Orbitální cykly a jejich možný odraz v sedimentech vnějších Západních Karpat

Abstract

The work deals with the study of possible traces of the so-called Milankovitch orbital cycles in the Lower Cretaceous sediments of the outer Western Carpathians in the Kotouč quarry site in Štramberk. Two sections for the analysis of cyclical climate change were selected: (1) the Plaňava Formation on the 6th layer of the quarry where significant cyclic lithological changes in the sedimentation record were clearly visible and (2) thick layers of Štramberk Limestone on the previously investigated profiles on the 5th layer of the quarry . The introduction focuses on the basic information about orbital cycles (the so-called Milankovitch cycles), the basic geology, and presents the target locations. The next part is devoted to the types and methods of the analyses carried out with the aim to obtain the course of changes in the content of selected minerals (calcite, quartz, pyrite, etc.) over time, elements (Ca, Si, C, S, Sr, Zr and a number of others), or isotopes (δ13C, δ18O). The detected and described changes are confronted with changes in lithology and time series of these changes are constructed based on the estimation of the sedimentation rate of the investigated layers. These are afterwards studied in terms of cyclic changes of selected parameters and their periodicity in relation to the known periods of orbital cycles. The detected results of changes in the rock composition are discussed in regard to the detected cycles, quantified, and compared with the known periods of our planet's orbital cycles. In addition to these results, some methodological procedures as well as a mutual comparison of two or more methods or analyses of techniques are discussed.