Prototype basin reconstruction during deposition of the Xiamaling Formation, North China Craton: Implications for the Mesoproterozoic paleoenvironment and atmospheric-oceanic oxygenation

The Xiamaling Formation, located on the northern margin of the North China Craton (Yanliao Basin), represents the earliest stratigraphic succession in North China recording the Mesoproterozoic Oxygenation Event, thereby attracting widespread research interest. However, intense post-depositional modification has generated considerable debate over whether the formation was deposited in a large, open marine basin or a restricted, small basin. Resolving this paleogeographic uncertainty is crucial for accurately assessing the formation’s global paleoenvironmental significance. By integrating lithostratigraphic characteristics, stratigraphic stacking patterns, spatial distribution of facies belts, basin-filling architecture, and magnetic fabric data, this study identifies shore sandstones along the southern proto-basin margin, reconstructs the basin-filling architecture, and constrains sediment provenance and transgression directions. Our results indicate that the Xiamaling Formation was deposited in a large marine basin connected to the open ocean, rather than in a small, enclosed basin, providing critical constraints for understanding the global implications of the Mesoproterozoic Oxygenation Event as recorded in the Xiamaling Formation.