Mid-Miocene onset of the NE Bohemian Massif (SW Poland, Europe) growth, landscape evolution, and paleoenvironmental changes unraveled using paleokarst sediment palynology

Abstract

Newly discovered paleokarst sediments with an abundant Miocene palynological record in the Eastern Sudetes bridge the gap in reconstructing the landscape and tectonic history of the NE Bohemian Massif during the Neogene. Palynological analysis performed for seven samples derived from the karst fissure allowed the examination of the sporomorph distribution (pollen grains and spores of plants) and nonpollen palynomorph content (algal and fungal microremains) in each layer. The results revealed the presence of numerous pre-Quaternary taxa, including “paleotropical” species, within the analyzed sediments. The pollen analysis results indicate a warm-temperate and humid climate during sedimentation of the Nowy Waliszów karst infill, along with the development of wetland vegetation (swamp forests, riparian forests, and shrub bogs) and mesophytic forests. Recorded taxa are typical for flat and hilly landscapes, predating growth of the present >1000-m relief mountainous topography and formation of the primary European triple drainage divide in the Śnieżnik Massif area. Paleokarst palynology strongly supports a mid-Miocene (∼15 ± 1.5 Ma) onset of environmental change in the Sudetes due to accelerated tectonic uplift of the Eastern Boundary Fault bounding the Upper Nysa Kłodzka Graben and Orlica–Śnieżnik Dome tectonic block. The data presented enhance our understanding of the pre-Pleistocene development of the NE Bohemian Massif, with a particular focus on the orogen-scale landscape evolution from flat, inland wetlands to hilly, mountainous topography.