文摘
Uranium (238U) and thorium (232Th) contents were evaluated in different stalagmite and stalactite samples belonging to a quaternary limestone cave by using a method based on determining mean critical angles of etching of the CR-39 and LR-115 II solid-state nuclear track detectors (SSNTDs). Annual absorbed α-, β- and γ-dose rates were determined in the stalagmite and stalactite materials. The stalagmite and stalactite samples were dated by exploiting data obtained for the total annual absorbed dose rates and measuring the corresponding paleodoses. Results obtained were compared with those obtained by classic thermoluminescence and U/Th disequilibrium methods. The studied speleothem began from about 121kyr and continued to about 69kyr, coinciding almost with the last interglaciation corresponding to the fourth and fifth isotope stages. The formation rates of the stalagmite and stalactite samples were found equal to 0.88 and 0.94cmkyr−1, respectively.