Stepwise closure of the Tethyan Seaway and its impact on the Earth's multi-sphere interactions during the Cenozoic
The Cenozoic era is an important period marked by significant changes in various Earth's spheres(lithosphere,hydrosphere,atmosphere,and biosphere),which include the break-up of the Gondwana Supercontinent,the opening and closure of oceanic straits,the reorganization of atmospheric circulation,the climate transition from greenhouse to icehouse,and the rapid evolution of animals and plants.Therefore,it is a key geological period for studying the coupling between the different Earth's spheres.This review takes the Tethyan Seaway as an example to explain the timing and process of the closure of the Tethyan Seaway and its main impact and feedback on the biosphere,ocean circulation,and atmosphere from the perspective of Earth System Science.Based on multidisciplinary research into different tectonic domains of the Iranian Plateau,we reveal that the closure of the Tethyan Seaway,which separates the Arabian and Eurasian Plates,has undergone a stepwise evolution.From the Oligocene to the early Miocene(34-19 Ma),the Tethyan Seaway was well connected with the Indian Ocean,the proto-Mediterranean,and the Atlantic,indicated by the mutual high commonality of marine gastropods between them.During the late early Miocene(19-17 Ma),when the Tethyan Strait was partially open,both the Nd isotopes of seawater and the commonality of marine gastropods demonstrate that the passage capacity of seawater decreased by 90％.During the Mid-Miocene Climate Optimum(MMCO)(17-15 Ma),despite rising sea levels caused by global marine transgression,the increased temperature during the MMCO enhanced seawater evaporation,resulting in an environment dominated by coastal lagoons and only occasionally replaced by shallow seas.During the Middle Miocene Climatic Transition(MMCT)(15-12.8 Ma),the Tethyan Seaway evolved into a continental environment but interrupted by short-term periodic marine transgressions,which had a quasi-period of 100-ka between 15 and 12.8 Ma.Such a cycle is likely to be related to periodic ice sheet expansion/melting and thus to the sea-level fluctuations caused by changes in solar radiation driven by the Earth's orbital eccentricity.After 12.8 Ma(the end of the MMCT),the Tethyan Seaway was permanently closed.The gradual closure of the Tethyan Seaway has had a significant impact on the biosphere.Marine invertebrates of gastropod and echinoderm tended to migrate from the proto-Mediterranean to the Indian Ocean and the Western Pacific in response to that gradual closure.For mammals,although there were sporadic migrations between Africa-Arabia and Eurasia in the early Miocene,the large-scale two-way migrations of mammals mainly occurred after 18-17 Ma,because the Tethyan Seaway was dominated by coastal lagoons,which were no longer geographical barrier for mammals.Proboscises,hyraxes and tubelodons in Africa migrated to Eurasia,whereas Eurasian carnivores,rhinoceros,clawed mammals,pigs,ruminants,lagomorphs and some rodents migrated to Africa.The closure of the Tethyan Seaway also had an important impact on ocean circulation,which reduced the injection of warm,salty water from the low-latitude Neotethys Sea into the Atlantic and the southern Indian Ocean,and thereby reduced,to some extent,the meridional heat transfer from low latitudes to the high-latitudes in the southern hemisphere resulting in the expansion of the East Antarctic ice sheet and the cooling of Antarctica.The retreat of the Neotethys Sea and the permanent closure of the Tethyan Seaway at～13 Ma also profoundly affected atmospheric circulations,manifested by the strengthening of the upwelling of cold seawater along the Arabian coast and the much enhanced Southwest South Asian summer monsoon.
Arabia-Eurasia convergenceclosure of the Tethyan Seawayland-sea distributioninteractions of Earth's spheresenvironmental effects
万方数据
维普
