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Late Rhaetian/Hettangian microfloras of three depositional environments of the NW Tethyan realm have been studied: platform to basinal limestones of the Csővár section (N Hungary), shallow marine limestones and marls of the Tatra Mountains (N Slovakia) and terrestrial coal deposits of the Mecsek Mountains (S Hungary). The analysis of the palynological assemblages and palynofacies patterns builds the base for interpretation and comparison of the different depositional environments. Additionally, the sporomorph distribution and diversity are investigated with respect to environmental and climatic change within the Triassic/Jurassic boundary interval and the processes that may have caused these changes. A striking spore spike was detected in all depositional areas studied. Palynological investigations were accompanied by geochemical (stable isotope) and clay mineral analyses. The results of this integrated analysis point to a relatively sudden climatic change most probably caused by the volcanic activity of the Central Atlantic Magmatic Province (CAMP) associated with the onset of rifting of Pangaea during early Mesozoic times. The data obtained in the course of this thesis strongly support this interpretation and depositional series of Hungary and Slovakia proved to be key sections of the NW Tethyan realm.