International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

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Campanian U–Pb ages of volcaniclastic deposits of the Haţeg Basin (Southern Carpathians): Implications for future intrabasinal lithostratigraphic correlations

Published: Oct 2023

Pages: 407 - 422

DOI: https://doi.org/10.31577/GeolCarp.2023.21

Authors: VIOLETA M. VORNICU, IOAN SEGHEDI, ZOLTÁN CSIKI-SAVA, MIHAI N. DUCEA

Abstract: Here we report new LA-ICP-MS zircon U–Pb ages of the Upper Cretaceous volcaniclastic deposits of the Haƫeg Basin (Southern Carpathians, Romania). These deposits crop out around the area of Densuş and Răchitova localities in NW Haţeg and were previously included in the Maastrichtian continental Densuş-Ciula Formation. They are interpreted as eruptive sequences generated by repeated explosive volcanic eruptions, probably related to the Apuseni–Banat–Timok–Srednogorie (ABTS) magmatic activity, that manifested in Eastern Europe during the Late Cretaceous. The three samples selected for U–Pb age determination were collected from the Densuş volcaniclastic sequences; they are primary andesitic–dacitic lithic clasts resulted directly from volcanic eruptions. The new zircon U–Pb ages of 80.44 ± 0.14, 80.22 ± 0.25, and 81.88 ± 0.17 (Early to earliest-Late Campanian), as well as geochemical analyses of the three sampled volcaniclastics, overlap with previously reported data for Banatite rock samples from the Banat and Apuseni segments of the ABTS belt. Age and composition similarities strongly suggest an affinity between the Late Cretaceous Neotethyan subduction-initiated magmatism and the volcaniclastic deposits of the Haţeg Basin. The Densuş–Ciula Formation unconformably overlies the Răchitova Formation – the youngest marine beds in this area, divided into Upper and Lower members. Recently, the age of the Upper Member was biostratigraphically restricted to the Early to earliest-Late Campanian, about the same period of time during which, according to the new U–Pb ages, subaerial volcanism took place. Considering their Early to earliest-Late Campanian age, the volcaniclastic deposits may represent a different lithostratigraphic unit from the Maastrichtian Densuş–Ciula Formation, to which they were formerly associated with. On these grounds, we suggest that the association of the volcaniclastic products with this formation, along with their stratigraphic and tectonic relationships, is revised.

Keywords: zircon U–Pb dating, volcaniclastic, Campanian, ABTS belt, Banatite, Haţeg Basin, Densuş–Ciula Formation

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