Conodont biostratigraphy of Upper Triassic dolomites of the Buda Hills (Transdanubian Range, Hungary)

Abstract

The precise dating of the Upper Triassic pelagic dolomites in the Buda Hills has always been a problematic point in the geologic research of the area. Previously found fossils were mostly unsuitable for the exact stratigraphic assignment of these formations due to their low number and poor preservation. Recently, sparse samples were collected from the dolomite sequence of the northern and southern ranges for conodont biostratigraphic investigations. The standard processing technique of dilute acetic acid provided a rich and diverse conodont fauna which enabled the chronostratigraphic subdivision of the Sashegy Dolomite Member of the Mátyáshegy Formation. Samples of the northern range yielded a Lower to Upper Norian conodont assemblage consisting mainly of the genera Epigondolella and Mockinabeside the genera Metapolygnathus, Norigondolella and Parvigondolella. The western part of the southern range is Upper Carnian in age indicated by genus Carnepigondolella and early epigondolellids. Eastwards, genera Epigondolella and Mockina suggest Lower to Middle Norian age. From the central part of the range towards the east the recurrence of the Upper Carnian to Lower Norian sequence was observed. The easternmost segment of the range is Upper Norian based on the genera Mockina and Parvigondolella. According to the new conodont biostratigraphic results, the Mátyáshegy Formation is confirmed to be coeval with the Csővár Formation that occurs on the east side of the River Danube. Detailed
studies on the conodont assemblages of the Buda Hills might offer a solution for the problems of Upper Triassic conodont phylogenesis and conodont zonation.