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doi:10.2204/iodp.proc.317.104.2011

Biostratigraphy

Core catcher samples from Holes U1352A–U1352D were examined for calcareous nannofossils, diatoms, planktonic and benthic foraminifers, and bolboformids to develop a preliminary biostratigraphic framework for the cored succession (Fig. F24; Table T5). Calcareous nannofossils and planktonic foraminifers provided the primary means of age control at Site U1352, but marine diatoms, bolboformids, and benthic foraminifers also contributed to dating. Benthic foraminifers were used to determine paleowater depths and interpret depositional environments. All depths in this section are reported in m CSF-A.

Integrated microfossil records from Site U1352 reveal a 1924 m thick sedimentary succession spanning the Holocene to Eocene. Although not identified biostratigraphically, the base of the Holocene was tentatively assigned in Hole U1352B at 1.2 m, the level at which shell-rich greenish gray marly sands with a sharp base overlie gray muds. The base of the Pleistocene was loosely constrained between Samples 317-U1352B-57X-CC and 61X-CC (491.74–525.34 m). The base of the Pliocene was constrained with planktonic foraminiferal evidence between Samples 317-U1352C-72R-CC and 73R-CC (1266.38–1283.95 m). The base of the Miocene was picked using calcareous nannofossil evidence between Samples 317-U1352C-139R-CC and 140R-CC (1848.49–1852.71 m), and the base of the Oligocene was placed between Samples 317-U1352C-146R-CC and 147R-CC (1903.29–1916.63 m). Calcareous nannofossil and planktonic foraminiferal dating indicate a late Eocene age of 35.2–36.0 Ma at the bottom of the hole (Sample 317-U1352C-148R-CC [1924.26 m]).

At least five biostratigraphically defined hiatuses were recognized. The first hiatus occurs between the Pliocene and Pleistocene (Samples 317-U1352B-57X-CC and 61X-CC [491.74–504.14 m]), where most, if not all, of the late Pliocene is missing. An intra-late Miocene unconformity was recognized between the New Zealand upper Kapitean and lower Tongaporutuan Stages (Samples 317-U1352C-90R-CC and 91R-CC [1394.62–1409.66 m]), where at least 5 m.y. is missing. Another hiatus was identified between the middle and late Miocene (Samples 317-U1352C-101R-CC and 102R-CC [1486.78–1496.50 m]), with at least 1.3 m.y. missing. A substantial unconformity, identified as the Marshall Paraconformity, was constrained between Samples 317-U1352C-139R-CC and 140R-CC (1848.49–1852.71 m), where the lower Miocene unconformably overlies the lower Oligocene. At least 12 m.y. is missing at this level. A hiatus was also recognized between the early Oligocene and late Eocene (Samples 317-U1352C-146R-CC and 147R-CC [1903.29–1916.63 m]), where at least 2.3 m.y. is missing.

Calcareous nannofossils

All core catcher samples from Holes U1352A–U1352D contained calcareous nannofossils, with the exception of Sample 317-U1352B-71X-CC (614.56 m). Abundances ranged from barren to very abundant, and preservation was generally good in the Pleistocene–Miocene and moderate to poor in the Oligocene and Eocene (Table T6). Nannofossil datums used for age determination at this site are summarized in Table T5.

Holocene–Pleistocene

All sediment samples from Hole U1352A were zoned in NN21 (0–0.29 Ma). Core catcher samples from Holes U1352A (317-U1352A-1H-CC through 5H-CC [4.21–43.06 m]) and U1352D (317-U1352D-1H-CC through 14H-CC [3.55–127.61 m]) contained rare Emiliania huxleyi, likely placing them below the acme of this species in Subzone NN21a (0.08–0.29 Ma).

Hole U1352B contained a thick Pleistocene section from Samples 317-U1352B-1H-CC through 61X-CC (7.93–525.34 m). Samples 317-U1352B-1H-CC through 12H-CC (7.93–112.82 m) were zoned in NN21a. Sediments recovered from Samples 317-U1352B-13H-CC through 17H-CC (121.1–155.99 m) were zoned in NN20 (0.29–0.44 Ma).

