Time series of δ<sup>18sup>O and δ<sup>13sup>C values were determined in individual shells belonging to two sympatric genera of viviparid gastropods: Viviparus apameae galileae and Bellamya sp. found in the sedimentary cycles 2 through 5. The total overall range of δ<sup>18sup>O in the time series of all the shells is from − 10.5‰ to − 5.2‰ (VPDB), and the δ<sup>13sup>C from − 9.2‰ to − 4.8‰ (VPDB). The δ<sup>13sup>C values of shells recovered from black mud are lower than those from the other sediment types suggesting a higher proportion of carbon of organic origin. The δ<sup>18sup>O values show only a weak relation with sediment type. The time series of the individual shells indicate a relative constancy in the water δ<sup>18sup>O and temperature whilst the variation in δ<sup>13sup>C could be related to the annual productivity cycle (growth and decay of aquatic plants) of the lake. The δ<sup>13sup>C patterns in the time series and winter rings indicate that the rate of growth of the individual snails was ca. 15–30 mm/year. The isotopic characteristics of the Viviparid shells from these beds indicate diverse sedimentary environments and suggest that above the MBB (cycles 2–5) the GBY lake received constant and isotopically consistent water inflow.
Our integrated data, isotopic and ecological of molluscs, and ecological of plants, indicates that the geophysical-magnetic phenomenon of MBB coincides with an environmental change from a relatively cold dry climate towards a warmer temperate subtropical climate in this region. This change coincides with the occurrence of hominin artifacts, which were found mainly in layers of the sedimentary cycles 3–5.