Sedimentology, lithostratigraphy, palaeogeography and water level changes in a lacustrine basin: the depositional model of Lake Pannon
Orsolya Sztanó, Attila Balázs, István Róbert Bartha, Hana Ben Mahrez, Anna Horányi, Ádám Kovács, Michal Šujan, Lilla Tőkés, Balázs Töró, Fanni Vallner, Gábor Varga, Imre Magyar
Abstract
Advances in sedimentology and basin analysis have provided the foundation for a comprehensive basin-fill model and lithostratigraphic framework of Lake Pannon, in the Neogene Pannonian Basin, highlighting the dynamic changes of the depositional environments. The lake's c. 8 Myr long evolution began with transgression and deepening, followed by normal regression, forming sediment fill up to 7 km thick. Initial coarse-grained coastal deposits are overlain by offshore to deep-water marls, with varying carbonate and organic-matter content and include both anoxic laminites and sediment gravity-flow deposits. Later, confined and unconfined turbidite systems developed due to interactions between basin-floor relief and shelf-slope progradation. Stacked deltaic cycles followed by clayey alluvial plain deposits with anastomosing and meandering sandy channel fills comprise the upper part of the succession. Repeated aggradational to progradational clinothem architectures, thickness and distribution of muddy to sandy delta lobes on the shelf, and distribution of turbidite lobes in the deep basins reflect lake-level fluctuations. While climate primarily controlled lake level, coastal sedimentation is identified as a new factor driving long-term lake-level rise. Therefore, Lake Pannon's stratigraphy demonstrates that, in contrast to marine systems, in supply-dominated endorheic lakes accommodation space is created by sedimentation.