Only six cores were drilled from Hole 897A (40°50.32'N, 12°28.44'W, at a water depth of 5320.0 m), and all are of Pleistocene age. The turbidite sediments consist mainly of nannofossil ooze, nannofossil clay, silty clay and clayey silt, silt, and fine sand. Calcareous nannofossils are well preserved and abundant in most samples (Table 2).
Samples 149-897A-1R-1, 95-96 cm, to 1R-1, 125-126 cm, are assigned to the Emiliania huxleyi Zone (NN21), based on the FO of Emiliania huxleyi. The dominant species are Calcidiscus leptoporus, Coccolithus crassipons, Gephyrocapsa spp. (<3 µm), and Reticulofenestra minuta.
Samples 149-897A-3R-1, 39-40 cm, to 4R-1, 58-59 cm, are assigned to the Gephyrocapsa oceanica Zone (NN20), based on the absence of both Emiliania huxleyi and Pseudoemiliania lacunosa.
Samples 149-897A-4R-1, 128-129 cm, to 6R-5, 56-57 cm, are assigned to the NN19h Subzone in the Pseudoemiliania lacunosa Zone (NN19), based on the co-occurrence of Pseudoemiliania lacunosa and Gephyrocapsa oceanica s.l. (>4 µm) and the absence of Reticulofenestra asanoi (>6.5 µm), large Gephyrocapsa (>5.5 µm), and Helicosphaera sellii.
The Pliocene-Pleistocene sediments from Hole 897C (40°50.33'N, 12°28.44'W, at a water depth of 5315.2 m) consist mainly of nannofossil ooze, nannofossil clay, silty clay and clayey silt, silt, and fine sand. Calcareous nannofossils are well preserved and abundant in most of the samples (Table 3, Table 4).
The first Gephyrocapsa oceanica s.l. was found in Sample 149-897C-14R-3, 14-15 cm. Therefore, Samples from 149-897C-1R-1, 45-46 cm, to 14R-3,14-15 cm, are assigned to the Pleistocene. Samples from 149-897C-14R-4, 88-89 cm, to 27R-1, 5-6 cm, are assigned to the Pliocene.
All of the Pleistocene samples from Hole 897C are assigned to the Pseudoemiliania lacunosa Zone (NN19), based on the co-occurrence of Pseudoemiliania lacunosa and Gephyrocapsa oceanica s.l. (>4 µm).
Additional events used to further subdivide the Pseudoemiliania lacunosa Zone are recognized as the following:
1. LO of Reticulofenestra asanoi (>6.5 µm): Sample 149-897C-8R-2, 105-106 cm.
2. Reoccurrence of Gephyrocapsa oceanica (>3 µm), which corresponds to the FO of Gephyrocapsa sp. C-D of Matsuoka and Okada (1990): Sample 149-897C-8R-3, 58-59 cm.
3. FO of Reticulofenestra asanoi (>6.5 µm): Sample 149-897C-9R-CC.
4. LO of large Gephyrocapsa (>5.5µm), which corresponds to the LO of Gephyrocapsa sp. A-B of Matsuoka and Okada (1990): Sample 149-897C-11R-2, 18-19 cm.
5. LO of Helicosphaera sellii: Sample 149-897C-11R-2, 18-19 cm.
6. FO of large Gephyrocapsa (>5.5 µm): Sample 149-897C-12R-5, 133-134 cm.
7. LO of Calcidiscus macintyrei: Sample 149-897C-14R-3, 14-15 cm.
8. FO of Gephyrocapsa oceanica s.l. (>4 µm): Sample 149-897C-14R-3, 14-15 cm.
Samples 149-897C-17R-2, 80-81 cm, to 14R-4, 88-89 cm, are placed within the uppermost Pliocene Zone NN19a, based on the absence of both Discoaster brouweri and Gephyrocapsa oceanica s.l. (>4 µm). The assemblage is also characterized by Calcidiscus leptoporus, Calcidiscus macintyrei, Gephyrocapsa caribbeanica, Gephyrocapsa sp., small Gephyrocapsa, Helicosphaera acuta, Helicosphaera carteri, and Helicosphaera sellii. It is noteworthy that the lowest occurrence of Helicosphaera acuta is peculiar in our sites: the species always occurs with the LO of Discoaster surculus or slightly above.
