At Site 1266, Pleistocene through upper Paleocene sediments were recovered. Nannofossils are present in all samples, showing generally moderate preservation with reworking and dissolution in the Miocene and reworking in the Pleistocene and in the lower Oligocene through upper Eocene (Fig. F20). Planktonic foraminifers are present, showing moderate to high abundance and variable preservation due to dissolution in the Miocene through the upper lower Eocene and reworking in the lower Pleistocene through upper Eocene (Fig. F20). Benthic foraminifers are rare and have good preservation in the upper (Pliocene–Pleistocene) and lower (lower Eocene–upper Paleocene) parts of the section. Between 33 and 267 mcd (middle Pliocene–upper lower Eocene), benthic foraminifers, large echinoid spines, and ostracodes are reworked and transported downslope from water depths no less than ~600–1500 m. Preservation of foraminifers deteriorates below 336 mcd, with specimens showing infill and some recrystallization.
Shipboard examination of calcareous nannofossils and planktonic foraminifers permitted preliminary zonal and stage assignments (Fig. F20; Tables T5, T6, T7, T8). Biochronological ages plotted against depth (mcd) delineate overall sedimentation rates (Fig. F21) ("Age Model and Mass Accumulation Rates"). Because of the extensive reworking and dissolution, the duration of unconformities is difficult to constrain, but two unconformities are recognized: one between 76 and 79 mcd corresponds to a time interval of at least 1.2 m.y. (upper Miocene), and a second one between 251 and 259 mcd corresponds to the time interval between ~37 and ~47 Ma (a large part of the middle Eocene).
Benthic foraminifers indicate lower abyssal depths (>3000 m) from the late Miocene through the Pleistocene. The paleodepth cannot be ascertained for the middle Miocene through the late Eocene (because of intensive downslope transport) or for the early Eocene. The paleodepth is transitional between upper and lower abyssal (~3000 m) in the latest Paleocene and upper abyssal (<3000 m) during the late Paleocene.
Calcareous nannofossil assemblages were examined in core catcher samples from all holes (Table T6) and in additional samples from Hole 1266A. Depths and age estimates of key biostratigraphic events are shown in Table T5. Nannofossils are abundant to common through the recovered section, and the preservation varies from good to moderate. From Cores 208-1266A-19H through 26H (199–254 mcd), the preservation deteriorates and the assemblages show variable degrees of dissolution and overgrowth. Reworking is present throughout the Miocene–lower Eocene.
Pleistocene nannofossil assemblages are rich and well preserved and contain abundant helicoliths, placoliths of Gephyrocapsa and Calcidiscus, and Rhabdosphaera. Sample 208-1266A-1H-1, 110 cm, contains an upper Pleistocene assemblage of Zone CN14 (NN20). Middle and lower Pleistocene assemblages occur from Samples 208-1266A-1H-3, 110 cm, through 2H-3, 40 cm (7.2–18.9 mcd), and are characterized by the presence of different morphotypes of the genus Gephyrocapsa. The Pliocene/Pleistocene boundary is placed at 18.9 mcd, between the lowermost occurrence (bottom [B]) of medium Gephyrocapsa spp. and the uppermost occurrence (top [T]) of Discoaster brouweri.
Pliocene nannofossils are well preserved, including a diverse Discoaster assemblage. D. brouweri, Discoaster pentaradiatus, Discoaster surculus, Discoaster asymmetricus, Discoaster tamalis, and Discoaster variabilis are common to abundant in the lower Pliocene, and Reticulofenestra pseudoumbilicus, helicoliths, and ceratolithids are common. Assemblages of Subzone CN10c have abundant D. surculus and D. pentaradiatus, common Amaurolithus delicatus, Amaurolithus primus, and rare Ceratholithus rugosus. Very rare ceratolithid specimens belonging to Ceratholithus acutus and Ceratholithus larrymayeri are present between Samples 208-1266A-7H-1, 30 cm, and 7H-2, 130 cm (69.0–71.5 mcd). Both species have short ranges that straddle the Miocene/Pliocene (M/P) boundary (Raffi et al., 1998); therefore, the M/P boundary is placed between Samples 208-1266A-7H-1, 130 cm, and 7H-2, 130 cm, at 70.7 mcd.
