Molluscan fauna from the loess series of Bohemia and Moravia

Abstract

Abstract In the European context, the malacofaunas from the loess series in Bohemia and Moravia provided relatively rich evidence of environmental conditions in distinct phases of the climatic cycle. This is particularly true of the Last Interglacial–Glacial cycle in which a number of minor documented phases have made it possible to reconstruct the sequence of detailed environmental changes. The major conclusions may be summarized as follows: (1) Loess malacocoenoses differ in their composition from all known molluscan assemblages in present-day Europe and show a relatively uniform character in space and time. (2) They reflect specific environments that may be called as loess steppe, characterized by severe cold-continental climate, grassland with discontinuous turf cover and raw soils rich in salts. (3) Malacocoenoses of the loess steppe differ considerably from those of the modern subpolar zone. (4) Differences in species distribution correspond to particular loess facies due to various depositional and climatic conditions. (5) Loess is the product of pleniglacial phases: in early glacial phases its occurrence is very limited, and the malacofauna of these loess horizons is characterized by an absence of most subpolar or alpine species. (6) Interstadials of the Early Glacial phase are characterized by assemblages of the chernozem steppe and indicate strongly continental conditions. (7) In the pedocomplex I (PK I = δ 18 O stage 3, Stillfried B) no malacological records are available which would indicate a warmer climate: its assemblages are very similar to those from the loess. (8) Interglacials have fully developed woodland malacocoenoses which reflect a warm and humid climate, even in areas where such assemblages did not develop during the Postglacial. (9) Loess formation and specific loess malacocoenoses decline in the earlier phase of the Late Glacial, being gradually replaced by much more diversified communities with a higher proportion of moisture-loving elements. (10) The above-mentioned development corresponds to the situation in dry loess areas that may be considered typical loess landscapes. At higher elevations and in moister areas, different sediments, soils and molluscan assemblages existed at the same time. Their correlation with sequences of the loess series is poorly documented due to the lack of reliable fossil and stratigraphic evidence.