Triassic in Iran

Except of the Nakhlak and Aghdarband regions, Lower and Middle Triassic strata in Iran consist almost exclusively of carbonate rocks built on vast platforms along the shelves of the Paleo- and Neotethys. The depositional environments varied from shallow shelf sea to lagoonal and near-shore tidal flats, becoming even evaporitic towards the coastal regions of the Persian Gulf. During the early Late Triassic the formerly dominating platform carbonates were strongly reduced, being restricted for the rest of the Early Mesozoic to Southwest Iran which remained on the northern passive margin of Gondwana (later Arabian Plate). On the Iran Plate otherwise, as a result of the closure of the Paleotethys and the continent-continent collision with the southern active margin of Eurasia (Turan Plate), there was a change to thick siliciclastic and molassic sediments with only minor carbonate content durig the Upper Triassic and Lower Jurassic. Geographically restricted and completely different sequences of thick volcanoclastic and basinal Triassic sediments are known from Nakhlak in Central and from Aghdarband in Northeast Iran, both interpreted as remanents of the northern Paleotethys margin (Turan Plate).