Two holes were drilled at Iceland Sea Site 907 (Shipboard Scientific Party, 1996b). Hole 907B was selected for planktonic foraminifer biostratigraphy (Table 2) and confirms the information obtained from Hole 907A drilled on ODP Leg 151 (Myhre, Thiede, Firth, et al., 1994). Planktonic foraminifers are found only in the upper part of the section. Assemblages are dominated by N. pachyderma (sinistral), indicating cold subpolar conditions. The start of the N. pachyderma (sinistral) Acme Zone is not recorded at this location because samples are nearly barren of planktonic foraminifers below Sample 162-907B-3H-CC, 37-40 cm (26.63 mbsf). The trace last occurrence (LO) of Neogloboquadrina atlantica in Sample 162-907B-5H-1, 39-41 cm, immediately below rare N. pachyderma (sinistral) in Sample 4H-CC, 17-20 cm, is consistent with previous observations in the Nordic Seas where the LO of N. atlantica approximates the Pliocene/Pleistocene boundary (Spiegler and Jansen, 1989; Spiegler, 1996).
Three holes were drilled at Feni Drift Site 980 (Shipboard Scientific Party, 1996c); Hole 980A was selected for planktonic foraminifer biostratigraphy. Planktonic foraminifers are abundant and well preserved throughout the lower Pleistocene to Holocene sediment sequence (Table 3). Common taxa include Globigerina bulloides, Globigerina quinqueloba, Globigerinita glutinata, Globorotalia inflata, Globorotalia scitula, and Neogloboquadrina pachyderma (both sinistral and dextral forms). Assemblage composition is dependent upon whether the sample happened to fall within a glacial or interglacial interval; sample resolution is insufficient to resolve glacial-interglacial cycles. Inferred glacial samples feature abundant N. pachyderma (sinistral), whereas inferred interglacial samples feature common Gg. bulloides and Gr. inflata. Paleoenvironmental conditions range from warm subpolar to cold subpolar. Hole 980A lies entirely within the N. pachyderma (sinistral) Acme Zone, which is Pleistocene in age.
Three holes were drilled at Feni Drift Site 981 (Shipboard Scientific Party, 1996c); Hole 981A was selected for planktonic foraminifer biostratigraphy. Planktonic foraminifers are abundant and well preserved throughout the lower Pliocene to Holocene sediment sequence (Table 4). Pleistocene taxa include Gg. bulloides, Gg. quinqueloba, Ga. glutinata, Gr. inflata, Gr. scitula, and N. pachyderma (both sinistral and dextral forms). As in Hole 980A, assemblage composition is dependent upon whether the sample happened to fall within a glacial or interglacial interval. Inferred glacial samples feature abundant N. pachyderma (sinistral), whereas inferred interglacial samples feature common Gg. bulloides and Gr. inflata. Paleoenvironmental conditions range from warm subpolar to cold subpolar. The base of the Pleistocene sediments is approximated by the start of the N. pachyderma (sinistral) Acme Zone between Samples 162-981A-11H-5, 9-11 cm, and 11H-6, 130-132 cm (98.09-100.80 mbsf).
The Pliocene is subdivided into four zones, following Weaver and Clement (1986): the latest Pliocene Gr. inflata Zone, the late Pliocene Gg. bulloides Zone, the mid-Pliocene N. atlantica Zone, and the early Pliocene Gr. puncticulata Zone (also the latest part of the latest Miocene to early Pliocene Gr. margaritae Zone). Common taxa in the Gr. inflata Zone include the nominate species, Gg. bulloides, Gg. quinqueloba, Ga. glutinata, Gr. scitula, N. pachyderma (dextral), and Orbulina universa. Common taxa in the Gg. bulloides Zone include the nominate species, Gr. crassaformis, Gr. scitula, N. pachyderma (dextral), and O. universa. Common taxa in the N. atlantica Zone include the nominate species, Gg. bulloides, Gr. crassaformis, Gr. scitula, N. pachyderma (dextral), and O. universa. Common taxa in the Gr. puncticulata Zone include the nominate species, Gg. bulloides, N. atlantica (sinistral), and N. pachyderma (dextral). Common taxa in the Gr. margaritae Zone include Gg. bulloides, N. atlantica (sinistral), N. pachyderma (dextral), and O. universa.
