New advances in the stratigraphy and geochemistry of the German Turonian (Late Cretaceous) tephrostratigraphic framework

Abstract

The lowest of the five bentonites in the German Turonian tephrostratigraphic framework, T_C, can be correlated for the first time from the Rotpläner (red limestone) standard section in the Söhlde-Loges Quarry (Lower Saxony) to highly condensed, near-swell successions of the nearby Woltwiesche Quarry and the Hoppenstedt Quarry (Saxony-Anhalt). A second bentonite, T_C2, only recently recognised at Söhlde-Loges, is now identified at Woltwiesche and in the distal/expanded white limestone successions of the Salzgitter-Salder Quarry and the Flöteberg road-cutting (both Lower Saxony). T_C2 can easily be located a short distance above a major lithofacies change (herein termed the Basal Upper Turonian Facies Turnover), making it an isochronous marker permitting correlation between condensed nearswell and expanded basinal sections. On this basis, a bentonite, previously identified as T_C at Hoppenstedt must be reassigned as T_C2. Examination of the major, trace, and rare-earth element (REE) data of all the five bentonites identified in Lower Saxony and Saxony-Anhalt shows that it is possible to discriminate between them to some extent. Bentonites T_C and T_C2 are geochemically similar and separable from T_D, which is itself distinct from T_E and T_F.