Calcareous nannofossils and planktonic foraminifers indicate that sediments recovered at Site 1134 range from Quaternary to middle Eocene in age. Several hiatuses were indicated. The first was in the Pliocene (nannofossil Zones NN18-NN13 missing at ~57 mbsf) and the second in the middle-upper Miocene (nannofossil Zones NN9-NN7 missing at ~114 mbsf). Several datum levels occurred together at the Oligocene/Miocene boundary, indicating a hiatus of ~1 m.y. In the Eocene section, the absence of nannofossil Zone NP17 suggests that a time interval of ~3 m.y. is not represented at the middle/upper Eocene boundary. Planktonic foraminifers indicate hiatuses at approximately the same depths as the calcareous nannofossils. However, poor core recovery in critical intervals within the Oligocene-Eocene makes determination of smaller scale hiatuses impossible.
Calcareous nannofossils are moderately well preserved above ~200 mbsf and become poorly preserved below this level. Planktonic foraminifers are moderately well preserved throughout most of Hole 1134A, with only the lowermost 30 m of the hole containing poorly preserved specimens. Benthic foraminifers are generally rare in comparison to the planktonic foraminifers and decrease in abundance significantly in the lowermost 130 m of Hole 1134A. The preservation of the benthic foraminifers is comparable to that of the planktonic foraminifers. The five main assemblages of benthic foraminifers recognized all indicate middle bathyal paleodepths and can be correlated with coevel assemblages at Site 1126.
The sedimentary successions at Site 1134 bear many similarities to those at Site 1126. Not only was a similar succession of zones recognized, but the hiatus positions are strikingly similar between the two sites. The uppermost hiatus in Site 1134 (~57 mbsf) appears to correlate with the first two hiatuses encountered in Site 1126 (~57 and ~67 mbsf), where most of the Pliocene is missing. The second hiatus encountered in Site 1134 (~114 mbsf) correlates well with the third hiatus in Site 1126 (~118 mbsf), with most of the middle-upper Miocene missing.
Calcareous nannofossils indicate that drilling at Site 1134 recovered a Pleistocene-middle Eocene succession. Two main disconformities occur and a third is suspected. The entire Pliocene is either missing or condensed between two successive core catchers. Similarly, the upper-middle Miocene Zones NN9-NN7 seem to be missing from the record. Poor recovery in the Eocene, between a chalk section containing Zone NP18 indicators and a limonitic sandstone containing rare nannofossils suggestive of Zone NP16, makes it difficult to ascertain whether the middle Eocene Zone NP17 is missing. The nature of the transition from the Neogene to the Paleogene (whether abrupt or gradational) could not be determined. The zones within a lower Miocene interval, ~61 m thick, between Zones NN3 and NP25, could not be determined during our shipboard study. Nannofossil preservation is moderate in the Quaternary and Neogene and poor in the Paleogene.
Sample 182-1132A-1H-CC contains Calcidiscus leptoporus, Gephyrocapsa caribbeanica, and small Gephyrocapsa spp., without Pseudoemiliania lacunosa, indicating the combined Zones NN21-NN20. The key species P. lacunosa occurs in Samples 182-1132A-2H-CC (14.21 mbsf) to 6H-CC (52.01 mbsf), together with Braarudosphaera bigelowii, C. leptoporus, Coccolithus pelagicus, small Gephyrocapsa spp., Syracosphaera pulchra, and Rhabdosphaera clavigera. In the absence of species of Discoaster, this association indicates Zone NN19. Gephyrocapsa spp. (small) have their highest abundance acme in the uppermost part of Zone NN19. Calcidiscus macintyrei has its highest occurrence at 33.12 mbsf in the lower part of the zone.
Braarudosphaera bigelowii reached its acme abundance in Sample 182-1134A-5H-CC. Below this peak abundance of B. bigelowii, the assemblage from Sample 182-1134A-6H-CC (52.01 mbsf) is indicative of the lowermost part of Zone NN19, with rare small Gephyrocapsa spp. and no larger Gephyrocapsa. Other species in this assemblage include C. leptoporus, C. macintyrei, C. pelagicus, Dictyococcites productus, Helicosphaera carteri, P. lacunosa, and Reticulofenestra minuta. However, intervals from ~36 to 42.5 mbsf, 49.5 to 56.2 mbsf, and 57.8 to 66.0 mbsf are clearly slumped (see "Lithostratigraphy"), so biostratigraphic relationships are in question.