Oligocene, Eocene, and Paleocene reworked nannofossils are present throughout the Miocene except for the interval corresponding to upper Miocene Zones CN7 and CN6 (NN9 and NN8) (70.7–94.0 mcd). In the uppermost Miocene assemblages, Discoaster berggrenii and Discoaster quinqueramus, the Zone CN9/CN8 (NN11/NN10) boundary markers, and Discoaster hamatus, the marker for the CN8/CN7 (NN10/NN9) and CN7/CN6 (NN9/NN8) zonal boundaries, are missing. Biostratigraphic classification is based on the presence of secondary markers such as Minylitha convallis and Discoaster bellus gr. Specifically, the range of M. convallis corresponds to Subzone CN9a and Zone CN8, whereas D. bellus gr. appears concomitantly with D. hamatus. We use the presence of M. convallis to define Zone CN8 (NN10) within Core 208-1266A-8H. The Zone CN7/CN6 boundary is defined by the lowermost occurrence of D. bellus gr. between Samples 208-1266A-8H-5, 120 cm, and 8H-6, 120 cm (86.8–88.5 mcd).
The presence of a nannofossil assemblage of Subzone CN9bA (Sample 208-1266A-7H-6, 30 cm; 76.5 mcd), directly above sediments with abundant M. convallis placed in Zone CN8 (Sample 208-1266A-7H-6, 70 cm; 76.9 mcd), indicates that an unconformity is present in the lower part of Core 208-1266A-7H (76–79 mcd), corresponding to a time interval of at least 1.3 m.y. to at most 2.2 m.y. In the middle and lower Miocene, biostratigraphic inversions are associated with turbidites (e.g., in Sections 208-1266A-9H-3, 9H-4, and 9H-5 and within Core 208-1266A-11H [111–129 mcd]). Intense reworking has also hampered the recognition of the biostratigraphic sequence. Assemblages of Subzone CN5a and Zones CN3 and CN2 (NN6, NN4, and NN3) occur in scattered intervals between 93 and 121 mcd. Abundant specimens of Discoaster druggii, the lower Miocene marker for Subzone CN1c (Zone NN2), are present between Samples 208-1266A-11H-6, 60 cm, and 11H-7, 20 cm (119.5–120.6 mcd). The same nannofossil assemblage occurs reworked between Samples 208-1266A-11H-1, 30 cm, and 11H-5, 130 cm (111.4–118.7 mcd), in samples placed in Zone CN2 (NN3) based on the presence of common Sphenolithus belemnos. The presence of Sphenolithus disbelemnos in samples within Sections 208-1266A-13H-1 through 13H-3 (133–139 mcd) and the presence of Sphenolithus delphix and Sphenolithus capricornutus in Sections 208-1266A-13H-7 through 13H-CC (142.4–143.2 mcd) indicate that the Oligocene/Miocene (O/M) boundary is at ~139 mcd.
Oligocene assemblages are present in Sections 208-1266A-13H-CC through 20H-CC (143–219 mcd). In this interval, nannofossils are abundant and preservation varies from good to poor. Reworked lower Eocene species are present in Core 208-1266A-18H. The upper Oligocene yields an assemblage mainly dominated by Dictyococcites bisectus, Cyclicargolithus abisectus, Zygrhablithus bijugatus, and the Discoaster deflandrei group. Sphenolithus ciperoensis and Sphenolithus distentus are rare, and the scarcity of Sphenolithus predistentus prevents the recognition of the base of Zone NP25.
The lower Oligocene zones and all the major nannofossil events that characterize the Eocene–Oligocene transition were recognized in Cores 208-1266A-17H through 19H (176.9–207.8 mcd). The zonal boundaries between Zone CP17 and Subzone CP16c and between Subzones CP16c and CP16b (NP23/NP22/NP21), defined by the uppermost occurrences of Reticulofenestra umbilicus and Ericsonia formosa, are recorded between Samples 208-1266A-19H-2, 30 cm, and 19H-2, 130 cm, and between Sample 19H-7, 75 cm, and Section 19H-CC (207.6–207.8 mcd), respectively. Rare specimens of Isthmolithus recurvus occur in Zones NP22 and NP21. The highest occurrence of Discoaster saipanensis is recorded between Samples 208-1266A-21H-1, 40 cm, and 21H-1, 120 cm (221.0–221.8 mcd) and defines the boundary between Subzone CP16a and Zone CP15 (NP21/NP20). The E/O boundary is thus placed between the bottom of Core 208-1266A-20H and top of Core 208-1266A-21H in a nonrecovered interval.
