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doi:10.2204/iodp.proc.320321.202.2012

Results

The zonal scheme of Sanfilippo and Nigrini (1998) was adopted for this study. The interval studied at Site U1331 was divided into nine radiolarian zones from Zone RP8 to RP16 (Sanfilippo and Nigrini, 1998). Terms used in this study to express events include evolutionary transition (ET), first occurrence (FO), and last occurrence (LO). The concept of evolutionary transition follows that of Sanfilippo and Nigrini (1998).

Zone RP16

Podocyrtis (Lampterium) goetheana interval zone (Moore, 1971, emend. Riedel and Sanfilippo, 1978)

The base of this zone is defined by the FO of P. goetheana. The interval from Samples 320-U1331A-6H-2, 105–107 cm (52.90 mbsf), to 7H-4, 95–97 cm (67.95 mbsf), was assigned to this zone. This zone contains the following species: Anthocyrtoma spp., Calocycloma ampulla, Dorcadospyris anastasis, and the Lithocyclia aristotelis group.

Zone RP15

Podocyrtis (Lampterium) chalara lineage zone (Riedel and Sanfilippo, 1970, emend. Riedel and Sanfilippo, 1978)

The base of this zone is defined by the ET of P. chalara. The interval from Samples 320-U1331A-7H-CC (72.41 mbsf) to 9H-4, 105–107 cm (88.6 mbsf), was assigned to this zone. This zone includes the following species: Lithochytris vespertilio, Lophocyrtis biaurita, Podocyrtis sinuosa, and Sethochytris triconiscus.

Zone RP14

Podocyrtis (Lampterium) mitra lineage zone (Riedel and Sanfilippo, 1970, emend. Riedel and Sanfilippo, 1978)

The base of this zone is defined by the ET of P. mitra. Samples 320-U1331A-9H-CC (92.97 mbsf) through 13H-2, 104–106 cm (130.21 mbsf), were assigned to this zone. In this zone, Eusyringium lagena, Podocyrtis fasciolata, Podocyrtis helenae, Podocyrtis trachodes, and Zealithapium anoectum were recognized at Site U1331.

Zone RP13

Podocyrtis (Podocyrtoges) ampla lineage zone (Riedel and Sanfilippo, 1970, emend. Riedel and Sanfilippo, 1978)

The base of this zone is defined by the ET of P. ampla. The interval spans from Samples 320-U1331A-13H-4, 104–106 cm (133.21 mbsf), to 14H-2, 104–106 cm (140.80 mbsf). This zone contains the following species: Calocyclas trichopa, Dendrospyris didiceros, Eusyringium fistuligerum, Thyrsocyrtis triacantha, and the Lithocyclia ocellus group.

Zone RP12

Thyrsocyrtis (Pentalacorys) triacantha interval zone (Riedel and Sanfilippo, 1970, emend. Riedel and Sanfilippo, 1978)

The base of this zone is defined by the FO of E. lagena. This zone was recognized from Samples 320-U1331A-14H-4, 104–106 cm (143.80 mbsf), to 16H-CC (159.38 mbsf). In Zone RP12 at Site U1331, Calocycloma ampulla, Lychnocanoma bajunensis, Periphaena tripyramis triangula, and Rhopalocanium ornatum were included in deep-sea sediments.

Zone RP11

Dictyoprora mongolfieri interval zone (Riedel and Sanfilippo, 1970, emend. Riedel and Sanfilippo, 1978)

The base of this zone is defined by the FO of D. mongolfieri. Samples 320-U1331A-17X-2, 104–106 cm (170.53 mbsf), through 19X-2, 25–27 cm (182.64 mbsf), were assigned to this zone. This zone includes the following species: Buryella clinata, Calocycloma castum, Lithochyrtis archaea, and Zealithapium plegmacantha.

Zone RP10

Theocotyle cryptocephala interval zone (Foreman, 1973)

The base of Zone RP10 is defined by the ET of T. cryptocephala. This zone was found in Sample 320-U1331A-19X-CC (182.76 mbsf) and contains the following species: Lithochytris vespertilio, the L. ocellus group, Phormocyrtis embolum, Phormocyrtis striata striata, and Stylosphaera coronata coronata.

Zone RP9

P. striata striata interval zone (Foreman, 1973, emend. Riedel and Sanfilippo, 1978)

The base of this zone is defined by the FO of Theocorys anaclasta. Zone RP9 was located in Sample 320-U1331A-20X-CC (187.40 mbsf) and includes the following species: Dictyophimus craticula, P. tripyramis triangula, P. embolum, and S. coronata coronata.

Zone RP8

Buryella clinata interval zone (Foreman, 1973, emend. Riedel and Sanfilippo, 1978)

The base of this zone is defined by the ET of B. clinata. The interval from Samples 320-U1331C-16H-2, 52–59 cm (200.27 mbsf), to 17H-2, 49–56 cm (lowermost sample in this study), was assigned to Zone RP8. This zone contains the following species: Giraffospyris lata, Lamptonium sanfilippoae, Lophocyrtis biaurita, Lychnocanoma auxilla, and Thyrsocyrtis rhizodon.

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