Calcareous nannofossils and planktonic foraminifers indicate that sediments recovered at Site 1130 are mainly of Pleistocene-middle Oligocene age. Part of the Pliocene is either missing or highly condensed into the Pleistocene-upper Miocene succession. Pleistocene-upper Pliocene calcareous packstones extend down to ~260 mbsf, overlying lowermost Pliocene and upper Miocene (260-328 mbsf) foraminifer nannofossil oozes. Middle-upper Oligocene wackestones and cherts occur between 328 and 367 mbsf, overlying a calcareous sandstone of middle-late Eocene age at the base of Holes 1130A and 1130C. Calcareous nannofossils and planktonic foraminifers indicate that the disconformity between the Neogene and Oligocene sections represents a hiatus of at least 14 m.y. The contact between Oligocene sediments and the sandstone is also probably disconformable, although its nature cannot be determined because of the absence of nannofossils and age-diagnostic planktonic foraminifers.
The three benthic foraminifer assemblages occurring within the Site 1130 succession correspond respectively to the Oligocene, Miocene-Pliocene, and upper Pliocene-Pleistocene, and indicate a shallowing-upward trend through these time periods. The Oligocene and Neogene assemblages are typically cosmopolitan, middle bathyal assemblages. The upper Pliocene-Pleistocene assemblage is a mixed assemblage of upper bathyal paleodepths, containing many well-sorted specimens redeposited from shelf environments.
The combined results from nannofossils, planktonic foraminifers, and paleomagnetism indicate that the sedimentation rate was as high as 240-260 m/m.y. during most of the Pleistocene. During the Pliocene-Miocene, the sedimentation rate fluctuated between 12 and 32 m/m.y. A similar rate of 10-30 m/m.y. was estimated for middle-upper Oligocene deposition, although datum constraint in this part of the section is limited by poor core recovery.
A Pleistocene-middle Oligocene succession of calcareous nannofossil assemblages is recorded from Site 1130. Common chert layers in the Oligocene section hampered both core recovery and biostratigraphic refinement (see "Operations"), and a calcareous sandstone below the Oligocene is barren of calcareous nannofossils. Two disconformities are indicated in the Pleistocene-middle Oligocene section, separating three discrete biostratigraphic packages: Pleistocene-upper Pliocene, lower Pliocene-upper Miocene, and upper-middle Oligocene. These disconformities coincide with significant lithologic changes and seismic stratigraphic boundaries (see "Lithostratigraphy" and "Seismic Stratigraphy"). The Pleistocene-upper Pliocene package of calcareous packstones is relatively thick (~255 m), in contrast to both the lower Pliocene-Miocene oozes (~175 m) and the Oligocene calcareous grainstones (~30 m).
The hiatus at the Paleogene/Neogene boundary has a longer duration than the younger hiatus recorded in the Pliocene. It is >14 m.y., with the lower and middle Miocene nannofossil Zones NN1-NN9 missing (Fig. F6).
The three Quaternary calcareous nannofossil zones, NN21-NN19, are recorded. Preservation is good to moderate, and is poor only in the lower part of the section. Reworking is very minor and detected only in two samples at 150.88 and 170.38 mbsf from the uppermost part of Zone NN19. The assemblages from the lowermost part of the combined Zones NN21-NN20 show some evidence of sorting in favor of small species, such as Reticulofenestra minuta. Assemblages from the Pleisto-cene section at Site 1127 showed similar evidence of sorting (see "Biostratigraphy" in the "Site 1127" chapter).
The key species for Zone NN21, Emiliania huxleyi, is identified down section to Sample 182-1130B-1H-CC (21.95 mbsf), in association with Braarudosphaera bigelowii, Coccolithus pelagicus, Gephyrocapsa caribbeanica, Gephyrocapsa oceanica, Helicosphaera carteri, Helicosphaera hyalina, Helicosphaera wallichi, and Umbilicosphaera sibogae. Assemblages indicative of the combined Zones NN21-NN20 are recorded down to Sample 182-1130A-14H-CC (131.91 mbsf). Species present throughout this interval include B. bigelowii, Calcidiscus leptoporus, G. caribbeanica, small Gephyrocapsa spp. (including Gephyrocapsa aperta), Helicosphaera carteri, and Syracosphaera pulchra. The warm-water Gephyrocapsa omega occurs in the upper part of the interval, indicating the influence of the Leeuwin Current.