The highest occurrence (HO) of Pseudoemiliania lacunosa (top of Zone NN19) was recognized between Samples 317-U1352B-17H-CC and 18H-CC (155.99–164.18 m). Within the P. lacunosa and small Gephyrocapsa subzones of NN19 (Gartner, 1977), several nannofossil bioevents were observed:

• The highest common occurrence (HCO) of Reticulofenestra asanoi between Samples 317-U1352B-29H-CC and 30H-CC (257.09–266.92 m; 0.91 Ma),

• The lowest common occurrence (LCO) of R. asanoi between Samples 317-U1352B-34H-CC and 35H-CC (292.54–295.24 m; 1.14 Ma),

• The HO of Gephyrocapsa >6.5 µm between Samples 317-U1352B-42X-CC and 43X-CC (348.59–360.08 m; 1.24 Ma), and

• The HO of Gephyrocapsa >5.5 µm between Samples 317-U1352B-43X-CC and 44X-CC (360.08–369.84 m; 1.26 Ma).

The top of the Helicosphaera sellii NN19 Subzone was tentatively picked between Samples 317-U1352B-46X-CC and 47X-CC (388.95–398.56 m; 1.34 Ma). The lowest occurrence (LO) of Gephyrocapsa >5.5 µm was observed within this subzone between Samples 317-U1352B-49X-CC and 50X-CC (412.30–427.34 m; 1.56 Ma).

The primary marker for the Calcidiscus macintyrei NN19 Subzone (C. macintyrei >11 µm) was not observed; however, secondary markers (LO of Gephyrocapsa >4 µm between Samples 317-U1352B-54X-CC and 55X-CC [463.67–469.84 m; 1.69 Ma] and LO of Gephyrocapsa caribbeanica between Samples 317-U1352B-55X-CC and 56X-CC [469.84–484.83 m; 1.73 Ma]) support the presence of this subzone.

The Pliocene/Pleistocene boundary was constrained between Samples 317-U1352B-57X-CC and 61X-CC (491.74–525.34 m) using nannofossil and foraminiferal markers that approximate the boundary. Below this boundary, Reticulofenestra ampla was observed in Sample 317-U1352B-62X-CC (542.58 m). The HO of this species is dated at 2.78 Ma (Kameo and Bralower, 2000), which suggests a hiatus spanning the late Pliocene.

Pliocene

Nannofossil biostratigraphy was problematic for Samples 317-U1352B-60X-CC through 94X-CC (514.61–821.74 m [total depth]) and 317-U1352C-2R-CC through 93R-CC (576.47–1419.06 m) because almost all standard zonal markers were absent. The Reticulofenestra lineage, however, was abundant in this cored succession, making it useful as a secondary proxy for age constraint. The HO of Reticulofenestra pseudoumbilicus was observed between Samples 317-U1352C-29R-CC and 30R-CC (884.91–894.37 m; 3.7 Ma), defining the base of the middle Pliocene. The base of the Pliocene was picked between Samples 317-U1352C-72R-CC and 73R-CC (1266.38–1283.95 m; 5.33 Ma) with planktonic foraminiferal evidence.

Miocene

Standard Miocene nannofossil zonal markers based on warm-water taxa were sparse at Site U1352, except in the early Miocene, where they were more common. Planktonic foraminifers and bolboformids show evidence of a major intra-late Miocene hiatus between Samples 317-U1352C-90R-CC and 91R-CC (1394.62–1409.66 m), where at least 5 m.y. is missing. The HO of Coccolithus miopelagicus (11.02 Ma) was observed between Samples 317-U1352C-94R-CC and 95R-CC (1438.43–1446.91 m). The first in situ discoaster was noted in Sample 103R-CC (1515.94 m). Below this level, discoasters (common in low- to mid-latitudes) occurred sporadically and were dominated primarily by Discoaster deflandrei; however, zonal marker species for the late Miocene were still absent.

The HO of Calcidiscus premacintyrei was observed between Samples 317-U1352C-101R-CC and 102R-CC (1486.78–1496.50 m), implying a late middle Miocene age (12.45 Ma). In addition, a marked increase in six-rayed discoasters was observed in Samples 317-U1352C-119R-CC and 120R-CC (1670.41–1669.36 m). Some of these were confidently identified as Discoaster deflandrei, but others were too overgrown to be distinguished at the species level. The interval between these samples was tentatively considered as the acme event of D. deflandrei (15.80 Ma), even though the position of this event is uncertain because of caved-in local sediments found between the two samples.

The lower Miocene HO of Sphenolithus heteromorphus was picked between Samples 317-U1352C-114R-CC and 115R-CC (1622.61–1632.61 m). Below Core 317-U1352C-115R, S. heteromorphus was consistently seen in core catcher samples down to Sample 317-U1352C-129R-CC (1749.66 m). The LCO of this species, dated at 17.71 Ma, was therefore placed between Samples 129R-CC and 130R-CC (1749.66–1760.69 m).

