Centennial- to decadal scale environmental shifts in and around Lake Pannon (Vienna Basin) related to a major Late Miocene lake level rise

Abstract

A detailed ultra-high-resolution analysis of a 37-cm-long core of Upper Miocene lake sediments of the long-lived Lake Pannon has been performed. Despite a general stable climate at c. 11-9 Ma, several high-frequency oscillations of the paleoenvironments and depositional environments are revealed by the analysis over a short time span of less than 1000 years. Shifts of the lake level, associated with one major 3rd order flooding are reflected by all organisms by a cascade of environmental changes on a decadal scale. Within a few decades, the pollen record documents shifting vegetation zones due to the landward migration of the coast; the dinoflagellate assemblages switch towards "offshore-type" due to the increasing distance to the shore; the benthos is affected by low oxygen conditions due to the deepening. This general trend is interrupted by smaller scale cycles, which lack this tight interconnection. Especially, the pollen data document a clear cyclicity that is expressed by iterative low pollen concentration events. These "negative" cycles are partly reflected by dinoflagellate blooms suggesting a common trigger-mechanism and a connection between terrestrial environments and surface waters of Lake Pannon. The benthic fauna of the core, however, does not reflect these surface water cycles. This forcing mechanism is not understood yet but periodic climatic fluctuations are favoured as hypothesis instead of further lake level changes. Short phases of low precipitation, reducing pollen production and suppressing effective transport by local streams, might be a plausible mechanism. This study is the first hint towards solar activity related high-frequency climate changes during the Vallesian (Late Miocene) around Lake Pannon and should encourage further ultra-high-resolution analyses in the area.

High-resolution analysis of upper Miocene lake deposits: Evidence for the influence of Gleissberg-band solar forcing

“…We use the total amount of ostracods and the presence of autochthonous mollusc populations as rough estimates for bottom water conditions; for a discussion on the species and genera constituting the assemblage see Harzhauser and Mandic (2004) and Harzhauser et al (2008). Within the studied core interval, the maximum abundance of ostracods/100 g sediment is observed from samples 1540 to 1525 (Supplementary Table 1; Fig.…”

“…This corresponds to a hypothetical time resolution of 13.7 years/cm, which represents the applied sample density. More detailed information on the lithology, paleontology and biostratigraphy of the Hennersdorf section has been published by Harzhauser and Mandic (2004), Harzhauser et al (2008) and Kern et al (2012a).…”

Meiofauna, trace metals, TOC, sedimentology, and oxygen availability in the Late Miocene sublittoral deposits of Lake Pannon

“…At that point, we also encounter the problem of renewal of deepwater and mixing of river and brackish waters in a hydrologically open lake under warm and humid climate where the salinity gradient is small (for salinity data see Kováč et al 1998;). The sediment discharge from rivers was high (Vakarcs et al 1994) and it reached basinal clay (Harzhauser et al 2008), far away from the supposed shoreline. Thus not only sublittoral, but also a deeper lake environment might have been efficiently supplied with oxygen and nutrients.…”

“…Thus, the fluvial-dominated lacustrine-deltaic system in the Vienna Basin carried a sufficient amount of nutrients and oxygen to the lake and induced a proliferation of the eutrophic green algae and meiofauna in the littoral (Pipík et al 2004;Harzhauser and Tempfer 2004) and sublittoral (Cziczer et al 2009;Harzhauser et al 2008), which benefit from a high nutrient input (Bodergat et al 2002).…”

Late Miocene fluvial distributary system in the northern Danube Basin (Pannonian Basin System): depositional processes, stratigraphic architecture and controlling factors of the Piešťany Member (Volkovce Formation)

“…The late Serravallian (Sarmatian) se quence re flects brack ish re gres sive sed i men ta tion, which con tin ued to the be gin ning of the late Miocene (11.6 Ma; Kováè et al, 2011). Af ter iso la tion of the Pannonian Ba sin Sys tem from the Med i ter ra nean and East ern Paratethys, Lake Pannon grad u ally flooded the sur round ing areas un til it reached its high est ex tent at ~10.5-10.0 Ma (e.g., Mag yar et al, 1999;Harzhauser et al, 2008). Progradation of the shelf mar gin that was fed by deltaic sys tems of the palaeo-Danube and rivers drain ing the West ern Carpathians led to a grad ual re treat of the Lake Pannon shore line to the south-east (Fig.…”