Biostratigraphic and isotopic record of the Cenomanian–Turonian deposits in the Ohaba-Ponor section (SW Haţeg, Romania)

摘要: Abstract The middle Cenomanian–lower Turonian deposits of Ohaba-Ponor section (Southern Carpathians) were studied from biostratigraphic and isotopic points view. Both the qualitative semiquantitative nannofloral analyses, as well stable isotope (δ 13 C δ 18 O) data support significant palaeoenvironmental changes in investigated interval. Two positive excursions recognized: (1) an excursion up to 1.8‰ (PDB) within middle/late Cenomanian boundary; (2) 2.2‰ Cenomanian/Turonian boundary oldest recorded (placed Acanthoceras jukes-brownei/Eucalycoceras pentagonum Ammonite Zone interval, NC11 Calcareous Nannofossil respectively) could be assigned Event II (MCEII). During above-mentioned event, increase abundance Watznaueria barnesae , followed by successive blooms Biscutum constans Eprolithus floralis observed. youngest was identified interval (in NC12 lower part NC13 Zones). Even amplitude this is section, generally reported, may represent regional record OAE2. peaks nannofossils Zeugrhabdotus erectus indicate episodes cooler surface water high fertility, which preceded lasted event. Additionally, fluctuations O values between −2 −6‰ suggest also conditions