The principles of growth and isotopic fractionation of stalagmites : A numerical model to reconstruct temperature and precipitation records from stalagmites grown under disequilibrium conditions

Speleothems and stalagmites in particular are frequently used as archives of paleoclimate. Their growth, isotopic carbon and oxygen profiles and the possibility of an exact dating provide time series in a high temporal resolution. However, the interpretation of these profiles is difficult since the isotopic signal in stalagmites underlies several influences outside and inside the cave. In this study the basic principles of stalagmite growth and isotopic enrichment under equilibrium and disequilibrium conditions in dependence on climate related parameters are described quantitatively using numerical models. In a final step these basics are used to develop a combined model, which enables the reconstruction of temperature and drip interval records from isotopic profiles of kinetically grown stalagmites. In contrast to former models, which have been limited in their application to samples developed under equilibrium conditions, this model is able to cope with kinetically grown samples and hence extends the number of stalagmites, which might be investigated. Furthermore the model exceeds the results of former models by yielding drip intervals in addition to temperature records. The model is applied to two stalagmites from Southern Chile and reveals first temperature and drip interval records obtained by stalagmites from extremely low latitudes. The study was carried out in the framework of the daphne Forschergruppe in Heidelberg