Samples were collected from the composite sections of Leg 162 Sites 982 and 985 (see Jansen, Raymo, Blum, et al., 1996). Site 982 is located in the North Atlantic on the Rockall Plateau (57º31'N, 15º52'W) in a water depth of 1134 m; Site 985 was drilled in the Norwegian Sea on the western slope of the Iceland Plateau into the Norway Basin (66º56.5'N, 6º27'W) at a 2788-m water depth (Fig. 1). The sedimentation rate at both sites varied between 1.5 and 3 cm/k.y. (Jansen, Raymo, Blum, et al., 1996). Samples were usually taken every 10- to 20-cm depth interval for bulk calcium carbonate measurements and at 20- to 30-cm depth intervals for faunal, floral, and sedimentological analysis. The stratigraphic resolution of these samples is relatively similar between the sites, usually between 3000 and 6000 yr for bulk carbonate measurements and ~10,000-15,000 yr for faunal, floral, and sedimentological data.
A LECO CS-125 infrared analyzer was used to determine calcium carbonate contents. This device measures only total carbon (TC) contents. In a subsequent analysis, the samples were therefore treated with hydrochloric acid to allow the determination of total organic carbon (TOC) content. The bulk carbonate content can be calculated from the weight percentage of the bulk sediment with the following equation:
CaCO3 wt% = (TC wt% - TOC wt%) × 8.33.
For the studies of the coarse fraction (planktonic foraminifers, IRD = all lithogenic particles, as well as all other biogenic and volcanic components), the samples were freeze-dried using a FINN-AQUA (lyvotac GT2). Part of the freeze-dried sample was weighed and then washed on a 63-µm sieve and further separated into 63- to 125-, 125- to 500-, 500- to 1000-, and >1000-µm fractions using an ATM-SONIC-Sifter. The 125- to 500-µm fraction was chosen for particle count procedure. A split of 300 to 1000 grains, depending on the amount of biogenic particles, was separated with a microsplitter and counted for biogenic and terrigenous components. Total foraminifer abundances and IRD data were converted to numbers per gram dry weight sediment. In this study, only numbers of total planktonic foraminifers and abundances of subpolar species-mainly N. pachyderma dex., Globigerina bulloides, Turborotalita quinqueloba, and species of Globigerinita and Globorotalia-are presented.
Coccolith species were counted under the scanning electron microscope (SEM). For preparation, a combined dilution/filtering technique as described by Andruleit (1996) was used. A small amount of sediment was weighed and brought into suspension. After dilution with a rotary splitter, the suspension was filtered through polycarbonate membrane filters (Schleicher and Schuell, 50-mm diameter, 0.4-µm pore size). A monolayer of all sediment particles was produced for investigation under the SEM. All coccoliths were recorded in numbers per gram dry sediment. Here, only numbers of total coccoliths as well as abundances of the cold water-adapted species Coccolithus pelagicus (Wallich) Schiller are shown. Subsequently, numbers and abundances of all species will be presented elsewhere.