AN ILLUSTRATED GUIDE TO THE BENTHIC FORAMINIFERA OF THE HEBRIDEAN SHELF, WEST OF SCOTLAND, WITH NOTES ON THEIR MODE OF LIFE

ABSTRACT

The Hebridean shelf presents a contrast in substrate type between higher energy open shelf sands, which are influenced by storm waves and lower energy muddy sands in depositional sinks called `deeps'. The latter reach outer shelf depths (>100 m) even when situated close to land (e.g., Muck Deep). The primary purpose of this paper is to illustrate the majority of the benthic foraminifera. For most species, information is provided on whether they are epifaunal or infaunal, based on their distribution in rose Bengal stained samples. Since the redox boundary is shallow in this area (less than 4-5 cm), infaunal taxa are most abundant in the top 1 cm of sediment and decrease in abundance down to 2 or 3 cm with no subsurface maxima as recorded elsewhere. Some dead tests are infilled with glauconite which preserves the form of the species even when the shell is lost. The organic-cemented agglutinated fauna was concentrated by treating the samples with dilute acid to dissolve the calcareous forms. The species diversity of the resultant acid-treated assemblage (ATA) has been compared with that of the original dead assemblage (ODA). The pattern for the Hebridean shelf matches that recorded from other northwest European shelf seas. This procedure has allowed the following agglutinated species to be recorded from the area for the first time: Cuneata arctica, Eggerella europea, Eggerelloides medius, Morulaeplecta bulbosa, Portatrochammina murrayi, and Recurvoides trochamminiformis. In addition, the following calcareous taxa are also newly recorded from the area: Cornuloculina balkwilli, Ammonia falsobeccarii, Nonionella iridea, Robertina subcylindrica and Rosalina anomala.

John W. Murray. School of Ocean and Earth Science, Southampton Oceanography Centre, European Way, Southampton SO14 3ZH, England.

KEY WORDS: foraminifera, benthic, SEM micrographs, mode of life

Copyright: Palaeontological Association. 28 March 2003
Submission: 21 May 2002 Acceptance: 21 October 2002