The thesis studies the reddish infilling of megalodontid bivalves of the Norian-Rhaetian Dachstein Limestone in the valley below the Peski Mountain in the Krn Range of the Julian Alps. Megalodontid shells are usually found in subtidal facies and are filled or neomorphically replaced with white calcite cement. In our case, in addition to the classic fillings, there are also specimens completely or at least partially filled with red or green, slightly marly limestone. A layer inside the Dachstein Limestone in the valley below the Peski Mountain provides the best insight into these picturesque infillings.
In addition to the filling of the megalodontid bivalves, we also examined the nearby neptunian dikes, which are filled with limestone breccia with reddish and sometimes yellow-green limestone matrix. There are two generations of neptunian dikes with different shivering and fillings in the explored area. The research hypothesis of the thesis was that the reddish sediment in the megalodontides, and of the matrix in the breccias of the neptunian dikes was the same. Samples of megalodontid bivalvia with red limestone fillings, white calcite cement, as well as samples from the neptunian dikes were collected. Fourty-three thin-sections were photographed, scanned and examined under a optical polarizing microscope. Using optical microscopy, four generations of fillings bivalves were defined, and it has been proven that at least some of the neptunian dikes were filled with Upper Cretaceous limestone. Unfortunately, we could not prove the age of the sediment in megalodontides, since there were no biostratigraphically characteristic fossils in the infill , but we assue it is a Jurassic sediment as in this period the extensional tectonics disintegrated and deepened the Julian carbonate platform, and consequently caused the formation of neptunian dikes. We assume that the matrix from dikes was laterally washed into the partially dissolved shells of bivalves and gastropods in the host rock. Further research should focus on carrying out a cathodoluminescence study to further define the cement generations.