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icr_ee    ods. The thickness of deposits is often between 5-1 Om (some 17m in Svaty

v Uj_e    Jan pod Skalou in Bohemian Karet), it usually covere the interval 9500 to about

?ojj_s    2200 yeare BP. The deposits can be studied by a number of complementary

2 k»    methods including stable isotope studies and correlations between archaeo-

ij\M    logical, biostratigraphical and geochemical methods (Jager 1982, Żak et al.

Lfr»    2002). The tufa outcrops located around resurgences in lower parts of karet

valleys indicate slope retreat, downcutting and standstill phases in slope dy-

i,    namics.

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The Holocene terrestrial biostratigraphy is founded on two groups of an-imals — Molluscs and Vertebrate, even when some other groups like Insecta or Ostracoda may provide additional evidence (Roberts 1998). Malacologi-cal analysis is, due to the carbonate naturę of mollusk shells, limited to cal-careous districts or sites where the shells are not dissolved by acidic Solutions. These districts are covering surprisingly large areas of Central Europę — all karet areas, sites located on smali outcrops of metamorphic carbonates and some volcanoclastic strata, some Artesian springs and thermal water deposits and travertines, calcareous layers — mostly sandstones and marls — of Mesozoic and Kenozoic (Paleogene) age, some floodplain sediments and Holocene soils derived from loessic substrate. The number of Mollusc spe-cies can reach in one profile (or even individual layers) some 20—40 species and the total number of all shells can be measured in an order of thousands to tens thousands individuals and expressed as histograms that resemble pollen graphs. Molluscs are environmentally sensitive and they tend to form assem-blages closely connected to basie phytocenological units. Therefore the fos-sil assemblage of an individual time slice may be directly attributed to giv-en habitats with the exception of acidophilous biotops such as heaths or pine woods.

Moiluscan evidence is at least twofold: besides a strong relation to a type of vegetation we find another important relation to thesoil cover(Lożek 1988). Their thanatococnoscs are composed of species that originally lived at the site in question and the transported species. While out-washed floodplain sediments may represent an “average” sarnple of few kilometere of the river course, the horizontal transport of shells in rocky habitats is restricted to few meters and the vertical transport corresponds to the fall-out from above lying terrain. This situation together with well-known ecological dcmands of individual.