Nannofossils are abundant and well preserved in Sample 180-1115A-1H-CC, and common to abundant and well preserved in Samples 180-1115B-1H-CC to 27X-CC. Nannofossils are common and preservation is moderate in Samples 180-1115B-28X-CC to 31X-CC, with the exception of 30X-CC, which is barren.
In Hole 1115C, Samples 180-1115C-1R-CC to 15R-CC contain common nannofossils with moderate to good preservation. Nannofossils are still common from Sample 180-1115C-16R-CC down to 23R-CC, but preservation is moderate to poor. Few to rare, mostly poorly preserved nannofossils are present in Samples 180-1115C-24R-CC to 36R-CC, with the exception of Samples 180-1115C-30R-CC, 31R-CC, 34R-CC, and 35R-CC, which are barren or almost barren of nannofossils. Nannofossil numbers increase and their degree of preservation improves below Sample 180-1115C-37R-CC, with nannofossils becoming few to common and preservation moderate from Sample 180-1115C-37R-CC to 41R-CC. Sample 180-1115C-42R-CC is nearly barren. Nannofossils in Samples 180-1115C-43R-CC to 54R-CC are few to common in abundance and preservation is moderate or poor (mostly moderate).
Sample 180-1115A-1H-CC is in Zone NN20/21, based on the presence of rare Emiliania huxleyi and lack of Pseudoemiliania lacunosa (Fig. F35; Table T4).
Samples 180-1115B-1H-CC to 2H-5, 96-98 cm are also in Zones NN20/21. We assign Samples 180-1115B-2H-CC through 9H-6, 95-97 cm, to the Subzone NN19C-NN19F interval because of the presence of Pseudoemiliania lacunosa and Helicosphaera sellii, and lack of Calcidiscus macintyrei. Calcidiscus macintyrei is present in Samples 180-1115B-9H-7, 10-12 cm, to 9H-CC, together with some small forms of Gephyrocapsa oceanica. We assign this interval to Subzone NN19B. Samples 180-1115B-10H-CC to 12H-1, 96-98 cm, lack G. oceanica and are therefore in Subzone NN19A. The last occurrence (LO) of Discoaster brouweri in Sample 180-1115B-12H-3, 96-97 cm, marks the Zone NN18/Subzone NN19A/B boundary. The LO of D. pentaradiatus in Sample 180-1115B-16H-5, 95-97 cm, marks the Zone NN17/NN18 boundary, and the LO of D. surculus in Sample 180-1115B-19H-CC marks the Subzone NN16B/Zone NN17 boundary. The LO of D. tamalis in Sample 180-1115B-20H-CC in this hole defines the Subzone NN16B/NN16A boundary.
The difficulty of recognizing the true Zone NN15/NN16 boundary in low latitudes is discussed in "Biostratigraphy" in the "Site 1109" chapter. In Hole 1115B, the LO of Sphenolithus spp. (the secondary species approximating the boundary) appears to be anomalously high in the section when compared to the first occurrence (FO) of the foraminifer Globorotalia tosaensis. We are not sure of the cause of this relationship, but because of it we have not separated Zone NN15 and Subzone NN16A in this hole. Instead, we assign Zone NN15/Subzone 16A undifferentiated to Samples 180-1115B-21H-CC through 31X-CC.
In Hole 1115C, undifferentiated Zone NN15/16A ranges from Sample 180-1115C-1R-CC to 16R-CC. The upper boundary of Zone NN14 is marked by the last common occurrence (LCO) of Reticulofenestra pseudoumbilicus in Sample 180-1115C-17R-CC. Discoaster asymmetricus is rare in these samples, and we could not confirm its first common occurrence (FCO), which defines the Zone NN13/NN14 boundary. Ceratolithus rugosus, whose FO defines the Zone NN12/NN13 boundary, is rare in these samples. Ceratolithus rugosus is present in Sample 180-1115C-19R-CC. However, the LO of C. acutus, which also is present at the Zone NN12/NN13 boundary, is in Sample 180-1115C-21R-1, 40-42 cm, and we consider this to be the top of Zone NN12. The LO of D. quinqueramus is in Sample 180-1115C-25R-CC, which defines the Zone NN11/NN12 boundary. We, therefore, assign all samples from Sections 180-1115C-17R-CC to 20R-CC to Zone NN13-NN14 undifferentiated, and assign Samples 180-1115C-21R-1, 40-42 cm, through 25R-1, 89-91 cm, to Zone NN12. Discoaster quinqueramus is present from Sample 180-1115C-25R-CC through 29R-CC, indicating Zone NN11. Samples 180-1115C-30R-CC through 33R-CC are barren or contain only a rare, middle to late Miocene assemblage. Samples 180-1115C-34R-1, 31-33 cm, through 54R-CC contain Sphenolithus heteromorphus and lack Helicosphaera ampliaperta and S. belemnos, indicating Zone NN5.
Specimens were abundant and their preservation good in core catcher samples from Cores 180-1115A-1H, 1115B-1H through 26H, and 1115B-31X; specimens were abundant and their preservation moderate from Samples 180-1115B-27X-CC through 29X-CC, and rare but with good preservation in 30X-CC. Core catchers from Cores 180-1115C-1R through 17R contained abundant specimens with moderate to good preservation; specimens were rare to few and their abundance moderate to good from Cores 180-1115C-18R-CC to 24R-CC; specimens were common to abundant and their preservation moderate to poor in Samples 180-1115C-31R-CC, 33R-CC through 35R-CC, and 43R-CC through 47R-CC; specimens were few to rare and their preservation moderate to poor in Samples 180-1115C-32R-CC, 37R-CC through 42R-CC, and 49R-CC through 54R-CC.
