Probing large paleoenvironmental variability during the Messinian-Zanclean transition in the Northern Apennines (Maccarone section), Italy, via multivariate statistical analysis on lipid biomarker-based proxies.

Quantitative reconstruction of paleoenvironmental and paleoclimatic changes that lack modern analogues is inherently challenging. A notable example of extreme paleoenvironmental transformation occurred in the Mediterranean Basin at the Messinian–Zanclean boundary (5.33 Ma), marked by the transition from the terminal Lago-Mare phase of the Messinian salinity crisis to the re-establishment of normal marine conditions starting with Zanclean. Despite its significance, the paleoenvironmental conditions of the Lago-Mare phase remain unresolved due to the conflicting fossil record, including both freshwater to brackish assemblages and marine microfossils. In this study, we applied a multivariate statistical approach to interpret a large dataset of terrestrial and aquatic biomarker indices from the Maccarone section in northern Italy. This analytical method was specifically tailored to address complexities associated with records originating from highly dynamic and contrasting, transitional environments (i.e., from lacustrine to marine) bringing the advantage of using statistical techniques to identify features that a traditional, visual, observation of complex array of proxies is unable to identify. Cluster analysis reveals a stepwise evolution of environmental conditions throughout the Messinian– Zanclean transition, while redundancy analysis indicates a sudden shift in the water column structure from stratified to well-mixed conditions at the Messinian–Zanclean boundary. Additionally, a gradual change is inferred in terrestrial vegetation, reflecting a progressive reconfiguration of coastal environments following the Zanclean marine transgression, with inland migration of the coastline and a decrease in wetland aquatic plant indicators.