The LO of Pseudoemiliania lacunosa, which indicates Zone NN19, occurs in Sample 182-1130A-15H-CC (140.32 mbsf), in which small Gephyrocapsa spp. have their greatest abundance. Similar Zone NN19 assemblages are recorded down to Sample 182-1130A-25X-CC (234.34 mbsf). In addition to those listed above, the assemblage in Samples 182-1130A-16H-CC (150.88 mbsf) and 17H-CC (170.38 mbsf) from the uppermost part of Zone NN19 also contains Calcidiscus macintyrei, Coccolithus miopelagicus, Cyclicargolithus floridanus, Dictyococcites productus, Helicosphaera carteri, Helicosphaera sellii, Pontosphaera japonica, P. lacunosa, Syracosphaera globulosa, and Rhabdosphaera clavigera. Reworking in these samples is indicated by the presence of Cyclicargolithus floridanus and C. miopelagicus from older sediments, probably of Miocene age. Helicosphaera sellii and Calcidiscus macintyrei are represented by a few poorly preserved specimens and appear to be also reworked. The highest occurrences of these two species could not be confidently located during our shipboard study.
An abundance peak of B. bigelowii is recorded at the base of Zone NN19 in Sample 182-1130A-25X-CC (234.34 mbsf). This species also shows an abundance peak within a narrow interval in the lower part of the expanded Pleistocene section at Site 1127 (see "Biostratigraphy" in the "Site 1127" chapter).
Subzone CN12b (Zone NN16 in part) of late Pliocene age is indicated by the presence of rare Discoaster surculus in association with Calcidiscus macintyrei, Calcidiscus leptoporus, C. pelagicus, Discoaster brouweri, Helicosphaera carteri, Pontosphaera japonica, and P. lacunosa in Sample 182-1130A-26X-CC (240.59 mbsf). Whether the two short Subzones CN12c-d (Zones NN17 and NN18) of the upper Pliocene are represented between this sample and Zone NN19 in Sample 182-1130A-25X-CC (234.34 mbsf) was not determined in our shipboard study.
A disconformity at the sharp lithologic contact between lithostratigraphic Units I and II, at ~259 mbsf (see "Lithostratigraphy"), separates assemblages of the upper Pliocene Subzone CN12b from that of the lower Pliocene Subzones CN10b-c. The missing Subzone CN12a and Zone CN11 suggest a hiatus of ~1.7 m.y. duration.
Both Amaurolithus ninae and Amaurolithus tricorniculatus are recorded in association with Discoaster asymmetricus, Discoaster brouweri, Discoaster pentaradiatus, D. surculus, Discoaster variabilis, Reticulofenestra pseudoumbilicus, Reticulofenestra minutula, Sphenolithus abies, and Sphenolithus neoabies in Sample 182-1130A-28X-3, 124-128 cm (258.54 mbsf), below the lithostratigraphic Unit I/Unit II boundary. In the absence of Triquetrorhabdulus rugosus, this association suggests the combined Subzones CN10b-c. Species of Ceratolithus (Ceratolithus acutus, Ceratolithus armatus, or Ceratolithus rugosus) are very scarce or completely absent. The assemblage in Sample 182-1130A-28X-2, 58-62 cm (256.38 mbsf), from above the lithostratigraphic Unit I/Unit II boundary, lacks species of Amaurolithus and Sphenolithus, as well as the key taxa R. pseudoumbilicus and Discoaster tamalis, but contains Ceratolithus rugosus, P. lacunosa, and D. surculus, indicating Subzone CN12b.
Assemblages assignable to Subzone CN10a of latest Miocene age are recorded in Samples 182-1130B-29X-CC (272.71 mbsf) through 31X-CC (291.46 mbsf). These are characterized by the presence of T. rugosus and species of the genus Amaurolithus. Also occurring in this subzone are Reticulofenestra gelida, Scyphosphaera spp., and Triquetrorhabdulus farnsworthii. Evidence of some reworking from Paleogene sediments into the upper part of Subzone CN10a is recorded by the presence of Coccolithus formosus, Coccolithus eopelagicus, and Discoaster trinidadensis.