A well-diversified assemblage is recorded from Samples 182-1134A-7H-CC (61.89 mbsf) and 8H-CC (70.83 mbsf), indicative of the lower part of Zone NN12 (Subzone CN10a) of latest Miocene age. This assemblage includes Amaurolithus ninae, Amaurolithus tricorniculatus, C. leptoporus, C. macintyrei, Discoaster pentaradiatus, Discoaster surculus, Discoaster variabilis, Scyphosphaera spp., Reticulofenestra gelida, Reticulofenestra pseudoumbilicus, and Triquetrorhabdulus rugosus. Zones NN18-NN13 and the younger part of NN12, representing the entire Pliocene, are either missing or contained in a condensed section between Samples 182-1134A-8H-CC and 182-1134A-7H-CC (at ~57 mbsf).
An upper Zone NN11 (Subzone CN9b) assemblage occurs in Samples 182-1134A-9H-CC (80.73 mbsf) to 11H-CC (108.35 mbsf). This assemblage is characterized by the co-occurrence of Discoaster quinqueramus (rare), and both A. ninae and A. tricorniculatus (few). These key taxa are absent from Sample 182-1134A-12H-CC (108.35 mbsf), although Minylitha convallis and Discoaster neohamatus are present instead, suggesting the upper Miocene Zone NN10. The assemblage from Sample 182-1134A-13H-CC (118.54 mbsf) indicates the middle Miocene Zone NN6. The upper-middle Miocene Zones NN9-NN7 are either missing or condensed in the 9.5-m interval between Samples 182-1134A-12H-CC and 13H-CC (at ~114 mbsf).
The association of Calcidiscus premacintyrei, Cyclicargolithus floridanus, Dictyococcites antarcticus, Discoaster exilis, D. variabilis, Helicosphaera rhomba, Reticulofenestra gelida, R. pseudoumbilicus, and T. rugosus characterizes Zone NN6 in Samples 182-1134A-13H-CC (118.54 mbsf) to 16X-CC (137.71 mbsf). Heavily calcified Discoaster deflandrei "group," B. bigelowii, and Micrantholithus entaster are present in the lower part of Zone NN6.
The stratigraphic range of Sphenolithus heteromorphus, the key species for the combined Zones NN5-NN4, is present between 147.10 and 144.17 mbsf (Samples 182-1134A-17X-CC and 18X-CC). This is a very thin interval for the combined Zones NN5-NN4 compared to other Leg 182 sites in which these zones occur. The thickness of the combined Zones NN5-NN4 ranges from ~85 m at the shallow-water Site 1132 to >100 m at the deeper water Site 1133 (where it was not totally penetrated). In addition to S. heteromorphus, C. leptoporus, C. premacintyrei, C. floridanus, D. variabilis, H. carteri, and R. pseudoumbilicus are present in Samples 182-1134A-17X-CC and 18X-CC.
Nannofossils in Sample 182-1134A-19X-CC (162.84 mbsf) are few and moderately preserved. These include Sphenolithus belemnos, the key species for Zone NN3 of early Miocene age, as well as C. floridanus, Helicosphaera euphratis, Sphenolithus conicus, and Sphenolithus moriformis. This is the only record of undeniable Zone NN3 from Leg 182 sites.
Below Zone NN3, a thick interval (between 162.84 and 224.05 mbsf, ~61 m thick) contains associations with an early Miocene aspect, although the interval lacks specific age-diagnostic taxa. At most levels, nannofossil preservation is moderate where the abundance is low, and poor where the abundance and diversity are relatively high. The taxa list from this interval (Samples 182-1134A-20X-CC to 26X-CC) includes B. bigelowii, D. antarcticus, Cyclicargolithus abisectus, C. floridanus, heavily calcified specimens of the D. deflandrei "group," H. carteri, H. euphratis, Helicosphaera obliqua, Micrantholithus sp., and S. moriformis.
