ABSTRACT
Non-marine molluscan faunas from sites of late Lower and early Middle Pleistocene age in Britain, The Netherlands, France, Germany and Denmark are reviewed. The fauna from the Cromerian stratotype at West Runton shares two extinct prosobranchs (Valvata goldfussiana and Tanousia runtoniana) with that of the Bavel Interglacial at its type locality. Conversely, two other prosobranchs, Lithoglyphus jahni and Fagotia wuesti, characteristic of the Bavelian and earlier periods, are absent at West Runton. These facts suggest that the two sites are close in age but that West Runton is the younger. Moreover, the stratigraphical range of V. goldfussiana in the Netherlands (Middle Tiglian — Cromerian Interglacial I) suggests that West Runton should be placed early in the ‘Cromerian Complex’.
British sites assigned to the ‘Cromerian’ Stage fall loosely into three groups. Group 1 is characterized by V. goldfussiana, T. runtoniana, Bithynia troscheli and Viviparus viviparus gibbus, and includes West Runton, Kessingland and Sugworth. The fauna of Group 2 with Valvata naticina, B. troscheli, Tanousia cf. stenostoma and Belgrandia marginata is known only from Little Oakley. Group 3 faunas, such as those from Sidestrand and Trimingham, with V. naticina, Bithynia tentaculata and B. marginata, lack distinctive ‘Cromerian’ elements and have close affinities with certain Hoxnian assemblages. The extinct water vole Mimomys savini has been recorded from sites assigned to each of these three Groups. At Ostend, Norfolk, an undiagnostic molluscan fauna has been recovered from beds that have yielded the vole Arvicola t. cantiana. It would appear from the malacological evidence that two, or more likely several, interglacials, currently assigned to the British Cromerian, are represented.
It is not possible to assign with confidence any of the continental sites discussed to these groups but the faunas from Noordbergum and Exmorra have closest affinities with Group 3, whereas those from IJsselstein and from North Sea borehole E8–4, both with V. goldfussiana, are closest to Group 1. The malacological data do not support correlation of Noordbergum (‘Interglacial IV) with West Runton but would support a recent suggestion, based on vertebrate evidence, that West Runton is older. It is not possible to correlate West Runton with any known parts of the four Dutch ‘Cromerian’ interglacials.