Sphenolithus belemnos (HO = 17.95 Ma) occurred in extreme paucity in cored sediments; however, the HCO of this species was questionably picked between Samples 317-U1352C-132R-CC and 133R-CC (1777.59–1789.60 m), and it is certainly common by Sample 135R-CC (1810.40 m). The LO of this species was questionably picked between Samples 317-U1352C-137R-CC and 138R-CC (1829.75–1841.54 m; 19.03 Ma).

A major hiatus, identified as the Marshall Paraconformity, occurred between Samples 317-U1352C-139R-CC and 140R-CC (1848.49–1852.71 m). This hiatus separates the early Miocene (18–19 Ma) from the early Oligocene (30.1–32.0 Ma), with ~12 m.y. missing based on nannofossil and foraminiferal biostratigraphy.

Oligocene

Nannofossil abundance was generally low in Oligocene sediments, and preservation was generally poor. Samples 317-U1352C-140R-CC through 143R-CC (1852.71–1878.85 m) were constrained between 30.0 and 32.0 Ma (early Oligocene) based on the presence of Dictyococcites scrippsae, Dictyococcites stavensis, Reticulofenestra filewiczii, and Chiasmolithus altus.

The HO of Reticulofenestra umbilicus (32.0 Ma) was identified between Samples 317-U1352C-143R-CC and 144R-CC (1878.85–1885.85 m). The HO of Isthmolithus recurvus was observed between Samples 317-U1352R-145R-CC and 146R-CC (1893.50–1903.29 m; 32.5 Ma).

A hiatus spanning at least 2.3 m.y. was recognized with calcareous nannofossil evidence between the early Oligocene and late Eocene (Samples 317-U1352C-146R-CC and 147R-CC [1903.29–1916.63 m]). Sediments above the hiatus were dated at 32.5–32.9 Ma, and those below were dated at 35.2–36.6 Ma.

Eocene

Calcareous nannofossil abundances were generally low in the Eocene, and preservation was better than in the Oligocene. Samples 317-U1352C-147R-CC and 148R-CC (1916.63–1924.26 m [total depth]) contained the late Eocene species Reticulofenestra reticulata, Isthmolithus recurvus, and Chiasmolithus oamaruensis, which constrains the age of the bottom of the hole between 35.2 and 36.6 Ma.

Planktonic foraminifers and bolboformids

Planktonic foraminiferal and bolboformid biostratigraphy at Site U1352, on the upper slope, was based on the examination of core catcher samples from Holes U1352A–U1352D (Tables T7, T8, T9, T10, T11, T12, T13, T14). The absolute ages assigned to biostratigraphic datums follow the references listed in Table T3 in the "Methods" chapter. The percentage of planktonic foraminifers in the cored Holocene–Eocene succession generally increased from ~70% in the upper part of the succession to ~95% in the lower part (Fig. F25). Preservation was variable but was generally good in the Pleistocene, moderate in the Pliocene, poor in the Miocene and Oligocene, and moderate to poor in the Eocene. Bolboformids only occurred in the late middle Miocene to early late Miocene.

Holocene

Although not identified biostratigraphically, the base of the Holocene was tentatively correlated with a distinct lithologic boundary at Section 317-U1352B-1H-1, 120 cm (1.20 m). Mudline samples from Sections 317-U1352A-1H-1, 0 cm (0.00 m), and 317-U1352D-1H-1, 0 cm (0.00 m), contained temperate assemblages and were dominated by the eutrophic species Globigerina bulloides s.l. They also contained abundant Globoconella inflata and Turborotalita quinqueloba and common Truncorotalia truncatulinoides (sinistral), Neogloboquadrina incompta, and Orbulina universa.

Pleistocene

The abundance of planktonic foraminifers varied throughout the Pleistocene sections of Holes U1352A, U1352B, and U1352D, but planktonic forms increased on average from 66% of the total foraminiferal assemblage in the upper part of the section to 74% in the lower part. This is consistent with deposition under suboceanic conditions on the upper slope. Preservation was generally good, and planktonic assemblages were dominated by small, thin- to thick-walled specimens. Larger thick-walled forms were found in some samples, especially in greenish gray sandy marls, where temperate species were more common.

