A new Berriasian to Coniacian composite carbon isotope record from the Boreal Realm

High-amplitude shifts in sedimentary δ¹³C characterize the Cretaceous system and have been proven to be of great use for supraregional chemostratigraphic correlation. Here we present an upper Berriasian to lower Coniacian (c. 142 – 88 Ma) composite carbon isotope record based on 14 drill cores, two outcrops and almost 5000 samples. The total record comprises a composite thickness of about 1500 m. All cores and successions are located in the larger Hanover area, which represents the depocenter of the North German Lower Saxony Basin (LSB) in early to mid-Cretaceous times.

Boreal Lower Cretaceous sediments are predominantly represented by CaCO₃-poor mud- and siltstones of up to 2000 m thickness in northern Germany, which become more carbonate-rich during the Albian-Cenomanian transition and even chalkier in the upper Cenomanian to Coniacian interval. A number of global carbon isotope key events including the Valanginian Weissert Event, the OAEs 1a, b and d (Aptian-Albian) as well as for the early Late Cretaceous the Mid-Cenomanian Event (MCE), the OAE 2 (Cenomanian-Turonian Boundary Event) and the Navigation Event, among others, have been identified allowing for a detailed comparison with Tethyan and other Boreal records. Thus, this new detailed chemostratigraphy provides a unique opportunity to potentially overcome many still existing Boreal–Tethyan correlation issues. The presented record can be considered to be almost complete, albeit a small gap in the early Albian cannot be ruled.