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In the central Iranian Esfahan-Sirjan and Qom basins sedimentation of the Oligo-/Miocene Qom Formation took place on extensive mixed carbonate-siliciclastic ramps. During this time, both basins were positioned at the Eurasian margin of the Tethyan Seaway, which connected the western and eastern regions of the Tethys Ocean at least until the late Burdigalian. During the so-called Terminal Tethyan Event the Tethyan Seaway was then closed due to the collision of the African/Arabian and Iranian/Eurasian plates. Facies analysis of the sedimentary record of both basins indicates paleoenvironments ranging from terrestrial to open marine settings, including mangrove, restricted inner shelf lagoon, seagrass meadow, reefal, and deeper offshore environments. Recognition of eight depositional sequences and elaboration of an integrated biostratigraphic framework (calcareous nannoplankton, planktic and larger benthic foraminifers, gastropods, and pectinids) allow us to construct a basin-spanning stratigraphy. The assignment of the recognized sea-level lowstands to the Ru 3 to Bur 3 lowstands of the global sea-level curve enables a comparison with time-equivalent sections from the Zagros Basin, which was part of the African/Arabian Plate on the opposing southern margin of the Tethyan Seaway. The so calibrated sections display restrictions of the Tethyan Seaway and interruption of the south Iranian gateways between the Qom Basin and the Proto-Indopacific in relation to ongoing plate collision during the early Burdigalian.

International audienceThe Tarim Basin in western China formed the easternmost margin of a shallow epicontinental seathat extended across Eurasia and was well connected to the western Tethys during the Paleogene.Climate modelling studies suggest that the westward retreat of this sea from Central Asia may havebeen as important as the Tibetan Plateau uplift in forcing aridification and monsoon intensificationin the Asian continental interior due to the redistribution of the land-sea thermal contrast. However,testing of this hypothesis is hindered by poor constraints on the timing and precise palaeogeographicdynamics of the retreat. Here, we present an improved integrated bio- and magnetostratigraphicchronological framework of the previously studied marine to continental transition in the southwestTarim Basin along the Pamir and West Kunlun Shan, allowing us to better constrain its timing,cause and palaeoenvironmental impact. The sea retreat is assigned a latest Lutetian–earliest Bartonianage (ca. 41 Ma; correlation of the last marine sediments to calcareous nannofossil Zone CP14and correlation of the first continental red beds to the base of magnetochron C18r). Higher up in thecontinental deposits, a major hiatus includes the Eocene–Oligocene transition (ca. 34 Ma). This suggeststhe Tarim Basin was hydrologically connected to the Tethyan marine Realm until at least theearliest Oligocene and had not yet been closed by uplift of the Pamir–Kunlun orogenic system. Thewestward sea retreat at ca. 41 Ma and the disconformity at the Eocene–Oligocene transition are bothtime-equivalent with reported Asian aridification steps, suggesting that, consistent with climatemodelling results, the sea acted as an important moisture source for the Asian continental interior

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