The Pleistocene succession included several useful planktonic foraminiferal bioevents, although primary age control was provided by calcareous nannofossils. Hirsutella hirsuta (0–0.34 Ma) was found in Samples 317-U1352B-19H-CC (173.71 m) and 317-U1352D-14H-CC (130.26 m). Truncorotalia truncatulinoides (0–1.1 Ma) was present in most samples in the upper part of the succession (Samples 317-U1352A-1H-CC through 4H-CC [4.21–33.43 m], 317-U1352B-1H-CC through 19H-CC [7.93–173.71 m], and 317-U1352D-1H-CC through 14H-CC [3.55–127.61 m]). The HO of Globoconella puncticuloides was recognized as a very well defined event in Sample 317-U1352B-22H-CC (198.87 m), ~20 m below the LO of the Haweran marker species Hirsutella hirsuta. It occurred persistently below this level down to the early Pliocene. The HO of Gc. puncticuloides was dated at 1.5 Ma at ODP Site 1123 (Cooper, 2004), but in Hole U1352B calcareous nannofossil and diatom dating suggests it occurs between 0.44 and 0.70 Ma. This suggests the disappearance of this species occurred ~1 m.y. later in the cold waters of the Canterbury Basin than in the warmer subtropical water surrounding Site 1123. Globoconella cf. puncticuloides, a distinctly inflated form with a flattened dorsal surface, occurred in most samples with Gc. puncticuloides between Samples 317-U1352B-24H-CC and 94X (217.96–821.74 m) and 317-U1352C-7R-CC and 43R-CC (671.20–1019.69 m). This distinctive form has a pustulate ultrastructure similar to Truncorotalia crassaformis, but it is distinguished from the latter species by its low-arched rather than slitlike aperture.

The abundance of the subantarctic species Neogloboquadrina pachyderma was highly variable in the Pleistocene succession. This cold-water species was common and sometimes dominant in gray mud lithologies and was often associated with high numbers of Gc. puncticuloides. Interbedded greenish gray sandy marls contained lower abundances of Nq. pachyderma, and the temperate species Neogloboquadrina incompta and the eutrophic species Globigerina bulloides s.l. and Turborotalita quinqueloba were generally more common. Subtropical species were absent except for rare occurrences of Globigerinella aequilateralis in Samples 317-U1352D-7H-CC (60.32 m) and 317-U1352B-50X-CC (427.34 m) and a single specimen of Globigerinoides cf. ruber in Sample 317-U1352B-21H-CC (189.06 m).

Pliocene

Tentative biostratigraphic evidence indicates that the late Pliocene is missing at Site U1352 (see discussion below).

Planktonic foraminifers were abundant and moderately well preserved in the middle Pliocene section in Samples 317-U1352B-61X-CC through 94X-CC (525.34–821.74 m) and 317-U1352C-2R-CC through 29R-CC (576.47–884.91 m) and moderate to poorly preserved in the early Pliocene section in Samples 317-U1352C-30R-CC through 72R-CC (894.37–1266.38 m). The abundance of planktonic foraminifers varied, but on average abundances increased down through the Pliocene from ~74% at the top of the section to 85% at the base. Such abundances are consistent with deposition under suboceanic conditions on the upper to middle slope.

Pliocene planktonic assemblages were dominated by Globigerina bulloides and other small species of Globigerina. Globoconella inflata, Gc. puncticuloides, Gc. cf. puncticulata, Gc. puncticulata s.s. (below Sample 317-U1352C-56R-CC [1147.41 m]), Neogloboquadrina pachyderma, Nq. incompta, Turborotalita quinqueloba, and related forms were common to abundant in some samples. Orbulina universa, Truncorotalia crassaformis, and Tr. crassaconica also occurred sporadically with rare Globigerinita glutinata, Globoconella cf. pliozea, and Zeaglobigerina woodi.

Biostratigraphically useful middle Pliocene events include the LO of Truncorotalia crassula between Samples 317-U1352B-60X-CC and 61X-CC (514.61– 525.34 m; 2.40 Ma) and the poorly constrained HO of Truncorotalia crassaconica? between Samples 317-U1352B-60X-CC and 61X-CC (514.61–525.34 m; >3.09 Ma). The juxtaposition of these events suggests the presence of a hiatus at this level with at least 0.7 m.y. missing. The HO of calcareous nannofossil Reticulofenestra ampla (2.78 Ma) between Samples 317-U1352B-61X-CC and 62X-CC (525.34–542.58 m) and the HO of planktonic foraminifer Zeaglobigerina woodi (>2.7 Ma) between Samples 317-U1352B-67X-CC and 68X-CC (573.33–583.56 m) support the presence of a hiatus, but it is uncertain whether the upper Pliocene is represented in part or is completely missing.

