Foraminifers and stable isotope record of the Dubivtsi chalk (upper Turonian, Western Ukraine): palaeoenvironmental implications

Abstract

A combined micropalaeontological and stable isotope study of the Dubivtsi chalk in the Western Ukraine indicates its middle late Turonian age. One long-term and clearly distinguishable positive excursion of the isotope curve (d13C) in the Dubivtsi chalk is probably equivalent to a widespread upper Turonian positive peak recorded in Western and Southern Europe and named Peak +1, Hyphantoceras Event or Hitch Wood Event. Such correlation is also supported by inoceramid fauna and increasing d18O values. Sedimentation of the pure Dubivtsi chalk occurred under highly oligotrophic conditions, reflected by the low diversity and very low abundance of planktonic and benthic foraminifera and a flood abundance of pithonellid calcispheres. These conditions probably were triggered by regression, a low level of regional tectonic activity, and near absence of uplifted areas in adjacent areas and hence the supply of nutrients to the basin was limited.