Foraminiferal Assemblage Variability and Paleoclimate Signals in the Early Cretaceous

The Early Cretaceous (145.0–100.5 Ma) represents a critical interval in Earth's climate history, characterized by greenhouse conditions, major oceanic anoxic events, and significant perturbations in the global carbon cycle. Foraminifera, as single-celled marine protists with excellent preservation potential and climate sensitivity, provide exceptional proxies for reconstructing paleoceanographic and paleoclimatic conditions during this greenhouse world. This comprehensive study examines the variability of foraminiferal assemblages across the Berriasian, Valanginian, Hauterivian, Barremian, Aptian, and Albian stages, integrating taxonomic, ecological, and geochemical approaches to extract paleoclimate signals. Through analysis of both planktonic and benthic foraminiferal assemblages from multiple paleocontinental settings, we document systematic changes in diversity, biogeography, depth stratification, and morphological adaptations that reflect evolving climate conditions. Key findings include the documentation of major foraminiferal turnover events associated with Oceanic Anoxic Events (OAEs), particularly OAE 1a (Selli Event) during the Aptian, and the identification of distinct paleoclimatic phases characterized by different assemblage compositions. Stable isotope analyses of foraminiferal calcite reveal temperature fluctuations ranging from extreme greenhouse warmth to transient cooling episodes, with tropical sea surface temperatures reaching 30–35°C during peak warmth intervals. The integration of foraminiferal assemblage data with sedimentological, geochemical, and paleontological evidence demonstrates that Early Cretaceous climate variability was driven by complex interactions between volcanism, orbital forcing, ocean circulation changes, and carbon cycle perturbations. This study establishes a refined biostratigraphic and paleoclimatic framework for the Early Cretaceous based on foraminiferal proxies and demonstrates the critical importance of these microfossils for understanding greenhouse climate dynamics and their implications for future climate scenarios.