Early Pliocene bioevents include the HO of Globoconella subconomiozea between Samples 317-U1352C-26R-CC and 27R-CC (855.29–864.94 m; 3.35 Ma), the LO of Gc. inflata s.s. and the HO of Gc. puncticulata s.s. between Samples 317-U1352C-56R-CC and 57R-CC (1147.41–1155.03 m; 4.3 Ma), and the HO of Gc. pliozea between Samples 317-U1352C-61R-CC and 62R-CC (1197.57–1206.27 m; 4.49 Ma). The LO of Gc. puncticulata s.s. (5.30 Ma) and the HO of Globoconella sphericomiozea s.s. (5.30 Ma), which serve as proxies for the Miocene/Pliocene boundary, were reliably identified between Samples 317-U1352C-72R-CC and 73R-CC (1266.38–1283.95 m).

Miocene

Planktonic foraminifers in Hole U1352C were abundant and moderately to poorly preserved in the late Miocene (Samples 317-U1352C-73R-CC through 101R-CC [1283.95–1486.78 m]), abundant to common and poorly preserved in the middle Miocene (Samples 317-U1352C-102R-CC through 121R-CC [1496.50–1678.60 m]), and common to few and poorly preserved in the early Miocene (Samples 317-U1352C-122R-CC through 139R-CC [1690.44–1848.49 m]). Foraminiferal tests were often recrystallized and infilled with sparry calcite, and some also exhibited microcrystalline overgrowths (Fig. F26). Planktonic foraminiferal abundances generally increased down through the Miocene succession of Hole U1352C from 85% of the total foraminiferal assemblage at the top of the section to 94% at the base. Such abundances are consistent with deposition on the lower slope and base of slope under suboceanic and oceanic conditions.

Planktonic assemblages in the Miocene succession were characterized by abundant Globigerina, including Gg. bulloides. Zeaglobigerina woodi and Turborotalita quinqueloba and related forms were also present along with rare Globigerinopsis obesa and Globigerinita glutinata. Globoconellids, including Gc. sphericomiozea (upper Kapitean; uppermost Miocene), Gc. miotumida (Tongaporutuan to upper Waiauan; upper Miocene), Gc. miozea (Lillburnian to Altonian; middle to upper lower Miocene), Gc. zealandica (middle Altonian; middle lower Miocene), and Gc. praescitula (early Altonian; lower Miocene), were present in respective parts of the Miocene section, but abundances varied. Neogloboquadrina pachyderma and Nq. incompta were present in the late Miocene, Paragloborotalia mayeri s.l. was abundant in the early late Miocene, Orbulina universa occurred sporadically down into the middle Miocene, and Orbulina suturalis was present in the early middle Miocene. Subtropical species were absent, except for single specimens of Globigerinoides trilobus in the middle Miocene (Sample 317-U1352C-105R-CC [1534.20 m]) and lower Miocene (Sample 317-U1352C-128R-CC [1743.51 m]).

The uppermost Miocene (upper Kapitean) species Gc. sphericomiozea s.s. (5.30–5.60 Ma) was common from Samples 317-U1352C-73R-CC to 90R-CC (1283.95–1394.62 m). Its presence immediately above the HOs of Globoconella miotumida (7.07 Ma), Bolboforma metzmacheri s.s. (8.85 Ma), and Bolboforma subfragoris s.l. (10.58 Ma) suggests a hiatus in the late Miocene section between Samples 317-U1352C-90R-CC and 91R-CC (1394.63–1409.66 m) with at least 3.25 m.y. missing. The concurrence of these two bolboformid species is also somewhat enigmatic because they have range zones that are separated in time, which suggests there may be another shorter hiatus between Samples 317-U1352C-91R-CC and 93R-CC (1409.66–1419.06 m).

The HCO of Paragloborotalia mayeri s.l. (10.97 Ma) occurred between Samples 317-U1352C-95R-CC and 96R-CC (1446.91–1448.00 m) and the LO of Bolboforma subfragoris s.l. (11.64 Ma) occurred between Samples 317-U1352C-101R-CC and 102R-CC (1486.78–1496.50 m). The HO of Globoconella conica (12.98 Ma) was noted immediately below the LO of B. subfragoris s.l., which suggests a hiatus between Samples 317-U1352C-101R-CC and 102R-CC (1486.78–1496.50 m). Bolboforma cf. reticulata, a bolboformid that has never before been recognized in New Zealand, occurred at the same level as the HO of Gc. conica and was not recorded in any other sample. Sample 317-U1352C-103R-CC (1515.94 m) is also significant in that it contained the HO of Gc. miozea, the LO of Orbulina universa (13.63 Ma), and B. cf. robusta, one sample above the HO of Or. suturalis in Sample 104R-CC (1525.67 m). The close stratigraphic spacing of these bioevents between Samples 317-U1352C-103R-CC and 104R-CC (1515.94–1525.67 m) suggests that the section is condensed or that parts of the section are missing.

