Seagrass development in terrigenous‐influenced inner ramp settings during the middle Eocene (Urbasa–Andia Plateau, Western Pyrenees, North Spain)

Since their first occurrence in the late Cretaceous, seagrasses have played a major role carbonate production and sedimentation across shallow-water nearshore environments, sustaining prolific factory contributing to sediment accumulation through combination of baffling trapping effects. Most reported Palaeogene seagrass occurrences developed oligo−mesotrophic shallow warm-water habitats are characterized by distinct associations small larger benthic foraminifers adapted low terrigenous influence. This study describes number episodes interbedded Bartonian (middle Eocene) San Fausto–Lazkua area (Navarra region, North Spain), within inner-ramp succession that, spite being deposited under general transgressive conditions, was highly influenced supply from adjacent land. Up twelve different bed intervals occur cyclical manner with high-energy siliciclastics inner ramp bioclastic carbonates rich mesophotic−oligophotic heterozoan biota (red algae, echinoderms, bryozoans). Seagrass deposits exhibit typical unsorted textures, abundant bioturbation moderate high content, comprise characteristic skeletal association epiphytic foraminifers, red algae and, most particularly, encrusting acervulinids, commonly hooked tubular growth forms. abundance suspension-feeders relative autotrophs mixotrophs may be indicative temperate waters, although taxonomic diversity foraminiferal assemblages both non-seagrass embedding supports interpretation shallow, conditions. The studied provide evidence that siliciclastic associated nutrient input determine temperate-like settings, analogous extensive modern shallow-tropical environments. Thus, identification correct past seagrass-vegetated environments crucial for reconstructing palaeoecological conditions ancient shallow-marine Therefore, comparison carbonate-dominated mixed terrigenous−carbonate volumetrically less important, presenting more irregular, patchy distribution, assemblage dominated heterotrophs, regardless water temperature.