Sample 182-1134A-27X-CC (238.64 mbsf) contains the key taxa Dictyococcites bisectus, Sphenolithus capricornutus, and S. delphix, which indicates the uppermost Oligocene NP25. Other species in this sample include B. bigelowii, Coccolithus miopelagicus, C. abisectus, C. floridanus, Micrantholithus sp., and S. conicus. Sample 182-1134A-32X-CC (281.96 mbsf) contains the highest occurrence of the key species, Reticulofenestra umbilicus, and no Coccolithus formosus, indicating Zone NP22 of early Oligocene age. The interval between Zone NP25 at 238.64 mbsf and Zone NP22 at 281.96 mbsf could not be assigned to a zone because of the lack of the low-latitude taxa Sphenolithus distentus and Sphenolithus ciperoensis in the core-catcher samples examined. This interval is tentatively assigned to the combined Zones NP23-NP25. The highest occurrence of Chiasmolithus altus is within this NP23-NP25 zonal interval, at 262.72 mbsf (Sample 182-1134A-30X-CC).
Shafik (1990) indicated that the presence of S. distentus and S. ciperoensis in southern Australia was probably caused by warm waters being brought from the Indian Ocean by an intermittent surface-water current, the proto-Leeuwin Current. The implications are that both the stratigraphic and geographic ranges of these taxa in southern Australia are probably sporadic. Detailed postcruise examination will be performed to document the distribution pattern of S. distentus and S. ciperoensis at this site and at Site 1132, for which biostratigraphic refinement is needed for the Zone NP23 or younger interval (see "Biostratigraphy" in the "Site 1132" chapter).
Zone NP21 assemblages are recorded from Samples 182-1134A-33X-CC (291.4 mbsf) to 35X-CC (310.93 mbsf). These include Chiasmolithus altus, Chiasmolithus oamaruensis, D. bisectus, Discoaster nodifer, Reticulofenestra hillae, R. umbilicus, and Zygrhablithus bijugatus.
The association Isthmolithus recurvus, Discoaster saipanensis, and C. oamaruensis in the assemblage from Sample 182-1134A-36X-CC (322.09 mbsf) indicates Zones NP19-NP20, of late Eocene age. Both D. saipanensis and C. oamaruensis occur downhole to 361.91 mbsf in Sample 182-1134A-40X-CC, although without the association of I. recurvus. This indicates Zone NP18 of late Eocene age. Other species present in Zone NP18 include Coccolithus eopelagicus, C. formosus, Cribrocentrum reticulatum, D. bisectus, D. nodifer, and Z. bijugatus.
Rare, poorly preserved nannofossils in the limonitic sandstone underlying the upper Eocene chalk in Sample 182-1134A-40X-CC indicate a middle Eocene age. The taxa identified from Sample 182-1134A-41X-CC (368.4 mbsf) include Chiasmolithus grandis, Chiasmolithus solitus, C. formosus, and R. umbilicus, suggesting Zone NP16. A disconformity may exist between the upper Eocene chalk in Sample 182-1134A-40X-CC and the middle Eocene sandstone in Sample 182-1134A-41X-CC, as Zone NP17 appears to be missing. This uncertainty mainly results from the poor core recovery in this interval (see "Operations"). The duration of this suspected hiatus is ~3 m.y.
Planktonic foraminifers in all core-catcher samples were studied from Hole 1134A. Selected samples from Hole 1134B were also examined, mainly for correlation purposes. The preservation of planktonic foraminifers is good to moderate throughout the Quaternary to Eocene sections, and poor only at levels with cherts or where the lithologies are lithified. All samples studied were assigned to the relevant planktonic foraminifer zones of Berggren et al. (1995) and Jenkins (1993). Preliminary results indicate that the sediment sequence recovered at Site 1134, which is similar to that at Site 1126, contains Pleistocene, Miocene, Oligocene, and upper Eocene intervals (Fig. F4). Slumping between ~36 to 66 mbsf makes stratigraphic relationships unclear in the lower Pleistocene-lower Pliocene section. A large part of the Pliocene is missing, representing a hiatus of at least 2 m.y. The upper/middle Miocene contact is also disconformable, and a hiatus of ~4 m.y. was estimated. Zonal resolution declines in lower Miocene-Eocene sediments partly because of the temperate planktonic foraminiferal assemblages, which contain few age-diagnostic species and datum levels.