Zone NN18 (Discoaster brouweri Zone) is recognized from Samples 149-897C-23R-1, 113-114 cm, to 17R-3, 17-18 cm, based on the presence of Discoaster brouweri and Discoaster triradiatus. The assemblage is characterized by rare to abundant Gephyrocapsa spp. (<3µm), rare to common Helicosphaera acuta, common to few Helicosphaera sellii and Helicosphaera carteri, and abundant to common Pseudoemiliania lacunosa.
Samples 149-897C-25R-CC, 5-6 cm, to 23R-2, 88-89 cm, are tentatively assigned to Zone NN17 (Discoaster pentaradiatus Zone). Discoaster pentaradiatus should characterize the zone, but the species is rare and sporadic, as it is also in the Discoaster surculus Zone. We choose to recognize the top of the zone above the relatively continuous range of the species. Reworked specimens of Discoaster asymmetricus, Discoaster tamalis, and Discoaster surculus are recorded in the same interval as are rare occurrences of Discoaster pentaradiatus so it is possible that these are reworked. The assemblage is common to abundant, with moderate to good preservation.
Zone NN 16 (Discoaster surculus Zone) is recognized from Samples 149-897C-26R-1, 93-94 cm, to 26R-1,4-5 cm, based on the absence of Reticulofenestra pseudoumbilicus and the presence of Discoaster surculus. Discoaster brouweri, Discoaster pentaradiatus, and Discoaster triradiatus are also recorded within this zone, as is the highest occurrence of Discoaster asymmetricus and Discoaster tamalis; Helicosphaera acuta is present in the uppermost part of the zone.
Samples 149-897C-26R-2, 108-109 cm, to 26R-2, 6-7 cm, are placed within the combined lower Pliocene Zones NN14-15. The FO of Pseudoemiliania lacunosa and the LO of Reticulofenestra pseudoumbilicus are used to define this interval.
Samples 149-897C-27R-1, 5-6 cm, to 27R-1, 1-2 cm, are placed in the lowermost Pliocene but no biozone can be recognized. Amaurolithus delicatus and Discoaster tamalis are recorded within this zone.
Hole 898A (41°41.100'N, 12°7.380'E, at a water depth of 5279.0 m) is the only hole that was drilled with the advanced hydraulic piston corer during Leg 149 and is therefore the only hole with good sediment recovery and reliable paleomagnetic data. Most of the sediments consist of clay, nannofossil ooze, nannofossil clay, silty clay and clayey silt, silt, and fine sand. Calcareous nannofossils are well preserved and abundant in most of the samples (Table 5, Table 6).
Samples 149-898A-1H-1, 2-3 cm, to 1H-4, 145-146 cm, are assigned to the Emiliania huxleyi Zone (NN21), based on the occurrence of E. huxleyi.
Samples 149-898A-1H-5, 40-41 cm, to 3H-4, 7-8 cm, are assigned to the Gephyrocapsa oceanica Zone (NN20), based on the absence of both Emiliania huxleyi and Pseudoemiliania lacunosa.
Samples 149-898A-3H-2, 14-15 cm, to 16X-3, 52-53 cm, are assigned to the Pseudoemiliania lacunosa Zone (NN19), based on the occurrence of P. lacunosa and Gephyrocapsa oceanica s.l. (>4 µm). Common nannofossil species are Calcidiscus leptoporus, Dictyoccoccites perplexa, Dictyoccoccites productus, Gephyrocapsa caribbeanica, Gephyrocapsa spp. (<3µm), Reticulofenestra minuta,
Reticulofenestra minutula, and Rhabdosphaera claviger. The additional events used to further subdivide the Pseudoemiliania lacunosa Zone (NN19) are recognized as the following:
1. LO of Reticulofenestra asanoi (>6.5 µm): Sample 149-898A-6H-2, 67-68 cm.
2. Reoccurrence of Gephyrocapsa oceanica (>3 µm), which corresponds to the FO of Gephyrocapsa sp. C-D of Matsuoka and Okada (1990): Sample 149-898A-6H-4, 79-80 cm.
3. FO of Reticulofenestra asanoi (>6.5 µm): Sample 149-898A-7H-3, 7-8 cm.
4. LO of large Gephyrocapsa (>5.5 µm), which corresponds to the LO of Gephyrocapsa sp. A-B of Matsuoka and Okada (1990): Sample 149-898A-11H-1, 105-106 cm.
