Abstract
We present belemnite-bearing strata (Upper Cenomanian) of the Bohemian Cretaceous Basin (BCB) at the onset of the Oceanic Anoxic Event II (OAE2). High-resolution climate records reveal considerable changes in temperature, carbon cycling, and ocean chemistry during the OAE2 (O'Connor et al. 2020).
A prominent cooling phase within the greenhouse Cretaceous period - the Plenus Cold Event (PCE) has for the first time been recognised in the English Chalk, based on an invasive Boreal fauna (North Boreal Group) and subsequently by stable-isotope excursions within the OAE2 (Jefferies 1963; O'Connor et al. 2020). The PCE is generally accompanied by faunal shift and temperature decrease worldwide.
We have investigated the occurrence and geochemical characteristics of the belemnite species Praeactinocamax plenus (de Blainville, 1827) within several parts of the BCB and we have received relevant data especially from NE part of the BCB. The characterisation of rostra is performed by δ18Obel, δ13Cbel and 87Sr/86Sr.
The Plenus beds represent a very narrow stratigraphical interval corresponding to a part of the Metoicoceras geslinianum ammonite Zone. Studied rostra of P. plenus are morphologically consistent with all typical morphotypes of this species distributed from Kazakhstan to Great Britain.
A relatively thin horizons bearing belemnite rostra show stratigraphical stability in the NE Bohemia. Based on biostratigraphy and stable isotope curve, these records can be correlated with Jefferies's beds in the Anglo-Paris Basin, Lower Saxony, Northern Peri-Tethys (France, Provence; Gale et Christensen 1996) and other sites.