ICE 2022


Eolian deposits not only recorded paleoclimate, paleoecology, and paleoenvironments but also are a basis for the reconstruction of the paleocontinent and paleogeography. Aridification happened in Central and East Asia in the Late Mesozoic and led to drastic environmental change, including widespread eolian deposits. However, the eolian deposits in the Junggar Basin in the late Mesozoic were contentious. We firstly report on the eolian deposits in the late Middle Jurassic in the Jurassic Basin which are the oldest reported inland eolian deposits in Asia. We systematically investigated the eolian deposits in the late Middle Jurassic and Early Cretaceous and driving mechanisms in the Southern Junggar Basin in northwestern China, Central Asia. Firstly, A 3D model using an unmanned aerial vehicle was built to characterize the eolian architecture. The plane view of the 3D model allows identifying interdune migration surfaces, superimposition surfaces, and reactivation surfaces easily. Secondly, we reconstructed the sedimentary evolution in the Late Mesozoic. The paludal environment changed to a fluvial environment with local eolian dunes from the late Middle Jurassic to Late Jurassic and erg environments with widespread eolian dunes in the earliest Cretaceous, which evolved into a lacustrine environment. The eolian dunes are characterized by well-sorted, round-grained, sandstones with little suspension load, thick, large-scale, and high-dip trough cross-bedding, inversely-graded lamination, dominant saltation grains, and typical eolian grain surface textures, including crescent-shaped, and dish-shaped impact scars. Thirdly, 53 heavy mineral data and 76 effective grains of detrital zircon ages were attained to analyze the provenance of the eolian deposits. Stable heavy minerals increased dramatically, such as ilmenites, zircons, garnet, and tourmalines. Synodepositional volcanic materials provided a large amount of sediments because Jurassic detrital zircons constitute 35.5% of the zircons. The detrital zircon age distribution was compared with the crystallization age in the potential provenances and collected detrital zircons, we assumed that the aeolian deposits were mainly fed by the North Tianshan Orogenic Belt and proposed a source-to-sink evolution model in the Mesozoic in the southern Junggar Basin. Lastly, the data of 70 dip-azimuths from large eolian cross-bedding foresets of in 3 sections demonstrates that eolian dunes in the Toutunhe Formation is the product of the easterly belt in the late Middle Jurassic, whereas the eolian dunes in the Kalazha Formation are a response to the westerly belt in the Early Cretaceous. We classify the paleowind belts in Central and East China combined with the paleocurrent data from other basins. The study demonstrates that the change of prevailing surface-paleowinds was the sedimentary response to the atmospheric circulation transition, caused by the true wander polar and the migration of the subtropical high belt. The true polar wander displaced the Junggar Basin from high latitude to middle latitude and the subtropical high belt was compressed from 40°N to 30°N. Keywords: erg environment, paleo-wind belt, Central Asia; unmanned aerial vehicle; source-to-sink system