Assemblages assignable to Subzone CN9b occur in Samples 182-1130B-32X-CC (301.05 mbsf) through 182-1130A-33X-CC (312.07 mbsf). These include the association Amaurolithus amplificus, A. ninae, A. tricorniculatus, and Discoaster quinqueramus. Sample 182-1130C-2R-CC (316.42 mbsf) contains rare Discoaster berggrenii and Minylitha convallis, and lacks the species of Amaurolithus, indicating Subzone CN9a.
Assemblages from Samples 182-1130A-34X-CC (320.12 mbsf), 3R-CC (323.34 mbsf), and 35X-5, 87-92 cm (328.57 mbsf), lack D. berggrenii, but contain rare Discoaster bellus, Discoaster calcaris, Discoaster neohamatus, and D. pentaradiatus, as well as few Helicosphaera rhomba, M. convallis, and T. rugosus, indicating Zone NN10 (or Zone CN8).
The Zone NN10 assemblage (upper Miocene) in Sample 182-1130A-35X-5, 87-92 cm (328.57 mbsf), is immediately underlain by a Zone NP25 assemblage (upper Oligocene) in Sample 182-1130A-35X-CC (328.89 mbsf). This indicates a major disconformity with the lower, middle, and the basal upper Miocene missing.
Assemblages of Zone NP25 of late Oligocene age are recorded from Samples 182-1130C-4R-CC (328.18 mbsf), 182-1130A-35X-CC (328.89 mbsf), and 182-1130A-36X-CC (331.30 mbsf). Sphenolithus distentus is absent from these assemblages, and Sphenolithus ciperoensis occurs only in the lower sample at 331.30 mbsf. The association B. bigelowii, Chiasmolithus altus, Cyclicargolithus abisectus, C. floridanus, Dictyococcites bisectus, Discoaster deflandrei, Helicosphaera recta, Reticulofenestra lockeri, and Zygrhablithus bijugatus, present in the other two samples, supports a Zone NP25 assignment.
Sample 182-1130C-6R-CC (357.06 mbsf) contains an impoverished assemblage, although the assemblages in Samples 182-1130A-38X-CC (351.37 mbsf) and 182-1130C-7R-CC (357.06 mbsf) are rich. The latter samples contain the association B. bigelowii, C. altus, Coronocyclus nitescens, Cyclicargolithus abisectus, C. floridanus, D. bisectus, Discoaster deflandrei "group," Helicosphaera euphratis, Helicosphaera intermedia, Helicosphaera obliqua, Helicosphaera recta, Sphenolithus predistentus, Sphenolithus sp. aff. Sphenolithus distentus, and Z. bijugatus, which suggests the zonal interval NN25-23.
Chiasmolithus altus is abundant throughout the Oligocene section at Site 1130, indicating a cool-water regime, although the presence of S. ciperoensis in Zone NP25 suggests warm-water influence. This supports the conclusion (Shafik, 1990) that a cool-water regime prevailed in the Great Australian Bight during the middle and late Oligocene, although with an intermittent warm-water influence inferred to result from a surface current intermittently bringing warm water from the Indian Ocean. Core-catcher samples examined from the calcareous sandstone at the bottom of both Holes 1130A and 1130C are barren of calcareous nannofossils.
Sediments recovered at Site 1130 contain planktonic foraminifer assemblages of the Pleistocene, Pliocene, upper Miocene, and Oligocene. Few planktonic foraminifers were detected in the calcareous sandstone from the lower part of Hole 1130B, between 365 and 390 mbsf. On the basis of the standard zonal scheme of Berggren et al. (1995a; 1995b), the Neogene and Oligocene successions are divided into relevant zones or zonal equivalents that can be correlated between sites and to regional biostratigraphy. The Pleistocene-upper Miocene succession appears to be truncated by a disconformity at the lower/upper Pliocene boundary. The disconformity between the upper Miocene and Oligo-cene represents a break in sedimentation of at least 14 m.y. (Fig. F6).
Planktonic foraminifers are relatively rare from Cores 182-1130A-1H through 5H and 182-1130B-1H through 5H in sediments dominated by shell debris consisting mainly of bivalves and gastropods. Their abundance increases downhole, comprising 10%-20% of the >63-µm residue, although preservation deteriorates. The faunal succession consists of two main assemblages characterized respectively by Globorotalia truncatulinoides and Globorotalia crassaformis. The G. truncatulinoides assemblage occurs down to ~225 mbsf (Cores 182-1130A-1H to 24X and 182-1130B-1H to 24X), whereas the G. crassaformis assemblage extends from this level down to a lithostratigraphic boundary at ~257 mbsf within Cores 182-1130A-28X and 182-1130B-29X (see "Lithostratigraphy").