The uppermost Eocene assemblage consists mainly of I. recurvus, the marker species of Zone NP19, Calcidiscus protoannulus, Bramletteius serraculoides, Discoaster barbadiensis, D. saipanensis, Dictyococcites spp., and Reticulofenestra spp. Unconformities are present at the base of the upper Eocene and in the middle Eocene. A condensed interval in the lower part of Core 208-1266A-24H and the upper part of Core 25H spans part of Zone NP18, based on the closely spaced occurrences of the B of I. recurvus (36.6 Ma; between Sample 208-1266A-24H-1, 45 cm, and Section 24H-CC; 250.8–251.3 mcd) and the T of Chiasmolithus grandis (37.1 Ma; between Section 208-1266A-24H-CC and Sample 25H-1, 15 cm; 251.3–251.8 mcd). An unconformity, spanning ~7 m.y. of Zones CP14–CP13 (NP16–NP15), occurs between Section 208-1266A-26H-CC and Sample 27H-1, 128 cm (254.0–259.2 mcd).
All the lower Eocene zones can be identified (Fig. F20) in Cores 208-1266A-29H through 31X (280.0–306.8 mcd), with the exception of the Zone CP11/CP10 boundary. The marker species of this zonal boundary, Toweius crassus, is present in older sediments within Subzone CP9b and thus is not a reliable marker, as observed at other Leg 208 sites. Preservation is moderate, with partially dissolved and overgrown Discoaster and Tribrachiatus orthostylus. The B of T. orthostylus and Sphenolithus radians in Samples 208-1266A-30X-3, 99 cm, and 30X-4, 40 cm (295.0–295.9 mcd), are used to approximate the base of Subzone CP9b (Zone NP11). The B of Discoaster diastypus (between Samples 208-1266A-30X-4, 102 cm, and 30X-5, 50 cm; 296.5–297.5 mcd), marker of the base of Subzone CP9a, is used to approximate the zonal boundary between Zones NP10 and NP9. The P/E boundary interval occurs between Samples 208-1266A-31X-3, 36 cm, and 31X-3, 38 cm (306.86 mcd). The lowermost occurrences of Rhomboaster cuspis and Rhomboaster calcitrapa (306.49–306.51 mcd) are followed uphole by the decrease in abundance of Fasciculithus (between Samples 208-1266A-31X-3, 3 cm, and 31X-3, 13 cm; 306.16–306.26 mcd). The uppermost occurrences of R. cuspis and R. calcitrapa are observed between Samples 208-1266A-30X-7, 49 cm, and 31X-1, 10 cm (300.6–303.2 mcd).
The upper Paleocene Zones NP9–NP5 (CP8–CP4) are represented in Sections 208-1266A-31X-3 through 34X-CC (306.8–343.9 mcd), 208-1266B-6H-CC through 11X-CC (306.9–358.3 mcd), and 208-1266C-16H-CC through 21X-CC (301.2–379.4 mcd). The nannofossil assemblages are generally diverse and moderately preserved. Common Discoaster multiradiatus and abundant Fasciculithus spp., Toweius spp., Chiasmolithus spp., and Ericsonia spp. characterize Zone NP9 (CP8). The lowermost occurrences of Heliolithus riedelii (Section 208-1266B-11X-CC and Sample 12X-1, 30 cm; 358.3–362.5 mcd), Discoaster mohleri (Samples 12X-2, 12 cm, and 12X-2, 115 cm; 361.5–362.5 mcd), and Heliolithus kleinpellii (Samples 208-1266C-21X-1, 19 cm, and 21X-1, 25 cm; 371.0–371.1 mcd) are recognized, allowing the identification of Zones NP8–NP6. The lowermost occurrence of Sphenolithus anarrhopus occurs in the upper part of Zone NP5 (CP4) between Samples 208-1266C-21X-2, 20 cm, and 21X-2, 25 cm (372.6–372.7 mcd). Reworked Cretaceous specimens occur in Core 208-1266B-11X, Section 12X-CC, Core 208-1266C-20X, and Section 21X-CC.
