Site 985 is located on Eocene Anomaly 22 crust (~50 Ma; Talwani and Eldholm, 1977). Geological evidence supports the notion of seafloor spreading in the Norwegian-Greenland Sea by Anomaly 24 (early Eocene), but crustal extension may have begun as early as Anomaly 29 (Talwani and Eldholm, 1977; Myhre and Thiede, 1995).
Site 985 was drilled on the gentle slope of the Iceland Plateau at a water depth of 2788 m at 66º56.49'N, 6º27.01'W (Fig. 1). It is part of the paleoenvironmental transect of the southern part of the Norwegian Sea and is composed of Sites 907 and 987 (Legs 151 and 162, respectively) and Sites 642, 643, and 644 (Leg 104). The sediments recovered are predominantly fine-grained siliciclastics. The dominant lithologies include silty clays, clays with silt, and clays. Biocarbonates are restricted to the upper parts of the sedimentary sequence. Clays and silty clays containing biosilica are encountered only between 240 and 290 meters below seafloor (mbsf). Disseminated volcanic ash, ash pods, and ash layers occur throughout the sedimentary sequence. Dropstones are confined to the upper sedimentary sequence (0-70 mbsf). The upper part of the sequence (1-60 mbsf) was dated to the latest Miocene by means of magnetic polarity records, but the underlying sequence proved difficult to correlate with the geomagnetic polarity time scale. Thus, it has poor age constraints. Siliceous microfossils and agglutinated benthic foraminifers provide some age information in the lower section, indicating that the drilled sequence terminated in the Oligocene.
Five lithologic units were recognized in Hole 985A, and the agglutinated assemblages described here appear within the lowermost part of Unit IV (155.2 to 465 mbsf) and Unit V (465 to 578.9 mbsf). The sediments of Unit IV are dominated by indurated clays, ranging from gray to very dark greenish gray to dark grayish brown. Disseminated ash is present as a lithologic component of the bulk sediments. The relevant subunit of Unit IV is defined from 289.6 to 465 mbsf and is characterized by the absence of biosilica and the gradual downsection increase in natural gamma counts. The base of Subunit IVC is defined by a sharp downhole increase in magnetic susceptibility. The sediments of Unit V comprise indurated dark greenish gray to very dark greenish gray clay, olive gray to dark greenish gray clay, and very dark greenish gray clay with glauconite and glauconitic clay. These sediments are distinguished from the overlying sediments by a sharp increase in magnetic susceptibility.
The lowermost sediments (Unit V) are believed to have been deposited during the late Oligocene to early Miocene when the basin was roughly half its modern dimensions; Site 985 was, therefore, shallower and closer to land. At this time, the Aegir spreading axis, the site of active seafloor spreading, was located to the east of Site 985. The lack of an intervening bathymetric high between Greenland and Site 985 may have permitted more effective transport of silt-sized terrigenous material to Site 985.