The G. truncatulinoides assemblage typifies the Pleistocene zone Pt1 of Berggren et al. (1995a; 1995b) and SN14 of Jenkins (1993) (Fig. F6). It is a cool temperate assemblage that mainly comprises Globorotalia inflata, G. truncatulinoides, Globigerina bulloides, and Globigerinoides ruber. In the 63- to 150-µm fraction, however, Globigerina falconensis, Globigerina quinqueloba, and Neogloboquadrina pachyderma are dominant. Minor constituents include Globigerinoides rubescens, Globigerinoides tenellus, Orbulina universa, and Neogloboquadrina dutertrei. Globorotalia hirsuta is recorded downhole to Sample 182-1130A-5H-CC, 9-11 cm (55.95 mbsf). The co-occurrence of typical Globorotalia tosaensis and G. trunca-tulinoides from Sample 182-1130A-15H-CC, 22-25 cm (140.32 mbsf), downhole can be used to define Subzone Pt1a.
As observed earlier at Site 1127 (see "Biostratigraphy" in the "Site 1127" chapter), the Pleistocene (Pt1) planktonic foraminifer assemblage as a whole is of the southern temperate type (Li et al., in press), and in only a few levels did we observe rare specimens of (sub)tropical species. They include Globigerinoides sacculifer s.l. in Samples 182-1130A-3H-CC, 10-12 cm, 5H-CC, 9-11 cm, and 7H-CC, 18-21 cm; Globorotalia tumida in Samples 182-1130A-10H-CC, 19-22 cm, and 14H-CC, 17-20 cm; and Sphaeroidinella dehiscens in Sample 182-1130A-22X-CC, 35-38 cm. These typical low-latitude species reflect warmer climatic conditions and/or stronger flows of the Leeuwin Current (McGowran et al., 1997a), probably in response to global climatic cycles.
The Pleistocene/Pliocene boundary cannot be positively identified, partly because temperate planktonic foraminifers contain few species suitable for age dating. The boundary in the region has been placed at the FO of G. truncatulinoides (Jenkins, 1993; McGowran et al., 1997b). If this traditional measure is applied, the Pleistocene/Pliocene contact lies within Core 182-1130A-24X, where the species first appears. However, this datum level seems to be diachronous: in the uppermost Pliocene (2.0 Ma; Berggren et al., 1995a), or even in the lower part of the upper Pliocene (Hornibrook et al., 1989). At Site 1130, the FO of G. truncatulinoides was found at two levels: 224.7 mbsf in Hole 1130A (Sample 182-1130A-24X-CC, 17-20 cm) and 214.03 mbsf in Hole 1130B (Sample 182-1130B-23X-CC, 28-31 cm). The interval encompassing this datum level between the holes is within a paleomagnetic normal zone, probably the Olduvai or older (see "Paleomagnetism"), and at the base of seismic Sequence 2 (see "Seismic Stratigraphy").
Cores 182-1130A-25X through 28X and 182-1130B-25X through 27X contain abundant, poorly preserved globorotaliid planktonic foraminifers, characterizing the tentatively termed "G. crassaformis interval" (Fig. F6). Together with some species that are common also in the cores above (such as Globorotalia inflata, Globigerina bulloides, and Globigerinoides ruber), the assemblage is mainly composed of Globorotalia puncticulata, G. crassaformis, and Globorotalia crassula. It has been also observed from Cores 182-1127A-45X through 50X at Site 1127. The assemblage is similar in composition to the upper Pliocene fauna of New Zealand (Hornibrook et al., 1989). Calcareous nannofossils indicate that this interval is either fully equivalent to the lowermost part of the Pleistocene Zone NN19 (see "Biostratigraphy" in the "Site 1127" chapter), or covers parts of Zone NN19 through the upper Pliocene Subzone CN12b (see "Calcareous Nannofossils"). Further study of the stratigraphy and related foraminifer datum levels is necessary to clarify the age of this interval.