Planktonic foraminifers were examined in all core catcher samples from Holes 1266A and 1266B and in three additional samples per core in the upper 100 mcd (Tables T7, T8). Generally, planktonic foraminifers are abundant. Preservation varies from good to poor with severe dissolution from 83 mcd (Sample 208-1266A-8H-3, 32–34 cm) to 219 mcd (Section 26X-CC). Several turbidites disrupt the Pliocene and Miocene sequences. Turbidite Sample 208-1266A-3H-6, 49–50 cm (33.0 mcd), is dominated by Globoconella conomiozea, Hirsutella scitula, and rare specimens of Pulleniatina primalis, indicating lower Pliocene to Miocene sediments reworked into the upper Pliocene. Sample 208-1266A-6H-6, 22–23 cm (65.5 mcd), contains Globoconella conoidea, Sphaeroidinellopsis seminulina, H. scitula, Hirsutella cibaoensis, Globigerinoides trilobus, Orbulina universa, and Globoturborotalita nepenthes reworked into sediments of similar age (M/P boundary interval). Reworking is common from 13 mcd (Section 208-1266A-1H-CC) through 245 mcd (Section 22H-CC).
Pleistocene samples show a mixture of well-preserved subtropical and temperate Pleistocene species. The fauna is dominated by Globorotalia crassaformis, Globorotalia truncatulinoides, Globoconella inflata, Globigerina bulloides, Globigerinoides ruber, Globigerinoides sacculifer, Globigerinoides conglobatus, Globigerinella siphonifera, H. scitula, and O. universa. The uppermost appearance of Globorotalia tosaensis is in Section 208-1266A-1H-CC (7.6 mcd). The Pliocene/Pleistocene boundary is between Sample 208-1266A-2H-3, 32–34 cm (uppermost appearance of Globigerinoides extremus), and Section 2H-CC (very rare G. truncatulinoides) (17.4–24.0 mcd). The Pliocene/Pleistocene boundary is placed at 19 mcd using calcareous nannofossil data.
As reported at other sites, Pliocene tropical/subtropical age-diagnostic taxa are missing because the environmental conditions are temperate. Globoconella crassaformis, G. conomiozea, G. conoidea, H. scitula, and G. inflata dominate the assemblage. Although warm water species are generally rare, G. ruber and G. sacculifer are present. The absence of Menardella miocenica prevents the definition of the base of Zone PL6, which was approximated by the uppermost appearance of Globoturborotalia woodi between Samples 208-1266A-3H-1, 32–34 cm (25.3 mcd), and 3H-3, 32–34 cm (26.8 mcd). The middle to upper Pliocene boundary is placed between Samples 208-1266A-3H-1, 32–34 cm, and 3H-3, 32–34 cm (25.3–28.3 mcd), constrained by the uppermost appearances of G. woodi (2.3 Ma) and Globigerina decoraperta (2.7 Ma).
It is impossible to distinguish Zones PL4 and PL3 because the uppermost appearances of S. seminulina (base of Zone PL4) and Neogloboquadrina acostaensis (base of Zone PL3) are both present between Samples 208-1266A-4H-1, 32–34 cm (36.2 mcd), and 4H-3, 32–34 cm (39.2 mcd).
The lower to middle Pliocene boundary, as bracketed by the uppermost occurrences of S. seminula and N. acostaensis, is between Samples 208-1266A-4H-1, 32–34 cm, and 4H-3, 32–34 cm (36.2 and 39.2 mcd). The Miocene/Pliocene boundary is placed between Samples 208-1266A-6H-5, 32–34 cm (64.1 mcd), and 7H-3, 32–34 cm (72.0 mcd) (lowermost occurrences of Sphaeroidinella dehiscens and G. conglobatus).
