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Late Eocene artiodactyl and creodont tracks have been reported from the Jianchuan Basin, southeastern Tibetan Plateau, representing the first and the oldest reported mammal tracks in Yunnan Province, China. Sedimentary facies analysis indicates that tracks from the upper Baoxiangsi Formation and the lower Shuanghe Formation occurred in lake shore and flood plain environments, respectively. Based on the morphological analysis, the artiodactyl tracks from the Baoxiangsi Formation are attributed to Anoplotheriipus zeuctus. Combined with fossil records and morphological characteristics, the artiodactyl and creodont tracks were probably produced by entelodonts and mesonychids, respectively. The superimposition of artiodactyl tracks with varying sizes indicates coexistence of juveniles and adults as well as their gregarious behaviour. The co-occurrence of artiodactyl tracks and creodont tracks suggests the predator–prey relationship and ecological chain during the late Eocene. The presence of mammal tracks in the Jianchuan Basin coincides with the climate change from dry to wet in the late Eocene, implying the climatic and ecological effects of the uplift of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

East Asia experienced a climatic transition from a zonal pattern (climate zones defined by latitude) to a monsoon-dominated pattern during the Cenozoic. However, hitherto little consideration has been paid to the atmospheric circulation of the planetary wind system that prevailed during the early uplift of the Tibetan Plateau, due to the lack of reliable proxies. Here, we conduct a study on the eolian successions from the Eocene Baoxiangsi Formation in the Jianchuan Basin, southeastern Tibetan Plateau to reconstruct regional atmospheric circulation and paleoclimate. Two facies associations are recognized in the eolian deposits of the Baoxiangsi Formation: a dominant eolian dune association and a subordinate interdune association. Eolian dune deposits are characterized by large-scale cross-stratified sets of strata composed internally of packages of grainflow, wind-ripple strata and pinstripe lamination. These packages of laminae and cross-stratified eolian dune sets are bounded internally by superimposition and reactivation surfaces and interdune surfaces, respectively. Interdune deposits are uncommon and composed dominantly of subcritical climbing translatent strata to form sets of strata and these are themselves bounded by interdune surfaces to form cosets of strata. The association of dominant eolian dune deposits, widely distributed interdune surfaces of great lateral extent (> 450 m) and that climb at a shallow but positive angle (< 1°) is consistent with the climbing dry eolian system. The commonly occurring superimposition surfaces indicate the presence of compound dunes (megadunes, draas). Based on the analysis of 715 dip–azimuth readings of foresets of eolian cross-beds, we reconstruct the prevailing wind directions: the paleowind in the northern basin flowed toward the northeast; in the southern basin it flowed toward the southwest. This wind regime indicates that the Jianchuan Basin was located at the zonal boundary between the westerlies and the trade winds, and the construction of the dry eolian system was controlled by the subtropical high-pressure belt during the middle–late Eocene. Following the accumulation of the dry eolian system, a monsoon climate regime gradually established itself and prevailed in the Yunnan Province; this expanded northward over time. This was closely related to the uplift of the central Tibetan Plateau and the retreat of the Paratethys ocean in the late Eocene. • Dry eolian system was identified in the Eocene Baoxiangsi Formation. • The Jianchuan Basin was located between the westerlies and trade winds. • The subtropical high-pressure belt controlled the eolian system's construction. • A monsoon climate gradually established following the dry eolian system. • Paleogeography plays an important role in the climatic transition. [ABSTRACT FROM AUTHOR]