Benthic foraminifera: indicators for a long-term improvement of living conditions in the Late Valanginian of the NW German Basin

Abstract. Foraminiferal occurrences in marine sediments of Late Valanginian age (Early Cretaceous) are described from NW Germany. The distribution patterns of benthic foraminifera are discussed with respect to their abundance and diversity. Benthic foraminifera are characterized in terms of moderate diversity and abundance. Vertical fluctuations in foraminifera contents are discussed with respect to their palaeoecology and palaeobiogeography. Benthic foraminifera, which are represented by a total of 101 species, show a gradual increase of diversity throughout the Late Valanginian. This improvement of living conditions in an epicontinental sea over a period of approximately 2 million years indicates a gradual recolonization of the formerly non-marine semi-restricted basin. The associations are dominated by agglutinated taxa with common Ammobaculites, Ammovertella, Bulbobaculites, Haplophragmoides, Proteonina, Psammosphaera and Reophax. The calcareous species Epistomina caracolla, which is extremely common in certain intervals, may reach significant abundances. Further agglutinated and calcareous taxa occur rarely. The early Late Valanginian is marked by the occurrence of the Tethyan species Cerobertinella subhercynica, reflecting a major sea-level highstand.