The authigenic 10Be/9Be dating method is a relatively new geochronological technique that shows great potential for use in epicontinental sedimentary successions, largely due to its ability to date ubiquitous mud. However, the factors influencing the applicability of this method are not yet fully understood, which limits its robust application. This study presents the first direct evidence that deep-water mud redeposition can lead to significantly older authigenic 10Be/9Be ages, with an offset of ca. 2 Myr in the studied example. The redeposition generated hybrid event beds (products of mixed gravity flows) on the Late Miocene basin floor of Lake Pannon. The source material for redeposition was the Middle Miocene successions exposed on the lake bottom, as indicated by reworked foraminiferal and calcareous nannoplankton fossils, as well as inorganic and organic geochemical proxies. This case study suggests that a thorough understanding of depositional processes and paleogeographic settings is essential when proposing future authigenic 10Be/9Be dating sampling strategies, to avoid the influence of deep-water mud redeposition by hybrid event beds. Additionally, a notable shift in geochemical signature was observed between syn- and post-rift phases. During the ca. 6 Myr-long rifting, sediment recycling and local provenance were dominant from the rifted basin margins, while the post-rift stage marked the onset of a regional-scale sediment routing system. Notably, organic matter preserved its compositional signature of the redeposited successions.