EVOLUTION OF CENOZOIC TETHYS AND ITS ENVIRONMENTAL EFFECTS ON INLAND DROUGHT

Abstract

The evolution and extinction of the Tethys was a major global geological event in Cenogoic and is one of the decisive influences on the formation and evolution of the arid environment in Eurasia,especially Asia.This paper briefly made a review of the progress of the international Tethys programs,combined with our researches.The evolution of the Tethys can be simply divided into three stages,the Tethys,Paratethys and Tethys extinction.In Late Mesozoic to early Cenozoic,most parts of Europe,Western and Central Asia region and the Southern Tibetan Plateau joined together and formed an inland sea named the Tethys which connected with the Atlantic Ocean to the west and with the Ceno-Tethys to the east.About 34 Ma ago,The Tethys connected with the Atlantic,Indian and Arctic oceans and the most eastern part of it extended into the Tarim area.With the collision of Indian and Eurasian plates,the Tethys retreated from the Southern Tibetan Plateau and the Tarim area.Then the Tethys was separated into the Mediterranean in the south and Paratethys in the north about 34 Ma ago.Under the joint effect of global sea level change,tectonic uplift,surface erosion and sediment filling,the Parathtys experienced a series of eustatic,and area changes and closing and opening of seawater channels,The greatest impact on the environment came from the channel closing-opening of the Paratethys,the ancient Mediterranean and the Indian Ocean.Since Oligocene there occurred at least four times of close-open cycles.The evolution and extinction of the Tethys especially since the withdraw of Tethys from the Tarim region 34 Ma,the rapid shrinkage of Tethys about 20 Ma and the closing of water channels with other oceans around 7-8 Ma may be the main factors leading to the drying up in Asian inland area.