Malakofauna górnego vistulianu i holocenu Wyżyny Krakowskiej

Stefan Witold Alexandrowicz



Sediments of the Upper Vistulian and Holocene of the Cracow Upland contain a molluscan fauna characterising the environment changes of the environment of the last thirty thousand years (Fig. 1). In profiles of loess a sequence of assemblages is noted. In its lower part the fauna contains Arianta arbustorum, Trichia hispida and Pupillan muscorum and upwards it is a poor fauna with Pupilla loessica and Succinea oblonga elongata. The age of this sequence ranges between 30-15 ka BP. Silts and slope sediments of .the Late Vistulian contain species that recently have reached high geographic latitudes, e.a. Nesovitrea hammonis, Punctum pygmaeum and Vertigo geyeri. Rich molluscan assemblages occur in a calcareous tufa of the Holocene age. In the lower parts of the profiles a fauna with mesophile snails and with woodland species (Discus ruderatus) is found, whereas in the middle parts the assemblages contain numerous species of different ecological groups including woodland elements, mesophile and hygrophile snails as well as open ground snails. Water molluscs dominate locally. Two types of malacological sequences are distinguished in calcareous tufa. One of them – the woodland snail sequence – occurs in narrow, deeply cut valleys, while the other – the open ground snail sequence – on wide and flat valley floors. Since the beginning of the Subboreal Phase organic alluvial loams aboundant in mollusc shells are the main sediments in the lower segment of the valleys. It reflects the initial deforestation of the upland during the Neolitic (Fig. 2-KPL). Successive phases are connected with the growth of the human population during the Lusitian Culture, Late Roman Period and mainly, the Middle Ages (Fig. 2 - A). As a result of the intensification of soil erosion and denudation the mineral alluvial loams with a poor molluscan fauna have been accumulated on floodplains of all the valleys. The related assemblages of snails are noted in slope sediments and in profiles of calcareous soils. Species indicative of extending open and xerothermic habitats as well as of developing agriculture are the significant elements of these assemblages. In the last centuries a few synanthropic species of land and water molluscs that can exist in artical and even polluted habitats have immigrated to the area in question (Fig.2-M).

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