Neogene climate evolution of the Tarim Basin, NW China: Evidence from environmental magnetism of the southern Tian Shan foreland

Abstract

The Tarim Basin, located in the rain shadow of the Tibetan Plateau and other central Asian active orogens, is one of the most arid areas in the mid-latitude of the Northern Hemisphere. Its aridification history is important for understanding climate changes in the context of global cooling and regional tectonics. In this study, we present an environmental magnetism study of the early Miocene-early Pliocene (~20–4 Ma) terrestrial sediments in the Southern Tian Shan foreland. Magnetic parameters representing the relative/absolute concentrations of hematite in the sediments, together with color parameters, are used to reconstruct the Neogene climate evolution of the Tarim Basin. Our results reveal that the Tarim Basin was dominated by relative warm and wet climate between ~17 Ma and ~14 Ma, corresponding to the Mid-Miocene Climatic Optimum (MMCO), followed by three stepwise cooling/drying events at ~14 Ma, ~7 Ma and ~5.3 Ma, respectively. The dramatic cooling event at ~14 Ma is attributed to the expansion of East Antarctic Ice Sheet. The stepwise aridification at ~7 Ma and ~5.3 Ma in the Tarim Basin was controlled first-order by global cooling but superimposed by regional tectonics. The late Miocene aridification at ~7 Ma is partly due to the reduced moisture transport to the Tarim Basin related to the Mediterranean Salinity. Basin-wide extreme aridification since ~5.3 Ma is dominated by the final collision between Pamir and Tian Shan, which blocked the water-vapor brought by the westerlies from the Paratethys Sea to the downwind Tarim Basin.