Two planktonic foraminiferal assemblages are present. The younger assemblage is mainly composed of Globorotalia inflata, Globigerinoides ruber, Globorotalia truncatulinoides, Globigerina falconensis, Globigerina bulloides, Globigerina quinqueloba, Neogloboquadrina pachyderma, Orbulina universa, and Globigerinita glutinata. With the index species G. truncatulinoides, it belongs to Zone Pt1 of Berggren et al. (1995), and encompasses the interval of Cores 182-1134A-1H through 3H. The first occurrence (FO) of G. truncatulinoides coincides with the last occurrence (LO) of the Subzone Pt1a marker species Globorotalia tosaensis at 33.41 mbsf (Sample 1134A- 3H-CC, 15-18 cm), indicating that much of Subzone Pt1a is probably missing or condensed above the slumps between ~36 to 66 mbsf (see "Lithostratigraphy").
Cores 182-1134A-4H and 7H contain an assemblage characterized by numerous globorotaliid forms, but lacking G. truncatulinoides. Common species are Globorotalia crassaformis, Globorotalia puncticulata, Globorotalia crassula, and many species that are also common in cores above (such as Globorotalia inflata, N. pachyderma, Globigerina bulloides, G. falconensis, and G. ruber). Chronostratigraphically, this "G. crassaformis" interval appears to straddle the Pleistocene/Pliocene boundary (see "Biostratigraphy" in the "Site 1129" chapter), although further studies are needed to clarify its exact age. Interpretation of this interval is further complicated by slumping.
The early Pliocene-late Miocene in Cores 182-1134A-7H through 12H is characterized by a relatively diverse planktonic foraminifer assemblage. Species restricted to this interval include Globorotalia menardii, Globorotalia margaritae, Globorotalia cibaoensis, Globorotalia conomiozea, Zeaglobigerina woodi, and Zeaglobigerina nepenthes. The occurrence of Globoconella sphericomiozea in Samples 182-1134A-7H-CC, 13-16 cm, and 8H-CC, 19-23 cm (61.89-70.83 mbsf), indicates Zone Pl1 across the lower Pliocene/upper Miocene boundary (Berggren et al., 1995). Zone Mt10 is assigned to Samples 182-1134A-9H-CC through 12H-CC with the consistent presence of Globorotalia conomiozea. However, the planktonic foraminiferal assemblages in all samples appear to be more or less homogeneous, probably as a result of slump accumulation during these periods (see "Lithostratigraphy").
Sediments underlying the late Miocene at 118.54 mbsf (Sample 182-1134A-13H-CC, 10-13 cm) are lower middle Miocene Zone Mt7, indicating a hiatus of ~4 m.y. across the middle/upper Miocene boundary. This boundary occurs at ~113 mbsf within lithostratigraphic Unit III (see "Lithostratigraphy") and correlates with the contact between dominantly dark gray packstones to light-colored foraminifer-nannofossil oozes and wackestones with cherts. The middle Miocene planktonic foraminifer assemblage is characterized by Globoquadrina dehiscens, Globorotalia conoidea, Sphaeroidinellopsis kochi, O. universa, Z. woodi, Zeaglobigerina druryi, and Zeaglobigerina apertura, although without Z. nepenthes. Further downhole, Samples 182-1134A-14H-CC through 17X-CC contain Zone Mt6 planktonic foraminiferal assemblages that include most of the species found in Zone Mt7 plus Fohsella peripheroronda. Some advanced forms of this species, resembling Fohsella peripheroacuta, were also recorded.
The first chert interval in Core 182-1134A-18X not only marks a lithologic change, but also the lower/middle Miocene boundary. The core-catcher sample at 162.84 mbsf (Sample 182-1134A-19X-CC, 29-32 cm) contains poorly preserved planktonic foraminifers indicating the lower Miocene Zone Mt3. They include few Globoquadrina venezuelana, Globoconella incognita, and Globorotalia praescitula. The absence of Zones Mt4 and Mt5 suggests either a hiatus of ~1 m.y. or a highly condensed section across the lower/middle Miocene boundary. Further downhole, the planktonic foraminifer assemblage is mainly composed of southern temperate-water species. Cores 182-1134A-20X through 26X contain Z. woodi, Zeaglobigerina connecta, Paragloborotalia cf. semivera, and Globorotaloides suteri. The absence of Globigerinoides trilobus from this association indicates Zone SN3 in the early part of the early Miocene. It is not known, however, whether the transition from Zone SN3 to Mt3 is continuous, as suggested by Jenkins (1993), because no paleomagnetic constraint has ever been applied to the SN zonal scheme.
