International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

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Surviving from transgression to regression of Lake Pannon: Fan deltas of the Nemčiňany Fm. persisted across the rifting until the post-rift stage of the Danube Basin, western Slovakia

Published: Dec 2023

Pages: 469 - 488

DOI: https://doi.org/10.31577/GeolCarp.2023.25

Authors: MICHAL ŠUJAN, KISHAN AHERWAR, ANDREJ CHYBA, BARBARA RÓZSOVÁ, RÉGIS BRAUCHER, MARTIN ŠUJAN, FRANTIŠEK ŠIPKA, ASTER TEAM

Abstract: Successions deposited under rifting and post-rift settings of an isolated epicontinental basin often exhibit contrasting characteristics. Facies linked to transgression during basin rifting are typically locally sourced fan deltas transporting coarse-grained sediment, whereas the post-rift setup generally involves a normal regression marked by more extensive catchments, sediment sourced from greater distances, and an overall decrease in average grain size compared to the transgressive facies. In this study, we present a specific scenario based on a sedimentological, stratigraphic, and authigenic 10Be/9Be analysis of the Nemčiňany Formation, an Upper Miocene fan deltaic succession in the eastern Danube Basin, Slovakia. Deposition of the Nemčiňany Fm. was initiated shortly after ~11.6 Ma by the fourth rifting phase of the Pannonian Basin System, triggering the transgression of Lake Pannon. The depositional system persisted until ~9.6 Ma, likely balancing the increased accommodation rate with sediment supply in the shallow lake area situated on a basement high. Subsequently, a relative decrease in the accommodation rate prompted the progradation of shelf-slope scale clinoforms, originating from the Nemčiňany depositional system, toward the center of the Komjatice depression at ~9.4 Ma, resulting in a normal regression of Lake Pannon. The persistence of the Nemčiňany fan delta system, unlike common stratigraphic patterns, was associated to the high sediment supply yielded by the paleo-Hron river, which entered the basin in the study area. These observations underscore the need for caution in predicting provenance shifts during changes in geodynamic stages of a basin.

Keywords: facies analysis, authigenic 10Be/9Be dating, cosmogenic nuclides, Pannonian Basin System, Late Miocene, supercritical flow bedforms

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