Tracking Late Cretaceous environmental change: Geochemical environment of the upper Campanian to lower Maastrichtian chalks at Kronsmoor, northern Germany

This high-resolution study (210 samples/44 m) of the uppermost Campanian-lower Maastrichtian chalk at Kronsmoor (northern Germany) intends to define the inorganic depositional setting of Late Cretaceous chalk deposition as well as to reconstruct contemporaneous sea-level fluctuations and palaeoenvironmental changes. A latest Campanian event associated with significantly decreased carbonate contents and palaeotemperatures is reflected in most geochemical palaeoproductivity proxies and indicates reduced marine fertility across the Campanian-Maastrichtian boundary. Sr/Ca and δ13C remain low afterwards while other productivity proxies show a significant rebound, indicating recovery and a potential qualitative change in marine productivity during the early Maastrichtian. Redox-sensitive proxies indicate overall well oxygenated conditions. The %terrigenous proxy tracks an argillaceous chalk depositional event related to an inferred glacio-eustatic latest Campanian sea-level fall followed by a low sea-level stand until the earliest Maastrichtian. It decreases and stays low up-section, reflecting an early Maastrichtian sea-level rise and highstand, parallelled by increasing and consistently high carbonate contents. However, the concomitant conspicuous variability and increase in other terrigenous input proxies indicate more strongly fluctuating and higher aeolian supply. Time-series analysis of selected geochemical proxies demonstrates the presence of the obliquity (∼40 kyr) the long-eccentricity (∼400 kyr) cycles of the Milankovitch Band. The covariance of productivity proxies and indicators of aeolian input suggests that obliquity forcing of dust input exerted control on (surface) water productivity, CaCO3 flux and the end-Cretaceous carbon cycle.