Several Pliocene planktonic foraminifer datum levels are recorded in Hole 981A. The first occurrence (FO) of Gr. inflata (2.09 Ma) is recorded between Samples 162-981A-13H-CC, 14-17 cm, and 14H-1, 49-51 cm (120.82-120.99 mbsf). The LO of N. atlantica (sinistral; 2.41 Ma) is recorded between Samples 162-981A-16H-4, 19-21 cm, and 16H-5, 19-21 cm (144.19-145.69 mbsf). The LO of Gr. puncticulata (2.41 Ma) is recorded between Samples 162-981A-16H-6, 19-21 cm, and 16H-7, 19-21 cm (147.19-148.69 mbsf). The LO of Globorotalia cf. crassula (3.3 Ma) is recorded between Samples 162-981A-23H-2, 30-32 cm, and 23H-CC, 9-12 cm (207.80-215.63 mbsf). Lastly, the FO of Gr. puncticulata (4.5 Ma) is recorded between Samples 162-981A-30H-4, 70-72 cm, and 30H-5, 70-72 cm (277.70-279.20 mbsf). The absence of both Gr. puncticulata and Neogloboquadrina acostaensis at the base of Hole 981A indicates an age between 4.5 and 5.29 Ma.
Four holes were drilled at Rockall Plateau Site 982 (Shipboard Scientific Party, 1996d). A limited number of samples was examined in Hole 982A (Table 5); Hole 982B was selected for planktonic foraminifer biostratigraphy (Table 6). Planktonic foraminifers are generally abundant from the top of the section to Sample 162-982A-20H-CC, 15-18 cm (188.86 mbsf); common from Sample 162-982A-21H-CC, 24-27 cm (198.54 mbsf), to Sample 162-982B-58X-CC, 30-33 cm (541.58 mbsf); and few to the base of the section. Preservation is generally good from the top of the section to Sample 162-982A-20H-CC, 15-18 cm (188.86 mbsf), and moderate from Sample 162-982A-21H-CC, 24-27 cm (198.54 mbsf), to the base of the section (Table 5, Table 6). Moderate preservation (numerous planktonic foraminiferal fragments) in the Miocene section significantly reduces the reliability of datum levels, as well as species richness.
The subpolar zonation of Weaver and Clement (1986) is applicable in the upper Miocene to Holocene sediment sequence, and the temperate zonation of Poore and Berggren (1975) is applicable in the lower to middle Miocene. The base of the Pleistocene sediments is approximated by the start of the N. pachyderma (sinistral) Acme Zone between Samples 162-982B-5H-2, 110-112 cm, and 5H-3, 110-112 cm (36.60-37.76 mbsf). The start of this zone is located based on the first consistent (rare) appearance of the nominate taxon, rather than trace occurrences (Table 6).
The Pliocene is subdivided into four zones as in Hole 981A: the latest Pliocene Gr. inflata Zone, the late Pliocene Gg. bulloides Zone, the mid-Pliocene N. atlantica Zone, and the early Pliocene Gr. puncticulata Zone (also the latest part of the latest Miocene to early Pliocene Gr. margaritae Zone). The Miocene is subdivided into four zones: the latest Miocene Gr. conomiozea Zone, the late Miocene N. acostaensis Zone, the middle Miocene Orbulina suturalis Zone, and the latest early Miocene Praeorbulina Zone (Table 6).
Pliocene planktonic foraminifer datum levels recorded in Hole 982B include the FO of Gr. inflata (2.09 Ma) between Samples 162-982B-5H-5, 110-112 cm, and 5H-6, 104-106 cm (41.10-42.54 mbsf); the LO of N. atlantica (sinistral; 2.41 Ma) between Samples 162-982B-6H-2, 54-56 cm, and 6H-3, 65-67 cm (45.54-47.15 mbsf); the LO of Gr. puncticulata (2.41 Ma) between Samples 162-982B-7H-3, 18-20 cm, and 7H-4, 18-20 cm (56.18-57.68 mbsf); the LO of Globorotalia cf. crassula (3.3 Ma) between Samples 162-982B-8H-4, 140-142 cm, and 8H-5, 140-142 cm (68.42-69.9 mbsf); and the FO of Gr. puncticulata (4.5 Ma) between Samples 162-982B-12H-7, 20-22 cm, and 13H-1, 30-32 cm (109.70-110.30 mbsf).
