Sedimentology and dinoflagellate cycst of the Cap Blanc Nez section

The stacking pattern in the natural gamma ray signal and the carbonate and TOC content has the same period and provides lithological support of the bundling. A shelf basin circulation model is proposed to explain the relation between orbitally forced climate change, its palaeoenvironmental consequences and the resulting sedimentary cyclicity. Variations in surface water circulation are reflected in the sediment by the chalk-marl couplets, the most distinctive couplets ocurring at the base and top of the bundles.

While the chalks reflect well-mixed surface water conditions, the marls, particularly those at the bundle boundaries, can be interpreted as the sedimentary expression of stratified water masses. During deposition of these marls, reduced oceanic mixing due to low seasonality during strong precession maxima at the eccentricity maxima caused periods of water column stratification that in turn led to nutrient depletion and decreased productivity in the surface water masses.