Studio geocronologico del complesso carsico "Grotta del Fiume - Grotta Grande del Vento" (Gola di Frasassi, Ancona) e implicazioni paleoambientali

Abstract

Chronological measurements have been carried out on speleothems from "Grotta del Fiume - Grotta Grande del Vento" karst system at Frasassi (Ancona, Italy) by means of the 230Th radiometric method in order to date hypogean karst levels and related geological events. Higher levels were found to be older than the lower ones according to standstills and sinkings of water table. The dated speleothems from the first and second levels formed less than 10,000 years ago; the minimum ages of the third and fifth levels, which are respectively 130,000 and 200,000 years, were correlated to climatic events. The dating of different portions of a speleothems allows the measurements of the radial and vertical accretion rates and their variation over time. Such data together with the 234U/ 238U activity ratio and the uranium content of the speleothems have been correlated with climatic variations connected with the pleistocenic climatic variations.The same data have been used to fit a hydrogeological model.Frasassi