Provenance and morphostratigraphy of the Pliocene-Quaternary sediments in the Celje and Drava-Ptuj Basins (eastern Slovenia)

This study presents the results of the first systematic morphostratigraphic and provenance analyses of the Pliocene-Quaternary fluvial sediments in the Celje and Drava-Ptuj intramontane basins. Based on the degree of terrace preservation, the dip of the terrace surfaces and fans, and the composition and degree of weathering of the sediments, low-, middle- and high-level terrace groups were constrained and tentatively attributed to Late Pleistocene, Middle Pleistocene and Plio-Early Pleistocene, respectively. The provenance analysis focused on the sediments from the high-level terrace (Plio-Early Pleistocene) and encompassed clast lithological analysis and microfacies analysis of the clasts. The results indicate a local provenance with relatively short transport, which is consistent with the morphology of the clasts. The source rocks of the Plio-Early Pleistocene deposits in the Celje Basin are attributed to the formations outcropping in the southern Pohorje Massif and the Upper Savinja River Valley corresponding to the paleo-Savinja. The possibility of resedimentation of the clasts from Miocene clastic sedimentary rocks located north of the Celje Basin also needs to be considered. The sediments of the Drava-Ptuj Basin originate from the Pohorje Massif, the Kozjak mountain range, and the area south of the Pohorje Massif which were deposited by the paleo-Drava and paleo-Dravinja rivers. Our study indicates that the drainage systems of the paleo-Savinja, paleo-Drava and paleo-Dravinja during the Plio-Early Pleistocene roughly correspond to those of the present day