Initial biostratigraphic determinations for calcareous nannofossils, planktonic foraminifers, and benthic foraminifers were based on core-catcher samples. Additional samples were subsequently investigated from selected core sections in order to refine the biostratigraphic zonal assignments. Abundance, preservation, and zonal data for each sample investigated were recorded in the JANUS paleontology database.

The nannofossil and foraminiferal biozonal schemes used are shown in Figure F12, with the events defining the zonal boundaries. Well-dated nannofossil and planktonic foraminiferal datums used during Leg 180 are shown in Table T6.

Slides for nannofossil investigations were prepared by smearing sediment across a glass slide and attaching a cover glass. Taxon identifications were made under plane- and cross-polarized light using a Zeiss Axioscope microscope. Relative abundance estimates for individual species were made using a magnification of 1000×; abundances were estimated as follows:

D = dominant (more than 100 specimens of a species per field of view);
A = abundant (10-100 specimens of a species per field of view);
C = common (one to 10 specimens per field of view);
F = few (one specimen per 10 fields of view);
R = rare (fewer than one specimen per 10 fields of view);
B = barren (no nannofossils found); and
T = trace (fewer than one specimen per transect of slide).

Preservation of nannofossil specimens was characterized as follows:

VG = very good (no dissolution or secondary overgrowths of calcite). All specimens can be identified with certainty.
G = good (little dissolution or secondary overgrowths). Essentially all specimens can be identified to the species level.
M = moderate (slight to moderate dissolution and/or overgrowths). Identification of some species is impaired, but most species can still be identified.
P = poor (severe dissolution, breakage, or secondary overgrowths largely destroy primary morphological features). Many specimens cannot be identified to the species level; some cannot be identified to the generic level.

Specimens that have been reworked are designated by "r."

The calcareous nannofossil zonation used here (Fig. F12) is that of Martini (1971), with modifications by Rio et al. (1990). We were unable to consistently distinguish between Subzones NN19C and NN19D (the subzonal boundary is based on the first occurrence of Gephyrocapsa spp. [>5.5 µm]). Therefore, these two subzones have been combined as NN19C/D in this report.

Planktonic Foraminifers

The planktonic foraminiferal biozones followed are those of Blow (1969) as modified by Kennett and Srinivasan (1983). Correlations of zones to magnetostratigraphy and geochronology (Fig. F12) as well as the first appearance datum (FAD) and last appearance datum (LAD) of species (Table T6) are according to Berggren et al. (1995a) for the middle to late Miocene and Berggren et al. (1995b) for the late Neogene. Planktonic foraminiferal zones recognized in Papua New Guinea and vicinity were reviewed by Haig and Perembo (1990), who proposed that the FAD of Globorotalia crassaformis be used to approximate the base of Zone N20 in the western equatorial Pacific.

Unlithified to semilithified core sediment samples were soaked in beakers of water, broken up by hand if necessary, wet sieved over a 63-µm mesh screen, and dried. Lithified material was crushed to pea size, boiled in Calgon solution, sieved, and dried as before. Because of the fine-mesh screen used, juvenile specimens and small species dominated most of the well-preserved planktonic assemblages. Although the reported data are incomplete with respect to the total planktonic assemblages, the species abundances indicated on the site report tables were estimated from a portion of the sand fraction spread evenly over a 6 cm × 9.5 cm tray containing 45 fields of view at 25× magnification. The abundances were reported in the following categories:

D = dominant (>10 specimens per field of view);
A = abundant (2-9 specimens per field of view);
C = common (if used, the lower range of abundant);
F = few (0.5-1.0 specimen per field of view);
R = rare (1-3 specimens per tray);
P = present (if used, 1 specimen per 2-3 trays); and
B = barren (no planktonic foraminifers).

Preservational characteristics were indicated as follows:

VG = very good (no evidence of breakage or dissolution);
G = good (>90% of specimens unbroken);
M = moderate (30%-90% of the specimens unbroken); and
P = poor (dominated by fragments and broken or corroded specimens).

Benthic Foraminifers

The generic classification of Loeblich and Tappan (1988) was used and updated in some instances. Benthic species found in the western equatorial Pacific are illustrated in several publications including Graham and Militante (1959), Barker (1960), Hughes (1977), Burke (1981), Van Morkhoven et al. (1986), Kurihara and Kennett (1986, 1988), Hermelin (1989), Clark et al. (1994), and Akimoto (1994).

The bathymetric divisions (biotopes) occupied by modern benthic foraminiferal assemblages were designated following Ingle (1980). Reference to the literature listed above as well as other Indo-Pacific sources given in Haig and Perembo (1990) suggests upper depth limits for various species within the bathymetric divisions, used here for bathyal and abyssal biotopes to avoid problems arising from downslope transport of tests. These species upper depth limits, as given in Haig and Perembo (1990) and Perembo (1994), as well as biofacies data based on species abundance (Resig, 1984; Resig and Cheong, 1997; J. Resig, unpubl. data), were used to interpret paleobathymetry of the samples. Some of the diagnostic species for the various bathymetric divisions are as follows:

Inner neritic (0-50 m): Alveolinella quoyi, Ammonia spp., Amphistegina spp., Baculogypsina sphaerulata, Calcarina calcar, Elphidium craticulatum, Lobatula lobatula, Marginopora vertebralis, Operculina spp., Pseudorotalia spp., and Quinqueloculina spp.;

Outer neritic (50-150 m): Anomalina glabrata, Anomalinoides colligerus, Baggina indica, Bolivina hantkeniana, Cancris auriculus, Rectobolivina striata, and Siphonina tubulosa;

Upper bathyal (150-500 m; upper depth limit): Brizalina alata, Bulimina alazanensis, Cibicidoides cicatricosus, Cribroparrella bengalensis, Globocassidulina murrhina, Oridorsalis umbonatus, Osangularia culter, Pyrgo depressa, Pleurostomella alternans, Siphonodosaria insecta, and Vulvulina pennatula;

Middle bathyal (500-2000 m; upper depth limit): Adercotryma glomeratum, Alabaminella weddellensis, Bathysiphon arenacea, Dentalina spirostriolata, Dorothia pauperata, Laticarinina pauperata, Melonis affinis, Melonis pompilioides, Parrelloides bradyi, Sigmella edwardsi, Uvigerina bradyana, Uvigerina hispida, and Valvulineria javana; and

Lower bathyal (2000-4000 m; upper depth limit): Cyclammina cancellata, Ehrenbergina hystrix, Favocassidulina favus, Globocassidulina crassa, Laevidentalina communis, and Nuttallides umbonifera (dominant below the lysocline).

Samples used for the study of benthic foraminifers were the same as those for planktonic foraminifers; therefore, the initial processing was the same--wet sieving on a 63-µm screen. For selected samples throughout the cored section, faunal reference slides were made, particularly in areas of lithologic and/or assemblage changes.