The standard zonation of Bukry (1973, 1975), emended by Okada and Bukry (1980) was primarily applied here, based on the zonal maker species that could be traced at the sites, with the exception of a few taxa including Discoaster bifax and Discoaster kuepperi. In the following, the intervals given for the ranges of zonal units are based on the suite of samples observed (Figs. F4, F5; Table T1, T2).
Definition. Interval from the last occurrence (LO) of Chiasmolithus grandis to the LO of D. barbadiensis and/or Discoaster saipanensis.
Hole 1052A. Samples 171B-1052A-3H-2, 85-87 cm, through 9H-5, 86-88 cm.
Remarks. The lower part of the D. barbadiensis Zone is recognized in Hole 1052A but not in Hole 1051A. I started to examine the samples from Section 171B-1052A-3H-2, but observed no Isthmolithus recurvus; therefore, I could not determine the upper limit of Zone CP15a in Hole 1052A.
Definition. Interval from the first occurrence (FO) of C. oamaruensis and/or the LO of C. grandis to the FO of I. recurvus.
Hole 1052A. Samples 171B-1052A-3H-2, 85-87 cm, through 9H-5, 86-88 cm.
Remarks. The C. oamaruensis Zone is present in Hole 1052A, but not in Hole 1051A. No I. recurvus specimens were observed (as mentioned above); therefore I could not determine the upper limit of this zone. C. oamaruensis occurs sporadically in this zone, therefore the lower limit of this zone is determined by the LO of C. grandis. Cribrocentrum reticulatum occurs consistently through out this zone and a large form of C. reticulatum (>10 µm) is found in both the lower and upper parts of this zone.
Definition. Interval from the FO of R. umbilicus to the LO of C. grandis.
Hole 1051A. Samples 171B-1051A-1H-2, 115-117 cm, through 24X-3, 66-68 cm.
Hole 1052A. Samples 171B-1052A-9H-6, 87-89 cm, through 19X-4, 63-65 cm.
Remarks. Most of the R. umbilicus specimens are present from Samples 171-B-1051A-1H-2, 115-117 cm, through 24X-3, 66-68 cm, and 171B-1052A-3H-2, 85-87 cm, through 19X-4, 63-65 cm, but Hole 1051A was recognized in downcore Sample 28X-CC, 27-29 cm. The FO of D. bisectus is not clear in Hole 1051A. Bralower and Mutterlose (1995) indicate that the LO of Sphenolithus furcatolithoides is very close to the FO of D. bisectus. However, the LO of S. furcatolithoides seems to be present at the bottom of the D. bisectus acme in Hole 1051A.
Definition. Interval from the LO of Chiasmolithus solitus and/or D. bifax to the LO of C. grandis.
Hole 1051A. Samples 171B-1052A-1H-2, 115-117 cm, through 12H-2, 85-87 cm.
Hole 1052A. Samples 171B-1052A-9H-6, 87-89 cm, through 19X-2, 69-71 cm.
Remarks. D. bifax is very rare and occurs sporadically, but the LO of C. solitus is recognized precisely in both holes. The FO of D. bisectus is mentioned above.
Definition. Interval from the FO of R. umbilicus and/or D. bifax to the LO of C. solitus and/or D. bifax.
Hole 1051A. Samples 171B-1051A-12H-3, 67-69 cm, through 24X-3, 66-68 cm.
Hole 1052A. Samples 171B-1052A-19X-3, 43-44 cm.
Remarks. The FO of R. umbilicus and the LO of C. solitus is mentioned above. The FO of C. reticulatum (>6 µm) is precisely determined at Sample 171B-1051A-17X-4, 45-47 cm. A large form of C. reticulatum (>10 µm) is present in the middle and upper parts of this zone.
Definition. Interval from the FO of N. quadrata (= N. fulgens) and/or the LO of Rhabdosphaera inflata to the FO of R. umbilicus.
Hole 1051A. Samples 171B-1051A-24X-4, 89-91 cm, through 38X-1, 27-29 cm.
Hole 1052A. Questionable.
Remarks. N. fulgens is present in the lower part (Sample 171B-1051A-37X-1, 77-79 cm, through 34X-CC, 50-52 cm) and upper part (Sample 171B-1051A-27X-CC, 36-38 cm, through 25X-4, 53-55 cm) of this zone. The LO and FO of R. inflata is precisely determined at Samples 171B-1051A-38X-4, 66-68 cm, and 40X-CC, 38-40 cm. An interval of Chiasmolithus gigas is recognized in Samples 1051A-27X-CC, 36-38 cm through 36X-4, 56-58 cm. Small-sized Reticulofenestra spp. (<10 µm), Coccolithus pelagicus, Braadosphaera bigelowii, and Dictyococcites spp. (<6 µm) are dominant in this zone. Only one sample (171B-1052A-19X-3, 43-44 cm) from Hole 1052A yields N. fulgens, R. umbilicus, and C. solitus. C. reticulatum and D. bisectus are absent from this sample. This sample assignment to Zone CP13 is questionable based on the presence of R. umbilicus.
