title: Precipitation driven decadal scale decline and recovery of wetlands of Lake Pannon during the Tortonian.
abstract: High resolution pollen and dinoflagellate analyses were performed on a continuous 98-cm-long core from Tortonian deposits of Lake Pannon in the Styrian Basin in Austria. The sample distance of 1-cm corresponds to a resolution of roughly one decade, allowing insights into environmental and climatic changes over a millennium of Late Miocene time. Shifts in lake level, surface water productivity on a decadal- to centennial-scale can be explained by variations of rainfall during the Tortonian climatic optimum. Related to negative fine scale shifts of mean annual precipitation, shoreline vegetation belts reacted in an immediate replacement of Poaceae by Cyperaceae as dominant grasses in the marshes fringing the lake. In contrast to such near-synchronous ecosystem-responses to precipitation, a delayed lake level rise of 4-6 decades is evident in the hydrological budget of Lake Pannon. This transgression, caused by a precipitation increase up to > 1200 mm/yr, resulted in a complete dieback of marshes. Simultaneously, "open-water" dinoflagellates, such asImpagidinium, took over in the brackish lagoon and fresh water dinoflagellates disappeared. As soon as the rainfall switched back to moderate levels of ~ 1100-1200 mm/yr, the rise of the lake level slowed down, the marsh plants could keep up again and the former vegetation belts became re-established. Thus, mean annual precipitation, more than temperature, was the main driving force for high-frequency fluctuations in the Tortonian wetlands and surface water conditions of Lake Pannon. Such high resolution studies focusing on Tortonian decadal to centennial climate change will be crucial to test climate models which try to compare the Tortonian models with predictions for future climate change.
authors.affiliation: Natural History Museum Vienna, Geological-Paleontological Department, Burgring 7, 1010 Vienna, Austria.
authors.forename: Andrea K
authors.initials: AK
authors.lastname: Kern
authors.forename: Mathias
authors.initials: M
authors.lastname: Harzhauser
authors.forename: Ali
authors.initials: A
authors.lastname: Soliman
authors.forename: Werner E
authors.initials: WE
authors.lastname: Piller
authors.forename: Martin
authors.initials: M
authors.lastname: Gross
keywords: High resolution analysis; Paleoclimate; Paleoenvironment; Plant–climate-interaction; Pollen; Tortonian