In the lower to middle Miocene sediments (before ~7-10 Ma), some planktonic foraminifer datum levels from subtropical (Blow, 1969, 1979; Bolli and Saunders; 1985) to temperate (Berggren, 1972; Poore and Berggren, 1975; Poore, 1979; Berggren et al., 1983; Weaver and Clement, 1986) zonations are applicable. Datum levels recorded in Hole 982B include the LO of N. acostaensis (5.29 Ma) between Samples 162-982B-18H-3, 24-26 cm, and 18H-4, 24-26 cm (160.74-162.24 mbsf); dextral to sinistral N. atlantica (6.4 Ma) between Samples 162-982B-26H-3, 19-21 cm, and 26H-4, 19-21 cm (236.69-238.19 mbsf); the FO of N. acostaensis (10.03 Ma) and LO of Paragloborotalia mayeri (10.30 Ma) between Samples 162-982B-35X-CC, 33-36 cm, and 36X-1, 19-21 cm (323.03-326.49 mbsf); the FO of O. suturalis (15.1 Ma) between Samples 162-982B-53X-6, 19-21 cm, and 53X-CC, 34-37 cm (497.39-498.61 mbsf); and the LO of Catapsydrax dissimilis between Samples 162-982B-58X-CC, 30-33 cm, and 59X-CC, 67-70 cm (541.58-548.07 mbsf). Interestingly, the small, biserial form Streptochilus globigerum is abundant in Sample 162-982B-40X-CC, 33-36 (372.28 mbsf), of earliest late Miocene age.
Lower to middle Miocene sediments at subpolar North Atlantic Site 982 can be correlated with subtropical to temperate zonation schemes, consistent with low meridional sea-surface temperature gradients. In particular, the latest early Miocene Praeorbulina Zone and the early part of the middle Miocene Orbulina suturalis Zone (Blow, 1969, 1979; Bolli and Saunders, 1985) are recognized. Use of the temperate late Miocene N. acostaensis Zone and the latest Miocene Gr. conomiozea Zone (Poore and Berggren, 1975) at Site 982 is consistent with increased meridional sea-surface temperature gradients in the subpolar North Atlantic after the middle Miocene.
Three holes were drilled at Gardar Drift Site 983 (Shipboard Scientific Party, 1996e); Hole 983A was selected for planktonic foraminifer biostratigraphy. Planktonic foraminifers are generally common and well preserved throughout the uppermost Pliocene to Holocene sediment sequence (Table 7). Faunal assemblages indicate distinctly cooler conditions than at Feni Drift Sites 980/981 and Rockall Plateau Site 982. Fauna are frequently dominated by N. pachyderma (sinistral), although Gg. bulloides, Gr. inflata, Gr. scitula, Ga. glutinata, Gg. quinqueloba, and N. pachyderma (dextral) are also recorded. Two barren intervals are recorded in Samples 162-983A-16H-CC, 20-23 cm (150.24 mbsf), and 25H-3, 20-22 cm (229.10 mbsf; near the base of the Pleistocene sediments). The base of the Pleistocene is approximated by the start of the N. pachyderma (sinistral) Acme Zone between Samples 162-983A-25H-4, 20-22 cm, and 25H-5, 20-22 cm (230.60-232.10 mbsf).
Four holes were drilled at Bjorn Drift Site 984 (Shipboard Scientific Party, 1996f). Hole 984A is entirely within the N. pachyderma (sinistral) Acme Zone; Hole 984B was selected for planktonic foraminifer biostratigraphy (Table 8). Planktonic foraminifers were generally common from the top of the section to Sample 162-984B-23H-CC, 8-11 cm (217.68 mbsf), and rare to barren from Sample 162-984B-24H-CC, 0-2 cm (226.94 mbsf) to the base of the section (Sample 162-984B-53X, 43-46 cm; 500.73 mbsf). Faunal assemblages indicate cooler conditions than at Gardar Drift Site 983 and the other subpolar North Atlantic sites. Fauna are generally dominated either by N. pachyderma (sinistral), N. pachyderma (dextral), or N. atlantica (sinistral). The base of the Pleistocene sediments is approximated by the start of the N. pachyderma (sinistral) Acme Zone between Samples 162-984B-21H-3, 35-37 cm, and 21H-4, 35-37 cm (192.35-193.85 mbsf).
