Calcareous nannofossils and planktonic foraminifers indicate that drilling at Site 1132 recovered a thick Pleistocene-middle Eocene sequence (~550 m thick) overlying a relatively thin barren section (~45 m) (Fig. F9). Calcareous nannofossils from the basal Pleistocene section registered a nannofossil event, the "Braarudosphaera Event," which previously was recorded at Sites 1127, 1130, and 1131, representing a brief and dramatic change in surface-water conditions over a large area. A thin interval (~20 m) with poor core recovery separates a thick Pleistocene-upper Pliocene? section (~230 m) with nannofossil combined Zones NN21-NN20 and Zone NN19 from an equally thick middle-lower Miocene section (~200 m) with nannofossil Zone NN6 and combined Zones NN5-NN4. Hiatuses are likely within this thin interval, as the contained nannofossils and planktonic foraminifers are suggestive of late Miocene age. Another similarly thin interval (~20 m) with poor core recovery, also likely to contain hiatuses, underlies the middle-lower Miocene section. Immediately below this thin interval is an ~45-m section with lower-middle Oligocene nannofossil and planktonic assemblages. The Eocene age indicated for the section below 517 mbsf was determined from foraminifers in thin section from two depths, ~530 and ~547 mbsf. In our shipboard examination, no calcareous nannofossils were found in this Eocene section.
Five main benthic foraminiferal assemblages are identified. These indicate upper to middle bathyal paleodepth for the Pleistocene-Oligocene section. A striking, well-preserved Pleistocene assemblage, characterized by many large (>1 mm) agglutinated forms, is found in bryozoan-rich accumulations. This assemblage probably reflects diverse, highly dynamic ecosystems that became established at the seafloor at various times during the Pleistocene, coincident with bryozoan mound development. Changes in the composition of this assemblage may relate to sea-level and/or circulation changes during the growth of bryozoan buildups.
A Pleistocene-lower Oligocene succession of calcareous nannofossil assemblages is recorded from Site 1132. Core recovery deteriorated rapidly below the Pleistocene section. Frequent chert layers in the Miocene and Oligocene sections hampered both core recovery and biostratigraphic refinement (see "Operations"). No calcareous nannofossils were found below the Oligocene section in our shipboard analysis.
The succession at Site 1132 is differentiated into three main biostratigraphic packages: Pleistocene (~230 m thick), middle-lower Miocene (~200 m thick), and lower-middle Oligocene (~45 m thick). These packages are separated by two thin intervals (each ~20 m thick) representing condensed sections that probably include one or more hiatuses. The younger interval contains assemblages of late Miocene age, separating the Pleistocene and middle-lower Miocene successions. The older interval contains an assemblage of earliest Miocene age, between the middle Miocene and the lower-middle Oligocene. Calcareous nannofossils from the basal Pleistocene section registered a brief crisis event in the surface-water ecosystem, the "Braarudosphaera Event," as previously recorded at Sites 1127, 1130, and 1131.
Assemblages indicative of the combined Zones NN21-NN20 are recorded down to Sample 182-1132B-12H-CC (111.10 mbsf). Species present throughout this interval include Calcidiscus leptoporus, Gephyrocapsa caribbeanica, small Gephyrocapsa spp. (including Gephyrocapsa aperta), Helicosphaera carteri, and Syracosphaera spp. The LO of Pseudoemiliania lacunosa is in Sample 182-1132B-13H-CC (121.05 mbsf), indicating Zone NN19. In this sample, Gephyrocapsa spp. (small) registered their highest abundance acme.
Zone NN19 assemblages are recorded down to Sample 182-1132B-26X-CC (236.55 mbsf). Preservation is mostly moderate in the upper part of the zone, but deteriorates rapidly in its lower part. The moderately preserved assemblages from the upper part of Zone NN19, at 121.05-139.17 mbsf, contain Calcidiscus? macintyrei, Dictyococcites productus, G. caribbeanica, Helicosphaera carteri, Helicosphaera? sellii, Rhabdosphaera clavigera, and Reticulofenestra minuta, in addition to abundant small Gephyrocapsa spp., and few P. lacunosa. Preservation of the few specimens of Helicosphaera sellii and Calcidiscus macintyrei observed in these assemblages is particularly poor, suggesting that they may be reworked. The highest occurrences of these two species could not be confidently located in our shipboard study.
