Facies characterisation of a Kungurian volcano lake of the Athesian Volcanic District (Italy)

The Athesian Volcanic District offers important insights into how volcanic activity influenced ecosystems during the Cisuralian, particularly at low latitudes, thanks to sedimentary successions intercalated with the volcanic units. By combining sedimentological, paleobotanical, palynofacies, qualitative and quantitative palynological, and stable carbon isotope studies, we reconstructed the depositional environments and vegetation dynamics across two distinct successions. The two studied sections reflect different depositional environments: one proximal and one more distal with respect to the margin of the lake and the source of the organic material. Pollen assemblages and plant fossils reconstruct a flora dominated by xeromorphic and xeromorphic-hygromorphic taxa, such as conifers (Collia, Feysia, Hermitia), seed ferns (Lodevia, Peltaspermum, Sphenopteris), and ginkgophytes (Sphenobaiera). Hygromorphic elements like lycophytes and ferns are rare but more abundant in the marginal succession of the lakes. The δ¹³C_org values are comparable with those of other Cisuralian continental successions, but a small variability is observed that correlates with the abundance of xeromorphic elements. This multidisciplinary approach suggests that one or more water bodies existed in a megacaldera setting, with water depth influenced by the palaeotopography. The climate was semiarid to arid, typical of the Cisuralian at low latitudes. The differences observed in the successions are not linked to climate shifts but to deposition of plant micro- and macroremains under different environmental conditions and, thus, reflect a taphonomic and paleoenvironmental signal.