Stable Isotopes Carbon C13 and Oxygen O18 as Indicators of Triassic Limestone Sedimentation Environment and Diagenesis
Abstract The results of researches of the stable isotopes, carbon 13C and oxygen 18O, measured in Triassic limestones of Opole Silesia in Poland were presented in this article. The study was carried out to obtain data for interpretation of the environment of these rocks formation. Moreover, it was possible to form the theory about diagenetic processes which influenced on the mineral composition of limestone and some of their carbonte phases. The results of study show a general differentiation of δ13C and δ18O contents in carbonate minerals. All δ18O values are less than 0 ‰. It indicates that the origin oxygen isotope composition could be probably reset by diagenesis. The crystallization temperatures of low-Mg calcite and high-Mg, calculated on the basis of δ18O values are greater than 25 oC. They are higher than typical for sea basin and are also not be related to the presence of hydrothermal solutions. The increased temperatures of calcites crystallization are related to diagenetic processes that took place after the deposition and burial of carbonate material. The preservation of high-Mg calcite, an ustable carbonate phase, which is usually trasformed into low-Mg calcite during diagenesis, is probably connected with the increased salinity of the sea basin in which studied limestones were formed.