An abundance peak of Braarudosphaera bigelowii is recorded at the base of Zone NN19 in Sample 182-1132B-25X-CC (222.91 mbsf). A similar acme of this species from a similar stratigraphic level has also been recorded at other Leg 182 shallow-water sites in both the eastern and western transects (see "Biostratigraphy" in the "Site 1127" chapter, "Biostratigraphy" in the "Site 1130" chapter, and "Biostratigraphy" in the "Site 1131" chapter). This indicates that a brief dramatic change in surface-water conditions occurred over a large area of the Great Australian Bight during the early Pleistocene.
Poorly to moderately preserved assemblages indicating a late Mio-cene age are recorded from Samples 182-1132B-27X-CC and 28X-CC; both sections contain chert nodules. The rare discoasters found in these assemblages are heavily calcified, making species identification uncertain. Only tentative zonal assignment can be made, as zonal assignment in much of the upper Miocene relies on species of Discoaster. The younger assemblage from Sample 182-1132B-27X-CC (241.60 mbsf) is assigned to Zone NN10, on the basis of the tentative identification of Discoaster bellus, Discoaster calcaris, and Discoaster variabilis; the key species for Zones NN9 and NN11. Discoaster hamatus, Discoaster berggrenii, and Discoaster quinqueramus were not found. Other species present include Dictyococcites antarcticus, Calcidiscus macintyrei, C. oamaruensis, Helicosphaera carteri, Helicosphaera rhomba, Reticulofenestra gelida, Reticulofenestra haqii, Reticulofenestra minutula, R. pseudoumbilicus, Sphenolithus abies, Sphenolithus neoabies, Syracosphaera spp., and T. rugosus. Reworking from Paleogene sediments is indicated by the presence of Calcidiscus oamaruensis. The assemblage from Sample 182-1132B-28X-CC (250.73 mbsf) probably belongs to Zone NN9, on the basis of tentative identification of D. hamatus. In addition to the taxa, other than the species of Discoaster, listed above for Zone NN10, the Zone NN9 assemblage contains B. bigelowii, Pontosphaera multipora, and Coccolithus pelagicus, as well as reworked Paleogene taxa (e.g., Dictyococcites bisectus).
The assemblages from Samples 182-1132B-29X-CC (257.43 mbsf) and 182-1132C-3R-CC (255.87 mbsf) to 13R-CC (348.10 mbsf) are readily assignable to the middle Miocene Zone NN6. Key elements of these assemblages include Dictyococcites antarcticus, Calcidiscus leptoporus, Calcidiscus macintyrei, Calcidiscus premacintyrei, Coccolithus miopelagicus, Helicosphaera carteri, Reticulofenestra pseudoumbilicus, and Triquetrorhabdulus rugosus. The index species for the combined Zones NN5-NN4, Sphenolithus heteromorphus, occurs in Samples 182-1132C-14R-CC (357.60 mbsf) to 22R-CC (432.3 mbsf). Calcidiscus premacintyrei ranges down into combined Zones NN5-NN4, together with Dictycoccites antarcticus, Calcidiscus leptoporus, Cyclicargolithus abisectus, Cyclicargolithus floridanus, and R. pseudoumbilicus.
Sample 182-1132C-23R-CC (441.68 mbsf) contains the association of B. bigelowii, C. abisectus, C. floridanus, Helicosphaera euphratis, Sphenolithus dissimilis, and Sphenolithus moriformis, which places it in Zone NN1, of early Miocene age.
Zones NN3-NN2 are missing or condensed in the interval between Samples 182-1132B-22X-CC and 23R-CC. The underlying Sample 182-1132B-24X-CC contains an assemblage assignable to Zone NP23, of early-middle Oligocene age, indicating that Zones NP25 and NP24 are either missing or condensed in the interval between Samples 182-1132B-23X-CC and 24R-CC. Thus, the ~20-m interval (between 432.30 and 450.94 mbsf) containing the lower Miocene Zone NN1 represents a highly condensed section with possible multiple hiatuses (see Fig. F10).