The late Oligocene is represented by three core-catcher samples. Sample 182-1134A-27X-CC, 34-37 cm (238.64 mbsf), contains an impoverished assemblage with common G. suteri, Catapsydrax spp., and Globigerina euapertura. The absence of the Miocene index species G. dehiscens indicates that this assemblage is of Oligocene age. Berggren (1992) used the LO of G. euapertura as a proxy of the Oligocene/Mio-cene boundary. This species, however, appears to range into the early part of the Miocene in southern Australia. At Site 1134, G. euapertura was found together with G. dehiscens at 215.19 and 224.05 mbsf (Sample 182-1134A-25X-CC, 34-37 cm, and 26X-CC, 15-18 cm), indicating that the LO of G. euapertura is probably diachronous. Although the chert sample at 243.42 mbsf was barren of planktonic foraminifers, a late Oligocene age is indicated by nannofossils (see "Calcareous Nannofossils"). The assemblage from 253.08 mbsf (Sample 182-1134A-29X-CC, 18-21 cm) is similar in composition to that observed above at 238.64 mbsf. With the presence of Paragloborotalia opima, the assemblage indicates upper Oligocene Zone P21b (Berggren et al., 1995).
The consistent occurrence of Chiloguembelina cubensis in the interval 262.72-304.51 mbsf (Cores 182-1134A-30X through 34X) suggests an early Oligocene age or older. It is associated with Globigerina ciperoensis, Globigerina officinalis, G. suteri, Globorotaloides testarugosa, and numerous Tenuitella spp. in Samples 182-1134A-30X-CC, 22-25 cm; 31X-CC, 0-4 cm; and 32X-CC, 16-19 cm. In the southern Australian region, the assemblage is probably equivalent to Zones P20-P21a (McGowran et al., 1997). The addition of Subbotina angiporoides and Subbotina praeturritilina to this assemblage in the interval of 291.4-304.51 mbsf (Samples 182-1134A-33X-CC, 0-2 cm, and 34X-CC, 31-34 cm) suggests Zone SP13 of Jenkins (1993), equivalent to Zones P18-P19 (Chaproniere et al., 1995).
An upper Eocene planktonic foraminifer assemblage was recorded in samples from 310.93 to 361.91 mbsf. It mainly includes Globigerinatheka index, S. angiporoides, Subbotina eocaena, Subbotina linaperta, and C. cubensis. Lacking typical middle Eocene taxa such as Acarinina, this association was correlated to the combined Zone P15-16 in Samples 182-1134A-35X-CC, 0-2 cm, through 40X-CC, 31-34 cm. Further downhole, dark brown, Fe-stained sands were found in Core 182-1134A-41X toward the base of Hole 1134A. Sample 182-1134A-41X-CC, 20-22 cm, the only core-catcher sample available from this interval, contains a rare, poorly preserved S. angiporoides-S. linaperta complex, indicating a middle-late Eocene age.
Benthic foraminifers were studied from every fourth core-catcher sample from Hole 1134A. Additional samples were also analyzed in intervals in which rapid lithologic or faunal change occurred. Abundant sponge spicules in many samples from that interval indicate an extended episode of increased biosiliceous sedimentation. A major lithologic change from light carbonate rocks to brown limonitic sandstones with skeletal fragments and quartz occurs in Core 182-1133A-41X. These Eocene sandstones contain an impoverished, poorly preserved, benthic foraminiferal assemblage.
Between 100 and 300 specimens were picked from the >63-µm fraction, except in samples in which benthic foraminifer abundance was low. Benthic foraminifers are generally rare in comparison with planktonic foraminifers, and abundance drops significantly in the lower part of Hole 1134A (Cores 27X to 40X). Preservation is good to moderate except in Core 182-1133A-41H, which contains a significant proportion of abraded and corroded specimens. The benthic foraminiferal assemblages studied include mainly calcareous taxa and only a few species and specimens of agglutinated taxa. Most species have a cosmopolitan bathyal distribution. However, further work is needed to determine more precisely the ranges of stratigraphically important taxa in the Great Australian Bight in comparison with published data. Postcruise studies will also allow integration of these ranges within regional and global biostratigraphic schemes. The following benthic foraminiferal assemblages are recognized in the Cenozoic succession of Hole 1134A.