G. conoidea, G. conomiozea, Globoconella miozea, Globigerina apertura, Hirsutella praescitula, and G. nepenthes are typical and frequent species in the Miocene. The preservation deteriorates downhole from Sample 208-1266A-8H-3, 32–34 cm (83 mcd). Fragmentation is severe so that dissolution-resistant species such as G. nepenthes, Globoquadrina dehiscens, Dentoglobigerina altispira, and G. conoidea dominate these assemblages. The close proximity of the lowermost occurrences of G. conglobatus (between Samples 208-1266A-7H-1, 32–34 cm, and 7H-3, 32–34 cm) and Hirsutella juanai (between Sample 7H-5, 32–34 cm, and Section 7H-CC) to each other (i.e., <6.3 m) indicates an unconformity in this core as corroborated by the sharp boundary between lithostratigraphic Units I and II (76.85 mcd). The common uppermost appearance of Globorotalia plesiotumida (8.91 Ma) and H. juanai (9.75 Ma) in the same sample corroborate this observation.
The well-preserved planktonic foraminiferal shells in Sections 208-1266A-7H-CC and 208-1266C-1H-CC and 208-1266A-8H-CC and 208-1266C-2H-CC are assigned to Subzone M13a and Zones M11–M12, respectively. The age determination of this section in Holes 1266A and 1266C is tentative because of dissolution and reworking. The reworked material is mainly Oligocene and Eocene in origin (i.e., acarininids, Pseudohastigerina spp., and globigerinids). The presence of D. altispira and Globoquadrina globularis in Section 208-1266A-9H-CC (99.2 mcd) restricts the age to early Miocene, but strong reworking makes this age assignment unreliable, particularly because the moderately well preserved assemblage lacks the dissolution-resistant taxon G. dehiscens, which is usually common in the lower Miocene at the Walvis Ridge sites. Section 208-1266A-10H-CC (109.8 mcd) contains rare planktonic foraminifers because of poor preservation, and the assemblage appears to be associated with the O/M boundary interval. A more detailed determination of this boundary is impossible because of the severe dissolution in Sections 208-1266A-10H-CC (109.8 mcd) through 13H-CC (143.2 mcd) and 208-1266C-8H-CC and 9H-CC (152.2 to 162.5 mcd). The uppermost appearance of Globigerina euapertura between Sections 208-1266A-12H-CC and 13H-CC points to the presence of the O/M boundary in Core 208-1266A-13H.
Dissolution and reworking of Eocene species are common in the interval, and planktonic foraminifers are rare in most samples. Upper Oligocene Sections 208-1266A-13H-CC through 16H-CC (143.2–176.0 mcd) are dominated by dissolution-resistant species such as Globigerina venezuelana, Dentoglobigerina globularis, Globigerina tripartita, and Catapsydrax dissimilis. The uppermost appearances of Paragloborotalia opima (141.9–164.8 mcd), Chiloguembelina cubensis (common) (176.0–186.2 mcd), and "Globigerina" ampliapertura (186.2–191.9 mcd) represent the few datums recognized in this sequence.
Section 208-1266A-17H-CC (186.2 mcd) is barren. Section 208-1266A-18H-CC (197.6 mcd) represents a massively reworked upper Eocene "Globigerinatheka sand" (Globigerinatheka subconglobata and Globigerinatheka index) with Morozovella caucasica (P10–P8) and Eocene acarininids. The uppermost common appearances of Subbotina angioporoides (30 Ma) and Pseudohastigerina spp. (32 Ma) in Section 208-1266A-20H-CC (219.3 mcd) indicate severe reworking in Zone P20 and the lower part of Zone P19 (lowermost Oligocene).
The uppermost clearly Eocene assemblage occurs in Section 208-1266A-21H-CC (230.6 mcd). The low-diversity assemblage, consisting mainly of G. index and G. subconglobata, is a product of dissolution and winnowing. Varying preservation and downhole contamination make age determination difficult in Sections 208-1266A-21H-CC to 26X-CC. Section 208-1266A-22H-CC (241.6 mcd) is assigned to Zones P12–P15 because G. index and Morozovella spinulosa are present. Section 208-1266A-23H-CC (249.4 mcd) is a Globigerinatheka sand.
Section 208-1266A-24H-CC (251.3 mcd) is tentatively assigned to Zone P12 because of the presence of G. index, Globigerinatheka subconglobata luterbacheri, Turborotalia centralis, Turborotalia pomeroli, Turborotalia possagnoensis, and the absence of acarininids and morozovellids. The co-occurrence of Globigerinatheka and Acarinina primitiva in Section 208-1266A-25H-CC (252.7 mcd) indicates an age range of Zones P12–P14 for this sample. The close proximity of the T of Morozovella aragonensis (43.6 Ma; base of Zone P12) and Morozovella formosa (50.8 Ma; base of Zone P8) within 12 m points toward an unconformity between 254.4 and 270.5 mcd (between Sections 208-1266A-26X-CC and 208-1266B-3X-CC).