Zone NP23 is based on the assemblages recorded from Samples 182-1132C-24R-CC (450.94 mbsf) to 30R-CC (507.27 mbsf). These assemblages contain B. bigelowii, Clausicoccus fenestratus, Chiasmolithus altus, C. abisectus, C. floridanus, D. bisectus, Helicosphaera obliqua, S. moriformis, and Zygrhablithus bijugatus. The key taxa for Zones NP25, NP24, and the upper part of Zone NP23, Sphenolithus distentus and Sphenolithus ciperoensis, are not present. Although this indicates that the assemblages are assignable to Zone NP23, it does not exclude the possibility of the assemblages being younger than Zone NP23. At Site 1130, S. ciperoensis was recorded within a short interval (see "Biostratigraphy" in the "Site 1130" chapter). The stratigraphic ranges of S. ciperoensis and S. distentus in southern Australia are unlikely to correspond to those in the tropics. Shafik (1990) concluded that the incursions of S. distentus and S. ciperoensis in southern Australia occurred as responses to brief episodes of warm-water influence, brought about by an intermittent proto-Leeuwin Current. A detailed postcruise study will be necessary to determine whether these species occur at Site 1132.
The key species for Zone NP22, Reticulofenestra umbilicus, is recorded from the lowest core-catcher sample obtained from Hole 1132C that contains calcareous nannofossils. The Zone NP22 assemblage in Sample 182-1132C-31R-CC (520.60 mbsf) is similar to those from Zone NP23 above, although without H. obliqua. It contains, in addition, Chias-molithus oamaruensis, Dictyococcites scrippsae, and Micrantholithus entaster.
Planktonic foraminifers indicate that sediments recovered at Site 1132 are of Pleistocene, late Pliocene, middle Miocene, Oligocene, and Eocene age. Except in the upper part of the section (<100 mbsf), planktonic foraminifers are generally poorly preserved because of cementation and recrystallization. Preliminary results indicate that the Pleistocene section extends down to at least 190 mbsf and overlies a succession of probable late Pliocene age (190-240 mbsf). A condensed upper Miocene unit lies unconformably between the Pliocene-Pleistocene section and the underlying middle Miocene sediments. The condensed unit and hiatus represent >6.5 m.y. Mainly middle Miocene assemblages were recorded from the Miocene sediments between 240 and 450 mbsf, suggesting that large parts of the lower and upper Mio-cene are either highly condensed or missing. Further downhole, an Oligocene succession (~440-515 mbsf) overlies disconformably a limestone of middle to late Eocene age, indicating a hiatus of ~1.5 m.y. at the Oligocene/Eocene boundary (Fig. F9).
Planktonic foraminifers are relatively rare from Cores 182-1132B-1H through 7H in sediments dominated by bryozoan debris. Their abundance increases slightly downhole, to ~10% of the >63 µm residue, although preservation deteriorates. Common species include Globorotalia truncatulinoides, Globorotalia inflata, Globigerinoides ruber, Zeaglobigerina rubescens, Globigerina bulloides, Globigerina falconensis, Globigerina quinqueloba, Neogloboquadrina pachyderma, and Orbulina universa. This assemblage occurs down to ~190 mbsf (Core 182-1132B-21X), indicating the Pleistocene Zone Pt1 of Berggren et al. (1995) and SN14 of Jenkins (1993) (Fig. F5, in the "Explanatory Notes" chapter). Globorotalia tosaensis is the species used by Berggren et al. (1995) to subdivide the zone, although its single occurrence in Sample 182-1132B-15H-CC, 14-17 cm (139.2 mbsf), cannot be applied here for a similar purpose. The exceedingly poor preservation makes reliable recognition of the taxon very difficult, and we suspect that we have not found its true last appearance in this section.
The G. truncatulinoides assemblage has been widely documented in Quaternary sediments around the Great Australian Bight as representative of the southern temperate planktonic foraminifer fauna (Almond et al., 1993; Li et al., 1996a, 1996b, in press; Wells and Okada, 1996). Rare specimens of such warm-water taxa as G. trilobus, Globigerinoides quadrilobatus, and Globorotalia menardii were found in Cores 182-1132B-8H, 9H, 14H, and 21X, although not all of them occurred together in a single sample. Their periodic appearances probably reflect warmer climatic conditions and/or stronger flows of the Leeuwin Current (McGowran et al., 1997a).
The Pleistocene/Pliocene boundary in the region has been placed at the first occurrence of G. truncatulinoides (Jenkins, 1993; McGowran et al., 1997b). At Site 1132, this datum level was recorded at 188.6 mbsf (Sample 182-1132B-21X-CC, 28-31 cm). However, whether the sediments across this level are conformable cannot be determined in this shipboard study.
