MATERIALS

Paleogene sedimentary sequences from Holes 1218A, 1219A, and 1220A are composed mainly of Oligocene nannofossil-rich calcareous ooze and chalk and underlying Eocene radiolarian-rich biosiliceous ooze and radiolarite.

Hole 1218A was drilled at 8°53.378´N, 135°22.00´W (water depth = 4828 m). The 274.3-m-thick lithologic succession overlying middle Eocene basalt basement is subdivided into four units (Shipboard Scientific Party, 2002b):

Unit II (52.1–216.9 mbsf): early Miocene–early Oligocene nannofossil ooze, clayey radiolarian nannofossil ooze, and chalk;

Unit III (216.9–252.2 mbsf): earliest Oligocene–middle Eocene radiolarite and nannofossil chalk with thin chert layers; and

Unit IV (250.2–274.3 mbsf): middle Eocene nannofossil chalk.

A total of 73 samples from the interval spanning Sample 199-1218A-25X-7, 75–77 cm (233.95 mbsf; Unit III), to 22X-1, 30–32 cm (196.20 mbsf; Unit II), were collected for examination of late Eocene–early Oligocene radiolarians (Fig. F2). The average sampling interval was ~0.52 m. Radiolarian preservation is moderate to good throughout the sequence except for Sample 199-1218A-25X-2, 32–34 cm (226.52 mbsf), which is barren of radiolarians.

Hole 1219A is located at 7°48.019´N, 142°00.940´W (water depth = 5063 m). The 244.8-m-thick sediment overlying early Eocene basalt basement is subdivided into four units (Shipboard Scientific Party, 2002c):

Unit II (30.0–150.8 mbsf): early Miocene–early Oligocene nannofossil ooze and nannofossil ooze with radiolarians and clay;

Unit III (150.8–234.2 mbsf): late–middle Eocene radiolarian clay, radiolarian ooze of Subunit IIIA, and middle Eocene radiolarite, chert, and zeolitic clay of Subunit IIIB; and

Unit IV (234.2–44.8 mbsf): early Eocene nannofossil chalk.

A total of 65 samples spanning the interval from Sample 199-1219A-18H-3, 130–132 cm (162.30 mbsf; Subunit IIIA), to 15H-1, 30–34 cm (129.80 mbsf; Unit II), were examined for radiolarians (Fig. F3). The average sampling interval in this hole was ~0.5 m. Radiolarian preservation is good to very good throughout the sequence examined.

Hole 1220A is situated at 10°10.600´N, 142°45.503´W (water depth = 5218 m). The 114.0-m sedimentary sequence of this hole is subdivided into four units (Shipboard Scientific Party, 2002d):

Unit II (19.1–37.2 mbsf): early Miocene–Oligocene radiolarian ooze with clay, nannofossil radiolarian ooze with clay, and nannofossil ooze with clay and radiolarians;

Unit III (37.2–69.2 mbsf): Oligocene nannofossil ooze, radiolarian ooze with clay and nannofossils, and nannofossil diatom ooze; and

Unit IV (Subunit IVA: 69.2–114.0 mbsf): late–middle Eocene radiolarian ooze with clay, clayey radiolarian ooze, and clay with radiolarians.

A total of 81 samples were collected for this study spanning the interval from Sample 199-1220A-9H-7, 63–65 cm (85.63 mbsf; Subunit IVA), to 6H-1, 25–27 cm (47.75 mbsf; Unit III) (Fig. F4). The average sampling interval was ~0.47 m. Preservation of radiolarians in this hole is moderate to very good.