Lake-floor lithology at the sampling site of Fonyód with indication of dreissenid colonies. An ultra high-resolution seismic line near the sample locations reveals the deep structure of the lake floor. Nearshore tilted Late Miocene strata comprise the floor of Lake Balaton without significant Holocene cover here (Novák et al., 2010), giving rise to dreissenid colonies. Description of the sediments are found in Figure 3, and in Table S2. DOI: https://doi.org/10.1525/elementa.380.f4