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Paleontology and biostratigraphy

Core catcher samples from Site U1394 contain calcareous nannofossils and planktonic and benthic foraminifers of varying abundances and at varying levels of preservation. Many core catcher samples are characterized by large volcanic clasts, coral fragments, and abundant reef-dwelling benthic foraminifers. The high fragmentation and relatively poor preservation of the foraminifers suggests the presence of much reworked material. Pteropods and heteropods were found in many samples and are often well preserved though highly fragmented. Ostracods are also present in low numbers (1–5 per sample). Biostratigraphic data derived from both calcareous nannofossils and planktonic foraminifers show that Site U1394 contains many levels of reworked sediment from the early Pleistocene amid a background of late Pleistocene sedimentation (Fig. F3).

Calcareous nannofossils

Only 18 of the 26 core catcher samples from Hole U1394A were prepared for nannofossil analysis. The remaining samples were not analyzed because of the coarse nature of the material. Sediment analyzed in Hole U1394A contains specimens of several species, including Gephyrocapsa caribbeanica, Pseudoemiliania lacunosa, Calcidiscus leptoporus, and Helicosphaera kamptneri. Recent species such as Rhabdospaera clavigera and Calciosolenia murrayi are found in many samples throughout the entire sequence. Emiliania huxleyi was not found in core catcher samples from Hole U1394A, possibly because of small sample size and poor preservation.

Two datum species and two older reworked species were found in core catcher samples from Hole U1394A. Helicosphaera inversa, a very important species because of its short range, is present within most of the hole, dating Hole U1394A to within the Pleistocene. P. lacunosa, a species indicative of early Pleistocene sediment, is also abundant in nearly all samples, with particularly large specimens (>7 µm) in Sample 340-U1394A-24X-CC. Helicosphaera sellii (Zones CN10–CN13) was identified in Samples 340-U1394A-1H-CC, 9X-CC, and 10X-CC, suggesting the presence of older reworked material. Some early Pliocene (Zone CN11) discoasterids were also found in Sample 340-U1394A-20X-CC; however, specimens were poorly preserved and detailed identification was not possible. Nannofossil evidence assigns Hole U1394A to Zone CN14 (Okada and Bukry, 1980) or the P. lacunosa Zone (Gartner, 1977). Hole U1394B contains a higher number of reworked species from the early Pliocene but is otherwise consistent with Hole U1394A. H. sellii (reworked) and H. inversa were also found in Hole U1394B, H. inversa placing the sediment within Zone CN14 (Okada and Bukry, 1980) or the P. lacunosa Zone (Gartner, 1977).

Planktonic foraminifers

Of the 26 core catcher samples collected in Hole U1394A, 20 were analyzed for planktonic foraminiferal content, along with all 21 of the samples collected in Hole U1394B. The remaining core catcher samples are unsuitable for analysis because of the coarse grain size of the sediment retrieved. Planktonic foraminifers are present in all samples, although some were found at very low abundances (few–present), possibly due to the high volume of volcanic material (Samples 340-U1394A-3H-CC and 4H-CC; 340-U1394B-20H-CC and 21H-CC). Samples 340-U1394A-26X-CC and 340-U1394B-13H-CC contain the lowest abundances (present), with only one specimen of planktonic foraminifer in each. In most samples, the assemblage of planktonic foraminifers is diverse but dominated by Globigerinoides ruber (white) and Globigerinoides sacculifer. Other abundant species include Globigerina falconensis, Globigerinita glutinata, Globigerinoides elongatus, Globorotalia tumida, and Neogloboquadrina dutertrei (dextral). The fauna does not change significantly throughout Site U1394, with two exceptions. Samples 340-U1394A-7X-CC and 9X-CC contain abundant specimens of the subtropical species Globigerina rubescens, which was only found in low abundances (few) in Hole U1394B (Samples 340-U1394B-3X-CC and 5X-CC) and was not found in any other samples. Additionally, Sample 340-U1394B-11H-CC appears to consist solely of juvenile planktonic foraminifers. Species present in all samples are indicative of warm subtropical waters. Three datum species were commonly encountered: Globorotalia flexuosa (0.07–0.40 Ma), Globigerinella calida (bottom occurrence [B] at 0.22 Ma), and Globorotalia tosaensis (top occurrence [T] at 0.61 Ma), dating the site to within the Pleistocene. Several of the samples (340-U1394A-2H-CC, 10X-CC, and 20X-CC; Cores 340-U1394B-14H, 15H, 17H, and 18H) contain species that indicates sediment from the late Pleistocene (presence of G. calida, B 0.22 Ma) as well as the early Pleistocene (presence of G. tosaensis, T 0.61 Ma), suggesting reworking of sediment. A more detailed postcruise investigation of samples throughout the core will be beneficial in understanding these variations.

Benthic foraminifers

A total of 53 genera and 53 species were identified at Site U1394. Samples examined for benthic foraminifers in Holes U1394A and U1394B varied in abundance, diversity, and preservation. Rotaliids have the highest diversity but are present in low abundances (1–5 specimens per sample) overall in Holes U1394A and U1394B. Several samples (340-U1394A-2H-CC, 7H-CC, 10H-CC, and 14X-CC; 340-U1394B-4H-CC, 9X-CC, and 10X-CC) are dominated by poor to moderately preserved Amphistegina sp. This genus is common of reef environments (≤100 mbsf), and its presence is indicative of reworking associated with volcaniclastic sediment. Cibicides sp. and Cibicidoides sp. are present in low abundances in most samples, with Cibicides wuellerstorfi being the most abundant species. Agglutinated foraminifers are very rare, with only one specimen of Reophax sp. and Ammobaculite sp. found in two samples. Based on the presence of the genera Osangularia, Globocassidulina, and Cibicides, as well as Laticarinina pauperata, a bathyal paleodepth is inferred for Holes U1394A and U1394B.