Recent Foraminifera from the North Sea (Forties and Ekofisk areas) and the continental shelf west of Scotland

John W Murray

doi:10.1144/jm.4.2.117

Abstract

Abstract. The regions studied are all of mid continental shelf depth (70–145 m) and have bottom waters of normal marine salinity. The North Sea has lower bottom water temperatures than those to the west of Scotland. However, the major difference between the two regions is one of tidal and/or wave energy: the northern North Sea is a low energy environment of muddy sand deposition whereas the sampled part of the continental shelf west and north of Scotland is a moderate to high energy environment of medium to coarse biogenic carbonate sedimentation.The physical differences between the two main areas are reflected in the living and dead foraminiferal assemblages. The northern North Sea is a region of free-living species whereas the continental shelf west of Scotland has immobile and mobile attached species living on firm substrates. The northern North Sea is very fertile and has high standing crop values.The dead assemblages are small in size and very abundant. To the west of Scotland the sea is less fertile, standing crop values are low, the dead assemblages are moderate to large in size and reasonably abundant due to the slow rate of dilution by sediment.

Highlights

The North Sea is an extensive epicontinental area opening northwards into the Norwegian Sea
MATERIAL AND METHODS Three samples from the Forties area of the North Sea were collected in June 1978 and a further 17 in June 1981.Five samples were collected from the Ekofisk area of the North Sea in August 1981
This is true of the dead assemblages these include rare attached immobile forms (Cibicides fobatufus). This is consistent with a low-energy area of fine grained sediment accumulation. Both Forties and Ekofisk come under the influence of Atlantic water which flows into the North Sea at the surface

Summary

INTRODUCTION

The North Sea is an extensive epicontinental area opening northwards into the Norwegian Sea. The values for bottom salinity are 35.0%, and 34.0%, for winter and summer at Ekofisk and 35.1%, throughout the year at Forties (Lee & Ramster, 1981).In both areas, the surface waters develop thermohaline stratification during the summer months. The mean bottom temperature is 7"C in the winter and 11"C in the summer for the Fair Isle Channel sampling area and -9" €or the summer for the shelf to the west of Scotland (no details available for the winter; Lee & Ramster, 1981). The bottom water salinity values are 35.1%, throughout the year in the Fair Isle Channel sampling area and 35.0 to >35.25%, to the west of Scotland (Lee & Ramster, 1981). All four areas are of mid-shelf depth and normal salinity and they differ only in lower bottom temperatures and terrigenous sedimentary substrate (North Sea) and higher bottom temperatures and a bioclastic sediment substrate (Fair Isle Channel and West Scottish Shelf)

MATERIAL AND METHODS

Findings

CONCLUSIONS