There were no planktonic foraminifers in the core-catcher samples of Cores 180-1115C-26R through 29R, which yielded shallow-water benthic foraminifers. The sandy sediment of Samples 180-1115C-25R-CC, 30R-CC, and 36R-CC was barren of all foraminifers.
The planktonic foraminiferal zonation of Holes 1115A, 1115B, and 1115C is shown in Figure F35 and the species are listed in Table T5. Samples 180-1115A-1H-CC and 180-1115B-1H-CC were assigned to Zone N23 because of the presence of Beella calida. Common to abundant specimens of pink Globigerinoides ruber in both samples indicate an age no younger than 120 ka. Samples 180-1115B-2H-CC through 16H-CC with Globorotalia truncatulinoides lie in Zone N22. Sample 180-1115B-10H-4, 65-67 cm, marks the LO of Globigerinoides fistulosus just above the Pliocene/Pleistocene boundary. Zone N21 extends from Sample 180-1115B-17H-CC to Sample 180-1115B-24X-CC, in which is found the first evolutionary appearance of Globorotalia tosaensis from its ancestor G. crassaformis. Zone N20, in which G. crassaformis is present without its descendent, extends through the remainder of Hole 1115B and continues in Hole 1115C to Sample 180-1115C-18R-CC (the sinistral to dextral coiling change in Pulleniatina dated at 3.95 Ma is present between 17R-CC and 18R-CC), after which a shallow-water facies lacking planktonic foraminifers is found from Sections 180-1115C-19R-CC through 30R-CC.
The stratigraphic section, interrupted by an unconformity, continues with a middle Miocene (Zone N12) section from Samples 180-1115C-31R-CC through 33R-CC. These samples contain Globorotalia praemenardii (with G. lenguaensis, which first occurs in Zone N12 in Sample 180-1115C-33R-CC). The presence of the larger foraminifer Lepidocyclina (Nephrolepidina) in Sample 180-1115C-34R-CC indicates a middle Miocene age. Sample 180-1115C-41R-CC contains G. praemenardii, which ranges from Zone N10 to N12. From Sample 180-1115C-43R-CC to 53R-CC Globorotalia archaeomenardii, Orbulina spp., and Globorotalia peripheroronda are present, indicating Zone N9 or N10. In Sample 180-1115C-54R-CC, the bottom of the hole, the presence of Orbulina spp. indicates an age no older than middle Miocene, Zone N9.
Site 1115, at a water depth of ~1150 m, has a surface assemblage of benthic foraminifers dominated by agglutinated species that are not preserved lower in the section, among them Ammolagena clavata, Reophax sp., Rhizammina sp., Saccorhiza ramosa, and Trochammina sp. (Sample 180-1115B-1H-1, 0-1 cm). From the seafloor surface through Sample 180-1115B-17H-CC (159.7 mbsf), a Holocene to middle upper Pliocene, upper middle bathyal assemblage (500-1150 m) contains the following characteristic species: Ceratobulimina pacifica, Cibicidoides rugosus, Parrelloides bradyi, Pyrgo murrhina, Sphaeroidina bulloides, and Triloculina tricarinata.
From Sample 180-1115B-18H-CC (169.2 mbsf) through 1115C-14R-CC (412.0 mbsf), a middle upper Pliocene to middle Pliocene assemblage is indicative of upper bathyal depths (150-500 m). The characteristic species are: Anomalinoides colligerus, Heterolepa praecincta, Rectobolivina columellaris, Melonis multicameratus, and Siphonina tubulosa/australis.
From Sample 180-1115C-15R-CC (425.8 mbsf) through 20R-CC (465.9 mbsf), an early Pliocene outer neritic (50-150 m) assemblage is sparsely populated by Angulogerina sp. and Lugdunum hantkenianum.
From Sample 180-1115C-21R-CC (480.3 mbsf) through 29R-CC (555.3 mbsf) the early Pliocene assemblage is indicative of inner neritic depths (<50 m), with large marine species such as Neoeponides bradyi, Asterorotalia gaimardii, Elphidium craticulatum, and Elphidium sp. from Sample 180-1115C-21R-CC through 23R-CC; followed by Ammonia sp. and Elphidium sp., indicating salinity variation from Sample 180-1115C-26R-CC through 29R-CC. Sample 180-1115C-30R-CC was pyritic and barren of all foraminifers.
The stratigraphic section continued downward with middle Miocene strata, indicative of an unconformity between Samples 180-1115C-29R-CC and 31R-CC. From Sample 180-1115C-31R-CC (572.3 mbsf) through 35R-CC (615.0 mbsf) benthic assemblages suggest an outer neritic (50-150 m) environment with larger foraminifers concentrated in Samples 180-1115C-34R-CC and 35R-CC. These include Amphistegina spp. and Lepidocyclina spp., with Lepidocyclina (Nephrolepidina) martini indicative of middle Miocene age (Fig. F36).
From Sample 180-1115C-37R-CC (629.0 mbsf) through 53R-CC (790.9 mbsf) the assemblages suggest upper bathyal to upper middle bathyal conditions; Hoeglundina elegans is frequently present, Uvigerina schwageri is found in Sample 180-1115C-41R-CC, and Ceratobulimina pacifica, Siphonina sp., and Globocassidulina pacifica are found in Sample 180-1115C-53R-CC.
We estimated the sedimentation rate based on nannofossil and foraminifer datum events and magnetic chron and subchron boundaries at Site 1115 (Fig. F37).
A conglomerate layer is found from Sample 180-1115C-30R-5, 47 cm, to 31R-1, 87 cm (566.5-571.87 mbsf). The very slow sedimentation rate (<5 m/m.y.) from 8.6 to 12.1 Ma is most likely the result of an unconformity at the base of this conglomerate layer (see "Lithostratigraphy").