PALAEO-TETHYAN MARGIN OF GONDWANA-LAND WAS AN EXTENSIONAL ARC

After the Hercynian collision in Europe, the activity of the Protogonos arc ceased, but it continued its activity farther east, east of present-day Bulgaria. In Turkey, during the Permian, the entire area of the country was affected by extensional tectonics leading to the generation of supra-subduction zone ensimatic arcs, pre-arc-spreading ophiolites and rifts. This was also the time when the Sanandaj-Sirjan arc began rifting from the Arabian hinterland; in Oman, medial Permian already had an oceanic basin that connected via the Sistan Ocean in eastern Iran with the Wašer Ocean between the Farah and the Helmand blocks in Afghanistan. The Wašer Ocean continued into the Rushan-Pshart Ocean in the Middle Pamirs that also rifted in the Permian. Farther east in Tibet, the Banggong Co-Nu Jiang ocean was a continuation of the Rushan-Pshart Ocean. Rifting in Thailand had already commenced during the Tournaisian. India was in extension already during the Carboniferous creating the famous Gondwana rifts and rifting was going on in the Himalaya just after the Permian. In Syria, the Palmyran Trough began rifting during the latest Carboniferous and was in full extension during the Permian. All around the eastern Mediterranean there is evidence for Permian rifting that continued into the Triassic. Where observations are available, the ocean basins associated with the rifting episode described above had crusts giving a supra-subduction zone signature. Where structural evidence is reported, the deformation along the Palaeo-Tethyan suture on the Gondwana-Land side was north-vergent. It seems as if the entire northern Gondwana-Land margin resembled the present-day western Pacific, fooling many into thinking that it was an Atlantic-type margin because of the extensive rifting events and the apparent paucity of evidence for convergence and arc activity. In places, as in northern Turkey, the extension had migrated into the Palaeo-Tethys leaving behind only rifted margins.