|mhorn||Дата: Sunday, 07.08.2011, 17:28 | Сообщение # 1|
|Arp G., Seppelt S. (2011) The bipolar bivalve Oxytoma (Palmoxytoma) cygnipes (Young & Bird, 1822) in the Upper Pliensbachian of Germany // Paläontologische Zeitschrift, in press. DOI: 10.1007/s12542-011-0113-1 |
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.
Middle Jurassic - Lower Cretaceous ammonites & aptychi