Phosphorus Enrichment in the Barremian Calcareous Shale: A Driver of Primary Productivity in the Qiangtang Basin, Eastern Tethys

ABSTRACT The Early Cretaceous period was marked by pronounced greenhouse events, driven by large‐scale greenhouse gas emissions, which induced environmental perturbations and widespread deposition of organic‐rich sediments. Understanding these mechanisms is critical for reconstructing the Cretaceous carbon cycle and Paleoenvironmental evolution in the Tethyan realm. However, most existing studies on the Late Barremian environmental events have focused on the western Tethyan and Boreal realms, while the organic matter enrichment processes and their response to global perturbations in the eastern Tethyan semi‐restricted basins remain poorly constrained. In this study, we conducted high‐resolution geochemical analyses on calcareous shale samples from the Cretaceous Bailongbinghe Formation in the Qiangtang Basin (Eastern Tethys). In the study section, the enrichment of organic matter is closely related to the palaeoclimate, primary productivity, terrigenous input, and redox environment. Geochemical data reveal that the organic‐rich interval was deposited under a background of overall arid‐hot paleoclimate with episodic warm‐humid intervals, which intensified continental weathering and increased continental precipitation. Moderate terrigenous input under these conditions brought abundant phosphorus and other nutrients, as well as terrestrial organic matter, which significantly promoted marine biological prosperity and elevated primary productivity.