DATE2022-06-21 20:58:29
TITLEEarly Pliocene environmental conditions in the South Aegean Sea (NE Mediterranean): calcareous nannofossil paleofluxes and evidence of the Zanclean reflooding in the Cretan basin.
AUTHORSElisavet Skampa (1) ,Maria Triantaphyllou (1) ,Margarita Dimiza (1) ,Agnieszka Arabas (2) ,Alexandra Gogou (3) ,Karl- Heinz Baumann (4)
  1. 1) National And Kapodistrian University Of Athens, Athens (Greece) ,2) Institute Of Geological Sciences, Polish Academy Of Sciences, Kraków (Poland) ,3) Hellenic Centre For Marine Research, Institute Of Oceanography, Anavyssos (Greece) ,4) University Of Bremen, Bremen (Germany)
ABSTRACTThe DSDP Leg 42A Site 378 located in the South Aegean Sea (Cretan basin) offers an exceptional opportunity to investigate in detail the Early Pliocene paleoenvironmental conditions through the study of calcareous nannofossil paleofluxes. In the DSDP sediment record we focus on the “warm Pliocene” interval, following the Zanclean reflooding event of the Aegean Sea after the Messinian Salinity Crisis (MSC) of the Mediterranean Sea. A detailed investigation on marine primary producers-calcareous nannofossils response to a high CO2 world will reveal their paleoproductivity trends affected by 23-kyr monsoon variability and their re-colonization in the Cretan basin after the "post-Messinian flood". Based on the produced age model, we present a composite dataset of the two Holes (Z and A) of Site 378 for the interval 3.8-5.09 Ma. The calcareous nannofossil paleofluxes are in accordance with the δ13Corg trend in the sapropel layers, suggesting that the sapropels presented in our study are not only formed by preservation factors but also reflect enhanced accumulation and increased primary productivity conditions. Reticulofenestra spp. prevailed in the calcareous nannofossil paleofluxes. The prevailing taxa of calcareous nannofossil assemblage support in general the occurrence of warm paleoclimatic conditions during the Early Pliocene. In addition, the two principal components that influence the calcareous nannofossil assemblage are the temperature and the stratification of the water column. The sapropelic layers of the present study, are characterised by intervals with increased temperature and low oxygen conditions as revealed by δ18O and δ15N isotopic analyses and by calcareous nannofossil species related to warmer and oligotrophic conditions. Moreover, a change in sapropel formation is depicted at 4.4Ma, with the low OC content sapropels do not capture the sapropel formation mechanism signal as intense as presented in the high OC sapropels of the same interval. Finally, the presence of PLG evaporites of the first stage of the MSC, suggests a fast evaporation and a possible isolation of the Cretan Basin. According to the present study and the produced age model, the oldest Zanclean sediment, dated at 5.09 Ma, is placed above the PLG gypsum (5.97–5.6 Ma), giving a first insight of the age of the deep-water marine paleoenvironment that was re-established in the Cretan Basin, thus the potential age of the Cretan Basin reflooding.