Uplift-driven climatic aridity during the middle Miocene: A case study of the Janggalsay section, southeast Tarim Basin

Abstract: Numerous studies suggest an intensification of climatic aridity during the middle Miocene (16-12 Ma) based on oxygen isotopes and pollen records in the foreland basins of the Central Asia, eolian deposits in China’s loess plateau and eolian flux from the northern Pacific Ocean. However, controversies remain existent as to the driving mechanisms that have dominated the intensifying aridity, which include global cooling, the rapid uplift of the central Asia, the attainment of a threshold elevation in southern Tibetan Plateau and the retreat of the Paratethys from the central Asia. As the timing of intensification of climatic aridity (16-12 Ma) is inconsistent with the onset age of global cooling (about 14 Ma), that of the attainment of a threshold elevation in the southern Tibetan Plateau (≥40 Ma), and that of the retreat of the Paratethys from the central Asia (＞34 Ma), the authors hold that these three factors may be only important boundary conditions or favorable auxiliary conditions for the intensification of aridity during the middle Miocene. Previous studies of the Janggalsay strata on the southeast margin of the Tarim Basin indicated that the rapid uplift of the Altun Mountains occurred at ~16 Ma. Combined with new magnetostratigraphic ages, the published carbon and oxygen isotopes data suggest a gradual intensification of climatic aridity since ~16 Ma for the Janggalsay area. Based on the simultaneous relationship, the authors attribute the middle Miocene increasing aridity to the rapid uplift of the Altun Mountains. Viewed from a broader context, the Mid-Miocene crustal shortening deformation is extensively existent within Central Asia. The multi-proxy analysis of red clay in China’s loess plateau and eolian dust from the northern Pacific Ocean indicates that the middle Miocene tectonic uplift and accompanying rain shadow effect acted as the major mechanism in driving the increased aridity in Central Asia.