Moderately preserved planktonic foraminifers occur in Samples 182-1130A-28X-3, 124-128 cm, through 35X-5, 87-92 cm (258.54-328.57 mbsf). This faunal change coincides with a lithologic change from grayish, glauconite-rich packstones above to light-colored foraminifer nannofossil oozes (see "Lithostratigraphy"). The assemblage is characterized by Globorotalia margaritae, Zeaglobogerina nepenthes, and, in the lower part, by Globorotalia cf. cibaoensis, indicating early Pliocene to late Miocene age (Berggren et al., 1995a). In Cores 182-1130A-29X to 30X and 182-1130B-29X to 30X, the FO of G. crassaformis and G. puncticulata was also recorded, although they become more frequent in the G. crassaformis interval in cores above. In contrast to those from above, however, G. crassaformis is represented mainly by sinistral specimens, similar to the lower Pliocene record from New Zealand (Hornibrook et al., 1989). Their association with upper Miocene taxa, such as Globorotalia sphericonomiozea, indicates that the uppermost part of the lower Pliocene is probably either condensed or missing. Therefore, if it is a disconformity, the lower/upper Pliocene contact represents a hiatus of ~1.7 m.y. duration.
Cores 182-1130A-31X through 33X and 182-1130B-31X through 33X contain assemblages more typical of Zones Pl1 and Mt10, as indicated by the coexistence of Z. nepenthes, G. margaritae, G. cf. cibaoensis, Globorotalia conomiozea, Globorotalia plesiotumida, and Globorotalia conoidea (including Globorotalia miotumida), as well as other upper Mio-cene to Pliocene taxa. The zones are combined at this site because the marker species G. sphericonomiozea was recorded, although discontinuously, throughout this interval (~260-310 mbsf). Some specimens resembling this species are also present in Sample 182-1130C-3R-CC, 16-19 cm (323.34 mbsf).
Planktonic foraminifers indicating the upper Miocene Zone Mt9 (upper part) occur in the interval of ~315-328.57 mbsf in Samples 182-1130A-34X-CC, 51-52 cm, 35X-5, 87-92 cm, 182-1130C-2R-CC, 8-11 cm, and 3R-CC, 16-19 cm. Common species include G. conoidea, G. cf. cibaoensis, G. plesiotumida, Z. nepenthes, Z. woodi, Globigerinoides extremus, and O. universa s.l.
According to Berggren et al. (1995a; 1995b), the Pliocene/Miocene boundary lies within Subzone Pl1a. Hornibrook et al. (1989), however, placed it at the FO of G. crassaformis in New Zealand, which occurs at 273.71 mbsf in Hole 1130A and at 281.79 mbsf in Hole 1130B. With an estimated age of 4.5 Ma (see "Planktonic Foraminifers" in the "Explanatory Notes" chapter), the datum level is 0.75 m.y. younger than the Pliocene/Miocene boundary defined in Berggren et al. (1995a). Pending further studies, we tentatively placed the boundary at ~273 mbsf (Fig. F6).
A sharp contact between the upper Miocene sediments in Core 182-1130A-35X and the core-catcher sample represents a hiatus of at least 14 m.y., as indicated by planktonic foraminifers of late Oligocene age found in Sample 182-1130A-35X-CC, 27-30 cm (328.89 mbsf). The assemblage is poorly preserved and contains numerous small Globigerina praebulloides, Globigerina officinalis, Globorotaloides suteri, Globorotaloides testarugosa, and tenuitellids, as well as some specimens of Globigerina euapertura, Globoquadrina venezuelana, Paragloborotalia nana, and Globigerina cf. ciperoensis. Further downhole in Samples 182-1130A-38X-CC, 17-20 cm (351.37 mbsf), and 182-1130C-7R-CC, 6-8 cm (356.96 mbsf), these species were found together with Catapsydrax dissimilis, Zeaglobigerina labiacrassata, and Paragloborotalia cf. opima, indicating Zone P21 of the middle Oligocene. The assemblage contains few specimens of Chiloguembelina cubensis, a species most common in the lower Oligo-cene and Eocene of middle to high latitudes (Berggren, 1992; Li et al., 1992).
The Oligocene succession at Site 1130 (328-365 mbsf) contains many chert intervals. The poor core recovery from these intervals yielded no suitable material for planktonic foraminifer study. Calcareous nannofossils, however, indicate that several chert samples are also of Oligo-cene age (see "Calcareous Nannofossils").
