Campanian paleoenvironmental and provenance evolution on a subsiding margin: Insights from the Gosau Group at Grünbach-Neue Welt, Eastern Alps, Austria

This study investigates the paleoenvironmental and provenance evolution of the sediments of the Campanian Gosau Group at Grünbach-Neue Welt, Eastern Alps of Austria. The area uniquely preserves a continuous transition from terrestrial/lacustrine to deeper marine facies during the Campanian, corresponding to the boundary between the Lower and Upper Gosau subgroups, primarily driven by tectonic subsidence along the northern margin of the Austroalpine microplate. The stratigraphic record provides a valuable archive for studying subsidence-controlled sedimentary and environmental changes in the Gosau Group and, more broadly, across the Northern Calcareous Alps. Fieldwork involved sampling from trenches and outcrops, which was followed by lithological, petrographic, micropaleontological, mineralogical, and geochemical analyses to reconstruct depositional environments, and their variations. The Grünbach Formation (upper Santonian to lower Campanian) represents a terrestrial-dominated setting with episodic marine incursions, evidenced by coal and marl interbeds with occasional marine fossils, which are corroborated by geochemical proxies. The overlying lower Piesting Formation (upper Campanian) consists of shallow-marine sandstones with terrestrial input, as indicated by plant debris and geochemical signatures. Across the deposits, a shift from more weathered, finer materials to less-weathered, coarser-grained sediments suggests modifications in sediment transport pathways and provenance, likely influenced by progressive subsidence, marine transgression and uplift in source areas. These findings establish a detailed framework for the Campanian paleoenvironmental and provenance shifts of the Gosau Group, highlighting the intricate interplay between subsidence, sea-level fluctuations, and sediment supply. By documenting this continuous stratigraphic record, this study advances our understanding of how coupled environmental and tectonic processes influenced basin evolution.