Abstract
Stable isotopes ( 13C, 18O), CaCO 3 contents, carbon content insoluble in HCl (C org) and in the carbonates (C carb), and foraminifers have been investigated in the Cenomanian-Turonian boundary interval (uppermost Rotalipora cushmani Zone and lower Whiteinella archaeocretacea Zone) in SE Poland. The stage boundary is defined by the appearance of the coccolith species Quadrum gartneri Prins & Perch-Nielsen. The higher content of C org in the uppermost Rotalipora cushmani Zone and lowermost Whiteinella archaeocretacea Zone, a δ 13C and δ 18O stable isotope anomaly in the uppermost Cenomanian, and substantial changes in the foraminiferal assemblages have been recorded. A major carbon stable isotope excursion with a shift of up to +2.0‰ δ 13C (PDB) is located a short distance above the Rotalipora cushmani-Whiteinella archaeocretacea boundary within marly limestones. The peak value of δ 13C corresponds to the minimum P/B ratio, and minima in the diversity and abundance of foraminiferal assemblages. A late Cenomanian expanding mid-water oxygen minimum zone is thought to be responsible for changes in foraminiferal assemblages in the uppermost Rotalipora cushmani and lower Whiteinella archaeocretacea Zones.
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