This is a relatively diverse assemblage, characterized by the rare or few occurrences of Planulina wuellerstorfi, Martinottiella communis, Sigmoilina obesa, Anomalinoides globulosus, Sigmoilopsis schlumbergeri, Hoeglundina elegans, Cibicidoides mundulus, Bulimina aculeata, Cibicidoides spp., Textularia spp., Pleurostomella spp., Lenticulina spp., and Pullenia spp. Middle bathyal paleodepths are indicated by the presence of H. elegans, C. mundulus, A. globulosus, S. schlumbergeri, and P. wuellerstorfi, generally found in water depths exceeding 500 m, and by the lack of deeper water indicators. Fluctuations in the relative abundance of some taxa may relate to carbon flux fluctuations, changes in sea level, or circulation. A high-resolution study is needed to analyze benthic foraminiferal distribution patterns in relation to paleoceanographic changes during the deposition of the sedimentary succession.
Slumped packages in Cores 5H through 6H (see "Lithostratigraphy") contain displaced benthic foraminiferal assemblages. For instance, Sample 182-1134A-6H-CC contains a relatively well-preserved upper bathyal assemblage including Bigenerina nodosaria, Heterolepa dutemplei, S. obesa, Sphaeroidina bulloides, Textularia spp., Loxostomum spp., Tritaxia spp., and Elphidium spp., together with numerous, diverse, well-preserved bryozoans. This assemblage is similar to the Pleistocene assemblages found in bryozoan-rich accumulations at Sites 1129, 1131, and 1132.
This assemblage occurs in a lithostratigraphic unit consisting of nannofossil ooze and calcareous foraminifer ooze (see "Lithostratigraphy"). It is characterized by the rare to few occurrences of P. wuellerstorfi, Rectuvigerina striata, Siphonina tenuicarinata, B. aculeata, Globocassidulina subglobosa, S. schlumbergeri, Karreriella bradyi and Laticarinina pauperata, C. mundulus, S. bulloides, Lagena sulcata, Uvigerina hispidocostata, Vulvulina spinosa, Stilostomella spp., Uvigerina spp., Lenticulina spp., Cibicidoides spp, Anomalinoides spp., Pullenia spp., and various nodosariids. Middle bathyal paleodepths are indicated by the presence of P. wuellerstorfi, R. striata, A. globulosus, and S. schlumbergeri. The FO of the stratigraphically significant species B. aculeata is observed in Sample 182-1134A-8H-CC, corresponding to combined Zones Pl1-Mt10 (late Pliocene-upper Miocene), which is in agreement with the published stratigraphic range of this taxon in the late Miocene (FO in Zone N16, according to van Morkhoven et al., 1986).
Assemblage 2B is found in a discrete lithostratigraphic unit (litho-stratigraphic Unit IV) consisting of alternating dark wackestones/packstones and light gray chalk (see "Lithostratigraphy"). The benthic foraminifer assemblage in the core-catcher samples examined includes many species also found in Assemblage 2A, but additionally contains Stilostomella subspinosa, Patellina corrugata, Elphidium spp., and Palliolatella spp. The presence of typically shallow-water species such as P. corrugata, Elphidium spp., and Palliolatella spp. within a typically middle bathyal assemblage suggests that sediments from shallower depths were redeposited into deeper water. A corresponding assemblage was recorded at Site 1126, which was drilled farther east in approximately the same water depth (see "Biostratigraphy" in the "Site 1126" chapter). The FO of the stratigraphically important species P. wuellerstorfi is noted in Sample 182-1134A-17-CC, within Zone Mt6, which agrees with the recorded FO for this species in Zone N9 (van Morkhoven et al., 1986). The LO of V. spinosa, with a stratigraphic range extending to Zone N12, is also recorded in the same sample. R. striata, which has a FO in the early middle Miocene (Zone N9), is also a stratigraphically significant species within the assemblage.
