Origin of deep-sea clastics of the Magura Basin (Eocene Makovica sandstones in the Outer Western Carpathians) with constraints of framework petrography, heavy mineral analysis and zircon geochronology

摘要

Petrographic examination, heavy mineral analysis and detrital zircon U-Pb dating were performed on the Eocene siliciclastic rocks in the Raca Unit of the Outer Western Carpathians in order to reveal their origin and establish the development of the Magura Basin during the Eocene. The medium- to fine-grained sublitharenites and quartzarenites were mainly derived from extra-basinal sources, and the deposits predominantly contain minerals from metamorphic rocks. The terrigenous material was derived from low- to medium-grade metapelites and granitoids. The sedimentation was also controlled by a sediment supply from the mafic source. The basic and metabasic rocks contain pyrope-rich garnets and Cr-spinels. Palaeo-currents document that the sedimentary material was supplied from the South-East. The first detrital zircon U-Pb ages confirm zircon-producing events occurring in the Proterozoic from approximately 2200 to 590 Ma; but predominantly in the Paleozoic between 550 and 60 Ma. The palaeocurrent indicators, petrographic data, heavy mineral spectra and zircon geochronology strongly suggest that the Tisza Mega-Unit Variscan crystalline basement erosion with accompanying sedimentary cover supplied the Magura Basin from the South. The Mecsek Zone is also suggested to support the Villani-Bihor and part of the Bekes-Codru zones in supplying the Magura Basin during the Eocene to Oligocene. The Eocene transport of significant detrital material to the Magura Basin is also related to erosion of the Marmarosh Massif Proterozoic-Ordovician low- to medium-grade crystalline basement. Therefore, it is most likely that Magura Basin sedimentation was dominated by supply from the sub-ophiolitic Fore-Marmarosh Suture Zone of the Eastern Carpathians.