| Abstract: | Natural radiocarbon measurements as contribution to definition of recent- or paleoclimatologic indicator horizons in Tunisia Main climatic boundary lines as well as paleoclimatic and quarternary stratigraphic indicator horizons of Tunisia are identified. Radiocarbon dates of 116 soil samples, derived from soil profiles or from quarternary cuts point to at least one indicator horizon of 7-8000 B. P., a Mollisol - paleosol of the Rharbien, covered by variable layers of “Historique”. Often it is a duplex horizon and superimposed by a younger mollic horizon of ca 5000 B. P. A further ochric fA horizon of 10 to 15000 B. P. (younger Soltanien) was found frequently, but not regularly. The C-content of even older soil samples - sauf one Paleargid of 23000 B. P. - is so low, that the organic carbon remaining from lithogenic carbonate-C destruction is insufficient for a normal size benzene sample or liable to falsification. 0.1 % C seems to be a reasonable lower threshold for reliable dating samples. Few profiles revealed in the lowest position, adjacent to the erosion plane of the wadi, an inflection in age: It indicates, that due to lateral attachment of younger alluvial substrates a misleading rejuvenation can happen. The results draw attention to the finding, that layerwise, sequential dating of the whole profile is advisable. Interpretation of individual samples appears in semiarid quarternary cuts daring and may be liable to error. In case of several horizons/layers, where change of sediment appeared to be possible, allelement analysis were conducted to assist recognition of discontinuities. An histogram of all I4C-dates, so far produced for tunisian soil, sediment or ground water samples, indicates frequency maxima, i. e. climatic phases, sufficiently moist for pedogenesis and groundwater formation at around 5000, 7-8000, 10-11000, and 13-15000 B. P. |
