Sources of Clastic Material for the Cretaceous‒Paleogene Boundary Deposits in Klementyev Mountain, Eastern Crimea: Results of the U‒Th‒Pb Dating of Detrital Zircon Grains and Their Significance for Regional Paleogeographic Reconstructions

The paper presents results of the U–Th–Pb isotope dating (LA-ICP-MS) of detrital zircons from sandstones of the Upper Cretaceous (Maastrichtian)–Lower Paleogene (Danian) boundary level sections, Klementyev Mountain section, Uzyn-Syrt Upland (eastern Crimean Mountains). The obtained data set from the Upper Maastrichtian Klementyev Formation (sample K22-001) contains the following number of dates: 5 Jurassic, 22 Triassic, 55 Paleozoic (including 10 Permian and 7 Carboniferous), 18 Neoproterozoic, 13 Mesoproterozoic (1014–1511 Ma), 27 Paleoproterozoic, and 10 Archean dates (including 1 Paleoarchean). The lower Danian Feodosiya Formation (sample K22-002) yielded the following number of dates: 2 Jurassic, 4 Triassic, 55 Paleozoic (including 11 Permian and 16 Carboniferous dates), 24 Neoproterozoic, 25 Mesoproterozoic (1008‒1525 Ma), 42 Paleoproterozoic, and 13 Archean dates. The very wide (Jurassic to Paleoarchean) age range indicates a diversity of primary provenances, including Archean, Paleoproterozoic, Mesoproterozoic, Neoproterozoic, and Paleozoic crystalline complexes. Such a provenance signal cannot be obtained during the accumulation of erosion products from one proximal local source. Thus, traditional paleogeographic schemes of Crimea are not confirmed for the Maastrichtian and Danian, according to which detrital material was delivered to the present-day Klementyev Mountain site from the south and/or southwest (present-day Crimean Mountains). The most probable sources of terrigenous material for the studied rocks were represented by the epi-Hercynian Scythian and ancient East European platforms located north of the Klementyev Mountain. Relative to the Danian sequences, the Klementyev Mountain section is marked by decrease in the share of the Triassic zircon and increase of the Neoproterozoic zircons in the Maastrichtian sequences.