Tectonic forcing to global cooling and aridification at the Eocene-Oligocene transition in the Iranian plateau

The transition from the extreme global warmth of the early Eocene 'greenhouse' climate to the present glaciated state is one of the most fundamental reorganizations of global climate known in the geologic record. The Middle to Late Eocene interval between 49 and 33 Ma was a globally important transition period from greenhouse to initial icehouse conditions. The Middle Eocene Climatic Optimum (MECO, -40 Ma) was a transient period of global warming that interrupted the secular Cenozoic cooling trend. The Eocene-Oligocene transition (ca. 33.5 Ma) marks the first major decline in Cenozoic global temperatures and the initiation of Antarctic glaciation. However, a major challenge comes from recent investigations of plateau uplift processes and resulting environmental changes. The tectonic evolution of the Iranian plateau offers an explanation for global cooling during the Cenozoic, as a result of the gradual closure of the Neotethyan Sea, which led to the disappearance of the Indian Ocean-Mediterranean Sea connection, mountain building, extensional collapse, rifting, and flare-up type volcanism, erosion, and exhumation. Increasing topography by shortening as a result of subduction of the distal Arabian margin beneath the Iranian Plateau and contemporaneous exhumation of a metamorphic core complex between 49 and 33 Myr ago led to aridification of Iranian plateau and to the some elevation of the plateau. This rise in elevation is roughly contemporaneous with the emplacement of flare-up-type volcanics in the Urumiyeh-Dokhtar zone and over large portions of Central Iran. Peak volcanism occurred during the transient warming event MECO. New findings suggest that this global transition is linked to significant aridification and cooling in southwest Asia, and thus support the idea that global cooling is associated with the Eocene-Oligocene transition. The good match of tectonic deformation and uplift of the Iranian Plateau with climatic changes is significant.