Molluscs in loess, their paleoecological significance and role in geochronology — Principles and methods

Abstract

The malacofauna of genuine wind-blown loess consists of a minor number of tolerant species occurring mostly in high amounts and reflecting open habitats with poorly developed calcareous soils. It shows a rather uniform character in space and time distinctly differing from all present-day assemblages of the temperate zone, and thus indicating a very peculiar environment characteristic of the loess steppe. In protected areas, particularly on valley slopes, the loess covers alternate with intercalations of slope sediments and soils including several other types of snail assemblages reflecting environmental changes in the course of the Quaternary climatic cycle. Among these malacocoenoses the interglacial faunas are of prime biostratigraphic importance. They are associated with strongly weathered forest soils and indicate woodland environments under very damp and warm climatic conditions. Transitional steppe and taiga assemblages occur in buried chernozem soils and in various slope sediments, e.g. in the pellet sands, overlying the interglacial soils and corresponding to early glacial periods. Although the fauna of proper loess shows a monotonous composition, it is possible to distinguish several types of loess assemblages corresponding to minor facies changes of loess environments in time and space; these are, for example, the Pupilla, Helicopsis striata and Columella faunas of Central Europe. A peculiar marshland fauna characterizes the so-called swamp-loess deposited in ephemeral swamps. In the marginal zones of the loess belt there occur also faunas partly differing from those of typical loess; this is true particularly of the Mediterranean region. The most important contribution provided by molluscan faunas from the loess series is the evidence of the maximum number of climatic cycles during the Quaternary period.