Plant taphonomy and palaeoenvironment from the Upper Cretaceous of Isona, Tremp Basin, southern Pyrenees, Catalonia, Spain

• Isona Sud is one of the rarest Maastrichtian plant localities in southern Europe.
• Plant megafossils consist of conifer twigs and angiosperm leaves.
• Sporomorphs show freshwater algal oospores, fern spores and spermatophyte grains.
• Overall the plant assemblage is dominated by angiosperms and ferns.
• It was parautochthonous and allochthonous and deposited in a freshwater floodplain.

Lower Maastrichtian plant fossils were newly collected from the base of the Xullí unit, Tremp Group, in Isona, Tremp Basin, southern Pyrenees. They consist of conifers, monocot and eudicot angiosperms. Palynology shows algal oospores, fern spores, gymnosperm and angiosperm pollen grains.Sedimentological and taphonomic analyses indicate that this assemblage is parautochthonous and allochthonous. The plant fragments probably came from a nearby exposed area and were deposited in the distal floodplain. These taphonomic data shed light on the exact location and sampling biases of the palaeobotanical collection from Isona gathered by Vicente i Castells in the 1980s.Angiosperms and ferns dominated the plant community, which grew inland in freshwater environments. Cheirolepids inhabited coastal freshwater lakes in the same basin (the Posa unit) and in the geographically close basin of Vallcebre.