The FO of Gr. inflata is not recorded at this location because of sparse occurrences. The LO of N. atlantica (2.41 Ma) in the lower part of Hole 984B (between Sample 162-984B-33X-1, 35-37 cm [302.15 mbsf] and 33X-2, 35-37 cm [303.65 mbsf]) provides an important age control point because of the absence of magnetostratigraphic data and calcareous nannofossil data in this interval. This datum level allows informal subdivision of the Pliocene into a latest Pliocene Gr. inflata/Gg. bulloides zone and a late Pliocene N. atlantica/Gr. puncticulata zone.
Holes 985A and 985B drilled at Iceland Sea Site 985 (Shipboard Scientific Party, 1996g) were examined for planktonic foraminifers (Table 9). Planktonic foraminifers are found only in the upper part of the Site 985 section. Assemblages are dominated by N. pachyderma (sinistral), indicating cold subpolar conditions. The start of the N. pachyderma (sinistral) Acme Zone is not recorded at this location because samples are generally barren of planktonic foraminifers below Samples 162-985A-3H-CC, 20-23 cm (26.94 mbsf), and 985B-2H-CC, 20-22 (13.13 mbsf).
Four holes were drilled at Site 986 on the Svalbard margin (Shipboard Scientific Party, 1996h). Holes 986A, 986C, and 986D were examined for planktonic foraminifers (Table 10). Planktonic foraminifers are found sporadically throughout the Site 986 section but are often common from the mid-Pleistocene to present. Specimens are generally few to rare from the top of the section to Sample 162-986A-17X-CC, 59-62 cm (137.73 mbsf), and often barren from Sample 162-986A-19X-CC, 21-24 cm (155.02 mbsf), to the base of the section, except for certain intervals. For example, rare N. pachyderma (sinistral) is recorded in Samples 162-986D-16R-CC, 9-12 cm (541.48 mbsf), and 17R-CC, 15-18 cm (546.57 mbsf), and rare N. atlantica is recorded in the interval from Sample 162-986D-34R-CC, 44-46 cm (705.94 mbsf), to 38R-CC, 9-11 cm (749.86 mbsf), and 43R-CC through 48R-CC (795.39-865.92 mbsf). Most of these rare specimens are well preserved and do not seem to be reworked. These occurrences provide limited age control for the sequence, together with limited magnetostratigraphic data and additional planktonic foraminifer data (Channell et al., Chap. 10, this volume; Eidvin and Nagy, Chap. 1, this volume).
Neither the start of the N. pachyderma (sinistral) Acme Zone nor the LO of N. atlantica (sinistral) is recorded at this location because of generally sparse planktonic foraminifers and poor core recovery from Samples 162-986D-18R-CC, 12-15 cm, to 34R-CC, 44-46 cm (558.92-705.44 mbsf). Significantly, the presence of N. atlantica below Sample 162-986D-34R-CC, 44-46 cm (705.94 mbsf), suggests an age >1.8 Ma for the lower part of the section. The LO of N. atlantica is significantly younger in the Nordic Seas (~1.8 Ma) than in the North Atlantic and approximates the Pliocene/Pleistocene boundary (Spiegler and Jansen, 1989; Spiegler, 1996).
Results from the Nordic Seas sites are consistent with previous findings that carbonate sediment preservation increased within the Quaternary at ~1 Ma. However, increased carbonate accumulation was delayed in the Arctic Gateway region; Svalbard margin Site 986 exhibits a distinct increase in planktonic foraminiferal abundances within approximately the past half m.y. (Table 10).
Four holes were drilled at Site 987 on the Greenland margin (Shipboard Scientific Party, 1996i). Hole 987A was examined for planktonic foraminifers (Table 11). Planktonic foraminifers are abundant from the top of the section to Sample 162-987A-3H-CC and rare from Sample 162-987A-4H-CC to 10H-CC. Preservation is moderate to good. Samples are generally barren from Sample 162-987A-11H-CC to the base of the section. Assemblages are dominated by N. pachyderma (sinistral), although rare occurrences of Globigerina quinqueloba were recorded in Sample 162-987A-18X-CC. The start of the N. pachyderma (sinistral) Acme Zone is not recorded at this location because of barren samples and poor recovery.