5. LO of Helicosphaera sellii: Sample 149-898A-11H-1, 105-106 cm.
6. FO of large Gephyrocapsa (>5.5 µm): Sample 149-898A-14H-4, 30-31 cm.
7. LO of Calcidiscus macintyrei: Sample 149-898A-16X-2, 100-101 cm.
8. FO of Gephyrocapsa oceanica s.l. (>4 µm): Sample 149-898A-16X-3,52-53 cm.
All of the lower Pliocene and most of the upper Pliocene are missing in this hole. Samples 149-898A-16X-4, 103-104 cm, to 18X-4, 58-59 cm, are placed in Zone NN19a, based on the absence of both Gephyrocapsa oceanica s.l. (>4µm) and Discoaster brouweri. Rare to common Calcidiscus macintyrei were observed in this interval along with few to abundant small Gephyrocapsa, rare to common Helicosphaera acuta, and few to abundant Helicosphaera carteri and Helicosphaera sellii; rare to few Gephyrocapsa caribbeanica occur in the uppermost part of this interval. Reworked Discoaster pentaradiatus, Discoaster tamalis, and Discoaster triradiatus were also recorded. The taxa are abundant to very abundant with moderate to good preservation.
Hole 899A (40°46.332'N, 12° 12.156'E, at a water depth of 5291.0 m) was drilled to 81.5 m below seafloor (mbsf) before a core was taken; therefore, all of the Pleistocene sediments were washed away. The first core was recovered from the Pliocene.
Samples 149-899A-1R-1, 23-24 cm, to 1R-2, 19-20 cm, contain neither Gephyrocapsa oceanica s.l. (>4 µm nor Discoaster brouweri; hence, they are assigned to the upper Pliocene Zone NN19a. These samples also contain common Calcidiscus macintyrei, abundant Pseudoemiliania lacunosa and Reticulofenestra minutula, and few Helicosphaera acuta. Nannofossils are very abundant and have good preservation in this zone.
NN18 (Discoaster brouweri Zone) is recognized from Samples 149-899A-1R-3, 135-136 cm, to 4R-1,40-41 cm. The relative abundance of Discoaster brouweri is few to rare in this interval. Discoaster triradiatus occurs in the uppermost part of the zone. Nannofossils are abundant to very abundant and exhibit moderate to good preservation.
The LO of Discoaster pentaradiatus occurs between Samples 149-899A-4R-1, 40-41 cm, and 4R-1, 61-62 cm, and marks the top of Zone NN17 (Discoaster pentaradiatus Zone), which is represented by a very short interval. In this zone, the lowest occurrence of Helicosphaera acuta is present. Samples 149-899A-4R-2,79-80 cm, to 6R-1, 86-87 cm, are placed in NN16 (Discoaster surculus Zone); Discoaster pentaradiatus and D. surculus are both present in this interval. The highest occurrences of D. asymmetricus (Sample 149-899A-4R, CC) and Discoaster tamalis (Sample 149-899A-5R-1, 72-73 cm) were also noted within the zone. The overall assemblage consists mainly of abundant to common Calcidiscus leptoporus, Coccolithus pelagicus, and Pseudoemiliania lacunosa; rare to common Calcidiscus macintyrei; and common Discoaster brouweri. Nannofossils are common to very abundant with moderate to good preservation.
Zone NN14 (Discoaster asymmetricus Zone) and Zone NN15 (Reticulofenestra pseudoumbilicus Zone) were combined in this hole, because the LO of Amaurolithus tricorniculatus was not found. The LO of Reticulofenestra pseudoumbilicus marks the top of this NN14-15 interval; the base is defined by the FO of Pseudoemiliania lacunosa. The highest occurrence of Amaurolithus delicatus is recognized at the top of Zone NN14-15. The co-occurrences of Helicosphaera sellii and Discoaster tamalis may suggest an unconformity at the base of Core 149-899A-6R. Nannofossils are very abundant with moderate preservation in this interval.
Samples 149-899A-7R-1, 40-41 cm, to 7R-CC, are assigned to the lower Pliocene. This interval is characterized by common Amaurolithus delicatus, rare Amaurolithus tricorniculatus, few to common Discoaster brouweri and Discoaster surculus, abundant to rare Discoaster pentaradiatus, rare Discoaster triradiatus, and common Reticulofenestra pseudoumbilicus and Reticulofenestra gelida. Nannofossils are abundant to very abundant with moderate to good preservation in this zone.