Definition. Interval from the LO of C. gigas to the FO of R. umbilicus and/or D. bifax.
Hole 1051A. Samples 171B-1051A-24X-4, 89-91 cm, through 27X-6, 75-77 cm.
Hole 1052A. Questionable.
Remarks. See above.
Definition. Interval from the LO of C. gigas to the FO of C. gigas.
Hole 1051A. Samples 171B-1051A-27X-CC, 36-38 cm, through 36X-4, 56-58 cm.
Hole 1052A. Questionable.
Remarks. See above.
Definition. Interval from the FO of N. fulgens and/or the LO of R. inflata to the FO of C. gigas.
Hole 1051A. Samples 171B-1051A-36X-CC, 34-36 cm, through 38X-1, 27-29 cm.
Hole 1052A. Questionable.
Remarks. See above.
Definition. Interval from the FO of D. sublodoensis to the FO of N. fulgens and/or the LO of R. inflata.
Hole 1051A. Samples 171B-1051A-38X-4, 66-68 cm, through 41X-CC, 16-18 cm.
Remarks. The interval of R. inflata is determined precisely, but D. sublodoensis is present only sporadically. The major assemblage change is recognized in the middle lower part of this zone. Two major cosmopolitan reticulofenestrids and Dictyococcites disappear dramatically below Sample 171B-1051A-42X-1, 81-83 cm, whereas Toweius and small-sized C. pelagicus (<4 µm) become dominant.
Definition. Interval from the FO of R. inflata to the LO of R. inflata and/or the FO of N. fulgens.
Hole 1051A. Samples 171B-1051A-38X-4, 66-68 cm, through 40X-CC, 38-40 cm.
Remarks. Medium to small forms of Reticulofenestra spp. and B. bigelowii are dominant in this zone. D. bisectus is also present.
Definition. Interval from the FO of D. sublodoensis to the FO of R. inflata.
Hole 1051A. Samples 171B-1051A-41X-1, 47-49 cm, through 41X-CC, 16-18 cm.
Remarks. D. sublodoensis and Tribrachiatus orthostylus are present together from Sample 171B-1051A-42X-1, 81-83 cm, through 44X-1, 75-77 cm. This makes it difficult to identify the CP12a/CP11 Subzone boundary. I determine this boundary at Sample 171B-1051A-42X-1, 81-83 cm, and interpret the presence of D. sublodoensis as reworking below Sample 171B-1051A-42X-1, 81-83 cm. This determination was made because of two reasons: abundant Toweius are present and discontinuous lithology is not observed in the interval.
Definition. Zone CP11 includes the interval from the FO of Toweius? crassus to the FO of D. Sublodoensis, and CP10 includes the interval from the FO of D. lodoensis to the FO of T. crassus.
Hole 1051A. Samples 171B-1051A-42X-1, 81-83 cm, through 47X-2, 72-74 cm.
Remarks. T. crassus is difficult to distinguish from Toweius callosus because the change between T. crassus and T. callosus is gradational. Therefore, the Zone CP10/CP11 boundary could not be recognized in these samples for this report. This zone is characterized by the presence of D. lodoensis and T. callosus. Toweius sp. A, Toweius sp. B, and C. pelagicus are dominant. Toweius sp. A is consistently abundant throughout the sequence, but Toweius sp. B gradually decreases in abundance upward through the sequence. Tribrachiatus spp. is very rare through the sequence and the preservation is poor.
Definition. Interval from the FO of D. diastypus and/or Tribrachiatus bramlettei to the FO of D. lodoensis.
Hole 1051A. Sample 171B-1051A-47X-4, 78-80 cm, through 55X-CC, 19-22 cm.
Remarks. The preservation of specimens in this zone is moderate to poor and is marked by the overgrowth of some species, including Tribrachiatus. In spite of the sporadic presence of T. bramlettei and D. diastypus, these two species are not present with Fasciculithus tympaniformis. For this reason, the Zone CP8/9 boundary lies between Sample 171B-1051A-55X-CC, 19-22 cm, and 56X-3, 65-66 cm. The FO of T. orthostylus is comparatively easy to determine on Sample 171B-1051A-48X-CC, 52-54 cm.
Definition. Interval from the LO of Tribrachiatus contortus to the FO of D. lodoensis.
Hole 1051A. Samples 171B-1051A-47X-4, 78-80 cm, through 48X-7, 70-72 cm.
Remarks. See above.
Definition. Interval from the FO of D. diastypus and/or T. bramlettei to the FO of D. lodoensis.
Hole 1051A. Samples 171B-1051A-48X-CC, 52-54 cm, through 55X-CC, 19-22 cm.
Remarks. Specimens found in the lowermost two samples are poorly preserved and abundance is rare.
Definition. Interval from the FO of D. multiradiatus to the FO of D. diastypus and/or T. bramlettei.
Hole 1051A. Samples 171B-1051A-56X-3, 65-66 cm, through 57X-CC, 48-50 cm.
Remarks. The uppermost sample contains F. tympaniformis and D. multiradiatus, but D. diastypus is not present, which suggests late Paleocene age.