An orange-brown, porous calcareous sandstone was recovered underlying the Oligocene cherts and wackestones. No planktonic foraminifers were detected at 369.85 mbsf in the single washed core-catcher sample (Sample 182-1130A-40X-CC, 35-37 cm). A thin section (Sample 182-1130A-40X-CC, 5-6 cm) prepared for lithologic analysis contains a few planktonic foraminifer tests resembling Subbotina linaperta-Subbo-tina angiporoides from the middle to upper Eocene. Therefore, the sandstone probably accumulated during the upper Eocene, although postcruise studies are needed to clarify this age (see "Lithostratigraphy" and "Seismic Stratigraphy").
Benthic foraminifers were studied from every fourth core-catcher samples in Cores 182-1130A-1H through 21X and from every core-catcher sample below Core 21X. Benthic foraminifers are generally abundant and well preserved at Hole 1130A, except between Cores 23X and 27X, where abundance fluctuates markedly and significant numbers of abraded and corroded tests with glauconite infilling are found in some of the samples examined. No benthic foraminifers were found in the disaggregated core-catcher sample (Sample 182-1130A-40X-CC) from the brown-orange calcareous sandstone recovered at the base of Hole 1130A. However, examination of a thin section (interval 182-1130A-40X-CC, 5-6 cm) revealed that the calcareous matrix contained miliolids and bolivinids, as well as the planktonic foraminifer tests of middle-late Eocene age noted above.
Between 100 and 300 benthic foraminifers were picked from the >63-µm fraction, except in Samples 182-1130A-23X-CC, 25X-CC, and 27X-CC, where abundance was low. The benthic foraminifer assemblages studied include mainly calcareous taxa and only a few species and specimens of agglutinated taxa. They show some similarity to shelf assemblages documented by Li and McGowran (in press) from Lakes Entrance in southeastern Australia. Although many of the species have a cosmopolitan distribution, some of the shelf species within the assemblages probably represent endemic taxa with a more restricted distribution. Further taxonomic studies are needed to clarify the distribution of benthic foraminifers in the Great Australian Bight during the Paleogene and Neogene. Three benthic foraminifer assemblages are recognized in the Cenozoic succession of Hole 1130A, which indicate a shallowing-upward trend from middle bathyal paleodepths in the upper Oligocene to upper bathyal paleodepths in the Pleistocene.
This Pleistocene assemblage is characterized by fluctuating abundances of Triloculina spp., Spiroloculina spp., Quinqueloculina spp., Elphidium spp., Bolivina spp., Loxostomum spp., Loxostomoides spp., and Uvigerina hispidicostata. Also present as rare to few constituents of the assemblage are Patellina corrugata, Spirillina spp., Sigmoilopsis schlumbergeri, Neolenticulina peregrina, Hoeglundina elegans, Heterolepa dutemplei, Uvigerina hispida, Planulina wuellerstorfi, Sphaeroidina bulloides, Cancris auriculus, Bulimina marginata, Siphonina australis, Anomalinoides spp., Textularia spp., Trifarina spp., Nodogenerina spp., Fissurina spp., Cibicidoides spp., Palliolatella spp., Pyrgo spp., Sigmoilina spp., Rosalina spp., Glandulina spp., Ehrenbergina sp., and various nodosariids. In some samples, the assemblage is dominated by small specimens (63-150 µm) of taxa typical of inner to middle neritic environments (Triloculina spp., Spiroloculina spp., Elphidium spp., Quinqueloculina spp., and Patellina spp.). This suggests that a large proportion of the tests within these samples originated from the adjacent shelf, before being sorted and redeposited further offshore. Upper bathyal paleodepths are otherwise indicated by the presence of the depth-sensitive species Sigmoilopsis schlumbergeri, Hoeglundina elegans, H. dutemplei, Uvigerina proboscidea, and S. bulloides. Fluctuations in the relative proportions of redeposited neritic taxa within the samples may relate to changes in climate, sea level, and oceanic circulation during the Pleistocene (McGowran et al., 1997a). However, high-resolution studies are needed to resolve the changes in benthic foraminifer distribution patterns and to integrate them within a sequence stratigraphic framework.
