Examination of the 49 samples from Core 162-985A-32X to the base of the hole (Section 162-985A-62X-CC) yielded 40 foraminiferal species and generic groupings (Table 1). Specimens throughout the studied interval are generally well preserved and uncrushed. The succession of foraminiferal assemblages, the ranges of some characteristic species, and a simple measure of species diversity observed in sediment from the hole are given in Figure 2.
Based on the ranges of characteristic species, we can subdivide the succession into three main assemblages. Because of the current lack of independent age control, we have refrained from establishing a formal zonation based on this site. Instead, we compare our stratigraphic record with the Paleogene assemblages described from Hole 643A (Kaminski et al., 1990) and from a well drilled on the Vøring Plateau (Gradstein et al., 1994), and with the quantitative zonation based on ranking and scaling of the Norwegian margin (Gradstein and Bäckström, 1996). The three assemblages are described in order from oldest to youngest.
The DWAF assemblage in the lower part of the studied section is characterized by coarsely agglutinated species such as Hyperammina rugosa Verdenius and van Hinte, Rhabdammina spp., Psammosphaera fusca Schultze, and numerous Ammolagena clavata (Jones and Parker) that are attached to large quartz grains. This indicates the availability of plentiful coarse material for the construction of the foraminiferal test. Other common species include Reticulophragmium amplectens (Grzybowski), Haplophragmoides walteri (Grzybowski), Reophax elongatus Grzybowski, and Recurvoides spp. A number of stratigraphically important forms are also present.
The lowermost sample collected from Hole 985A (Sample 162-985A-62X-CC) contains the index species Spirosigmoilinella compressa (Matsunaga), Adercotryma agterbergi Gradstein and Kaminski, and Karreriella siegliei (Gradstein and Kaminski). These species are characteristic of the lower Oligocene recovered from exploration wells on the Vøring Plateau (Gradstein et al., 1994). An early Oligocene age for the base of the drilled section is corroborated by the absence of Eocene index forms such as Spiroplectammina spectabilis (Grzybowski) and Ammomarginulina aubertae Gradstein and Kaminski.
The first occurrence (FO) of the
species Reticulophragmium rotundidorsatum (Hantken) was found in Sample
162-985A-59X-CC; in the next sample above (59X-4, 32-37 cm), it is especially common. This
species is present in large numbers at certain horizons. The FO of the species Psamminopelta
gradsteini Kaminski and Geroch
[ = Psamminopelta sp. of Kaminski et al., 1990] was observed in Sample
162-985A-53X-7, 36-0 cm. This occurrence implies a correlation with the Oligocene "Psamminopelta
sp. assemblage" observed in the Oligocene sediments at Site 643 on the Vøring Slope
(Kaminski et al., 1990).
A faunal change is observed within Core 162-985A-50X characterized by the loss of coarsely agglutinated forms. The last occurrence (LO) of the coarsely agglutinated species Hyperammina rugosa was observed in Sample 162-985A-50X-7, 36-40 cm. In Sample 162-985A-50X-CC, the LO of Psammosphaera fusca was observed. Above Core 162-985A-50X, the DWAF assemblage is dominated by finely agglutinated taxa. The characteristic species in this interval are Bathysiphon spp., Spirosigmoilinella compressa, Verneuilinoides sp., Cystammina sp., Karreriella siegliei, and Ammodiscus latus Grzybowski.
The diversity and abundance of DWAF decrease upsection in Hole 985A. A reduction in diversity is observed within the interval from Cores 162-985A-45X through 43X. The LOs of 12 species are observed within this interval, including Reophax elongatus, Adercotryma agterbergi, Reticulophragmium rotundidorsatum, Ammodiscus latus, and Haplophragmoides walteri. Many of these last occurrences can be traced to a level within the Oligocene in the North Sea region (Gradstein et al., 1994).
In the uppermost part of the studied interval, the assemblages contain common pyritized diatom and radiolarian steinkerns. Some authigenic pyrite, in the form of burrow infillings, was also observed. Foraminifers are rare and consist mainly of Psamminopelta gradsteini in association with rare tubular forms and Recurvoides spp. These findings agree with the observations of Verdenius and van Hinte (1983) in the Leg 38 DSDP holes (Sites 338, 345, and 348), where low-diversity assemblages with "Spirosigmoilinella and Spirolocammina" were reported from strata assigned a late Oligocene to Miocene age.