The LO of Globoconella miozea (16.7 Ma), a bioevent that marks the base of the upper Altonian, was identified between Samples 317-U1352C-125R-CC and 126R-CC (1714.42–1725.45 m; 16.7 Ma). Other bioevents include the poorly constrained HO of Globoconella praescitula (16.7 Ma) between Samples 317-U1352C-123R-CC and 124R-CC (1697.39–1707.63 m), the HO of Gc. zealandica (16.7 Ma) between Samples 317-U1352C-125R-CC and 126R-CC (1714.42–1725.45 m), the HO of Gc. incognita (18.3 Ma) between Samples 317-U1352C-131R-CC and 132R-CC (1769.18–1777.59 m), and the poorly constrained HO of Zeaglobigerina connecta (18.5 Ma) between Samples 317-U1352C-135R-CC and 136R-CC (1810.4–1819.56 m). The early Miocene marker species Catapsydrax dissimilis was also tentatively identified in Samples 317-U1352C-133R-CC (1789.6 m) and 135R-CC (1810.40 m). The range of this species is reported by Cooper (2004) to extend to the top of the lower Miocene Otaian Stage (18.7 Ma), but its HO in Hole U1352C appeared to be slightly younger. This is consistent with unpublished data from ODP Site 1171 (50°S) on the South Tasman Rise, where Cs. dissimilis occurs in conjunction with the early Miocene (lower Altonian) species Gc. praescitula (M.P. Crundwell, pers. comm., 2009).

Oligocene

The top of the Oligocene was identified using calcareous nannofossil evidence between Samples 317-U1352C-139R-CC and 140R-CC (1848.49–1852.71 m). This coincides with a significant change in planktonic foraminiferal assemblages at the same level. The HO of the early Oligocene (lower Whaingaroan) marker species Subbotina angiporoides was identified between Samples 317-U1352C-140R-CC and 141R-CC (1852.71–1862.57 m). These biostratigraphic events suggest the presence of a major hiatus (Marshall Paraconformity) between Samples 317-U1352C-139R-CC and 140R-CC (1848.49–1852.71 m), where at least 12 m.y. is missing.

Foraminiferal assemblages in the Oligocene (Samples 317-U1352C-140R-CC through 146R-CC [1852.71–1903.29 m]) are characterized by low abundances and poor preservation, which is attributed to the cemented nature of the Oligocene limestone. Planktonic foraminifers in the Oligocene composed >95% of the total foraminiferal assemblage, except in Sample 317-U1352C-144R-CC (1885.85 m). Such abundances are consistent with basin-floor deposition under open oceanic conditions. Planktonic assemblages include Zeaglobigerina euapertura, Subbotina angiporoides, Globorotaloides suteri, and Zg. brevis?

Eocene

The top of the Eocene is marked by the HO of the late Eocene (Runangan) marker species Globigerinapsis index (34.4–36.0 Ma) between Samples 317-U1352C-146R-CC and 147R-CC (1903.29–1916.63 m). The HO of this species coincides with a change in lithology to less cemented chalky limestone and more common, better preserved foraminiferal assemblages. Calcareous nannofossil dating (Table T5) suggests the presence of a hiatus between the early Oligocene and the late Eocene with at least 2.3 m.y. missing.

Eocene planktonic foraminiferal assemblages are characterized by abundant Globigerinapsis index, along with Subbotina minima, Tenuitella gemma?, and Turborotalita ciperoensis. Planktonic foraminifers and calcareous nannofossils indicate a late Eocene age of 35.2–36.0 Ma at the bottom of the hole.

Benthic foraminifers

Benthic foraminifers from 242 core catcher samples from Holes U1352A–U1352D were examined (Table T15). Benthic foraminifer abundances varied throughout the cored section, ranging from rare to dominant. Preservation was generally good in the Pleistocene, poor to moderate in the Pliocene and Miocene, and poor in the Oligocene and Eocene. Eleven benthic foraminiferal bioevents were identified at Site U1352 (Table T5). The calibration of benthic bioevents, in general, was poorly constrained, but these bioevents provided useful age control where planktonic foraminifers and calcareous nannofossils were poorly represented.

Holocene–Pleistocene

The HO of Proxifrons advena (~0.4 Ma; Table T5) was identified between Samples 317-U1352B-14H-CC and 15H-CC (130.26–141.17 m). The HO of Bolivinita pliozea (0.6 Ma) was identified between Samples 317-U1352B-16H-CC and 17H-CC (150.74–155.99 m). The latest Pleistocene–Holocene (Haweran) restricted species, Loxostomum karrerianum (0–0.34 Ma), was recognized in Samples 317-U1352D-1H-CC (3.55 m) and 8H-CC (70.00 m) and 317-U1352B-20H-CC (180.38 m). These ages are generally consistent with those from calcareous nannofossils and planktonic foraminifers.

