Correlation Between the Type Chattian in NW Europe and the Rupelian–Chattian Candidate GSSP in Italy
The original type section for the Chattian stage is situated in northwestern Germany, that is, in the southern part of the semi-enclosed North Sea Basin. A recent magneto-and biostratigraphic study from the eastern North Sea Basin allows a new correlation to be established between sections in the original Chattian type area and sections in central Italy. One of the Italian sections is the Monte Cagnero section, a proposed Global Stratotype Section and Point (GSSP) for the Chattian stage. Our observations from the eastern North Sea and Denmark include a new method to identify NP zones in the mid-Oligocene of the North Sea Basin and confirm previous findings that a mid-Oligocene interval with the dinocyst Svalbardella in the North Sea Basin is synchronous with the global Oi-2b isotope cooling event as recognized in the Italian sections. However, we recorded the Svalbardella interval within the benthic foraminifera Asterigerina guerichi guerichi acme, a prominent North Sea Basin marker horizon. This points to a position of the Oi-2b within the lower Chattian deposits in the original type area and contradicts previous assumptions that the Oi-2b event correlates with an unconformity below the type Chattian. Our new correlations are in agreement with recently published absolute datings, calcareous nannofossil zonation, and the occurrence of Svalbardella. We suggest that the erosional base of the Chattian deposits in NW Europe is most probably synchronous with the global Oi-2a cooling event.
KeywordsSvalbardella Rupelian–Chattian boundary Oi-2a event Oi-2b event GSSP
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