Cyclostratigraphy of the reference section for the Cretaceous white chalk of northern Germany, Lägerdorf–Kronsmoor: A late Campanian–early Maastrichtian orbital time scale

Abstract

New carbonate records of the upper Campanian–lower Maastrichtian white chalk of northern Germany at Lägerdorf–Kronsmoor represent a continuous succession suitable for time series analysis. The boreal chalk succession is characterized by several intervals of reduced carbonate content in the basiplana/spiniger, polyplocum, upper langei and upper grimmensis/granulosus to pseudoobtusa boreal macrofossil zones, which are mainly related to periods of increased detrital supply. Results of spectral analysis on the carbonate time series allow the detection of the periodicities of long and short eccentricity. The long eccentricity signal can be extended to the entire Upper Campanian comprising a total of 15.25 long eccentricity cycles, a minimum time span of 6.2 Ma and an age of 77.5 ± 0.4 Ma for the lower–upper Campanian boundary. The long eccentricity cycles detected from chalk carbonate contents correlate with long eccentricity cycles detected in self-potential logs of boreholes proving their significance within different depositional settings and rates of subsidence in the North German Basin. The biostratigraphic consistent occurrence of long eccentricity cycles provides evidence for the completeness of the sedimentary record. The long-term intervals of increased detrital supply are the expression of increased progradation of clay minerals related to a long-term sea-level fall with superimposed short sea-level falls within a 2.5 million year interval spanning the Campanian–Maastrichtian boundary. It cannot be decided from the present state of knowledge if this signal is controlled by increased erosion due to uplift of inverted structures, by eustatic sea-level fall or a combination of both. The detection of the long eccentricity suggests an orbital forcing superimposed on a long-term regressive trend.