. However, Siberia was not fully joined to Pangea in the Late Palaeozoic.
We consider that the so-called Arctic Uralides, which have been thought to include Novaya Zemlya and the Taimyr margin of Siberia, were not part of the Uralides proper, but instead represent a younger Mesozoic deformation event. During the Late Triassic-Early Jurassic, the Barents Sea and North Siberian margins are dominated by uplift, folding and thrusting that clearly post-dated the Late Palaeozoic Uralian fold-belt and the Late Permian-Early Triassic Siberian traps. The Taimyr margin is a Late Triassic-Early Jurassic fold-and-thrust belt that must be the result of the final convergence between Siberia and the Kara plate. At the same time, Novaya Zemlya experienced a westward movement into the East Barents Sea, crustal deformation took place in Pay-Khoy, and gentle Late Triassic-Jurassic inversion occurred within the West Siberian Basins. All this points to the fact that the Siberian plate must have undergone Late Triassic-Early Jurassic convergence with Baltica/Barents Sea/Kara. The fold-and-thrust belt associated with this convergence (the Byrranga Fold-belt) probably developed simultaneously with the Lomonosov fold-belt and with strike-slip faulting along the West Barents margin.