Sedimentary deposition of Bozeş Formation (Apuseni Mts., Romania) – detrital zircon dating and micropaleontological ages

In order to establish the age of the Bozeş Formation, which crops out in the SE Apuseni Mts., calcareous nannofossils investigations and U-Pb detrital zircon dating were performed on Stăuinii Valley deposits. The results were correlated, and further compared with previous fossil age data. The U-Pb detrital zircon age spectrum reveals a consistent Upper Cretaceous grain population, which yielded an age of 83 Ma (concordia age of 82.87±0.59 Ma), interpreted as the maximum deposition age, thus, marking the Lower Campanian as the initiation of sediment deposition. Based on the presence of some important taxa in the calcareous nannofossils assemblage, the age of studied deposits were assigned to Upper Santonian? – upper Upper Campanian. The Upper Santonianage is presumed by the presence of curved Lucianorhabdus cauyeuxii, reworked from older deposits. The Campanian stage is confirmed by the presence of Broinsonia parca parca, Broinsonia parca constricta and rare specimens of Ceratolithoides aculeus and Uniplanarius sissinghii. Both Reinhardtites anthophorus and Eiffelithus eximius indicate that the upper part of the Stăuinii section is ending in CC22 / UC15dTP – UC15eTP Subzones, thus in upper Upper Campanian. FO of Eiffellithus parallelus points to the same age. The calcareous nannofossils assemblages do not sustain the presence of the Lower Maastrichtian deposits on Stăuinii Valley, as mentioned by few previous studies based on Pachydiscus neubergicus