Ostracods from the Purbeck-Wealden Beds in Bornholm

Ole Bruun Christensen

doi:10.34194/raekke2.v86.6876

Abstract

An account of the Purbeck-Wealden beds in Bornholm and a brief summary of similar beds in the Scanian-Pomeranian area are given.Two faunas are described from the Jydegaard Formation. A Cypridea-fauna is correlated with Wealden 3 in Northwest Germany. It is followed by an ostracod-assemblage, known from Northwest Germany, indicating brackish-marine environments corresponding to Wealden 3 or 4 of the German subdivision. Two new ostracod species are described.Two other faunas have moreover been identified, a brackish one in the Rabekke Formation and a brackish-marine one in the inlier at Salene. The former contains elements suggesting a Middle Purbeck age.

Highlights

Green, and dark-grey limnic clays with soil sections and 1 or 2 beds of red variegated clay, which have been interpreted as weathering layers by GRY
The formation may attain a thickness of 100 metres and consists of grey clay with beds of silt, sand, gravel, and clay-ironstone
On the basis of recent literature and not least in consequence of extensive sortings providing more well preserved material, it can be demonstrated that the Cypridea-material from the Jydegaard Formation identified by GRY does not belong to Cypridea parallela MARTIN but to Cypridea altaformosa WOLBURG

Summary

INTRODUCTION

The upper member of the Rabekke Formation is 10-80 metres thick It consists of sticky, green, and dark-grey limnic clays with soil sections and 1 or 2 beds of red variegated clay, which have been interpreted as weathering layers by GRY. This formation is the uppermost one in the Purbeck-Wealden sequence, and is defined as stratified clays and sands, partly coarse grained, with chamositeoolite. The formation may attain a thickness of 100 metres and consists of grey clay with beds of silt, sand, gravel, and clay-ironstone. In this small inlier there are steeply dipping beds of sandstone with kaolin-like clay, together with darkish grey and greenish clays. On the basis of recent literature and not least in consequence of extensive sortings providing more well preserved material, it can be demonstrated that the Cypridea-material from the Jydegaard Formation identified by GRY does not belong to Cypridea parallela MARTIN but to Cypridea altaformosa WOLBURG

PURBECK-WEALDEN BEDS

Dunkle Sande mit Ton und Kohle-Lagen

STRATIGRAPHICAL INVESTIGATIONS

DESCRIPTION OF SPECIES