Pliocene

The HO of Haeuslerella morgani (3.62–5.30 Ma) was identified between Samples 317-U1352B-64X-CC and 65X-CC (557.28–562.35 m). The HO of the deep middle bathyal species Hopkinsina mioindex (3.62 Ma) was recognized between Samples 317-U1352C-64R-CC and 65R-CC (1217.80–1222.21 m). The stratigraphic suppression of this species relative to planktonic events suggests that the disappearance of H. mioindex in Hole U1352B might have been controlled by water depth.

Miocene

The LO of Uvigerina pliozea (5.30 Ma) was observed between Samples 317-U1352C-84R-CC and 85R-CC (1342.48–1352.39 m), ~50 m above the Miocene/Pliocene boundary, located between Samples 317-U1352C-72R-CC and 73R-CC (1266.38–1283.95 m; 5.33 Ma) using planktonic foraminiferal evidence. Other useful benthic foraminifer bioevents include a single record of Loxostomum truncatum (8.95–12.76 Ma) in Sample 317-U1352C-94R-CC (1438.43 m), the LO of Notorotalia taranakia (11.01 Ma) between Samples 317-U1352C-95R-CC and 96R-CC (1446.91–1448.00 m), occurrences of Notorotalia wilsoni (11.01 Ma) in Samples 317-U1352C-95R-CC and 96R-CC (1446.91–1448.00 m), and the LO of H. morgani (~11.01 Ma) between Samples 317-U1352C-95R-CC and 96R-CC (1446.91–1448.00 m). The LO of H. mioindex (15.10 Ma) was tentatively recognized between Samples 317-U1352C-104R-CC and 105R-CC (1525.67–1534.20 m). These events generally agree with other microfossil dating.

Oligocene–Eocene

Sample 317-U1352C-147R-CC (1916.63 m) contained the late Eocene to early Oligocene species Cibicidoides parki.

Paleowater depths

Paleowater depths were estimated by the analysis of benthic foraminiferal assemblages from Holes U1352A–U1352D (Table T15; Fig. F27). Terminology used for paleowater depth estimates is given in Figure F7 in the "Methods" chapter.

Holocene–middle Pliocene sediments were dominated by inner to outer shelf benthic foraminiferal taxa, although the rare but persistent presence of bathyal marker species suggests the shelfal taxa composing the bulk of the benthic assemblage were transported downslope. Paleodepths generally increased downhole to lower bathyal depths in the lower part of the cored succession. Middle to deep bathyal taxa occurred in lower Pliocene and older sediments, which is consistent with a general downhole increase in the abundance of planktonic foraminifers through the progradational foreset sequence into the bottom sets and basin-floor facies. It also coincides with the change from suboceanic to open oceanic conditions.

Estimates of paleowater depths, based on the general composition of benthic foraminiferal assemblages, ranged from outer shelf to upper bathyal during the middle–late Pleistocene. The estimated upper depth limits are shallower than seismic data interpretation at this site suggests, which is consistent with the bulk of the assemblage being reworked downslope. The subtidal to inner shelf species Elphidium charlottense and Notorotalia aucklandica were abundant in upper Pleistocene Samples 317-U1352A-1H-CC through 5H-CC (4.21–43.06 m) and 317-U1352D-1H-CC through 10H-CC (3.55–88.92 m). These species occurred consistently with the outer shelf to uppermost bathyal species Globocassidulina canalisutulata (Eade, 1967) down to Sample 317-U1352D-14H-CC (127.61 m). In Samples 317-U1352B-1H-CC through 31H-CC (7.93–272.44 m), outer shelf species G. canalisutulata and Nonionella flemingi were dominant and the upper bathyal indicator Trifarina angulosa was abundant, particularly between Samples 317-U1352B-22H-CC and 28H-CC (198.87–250.70 m).

In the lower Pleistocene to upper middle Pliocene section between Samples 317-U1352B-32H-CC and 65X-CC (280.84–562.35 m), the outer shelf species Nonionella flemingi and Notorotalia profunda were dominant. Uvigerinids that characterize deeper water, including Uvigerina peregrina and Trifarina angulosa, were present throughout most of this section and indicate deposition in upper bathyal water depths. The middle to lower bathyal species Bulimina exilis (van Morkhoven et al., 1986) was also present sporadically between Samples 317-U1352B-38X-CC and 48X-CC (310.85–408.18 m), suggesting even deeper bathyal water depths in this interval.

