Early Cretaceous (late Barremian-Early Albian) expanding aeolian activity in East Asia: Evidence from the stratigraphic evolution of aeolian deposition in the Baiyin-Jingyuan Basin, northern China

Cretaceous aeolian deposition is important for understanding variations of the tropical-subtropical atmospheric circulation under the greenhouse background. Nevertheless, detailed records revealing the response of aeolian deposition to rising atmospheric CO2 are still lacking. To shed light on their linkage, we examined the Early Cretaceous stratigraphic evolution of the Hekou Group in the Baiyin-Jingyuan Basin, northern China, using multiple methods. The results indicate that the lower Hekou Group is characterized by a transition from submerged alluvial to shallow lacustrine deposition. Overlying these facies is loess -like deposition without bedding, distinguished by grain -size distribution, surface microtextures, and geochemical analysis, which is followed by palustrine deposition. In the palustrine deposition, aeolian sand -dune and sand -sheet deposition can be identified, which gradually developed upward in the Hekou Group, with intercalated wet interdunes, damp interdunes, and pebble -sand sheetflood beds. Finally, aeolian sand dunes and sand sheets dominated the upper Hekou Group. Overall, the upwardchanging facies indicated the development of aeolian deposition from an aqueous environment, revealing a long-term paleoclimatic shift from semi -humid, semi -arid to extremely arid, which reflects the expanded aeolian activity in East Asia during the Early Cretaceous. Furthermore, various records were combined to investigate the expanding aeolian activity in East Asia, which indicates a west-east-trending arid belt that was wider than the modern counterpart during the late Barremian-Early Aptian and late Aptian- Early Albian, respectively. These stepwise expansions of aeolian activity were mainly driven by rising atmospheric CO2, which strengthened the subsiding branches of Hadley circulation and the subtropical high, eventually leading to intensified aridification.