"Zdarzenie beztlenowe" na granicy cenomanu i turonu w Polsce południowo-wschodniej
Abstract
"ANOXIC EVENT" AT THE CENOMANIAN-TURONIAN BOUNDARY, SOUTH-EASTERN POLAND
Summary
In the Cenomanian-Turonian boundary interval (uppermost Rotalipora cushmani Zone and lower Whiteinella archaeocretacea Zone) in SE Poland stable isotopes δ 13C, 18O), carbonate conten ts, Corg and Ccarb contents and foraminifers are investigated. The stage boundary is defined by the appearence of coccolith species Quadrum gartneri Prins and Perch-Nielsen. The higher content of Corg in the uppermost Rotalipora cushmani and lowermost Whiteinella archaeocretacea Zones, 13C and 18O anomaly in uppermost Cenomanian as well as substantial changes of foraminiferal populations are recorded. A major carbon isotope excursion with a shift of up to + 2.0‰ δ13C (PDB) is located a short distance above the Rotalipora cushmani-Whiteinella archaeocretacea boundary within marly limestones. The peak value of δ13C corresponds to the minimum P/B ratio and minima in diversity and abundance of foraminiferal populations. A late Cenomanian expanding mid-water oxygen minimum zone is thought to be responsible for changes in foraminiferal assemblages in uppermost Rotalipora cushmani and lower Whiteinella archaeocretacea Zones.
Summary
In the Cenomanian-Turonian boundary interval (uppermost Rotalipora cushmani Zone and lower Whiteinella archaeocretacea Zone) in SE Poland stable isotopes δ 13C, 18O), carbonate conten ts, Corg and Ccarb contents and foraminifers are investigated. The stage boundary is defined by the appearence of coccolith species Quadrum gartneri Prins and Perch-Nielsen. The higher content of Corg in the uppermost Rotalipora cushmani and lowermost Whiteinella archaeocretacea Zones, 13C and 18O anomaly in uppermost Cenomanian as well as substantial changes of foraminiferal populations are recorded. A major carbon isotope excursion with a shift of up to + 2.0‰ δ13C (PDB) is located a short distance above the Rotalipora cushmani-Whiteinella archaeocretacea boundary within marly limestones. The peak value of δ13C corresponds to the minimum P/B ratio and minima in diversity and abundance of foraminiferal populations. A late Cenomanian expanding mid-water oxygen minimum zone is thought to be responsible for changes in foraminiferal assemblages in uppermost Rotalipora cushmani and lower Whiteinella archaeocretacea Zones.