Relationship between natural radioactive elements (Th, U, K) and Triassic carbonate lithofacies in Hronicum and Silicicum of Male Karpaty Mts

Natural radioactive element contents (Th, U) were examined in Triassic limestones and dolomites of the Little Carpathian Mountains. Four basic facies were distinguished in the formation: Middle Triassic shallow-water shelf limestones and dolomites, basin and slope pelagic limestones, forereef and reef limestones and dolomites, and Upper Triassic shallow-water limestones and dolomites. A direct interdependence was observed between the Th and K values and the IR contents. The Th and K contents are decisive for the bulk gamma activity of samples with high IR. In low-IR carbonates, the effect of U is decisive, its contents in the distinguished facies being variable. The U contents vary over a relatively wide range, although its average values are not anomalously high. The most marked differences in the concentrations of U, viz. 0.2-6.6 ppm, were found in forereef facies, where material from various facial zones had accumulated. (author). 1 tab., 7 figs., 24 refs