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Oligocene palaeoenvironmental changes in the Romanian Carpathians, revealed by calcareous nannofossils

Melinte M. C.

Studia Geologica Polonica

2005

Vol. 124

341-352

Calcareous nannofossils from five sections from the Eastern Carpathians (Romania) have been investigated to identify palaeoenvironmental and palaeoclimatic changes during the Oligocene. Both qualitative and quantitative analysis hade been performed. The nannofloral assemblages reflect cool surface water conditions during Early Oligocene (corresponding to the upper part of NP21 through lower part of NP24 nannofossil zones) and warm water conditions during Late Oligocene (upper part of the NP24 and lower part of the NP25 nannofosil zones). A cooling interval was assumed for the latest Oligocene-basal Miocene (upper part of the NP25 and base of NN1 nannofossil zones), followed by a restoration of a warmer climatic mode in the earliest Miocene. A sea-level fall characterized the early Rupelian, interval when the salinity strongly decreases. These palaeoenviron- mental conditions are reflected by the bloom of endemic nannofloras. A sea-level rise characterized the late Rupelian as well as the early Chattian. The deposition of coccolithic limestones, containing bloom of cosmopolitan nannofloral species (within the NP24 Nannofosil Zone) could indicate the Late Oligocene Warming Event in the Romanian Carpathians. The sea-level dropped again in the late Chattian, followed by a new transgression within the latest Chattian-earliest Aquitanian interval.