Integrating dinoflagellate cyst assemblages and geochemical proxies to reconstruct Campanian–Maastrichtian environments in the James Ross Basin, Antarctic Peninsula

The Cape Lamb Member at The Naze Peninsula, James Ross Island, captures an upper Campanian–lower Maastrichtian record that offers unique insights into dinoflagellate cyst ecology and environmental dynamics at southern high latitudes. In this study, palynological concentrations of autotrophic (AUT), heterotrophic (HET), and total (TOT) dinocysts were integrated with geochemical proxies (Ti/Al, Fe/Al) to evaluate trophic dynamics and their drivers. Stratigraphic profiles, correlation matrices, breakpoint detection, multivariate analyses, and cross-correlation functions were applied to assess covariation and temporal structure. The results revealed that dinocyst communities exhibited threshold-like reorganisations, with breakpoints marking ecological responses beyond tolerance limits. AUT dominance is consistently associated with elevated Ti/Al ratios, interpreted as increased terrigenous input and nearshore influence, whereas HET expansion aligns with Fe/Al enrichment, suggesting that episodic iron availability is a key trigger for trophic restructuring. Cross-correlation analyses revealed that Fe/Al variations typically preceded heterotrophic increases, whereas Ti/Al ratios lagged trophic shifts, highlighting asynchronous forcing mechanisms. The integrated evidence supports a conceptual model of nearshore–upwelling alternation in which stable terrigenous supply promoted autotrophic states, whereas discrete Fe/Al excursions triggered transient heterotrophic blooms. This dual control emphasises the sensitivity of high-latitude ecosystems to both local and regional drivers during the Maastrichtian, with The Naze section capturing ecological instability that mirrors wider Antarctic and global trends. These findings help refine palaeoceanographic reconstructions in the James Ross Basin and underscore the importance of combining palynological and geochemical approaches to understand marine ecosystem thresholds. • Palynology–geochemistry reveals abrupt trophic shifts in Late Cretaceous Antarctica. • •Autotrophs track terrigenous input (Ti), while heterotrophs reflect Fe enrichment. • •Cross-correlation shows Fe enrichment as the main trigger of trophic reorganisation.