A FOSSIL FOREST FROM ITALY REVEALS THAT WETLAND CONIFERS THRIVED IN EARLY PERMIAN PERI-TETHYAN PANGEA

Abstract

Abstract In-situ fossil forests are valuable biogenic archives for the structure and setting of paleocommunities and the ecology of their organisms. Here, we present the first trees preserved in growth position in their embedding strata from the Kungurian (lower Permian) Athesian Volcanic Group, Northern Italy—one of the most extensive volcanic successions of post-Variscan Euramerica. We reconstruct the structure, rise and demise, and paleoecology of the forest based on high-resolution documentation of facies architectures and petrography, and the paleontological and taphonomic characters of the fossil content. Generally, the fossiliferous strata record a volcanotectonically controlled base-level rise in a limnic, possibly endorheic wetland basin from a low-relief volcanic landscape. The forest, preserved as calcified stem bases with roots, grew during a short interval of lake-level stasis on a small deltaic sheetflood fan. The forest comprised trees less than 5 m tall with tabular root systems adapted to the waterlogged substrate, and was buried and destroyed by mass flows following rapid submergence. These mass-flow deposits yield parautochthonous woody debris providing anatomical evidence of conifers as the major arborescent plants of the fossil forest. Our results not only elucidate the root architecture of Paleozoic conifers, but also document the ecomorphological plasticity of these plants and substantiate the presence of coniferopsids in wetlands around the Carboniferous/Permian boundary. Further, the evidence of lake perenniality in the studied succession is among the youngest known from the Permian of Europe, pointing to the highly differentiated late-icehouse impacts on continental environments in the Euramerican tropics.