Samples 180-1118A-1R-CC to 32R-CC contain few to abundant (mostly common), moderately to well-preserved nannofossils. In Samples 180-1118A-33R-CC through 36R-CC, nannofossils are common, but poorly preserved. From Samples 180-1118A-37R-CC through 59R-CC, nannofossils are mostly common and preservation is moderate, with the exception of Sample 180-1118A-52R-CC, in which nannofossils are rare and preservation is poor. Nannofossils are few to common in abundance from Samples 180-1118A-60R-CC through 68R-3, 109-110 cm, and preservation is moderate. Samples 180-1118A-68R-CC to 70R-CC are barren. Sample 180-1118A-71R-CC and Cores 72R to 76R contain no sediment.
The nannofossils zonation for Hole 1118A is given in Figure F53; nannofossils present are listed in Table T7.
The last occurrence (LO) of Discoaster brouweri marks the top of Zone NN18. Although this species occurs consistently from Samples 180-1118A-1R-CC through 6R-CC, the numbers present are relatively less than the numbers of D. brouweri in Sample 180-1118A-9R-CC and below (we found no specimens of D. brouweri in Samples 180-1118A-7R-CC and 8R-CC). We therefore assign Samples 180-1118A-1R-CC through 8R-CC to Zone NN18/Subzone NN19A undifferentiated (Gephyrocapsa oceanica is absent), and Samples 180-1118A-9R-CC through 14R-CC to Zone NN18 (Fig. F53). The LO of D. pentaradiatus in Sample 180-1118A-15R-CC marks the top of Zone NN17. The top of Subzone NN16B is indicated by the LO of D. surculus in Sample 180-1118A-19R-CC. The LO of D. tamalis in Sample 180-1118A-37R-CC marks the top of Subzone NN16A. Samples 180-1118A-37R-CC to 68R-3, 109-110 cm, are in Subzone NN16A.
The abundance of planktonic foraminifers at this site was greatly affected by the input of detrital sand. From Samples 180-1118A-1R-CC through 24R-CC specimens were common to abundant and their preservation was good, except for Samples 180-1118A-12R-CC, 15R-CC, and 21R-CC, which had rare to few well-preserved planktonic specimens. From Sample 180-1118A-25R-CC through 30R-CC planktonic specimens were common to abundant and moderately well preserved, except for Sample 180-1118A-28R-CC in which the specimens were few with moderate preservation. From Samples 180-1118A-31R-CC through 36R-CC specimens were rare to few and moderately well preserved. Samples 180-1118A-37R-CC through 51R-CC had common to abundant planktonic specimens, which had moderate to good preservation, except for Samples 180-1118A-38R-CC, 41R-CC, 43R-CC, 45R-CC, and 51R-CC in which the specimens were rare or few with variable preservation. From Samples 180-1118A-53R-CC through 63R-CC planktonic specimens were common and with moderate to good preservation, except for Samples 56R-CC and 58R-CC in which the specimens were few, with moderate to good preservation. Samples 180-1118A-64R-CC through 66R-CC had rare to few specimens, which were moderately well to poorly preserved. The final samples above the limestone, Samples 180-1118A-67R-CC and 68R-1, 0-1 cm, had common to abundant planktonic specimens that were moderately well preserved. In Sample 180-1118A-68R-3, 109-110 cm, the abundant planktonic specimens were poorly preserved.
The planktonic foraminiferal zonal stratigraphy for this site is presented in Figure F53 and the species distribution is shown in Table T8. Coring began at 205 mbsf in Zone N22 of late Pliocene age. Samples 180-1118A-1R-CC through 19R-CC are assigned to early Zone N22 and on the co-occurrence in most of the samples of Globorotalia tosaensis, Globigerinoides fistulosus, and Globorotalia truncatulinoides, which first appears in Sample 180-1118A-19R-CC (384.2 mbsf). Samples 180-1118A-20R-CC through 51R-CC contain G. tosaensis, indicative of Zone N21. The LO of Dentoglobigerina altispira (LAD 3.09 Ma) is in Sample 180-1118A-42R-CC (608.2 mbsf). Samples 180-1118A-52R-1, 27-30 cm, through 68R-1, 0-1 cm, were assigned to Zone N20, based on the presence of Globorotalia crassaformis in the absence of G. tosaensis. Sample 180-1118A-68R-3, 109-110 cm, taken 5 cm above limestone, was assigned to Zone N20 because of the presence of only dextral Pulleniatina. The limestone in Core 180-1118A-68R contained common planktonic foraminifers in Sample 180-1118A-68R-4, 46-48 cm, including Globorotalia tumida, suggesting continued deposition in Zone N20 or at least in the latest Miocene or early Pliocene.
This site was drilled in 2304 m water depth, but the upper 205 m were not cored. The paleobathymetry is indicated in Figure F54. Benthic foraminiferal assemblages suggest a middle bathyal (500-2000 m) paleodepth from Samples 180-1118A-1R-CC through 18R-CC (375.4 mbsf) with such characteristic species as Cibicidoides rugosus, Laticarinina pauperata, Quinqueloculina venusta, Sphaeroidina bulloides, and Uvigerina bradyana represented in the samples. From Samples 180-1118A-19R-CC through 68R-3, 109-110 cm (396.8-853.2 mbsf), the assemblage suggests upper bathyal depths (150-500 m). Representative species include Martinottiella communis, Rectobolivina columellaris striate var., Rotalia sp., Siphonina tubulosa/australis, and Uvigerina schwageri. Benthic foraminifers were rare in many of these samples, which contained ash and various turbidite layers. Core 180-1118A-68R below Section 3, 117 cm, contains limestone with calcareous algae, corals, smaller benthic rotaliine and milioline foraminifers, and rare larger pre-middle Miocene orbitoid and miliolid species, as well as common planktonic foraminifers. As mentioned above, in Sample 180-1118A-68R-4, 46-48 cm, Globorotalia tumida was among the planktonic species embedded in the limestone. The overlying upper bathyal foraminiferal assemblages (sample taken 5 cm above the limestone) also contain abundant planktonic foraminifers, including the relatively deep dwelling Globorotalia tumida, suggesting these limestones represent shallow-reef material, redeposited in upper bathyal depths.
We estimated the sedimentation rate based on nannofossil and foraminifer datum events and magnetic chron and subchron boundaries at Site 1118 (Fig. F54). The biostratigraphic data are indefinite above ~340 mbsf, and we have used only the paleomagnetic data to draw the sedimentation curve there.