In the lower Pliocene section between Samples 317-U1352B-66X-CC and 94X-CC (572.40–821.74 m) and 317-U1352C-2R-CC and 65R-CC (576.47–1222.21 m), the outer shelf species Notorotalia profunda was abundant and was associated with upper bathyal uvigerinids, including Uvigerina peregrina, Astrononion spp., and Bolivinita pliozea. Notorotalia taranakia was also abundant in this same interval; however, the ecological preferences of this species are not fully understood. Melonis pompilioides (an extant deep lower bathyal species) occurred sporadically between Samples 317-U1352C-2R-CC and 65R-CC (576.47–1222.21 m), becoming more common in the lowermost Pliocene between Samples 317-U1352C-56R-CC and 64R-CC (1147.41–1217.80 m). Paleodepth markers that are considered to be in situ suggest that paleowater depths increased downhole from outer shelf–uppermost bathyal depths in the uppermost part of the lower Pliocene section to lower bathyal depths in the lowermost part of the lower Pliocene section.

Assemblages in the lowermost Pliocene to uppermost Miocene section, between Samples 317-U1352C-65R-CC and 88R-CC (1222.21–1379.88 m), are characterized by a decrease in shelfal species and a reciprocal increase in upper bathyal marker species, including Cibicidoides neoperforatus and Uvigerina spp.

The upper Miocene to upper middle Miocene section between Samples 317-U1352C-89R-CC and 104R-CC (1386.04–1525.67 m) was dominated by benthic taxa indicative of middle bathyal water depths, including Karreriella bradyi and Sigmoilopsis schlumbergeri, and occasional specimens of the deep middle bathyal species Hopkinsina mioindex.

In the middle Miocene section between Samples 317-U1352C-105R-CC and 112R-CC (1534.20–1597.08 m), benthic foraminifers were poorly preserved and too sparse for reliable estimates of paleodepths based on benthic assemblages. Deep middle to deep lower bathyal water depths are inferred, however, based on the presence of Cibicidoides robertsonianus and Melonis dorreeni, which is morphologically similar to the extant deep lower bathyal species M. pompilioides. Benthic foraminifers were very sparse to absent in samples from the middle Miocene to Eocene (Samples 317-U1352C-113R-CC through 148R-CC; 1611.72–1924.26 m).

Diatoms

Samples 317-U1352A-1H-CC through 5H-CC (4.21–43.06 m) were barren of diatoms (Table T16).

Core catcher samples from Hole U1352B were examined for diatoms (Table T16). In the majority of the 50 samples containing diatoms, abundances were low, and preservation was moderate to poor. Several robust diatom species with thickly silicified valves (e.g., Paralia sulcata, Thalassionema nitzschoides, and Chaetoceros resting spores) were better preserved than delicate forms with weakly silicified valves.

The HO of marker species Fragilariopsis fossilis (0.70 Ma) was identified in Sample 317-U1352B-23H-CC (208.46 m), although this species occurred only sporadically below this level and the reliability of its HO is uncertain. A single record of Actinocyclus karstenii (HO 1.73 Ma) was also identified in Sample 317-U1352B-55X-CC (469.84 m). The distribution of these species is consistent with calcareous nannofossil dating.

Most diatom assemblages in Hole U1352B contained marine resting spores of the genus Chaetoceros, which is indicative of high productivity in near-shore upwelling regions and coastal areas. Also included was a mixture of coastal, brackish, and freshwater species, which suggests marine deposition with an influence from coastal upwelling and some river input.

Core catcher samples from Hole U1352C were examined for diatoms, and their distribution is reported in Table T15. Diatoms were only found in six middle Pliocene samples from this hole, between Samples 317-U1352C-7R-CC and 12R-CC (671.20–719.46 m). Preservation was moderate to poor. Cyclotella, a genus diagnostic of brackish and freshwater, occurred in greater abundances than other taxa in these samples. Other diatoms included coastal and brackish water species. The diatom assemblage shows evidence of some river and/or estuarine input.

All core catcher samples from Samples 317-U1352D-1H-CC through 14H-CC were examined for diatoms (3.55–127.61 m) (Table T15). Diatoms were found in 7 of the 14 samples examined and were relatively rare. The assemblages and preservation were similar to those of samples from the equivalent section in Hole U1352B. The presence of a single record of Hemidiscus karstenii (HO 0.30 Ma) in Sample 317-U1352D-12H-CC (108.55 m) is consistent with calcareous nannofossil dating.

Macrofossils

Macrofossils were examined in cored sediments from all Site U1352 holes. Provisional identification, age, and habitat preference are provided in Table T17.

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