The Carnian-Norian basin-platform system of the Martuljek Mountain Group (Julian Alps, Slovenia): progradation of the Dachstein carbonate platform

摘要

In the Martuljek Mountain Group (MMG), positioned in the northern part of the Julian Alps (NW Slovenia),a widespread drowning of the middle Carnian carbonate platform is marked by the onset of a thin (approximately 25 m)horizon of reddish pelagic platy basinal limestones (Martuljek platy limestone). According to conodont data, differentages of the upper part of the Martuljek platy limestone are documented, namely late Carnian in the SW and early Norianin the NE part of the MMG. The rimmed Dachstein carbonate platform progrades into the basin with typically devel-oped facies zones: slope and reef margin (approximately 300 m thick) with abundant coral fauna with other framebuildersand the Lofer cyclic Dachstein Limestone in the backreef peritidal area. In the NW face of the Mt Skrlatica, platform tothe basin transition is spectacularly exposed. The interfingering of slope to basin sediments and the dip of theclinostratification, indicate SW to NE progradation of the Dachstein platform (in recent orientation), which is also inaccordance with conodont data estimation of the underlying Martuljek platy limestones. The margin of the Dachsteinplatform in the MMG is thus progressively younger from the SW direction to the NE. After (and during) the filling ofthe basin, the peritidal carbonate platform, with a more than 1 km thick succession of the Dachstein Limestone pre-vailed until the end of the Triassic Period in the central part of the Julian Alps. The Carnian drowning event in the JulianAlps and also in the Kamnik-Savinja Alps is not just a locally limited phenomenon, as described so far, but a wide-spread event, triggering the growth of the Tuvalian-Norian reefs, facing more open marine areas.