Evolution of the charophyte meadows in an Early Cretaceous karstic lake (La Pedrera de Meià Konservat-Lagerstätte, Southern Pyrenees): integration of charophyte paleoecology and geochemical proxies

Abstract The combined taxonomic and palaeoecological analysis of charophyte-rich carbonate microfacies is proven to be a useful methodology for the palaeoenvironmental reconstruction of continental settings. However, the integration of these charophyte assemblages with geochemical proxies has not been explored, yet. In the present work, the charophyte-rich muddy carbonates of the Barremian La Pedrera de Meià Konservat-Lagerstätte (Southern Pyrenees, Spain) were studied from a taxonomic, taphonomic, and palaeoecological viewpoint, and the results were later compared with previously published paleoenvironmental proxies (δ13C, δ18O, and elemental geochemistry). In the studied locality, monospecific Echinochara cf. lazarii-Charaxis spicatus meadows are only found in the ephemeral lakes recorded in the lower stages of lake infilling. The high Al, K, Fe and Ti concentrations and δ18O values previously described in these carbonates indicate meteoric infilling followed by evaporation periods. Freshwater and brackish communities are found in the upper stage of lake infilling. Freshwater settings had mixed meadows with Atopochara-Clavatoraxis, Clavatoroid-Clavatoraxis, and Ascidiella-Favargerella plants, while the brackish environments, that occurred laterally to freshwater, contain meadows dominated by Porochara? – Charaxis sp., and Echinochara cf. lazarii-Charaxis spicatus plants. Miliolids and broken dasycladaceans also occur in these facies. Sr/Ba ratios, REE + Y concentrations, and δ13C and δ18O values previously described in the carbonates of this part of the section indicates prevalence of freshwater environments with occasional marine influence, which agrees with the occurrence of distinct brackish and freshwater charophyte assemblage and marine-affinity organisms, suggesting that during the last stage of evolution, the lake was part of a coastal wetland. This work demonstrates that the integration of geochemical, palaeontological and palaeoecological datasets improves the understanding of the fossil continental settings and their evolution.