Quantitative analysis of the Arkhangelskiella cymbiformis Group and Biostratigraphic usefulness in the North Sea Area

Abstract

Abstract. Based upon a combination of biometric and quantitative analysis on the Arkhangelskiella cymbiformis group, six additional datums were obtained in the Campanian to Maastrichtian interval of the North Sea area. These datums are in ascending order: 1. first common to abundance occurrence of A cymbiformis (Var. NT); 2. last common to abundance occurrence of A. cymbiformis (Var. NT); 3. first common to abundant occurrence of A. cymbiformis (var. N); 4. first common to abundant occurrence of A. cymbiformis (Var. W); 5. last common to abundant occurrence of A. cymbiformis (Var. N); and 7. last common to abundant occurrence of A. cymbiformis (Var. W). The width of the shield is taken as a main criterion for biometric analysis.