As found previously at Sites 1127, 1130, and 1131, the Pleistocene G. truncatulinoides assemblage was succeeded downhole by an assemblage mainly composed of Globorotalia crassaformis, Globorotalia puncticulata, and Globorotalia crassula. The "G. crassaformis interval" occurred at Site 1132 between 190 and 240 mbsf, in Cores 182-1132B-22X through 26X (Fig. F9). Also present are Globorotalia inflata, Globigerina bulloides, and G. ruber. The assemblage is similar in composition to the upper Pliocene fauna of New Zealand (Hornibrook et al., 1989). Accordingly, we tentatively place this interval in the upper Pliocene.
Poorly preserved planktonic foraminifers indicating a Miocene age were recorded in the interval between 241 and 442 mbsf (Cores 182-1132B-27X through 29X, and 182-1132C-3R through 23R). Except for the lowermost and uppermost samples, this interval is characterized by middle Miocene planktonic foraminiferal assemblages. Sample 182-1132B-27X-CC, 34-37 cm (241.8 mbsf), contains Zeaglobigerina woodi, Jenkinsiana mayeri, and typical specimens of the Globoconella miozea-Globoconella conoidea bioseries, as well as other lower-upper Miocene species. Their association with Globorotalia plesiotumida and Globoco-nella conomiozea suggests the late Miocene rather than middle Miocene because these two taxa did not appear until the middle part of the late Miocene (see Table T4 in the "Explanatory Notes" chapter). The middle Miocene from ~260 to 425 mbsf is indicated by the consistent occurrence of Fohsella peripheroronda, Z. woodi, Globigerinoides trilobus, and Globoquadrina dehiscens. On the basis of the successive occurrences of Zeaglobigerina nepenthes, Zeaglobigerina druryi, Orbulina suturalis, Praeorbulina glomerosa, and Globigerinoides sicanus, Sample 182-1132B-28X-CC, 32-35 cm, was assigned to Zone Mt8; Samples 182-1132B-29X-CC, 23-26 cm, and 182-1132C-3R-CC, 7-8 cm, to Zone Mt7; Sample 182-1132C-15R-CC, 0-2 cm, to Zone Mt6; Sample 182-1132C-20R-CC, 22-25 cm, to Subzone Mt5b; and Samples 182-1132C-21R-CC, 23-26 cm, and 22R-CC, 10-13 cm, to Subzone Mt5a (Fig. F9). A more detailed biostratigraphy for this interval was not possible because of poor recovery (see "Operations"). Further downhole, Sample 182-1132C-23R-CC, 18-21 cm (441.7 mbsf), contains few planktonic foraminifers, although the sparse assemblage does include G. dehiscens, a species first appearing in the early Miocene.
The Miocene planktonic foraminifer biofacies was succeeded at 450.9 mbsf (Sample 182-1132C-24R-CC, 14-17 cm) by assemblages of probable early Oligocene age. This indicates that much of the early Miocene and late Oligocene are either missing or highly condensed.
Unlike those found in the Neogene, the Oligocene assemblages from Cores 182-1132C-24R through 29R are characterized by poorly preserved, small specimens. They mainly include Globorotaloides suteri, Globorotaloides testarugosa, Tenuitella munda, Tenuitella clemenciae, Tenuitellinata juvenilis, Globigerina praebulloides, Globigerina officinalis, and Paragloborotalia opima nana. Their co-occurrence with Globigerina euapertura (in Cores 182-1132C-24R through 27R) and Zeaglobigerina cf. labiacrassata (in Sample 182-1132C-25R-CC, 17-20 cm) suggests a middle Oligocene age (Li et al., 1992). Subbotina angiporoides is common in the interval from 487.9 to 497.6 mbsf (Samples 182-1132C-28R-CC, 20-21 cm, and 29R-CC, 24-26 cm). Berggren (1992) dated the LO of S. angiporoides at ~30 Ma, in the early Oligocene. Its presence indicates an association equivalent to the early Oligocene Zone SP13 of Jenkins (1993) or older. An early Oligocene age, however, appears to be contradicted by the absence of Chiloguembelina cubensis, the most conspicuous Eocene-lower Oligocene species. Chiloguembelina cubensis has been widely recorded in southern middle to high latitudes, including southern Australia (Berggren, 1992; McGowran et al., 1992). It is also common in the lower Oligocene assemblage from Site 1126 (see "Biostratigraphy" in the "Site 1126" chapter). This suggests that a more accurate dating of the Oligocene section at Site 1132 is not possible without detailed postcruise studies.
