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.