Overall preservation improves from Sections 208-1266B-2X-CC and 208-1266A-27X-CC (262.6–267.3 mcd) downhole. Zone P8 through Subzone P6a are all represented. Sections 208-1266A-28X-CC (275.1 mcd) and 208-1266B-3X-CC (273.6 mcd) contain well-preserved lower Eocene assemblages with A. primitiva, Acarinina spinuloinflata, Acarinina angulosa, Morozovella lensiformis, M. formosa, and Morozovella quetra.
Section 208-1266A-30X-CC (300.6 mcd) contains a diverse, well-preserved assemblage that contains common biserial planktonic taxa and is assigned to Zone P5. Preservation is good within the lowermost Eocene but deteriorates downhole toward the P/E boundary. Samples 208-1266B-6H-7, 100 cm, through 6H-CC bracket the clay layer that marks the P/E boundary at ~306.84 mcd. Assemblages within this clay layer have suffered severe dissolution and contain mostly foraminiferal fragments and few whole specimens. Section 208-1266B-6H-CC (306.86 mcd), just below the clay layer, contains a well-preserved, diverse assemblage. This Zone P5 assemblage consists of A. soldadoensis, Acarinina coalingensis, Morozovella velascoensis, M. acuta, Morozovella subbotinae, Morozovella aequa, Morozovella occlusa, Globanomalina planoconica, and assorted subbotinid species. No "excursion taxa" were identified within the P/E boundary interval assemblages.
The upper Paleocene is represented in Sections 208-1266A-31X-CC through 34X-CC (308.4–343.9 mcd), 208-1266B-6H-CC through 11X-CC (306.86–358.28), and 208-1266C-16H-CC through 21X-CC (301.2–379.4 mcd). As at the other Leg 208 sites, M. velascoensis is rare in Zone P5. Typical species are A. soldadoensis, M. aequa, M. occlusa, Morozovella angulata, M. subbotinae, Subbotina triangularis, and Subbotina velascoensis.
Sections 208-1266A-32X-CC (321.1 mcd) through 208-1266C-20X-CC (367.2 mcd) can be assigned to Zone P4. The assemblages are dominated by M. acuta, M. angulata, A. aequa, M. occlusa, Igorina tadjikstanensis, and Globanomalina pseudomenardii. The lowermost recovered subzone is P3b in Section 208-1266C-21X-CC (379.4 mcd). Primary faunal elements of Section 208-1266C-21X-CC include Globanomalina ehrenbergi, Globanomalina chapmani, Morozovella acutispira, M. angulata, Morozovella conicotruncata, Acarinina nitida, I. tadjikstanensis, and various species belonging to the spinose genera Subbotina and Parasubbotina.
All core catcher samples from Holes 1266A and 1266B, Sections 208-1266C-15X-CC through 21X-CC, the mudline sample, and samples across the P/E boundary in Hole 1266B were semiquantitatively investigated for benthic foraminifers (Table T9).
In samples above 33 mbsf and below 267 mcd, benthic foraminifers are rare compared to planktonic foraminifers and are generally well preserved, with the exception of a few samples from the lowermost Eocene (306–307 mcd), where assemblages have suffered strong dissolution and benthic foraminifers are more common relative to planktonic foraminifers. Benthic foraminifers are common and even abundant in many samples between 33 and 267 mcd (Sample 208-1266A-3H-6, 49–50 cm, and Section 27X-CC) (Table T9). In these samples, preservation is extremely variable (good to poor). Delicate thin-walled specimens have good preservation, whereas very large thick-walled specimens are broken and/or abraded. Benthic faunas indicate downslope transport from depths that are not shallower than middle to lower bathyal (~600–1500 m).
