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    STUDIA GEOLOGIA - Issue no. 2 / 2013  
         
  Article:   SEDIMENTARY DEPOSITION OF BOZEŞ FORMATION (APUSENI MTS., ROMANIA) – DETRITAL ZIRCON DATING AND MICROPALEONTOLOGICAL AGES.

Authors:  RAMONA BĂLC, LUMINIŢA ZAHARIA. 		 
       
         
  Abstract:  In order to establish the age of the Bozeş Formation, which crops out in the SE Apuseni Mts., calcareous nannofos-sils investigations and U-Pb detrital zircon dating were performed in the Stăuinii Valley section. The results were correlated, and further compared with previous fossil age data. The U-Pb detrital zircon age spectrum reveals a consistent Late 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 Early Campanian as the initiation of sediment deposition. Based on the presence of some important taxa in the calcareous nannofossil assemblage, the age of studied section was assigned to Late Santonian? – late Late Campanian. The Late Santonian age 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 late Late Campanian. First occurrence (FO) of Eiffellithus parallelus points to the same age. The calcareous nannofossil assemblages do not sustain the presence of the Lower Maastrichtian deposits in the Stăuinii Valley, as mentioned by few previous studies based on Pachydiscus neubergicus.

Keywords: calcareous nannofossils, Campanian, bioevent, marker species, siliciclastic rocks 		 
         
     
         
         
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