A major lithologic change occurs in Core 25X from the cyclic succession of dark wackestones and light packstones (lithostratigraphic Unit IV) to a uniform light nannofossil ooze (lithostratigraphic Unit V) containing abundant sponge spicules (see "Lithostratigraphy"). The impoverished benthic foraminifer assemblage in Cores 25X and 26X is dominated by small specimens of Bolivina spp., Cibicidoides spp., and Trifarina spp. Also present are a few Patellina spp. A similar assemblage occurs in coeval sediments at Site 1126 (Cores 24X through 25X). Upper to middle bathyal paleodepths are tentatively suggested from the overall composition of the assemblage, as no distinctive paleobathymetric indicator was found.
This is a diversified, generally well-preserved assemblage, which is characterized by the rare to few occurrences of Oridorsalis umbonatus, Cibicidoides praemundulus, S. tenuicarinata, G. subglobosa, V. spinosa, Hanzawaia ammophila, L. pauperata, Gyroidinoides soldanii, Stilostomella spp., Uvigerina spp., Cibicidoides spp., Pullenia spp., and various nodosariids. Middle bathyal paleodepths are suggested for the assemblage by the presence of L. pauperata, C. praemundulus, S. tenuicarinata, G. subglobosa, and V. spinosa. Stratigraphically significant species within Assemblage 3 are C. praemundulus with a stratigraphic range from the early Eocene (P6b) to early Oligocene (P22) and S. tenuicarinata with FO in the late Eocene (P16) and LO in the early middle Miocene (N9).
Site 1134 is located ~60 km west of Site 1126, which was drilled in comparable water depths. There is a strong similarity in the composition of the benthic assemblages at the two sites: Assemblages 1, 2A, 2B, 2C, and 3 can be recognized at both sites, although there are differences in the relative abundances of some species within these assemblages. For instance, Uvigerina spp. is present in higher numbers in Assemblage 1 at Site 1126. Assemblage 2B at Site 1134 contains Elphidium spp., whereas Patellina spp. are more common in the corresponding assemblage at Site 1126.
Assemblage boundaries between Assemblages 2B, 2C, and 3 appear to be coeval. This suggests that changes in benthic foraminifer distribution were controlled by major environmental changes during the late Oligocene and early Miocene. Some discrepancies are observed between the boundaries of Assemblages 1, 2A, and 2B. These may relate to stratigraphic or lithologic differences caused by distinct depositional regimes at these two sites during the middle and late Miocene. The overall faunal changes and the variability within each of the assemblages need to be better defined, and the timings of the faunal changes need to be related to carbon and oxygen isotopic events during postcruise studies. The benthic foraminifer record at Sites 1126 and 1134, however, appears excellent for evaluating changes in deep-water circulation in the Great Australian Bight during the Oligocene and Miocene.
Sediment accumulation rates, shown in Fig. F5, were calculated from preliminary biostratigraphic and paleomagnetic results at Site 1134 (see "Paleomagnetism"). The biostratigraphic datum levels and relevant paleomagnetic data used to calculate sedimentation rates are listed in Table T2.
Figure F5 shows three hiatuses: one at the upper/lower Pliocene boundary, one at the upper/middle Miocene boundary, and one possible hiatus within the Eocene. The two in the Neogene are more confidently delineated by the biostratigraphy than the Eocene hiatus.
The Pleistocene section registered a sedimentation rate of 28-30 m/m.y., whereas the late Miocene recorded a rate of ~17 m/m.y. A hiatus associated with slumps occurred during much of the Pliocene (2-4 Ma). Preliminary biostratigraphic data suggest that nannofossil Zones NN18-NN13 and planktonic foraminifer Zones Pl2-Pl5 are missing.
The second hiatus occurred during the early late and late middle Mio-cene, coincident with the nannofossil Zones NN9-NN7 and the planktonic foraminifer Zones Mt9 (part)-Mt8. The duration of this hiatus is ~4 m.y. The sedimentation rate during the middle-early Miocene fluctuated. The middle Miocene registered a rate of 15-16 m/m.y., and the early Miocene recorded an average rate of 10-14 m/m.y.
The sedimentation rate was only 7 m/m.y. in the Oligocene and was as fast as 38 m/m.y. in the Eocene. The oldest hiatus occurred between the upper Eocene chalk and the middle Eocene limonitic sandstone. The nannofossil Zone NP17, which spans ~3.2 m.y, is missing.