Sediments of lithostratigraphic Unit VI from 517 to 555.95 mbsf at Site 1132 are assigned to the Eocene (see "Lithostratigraphy"). No planktonic foraminifers were found in the washed core-catcher samples. However, several thin-section samples prepared for lithologic analysis contain middle-upper Eocene assemblages. Although extremely rare, specimens of S. angiporoides-Subbotina linaperta complex were detected in Sample 182-1132C-32R-1, 40-42 cm. In Sample 182-1132C-35R-CC, 45-47 cm, A. collactea, Globigerinatheka? index, and S. linaperta, together indicating a later middle Eocene age, occur in a matrix with numerous benthic foraminifers. This species association has been documented in Eocene sediments from Jerboa-1 in the operational area of Leg 182 (McGowran, 1991) and from the St. Vincent Basin, South Australia (McGowran, 1989, 1990; McGowran et al., 1992).
Benthic foraminifers were studied in all core-catcher samples from Holes 1132B and 1132C. However, poor core recovery below Core 27X in Hole 1132B and throughout Hole 1132C led to an extremely discontinuous faunal record in older sediments. Benthic foraminifers are relatively abundant and well preserved down to Core 182-1132B-21X, although abundance decreases significantly and preservation deteriorates markedly below Core 182-1132B-21X. Between 100 and 300 benthic foraminifers were picked from the >63-µm fraction, except in samples in which abundance was low. The benthic foraminiferal assemblages at Site 1132 include a high proportion of cosmopolitan taxa; however, they probably also contain species with a more geographically restricted distribution. Postcruise studies are needed to fully document benthic foraminiferal distribution at Site 1132 during the Pleistocene and to investigate how faunal changes relate to climate, sea-level, and/or circulation fluctuations within a sequence stratigraphic framework. The following benthic foraminiferal assemblages are recognized in the Cenozoic succession of Site 1132.
This is a diversified, extremely well-preserved assemblage found in samples containing abundant and well-preserved bryozoan fragments. The assemblage includes unusually large specimens (>1 mm) of Bigenerina nodosaria, Hoeglundina elegans, Textularia spp., Cibicidoides spp., and miliolids. Also present are Sphaeroidina bulloides, Sigmoilina obesa, Can-cris auriculus, Martinottiella communis, Uvigerina hispidocostata, Bulimina marginata, Loxostomum spp., Loxostomoides spp., Sigmoilina spp., Tritaxia spp., and Anomalinoides spp. The presence of S. bulloides, H. elegans, B. nodosaria, and B. marginata indicates upper bathyal paleodepths. Similar benthic foraminifer assemblages were found in comparable bryozoan buildups at Sites 1129 and 1131. The assemblages probably represent a diverse, highly dynamic ecosystem that became established at the sea-floor at various times during the Pleistocene, coincident with bryozoan buildup development. Changes in the composition of this assemblage may relate to different stages during growth of bryozoan buildups. Further work on the benthic and planktonic foraminiferal assemblages is likely to provide a record of sea-level, circulation, and surface productivity changes during the growth of these Pleistocene bryozoan buildups.
This assemblage is characterized by fluctuating abundances of U. hispidocostata, Loxostomum spp., Loxostomoides spp., Tritaxia spp., Triloculina spp., Quinqueloculina spp., Spiroloculina spp., Elphidium spp., and Rosalina spp. Also present as rare to few constituents of the assemblage are H. elegans, S. bulloides, Cibicides refulgens, Planulina wuellerstorfi, Spiroloculina spp., Patellina corrugata, Spirillina spp., Cibicidoides spp., Anomalinoides spp., Siphonina spp., and various nodosariids. Upper bathyal paleodepths are suggested by the presence of the depth-indicative species H. elegans, S. bulloides, and U. hispidocostata. Small, sorted specimens (63-150 µm) of Triloculina spp., Spiroloculina spp., Elphidium spp., Quinqueloculina spp., and Patellina spp., typical of inner to middle neritic environments, are also present in variable abundance, indicating that downslope transport periodically varied in intensity during the Pleistocene. The scale and the nature of this cyclicity remains to be determined by high-resolution postcruise studies. Remarkably high numbers of U. hispidocostata, Tritaxia spp., and Loxostomum spp. are found in the lowermost sample (Sample 182-1132B-21X-CC), above an interval in which benthic foraminiferal diversity and abundance are extremely low (Cores 182-1132B-22X through 26X). Their unusual abundance in Sample 182-1132B-21X-CC indicates an enhanced carbon flux to the seafloor after a major oceanographic change. Similar high-productivity assemblages were documented from Holocene sediments off northwest Africa (Lutze and Coulbourne, 1984) and from Cretaceous organic-rich sediments along the West African margin (Holbourn et al., 1999).