Site 1130 is situated ~50 km west of Site 1127, at comparable water depths. Expanded Pleistocene sedimentary successions were recovered at these two sites, although sedimentation rates were significantly lower at Site 1130 than at Site 1127 (see Fig. F6 and Fig. F7 in the "Site 1127" chapter). Although the Pleistocene benthic foraminifer assemblages at these two sites show close similarity in composition, the assemblage at Site 1127 contains a greater proportion of small, reworked tests than the coeval assemblage at Site 1130 and does not exhibit such marked fluctuations in composition. Variations in assemblage composition and in sediment accumulation rates at the two sites probably reflect different hydrographic regimes at these two upper slope settings during the Pleistocene.
The FO of Assemblage 2 coincides with the marked lithologic change from glauconite-rich, bioclastic packstones to nannofossil foraminifer oozes in Core 182-1130A-28X (see "Lithostratigraphy"). Assemblage 2 is characterized by the few to common occurrence of H. dutemplei, Stilostomella spp., and Loxostomum spp. Also present are U. hispidicostata, U. proboscidea, Bulimina marginata, Globocassidulina subglobosa, P. wuellerstorfi, Oridorsalis umbonatus, Laticarinina pauperata, Eggerella bradyi, Martinottiella communis, S. bulloides, Anomalinoides globulosus, Vulvulina spinosa, Osangularia spp., Pyrgo spp., Siphonina spp., Cibicidoides spp., Trifarina spp., Bolivina spp., and various nodosariids. Abundance is generally low and there is no strong evidence of preferential test size sorting within the assemblage. Middle bathyal paleodepths are suggested by the presence of the depth-indicative species L. pauperata, Globocassidulina subglobosa, and Eggerella bradyi. Assemblage 2 differs markedly in composition from the Miocene benthic foraminifer assemblage identified at Site 1127, which was indicative of upper bathyal paleodepths, but also contained a significant proportion of reworked neritic taxa.
A major lithologic change from nannofossil foraminiferal ooze to chert occurs at ~328 mbsf. This change coincides with a major unconformity, spanning ~14 m.y. between the upper Miocene and upper Oligocene (see "Calcareous Nannofossils" and "Planktonic Foraminifers"). The benthic foraminifer assemblage within this interval of poor core recovery is characterized by numerous, relatively well-preserved, small tests of Bolivina spp., Trifarina spp., and Stilostomella spp. Also present as rare to few constituents of the assemblage are Globocassidulina subglobosa, Cibicidoides laurisae, V. spinosa, Siphonina tenuicarinata, and Cibicidoides spp. Middle bathyal paleodepths are suggested for this assemblage by the presence of Cibicidoides laurisae, a predominantly middle bathyal to abyssal species (van Morkhoven et al., 1986), and by the absence of deeper bathymetric indicators. Cibicidoides laurisae is also a stratigraphically significant species within this interval, with a stratigraphic range extending from the middle Eocene (P10) to the upper Oligocene (P22), according to van Morkhoven et al. (1986).
Sediment accumulation rates shown in Figure F7 were calculated from preliminary biostratigraphic and paleomagnetic results (see "Paleomagnetism"). The onset of the Brunhes Chron was identified with confidence, but the onsets and terminations of the Jaramillo and Olduvai Subchrons are less certain (see "Paleomagnetism"). The paleomagnetic datum levels are generally consistent with the bio-stratigraphic datum levels. The biostratigraphic datum levels and relevant paleomagnetic data used to calculate sedimentation rates are listed in Table T2.
A very high sedimentation rate, between 240 and 260 m/m.y., is calculated for the greater part of the Pleistocene section. In contrast, the rates recorded below the Brunhes/Matuyama boundary are significantly lower, between 15 and 20 m/m.y. The Pliocene record is punctuated at ~258 mbsf by a hiatus of ~1 m.y. duration. This is clearly delineated by the simultaneous LOs of the nannofossil species Amaurolithus and Sphenolithus, as well as R. pseudoumbilicus. However, the most spectacular hiatus recorded at Site 1130 is at the Neogene/Paleogene boundary, from which the entire lower Miocene-lower upper Miocene succession is missing. The duration of this hiatus is ~14 m.y.
The middle-upper Oligocene section registered relatively low sedimentation rate of 10-30 m/m.y. At Site 1128, by comparison, sedimentation rates of 50-60 m/m.y. were recorded for the lower-middle Oligocene section (see "Sedimentation Rates" in the "Site 1128" chapter).