Typical indicators of downslope transport in benthic foraminiferal assemblages throughout this interval are abundant large siphonodosariid species (e.g., Siphonodosaria pomuligera), large nodosariids, and large specimens of Oridorsalis umbonatus, Globocassidulina subglobosa, and Vulvulina spinosa. Large and broken abraded specimens of Cibicidoides species, which were not otherwise observed or rare at Leg 208 sites (e.g., Cibicidoides havanensis, Cibicidoides grimsdalei, and Cibicidoides eocaenus), are common in samples between 99 and 267 mcd (Sections 208-1266A-9H-CC and 208-1266B-2X-CC). Plectofrondicularia paucicostata (Table T9), recorded as Plectofrondicularia lirata in the upper Eocene at several South Atlantic DSDP sites to the east and west of the Mid-Atlantic Ridge (Tjalsma, 1983; Clark and Wright, 1984), occurs in samples between 198 and 242 mcd (Sections 208-1266A-18H-CC and 22H-CC) and is abundant in the latter sample.
Benthic foraminiferal assemblages between 0 and 109 mcd (Sample 208-1266B-1H-1, 0–2 cm, through Section 208-1266C-4H-CC) indicate deposition at lower abyssal depths (>3000 m). Paleodepths cannot be determined for samples between 121 and 267 mcd (Sections 208-1266A-11H-CC through 208-1266B-2X-CC) because of extensive downslope transport. Paleodepths cannot be estimated for samples between 274 and 307 mcd (Section 208-1266B-3X-CC through Sample 6H-CC, 6–7 cm) because benthic foraminifers are not reliable depth indicators in the lower Eocene (Müller-Merz and Oberhänsli, 1991). Sample 208-1266B-6H-CC, 22–23 cm (306.82 mcd), is barren. Samples from 307 through 348 mcd (Sample 208-1266B-6H-CC, 26–27 cm, through Section 10X-CC; upper Paleocene) were deposited at depths transitional between upper and lower abyssal (~3000 m), and samples between 358 mcd and the bottom of the hole (379 mcd) were deposited at upper abyssal depths (2000–3000 m).
Benthic foraminiferal assemblages between 0 and 3 mcd (Samples 208-1266B-1H-1, 0–2 cm, and 1H-3, 148–150 cm) contain assemblages with common Epistominella exigua, Alabaminella weddellensis, G. subglobosa, Cibicidoides wuellerstorfi, Cibicidoides mundulus, O. umbonatus, and Pyrgo spp., along with the Uvigerina peregrina group, Pullenia spp., and Nuttallides umbonifera. These samples do not contain pleurostomellid and siphonodosariid species and were probably deposited after the "Stilostomella extinction" at 0.65 Ma (Hayward, 2002). At present, similar assemblages occur along Walvis Ridge between ~2000 and 3800 m (Schmiedl et al., 1997). The common occurrence of E. exigua indicates seasonally fluctuating primary productivity in the overlying waters.
Samples between 7 and 89 mcd (Sections 208-1266B-1H-CC through 208-1266A-8H-CC) resemble those in the upper samples but lack common E. exigua and contain pleurostomellid and siphonodosariid species in addition to those listed above (Table T9). In these samples, the relative abundances of N. umbonifera, Uvigerina spp., and Melonis spp. fluctuate strongly, possibly indicating fluctuations in surface productivity and bottom water mass characteristics. These faunas resemble those living at depths between 2600 and 4000 m presently in the Walvis Ridge area (Schmiedl et al., 1997). C. wuellerstorfi and Pyrgo spp. have their joint lowest occurrences in Section 208-1266A-8H-CC (89 mcd).
Between 99 and 219 mcd, in situ components of the assemblages include long-lived species such as Gyroidinoides spp., O. umbonatus, G. subglobosa, Bolivinoides huneri, Pullenia spp., N. umbonifera, and common Siphonodosaria spp. and pleurostomellid and unilocular taxa. The transition between Cibicidoides praemundulus and C. mundulus occurs in this interval, and Anomalinoides spissiformis and Nonion havanense have their highest occurrence. Bigenerina nodosaria and Astronion pusillum have their lowest occurrence in Section 208-1266A-20H-CC (219 mcd) at the base of this interval. Reworked components include S. pomuligera, Siphonodosaria hispidula, various large nodosariid and orthomorphinid species, Clavulinoides spp., V. spinosa, C. havanensis, and C. grimsdalei.