Pliocene-Pleistocene sediments recovered in the top 11 cores of Hole 900A (46°40.992'N, 11°36.252'E, at a water depth of 5036.8 m) consist mainly of nannofossil ooze, nannofossil clay, nannofossil chalk, nannofossil claystone, clay, claystone, silt, and fine sand. Calcareous nannofossils are well preserved and abundant in most of the samples (Table 8, Table 9).
Samples 149-900A- 1R-1, 24-25 cm, to 2R-CC are assigned to the Gephyrocapsa oceanica Zone (NN20), based on the absence of both Emiliania huxleyi and Pseudoemiliania lacunosa.
Samples 149-900A-3R-1, 8-9 cm, to 6R-2, 110-111 cm, are assigned to Pseudoemiliania lacunosa Zone (NN19), based on the occurrence of Pseudoemiliania lacunosa and Gephyrocapsa oceanica s.l. (>4µm). The additional events used to further subdivide the Pseudoemiliania lacunosa Zone are recognized as the following:
1. LO of Reticulofenestra asanoi (>6.5 µm): Sample 149-900A-4R-1, 19-20 cm.
2. Reoccurrence of Gephyrocapsa oceanica (>3 µm), which corresponds to the FO of Gephyrocapsa sp. C-D of Matsuoka and Okada (1990): Sample 149-900A-4R-1, 46-47 cm.
3. FO of Reticulofenestra asanoi (>6.5 µm): Sample 149-900A-4R-4, 132-133 cm.
4. LO of large Gephyrocapsa (>5.5 µm), or LO of Gephyrocapsa sp. A-B (Matsuoka and Okada, 1990): Sample 149-900A-5R-1,74-75 cm.
5. LO of Helicosphaera sellii: Sample 149-900A-5R-1, 74-75 cm.
6. FO of large Gephyrocapsa (>5.5 µm): 149-900A-5R-3, 37-38 cm.
7. LO of Calcidiscus macintyrei: Sample 149-900A-6R-2, 30-31 cm.
8. FO of Gephyrocapsa oceanica s.l. (>4 µm): Sample 149-900A-6R-2, 110-111
The uppermost Pliocene Zone NN19a is assigned from Samples 149-900A-6R-3, 86-87 cm, to 6R-5, 136 cm, where neither Gephyrocapsa oceanica s.l. (>4 µm) nor Discoaster brouweri is present. This interval is characterized by abundant to rare small Gephyrocapsa, common Gephyrocapsa caribbeanica in the upper part of the zone, and few to common Calcidiscus macintyrei, Helicosphaera acuta, and Helicosphaera sellii.
Zone NN18 (Discoaster brouweri Zone) is recognized from Samples 149-900A-6R-6, 78-79 cm, to 8R-CC, where Discoaster brouweri is present. Discoaster triradiatus is present in the upper part of this zone, as is Helicosphaera acuta. Nannofossils are common to very abundant with moderate to good preservation.
Samples 149-900A-9R-1, 45-46 cm, to 10R-4, 69-70 cm, are assigned to the Zone NN16 (Discoaster surculus Zone). The highest occurrences of Discoaster pentaradiatus and Discoaster surculus were found in the same sample, and Zone NN17 is missing in this hole. The main assemblage in this zone is characterized by rare to common Discoaster brouweri, Discoaster pentaradiatus, and Discoaster surculus; rare Discoaster triradiatus; few to rare and sporadic Helicosphaera sellii; and few to abundant Pseudoemiliania lacunosa. The highest occurrences of both Discoaster asymmetricus and Discoaster tamalis were recorded within this zone in the same sample. Nannofossils are abundant to very abundant and exhibit good preservation.
Samples 149-900A-11R-1,72-73 cm, to 11R-4, 119-120 cm, are assigned to the combined Zones NN14 and NN15 (Discoaster asymmetricus Zone/Reticulofenestra pseudoumbilicus Zone) according to the presence of Pseudoemiliania lacunosa and Reticulofenestra pseudoumbilicus. Discoaster asymmetricus is not present at the base of this interval. The LO of Amaurolithus delicatus is recorded within this interval, as is the FO of Discoaster tamalis. Nannofossils are abundant to very abundant with good preservation. Part of the lower Pliocene is missing in this hole.