This impoverished assemblage is characterized by P. wuellerstorfi, U. hispidocostata, Bolivina spp., Loxostomum spp., and Cibicidoides spp. Calcareous nannofossil assemblages from this interval are dominated by B. bigelowii (see "Calcareous Nannofossils"), suggesting that a major ecological crisis affected the planktonic ecosystem during the late Pliocene. The acme of B. bigelowii occurs in Sample 182-1132B-25X-CC, which is virtually barren of benthic foraminifers. This suggests that the ecological crisis may have affected organisms throughout the water column.
This assemblage is characterized by Cibicidoides mundulus, S. bulloides, Rectuvigerina striata, Heterolepa dutemplei, Hanzawaia ammophila, Laticarinina pauperata, Siphonina tenuicarinata, P. corrugata, Dorothia sp., Elphidium spp., Tritaxia spp., and Rosalina spp. Abundance is generally low and preservation poor in the lower Miocene cores, which recovered mainly hard chert fragments. Higher abundance and improved preservation are recorded in Sample 182-1132B-27X-CC of late Miocene age, which occurs in an interval of bioclastic packstone (see "Lithostratigraphy"). Upper to middle bathyal paleodepths are indicated by the presence of S. bulloides, R. striata, L. pauperata, and S. tenuicarinata. However, this interpretation is tentative as few bathymetric indicators are present in this sparse assemblage.
This assemblage is characterized by numerous, small Trifarina spp. and Bolivina spp. Also present are P. corrugata, H. ammophila, Globocassidulina subglobosa, and S. tenuicarinata. Assemblage 3 is found in a discrete lithostratigraphic unit consisting of bioclastic packstone and grainstone, lacking chert, but with abundant glauconite (see "Lithostratigraphy"). Upper bathyal paleodepths are suggested by the presence of the depth-indicative species H. ammophila, G. subglobosa, and S. tenuicarinata, and by the absence of deeper water indicators.
A marked lithologic change from bioclastic packstone and wackestone to lithified bioclastic packstone and wackestone with prominent firmgrounds, hardgrounds, and solution seams occurs below Core 182-1132C-30R (see "Lithostratigraphy"). Disaggregated samples from this lithostratigraphic unit were barren of benthic foraminifers, except for Sample 182-1132C-31R-CC, which contained a single miliolid test. However, study of thin sections revealed the frequent occurrence of Stilostomella spp., Cibicidoides spp., Bolivina spp., and miliolids in the calcareous cement of the sandy limestone.
Sediment accumulation rates, shown in Fig. F10, were calculated from preliminary biostratigraphic and paleomagnetic results for Site 1132. The biostratigraphic datum levels and relevant paleomagnetic data used to calculate sedimentation rates are listed in Table T2. The placement of the onset of the Brunhes Chron is made with confidence, whereas the placement of the termination of the Jaramillo is tentative (see "Paleomagnetism").
A very high sedimentation rate, between 250 and 260 m/m.y., was determined for the upper part of the Pleistocene section, and a significantly lower rate of 85-95 m/m.y. for the remainder of the Pleistocene and upper Pliocene?. Paleomagnetic data support the lower accumulation rate for the lower Pleistocene section, between 180 and 220 mbsf.
A condensed upper Miocene unit lies between the Pliocene-Pleistocene and middle Miocene sections. A hiatus of 4 m.y. (~1.7-5.8 Ma) is inferred above the condensed unit and a hiatus of 3.5 m.y. (8.3-11.8 Ma) is inferred beneath it. Poor core recovery, however, makes the interpretation uncertain. The middle and lower Miocene sections recorded an average sedimentation rate of 21 m/m.y. A condensed unit of lowest Miocene occurs at 440 m in a condensed unit with hiatuses inferred above and below. Poor core recovery combined with few datum levels obscures the details. Based on the absence of zones, it appears the upper hiatus lasts 5 m.y. from 18.3 to 23.2 Ma, and the lower hiatus may last 4.5 m.y. from 23.9 to 28.5? Ma, spanning the Paleogene/Miocene boundary.