Nuttallides truempyi has its uppermost, nonreworked occurrence in Section 208-1266A-21H-CC (231 mcd). Samples between 231 and 267 mcd (Sections 208-1266A-21H-CC through 27H-CC) contain typical species-rich abyssal middle–upper Eocene assemblages, with abundant N. truempyi, C. praemundulus, C. grimsdalei, O. umbonatus, Gyroidinoides spp., A. spissiformis, N. havanense, and common Siphonodosaria spp., as well as unilocular, laevidentalinid, and pleurostomellid taxa. Reworked components are as in the interval described above (Table T9).
Section 208-1266B-3X-CC through Sample 6H-CC, 6–7 cm (274–307 mcd), contain assemblages that are less species rich, as is typical for the lower Eocene in the South Atlantic over a large depth range (Clark and Wright, 1984; Müller-Merz and Oberhänsli, 1991; Thomas and Shackleton, 1996). These assemblages are characterized by the presence of Aragonia aragonensis and common to abundant small smooth-walled species of Abyssamina and Clinapertina, small smooth-walled buliminid species (e.g., Bulimina kugleri and Bulimina simplex), and small specimens of N. truempyi, O. umbonatus, A. spissiformis, and N. havanense. Tappanina selmensis and Siphogenerinoides brevispinosa vary strongly in relative abundance, and unilocular, laevidentalinid, and pleurostomellid taxa are present. A sample in a relatively clay rich interval at 293 mcd (Sample 208-1266A-30X-2, 56–57 cm) contains an assemblage with a relatively low species richness and common to abundant Clinapertina and Abyssamina spp.
In the lowermost part of this interval (306.10–306.66 mcd; Samples 208-1266B-6H-7, 100–101 cm, through 6H-CC, 6–7 cm), species richness is extremely low and long-lived unilocular and laevidentalinid taxa are absent. Similar assemblages have been described from immediately after the P/E benthic foraminiferal extinction event (BEE) (Müller-Merz and Oberhänsli, 1991; Thomas and Shackleton, 1996) and occur at other Leg 208 sites. Minute specimens of Abyssamina quadrata, B. kugleri, Clinapertina inflata, Quadrimorphina profunda, and small specimens of O. umbonatus and N. truempyi are common to abundant. The latter two species dominate most samples, but the lowermost sample is dominated by A. quadrata and B. kugleri.
The BEE occurs between Samples 208-1266B-6H-CC, 22–23 cm, and 6H-CC, 26–27 cm (306.82 and 306.86 mcd), Sample 208-1266A-31X-3, 0–2 cm, and Section 1X-CC (306.13 and 308.39 mcd), and Sections 208-1266C-16H-CC and 17H-CC (301.24 and 313.54 mcd). One sample (208-1266B-6H-CC, 22–23 cm; 306.82 mcd), immediately above the lithologic contact of clay-rich material over carbonate-rich material, is barren.
Samples below the BEE through Section 208-1266B-10X-CC (307–348 mbsf) contain species-rich Paleocene assemblages with Stensioeina beccariiformis, Paralabamina lunata, Paralabamina hillebrandti, Pullenia coryelli, large thick-walled species of Gyroidinoides such as Gyroidinoides beisseli and Gyroidinoides globosa, and large agglutinant taxa (e.g., Clavulinoides spp., Marssonella oxycona, and Gaudryina pyramidata), as well as relatively common Aragonia velascoensis. As at Site 1262, but not at Sites 1263 and 1265, these assemblages are characterized by strongly fluctuating relative abundances of S. brevispinosa, Bulimina thanetensis, and Rectobulimina carpentierae.
Several species commonly thought to be lower bathyal indicators (e.g., Alabamina creta, Bolivinoides delicatulus, and Coryphostoma midwayensis) have rare and scattered occurrences in this interval, but the relative abundances of various agglutinated taxa, Abyssamina spp., and A. velascoensis indicate a paleodepth transitional between upper and lower abyssal (~3000 m).
Assemblages between 358 mcd and the bottom of the hole (Sections 208-1266B-11X-CC through 208-1266C-21X-CC) resemble those between the BEE and 348 mcd but have much more even species distributions. These samples have less common Abyssamina spp. and more common S. beccariiformis, Bulimina velascoensis, large Gyroidinoides spp., and A. velascoensis, indicating deposition at upper abyssal depths (between 2000 and 3000 m).