Mt. Begunjšcica is a mountain range in the Southern Karavanke Mountains. The Jurassic beds of Mt. Begunjšcica are relatively well exposed on its southern slope and therefore Mt. Begunjščica represent an important section for the understanding of Jurassic sedimentary evolution of Julian High. Jurassic beds are separated by at least one stronger fault, which divides them into the north and south block. In my master's thesis, I studied and described the Jurassic succession in the southern tectonic block of Mt. Begunjščica. A sedimentological section was logged and sampled for thin sections. I interpreted the sedimentary evolution of the Jurassic succession from detailed microfacial and biostratigraphic analysis.
The succession is composed of four major lithostratigraphic units. The section begins with micritic limestones with biogenic debris and intermediate limestone breccias deposited in a deepened environment in the Early Jurassic. Manganese nodules and crusts are also present, indicating extremely slow sedimentation rates. After that irregular boundary follows and a short succession of shales, marls, cherts and limestones heavily enriched with manganese, with the lower part very likely deposited during the Early Toarcian oceanic anoxic event. The Toarcian sequence continues with condensed limestones of Ammonitico Rosso type, among which limestone breccias also occur, with manganese clasts and older rocks. Towards the top of the profile, the sequence changes more to the highly deformed limestone created by slumps. The age of these layers is questionable, they may still be of the Toarcian age, but it is also possible that they are Middle Jurassic in age and deposited above the stratigraphic gap. The section ends with alternating pelagic and turbiditic sediments, representing more calcareous development prior to radiolaritic deposits, which begin depositing at the northern block of the Mt. Begunjščica at the end of the Middle Jurassic but are not covered by the profile of the southern block anymore.
The analysis of Jurassic beds on the south block of Mt. Begunjščica confirmed similarities with the section of the north block, which proves that the Jurassic sequence is repeated several times due to minor folds and a fault. The successions differ, in particular, in the thickness of the beds, indicating probably more submerged southern block already in the Jurassic. Today's fault is probably just a reactivated Mesozoic normal fault. The regional correlation shows that there are no comparable successions with Toarcian Ammonitico Rosso limestones in the narrower Julian Carbonate Platform, but they are typical for other paleogeographic units of the Southern Alps as well as other areas of the Jurassic passive margin of the Adriatic microplate.
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