The bipolar bivalve Oxytoma (Palmoxytoma) cygnipes (Young & Bird, 1822) in the Upper Pliensbachian of Germany

• Main Authors: Arp, Gernot, Seppelt, Stephan
• Format: Text
• Language: English
• Published: Springer-Verlag 2011
• Subjects: Arctic
• Online Access: https://dx.doi.org/10.23689/fidgeo-2500; https://e-docs.geo-leo.de/handle/11858/6813

The morphologically conspicuous bivalve Oxytoma (Palmoxytoma) cygnipes (Young & Bird, 1822), known for its palaeogeographically bipolar distribution, from a limestone bed in the boundary “Belemniten–Schichten”/Amaltheenton formation, Lower Jurassic, in N Germany is described. The occurrence of this palaeoceanographically significant bivalve points to an influx of cool seawater from the Arctic to the North-German Basin at the base of the Upper Pliensbachian, just before the deposition of the Amaltheenton formation. A review of previously reported occurrences on the NW European Shelf indicates two distinct stratigraphic intervals of occurrence of this taxon: the Rhaetian–Hettangian boundary and the Upper Pliensbachian. Whereas the former interval of occurrence may be related to short-term cooling in the course of the end-Triassic extinction event, the latter is interpreted as reflecting the influx of a cool water current to the eastern part of the NW European Shelf, which continued southwards parallel to the coast of the Bohemian–Vindelician High.