Evolution and migration of the highest megadunes on Earth

摘要

? 2023Giant aeolian sand dunes, over 100 m high, occur in the major deserts on Earth, and they can provide valuable insights into past wind regimes and climatic conditions in desert areas. However, the formation and evolution of these megadunes remains poorly understood. The highest aeolian sand dunes on Earth are in the Badain Jaran Desert (BJD) in northwestern China, where hundreds of giant transverse dunes are at least 200–300 m high, with some as high as ～500 m. We present sedimentary records from eight cores from five megadunes (200–400 m in height), including a 320-m drill core from a ～ 430-m-high megadune in the centre of this desert, which is the first detailed investigation of Earth's tallest sand dune. The results of high-resolution optical dating show that these huge transversal dunes migrated downwind, with the dune migration taking some tens of thousands years to complete a single cycle of turnover. We present a model for the migration of the largest free-standing aeolian landform, which demonstrates that the formation and migration of megadunes is closely linked to global climate change. Although there was negligible dune migration during warm and humid interglacial periods, the dunes were still able to rapidly accrete vertically. The migration of these dunes occurred during the coldest and driest periods (e.g., Marine Isotope Stages 4 and 2), at the rate of a few centimeters per year, highlighting the slow net downwind transport of dunes in the Badain Jaran Desert. Our results highlight the role of global climate change over the last glacial cycle in the formation and migration of megadunes.