At Site 1265, Pleistocene through upper Paleocene sediments were recovered. Nannofossils are present in all samples with generally moderate preservation, and reworking occurs in lower Miocene, lower Oligocene, and upper and middle Eocene samples (Fig. F24). Planktonic foraminifers are present at moderate to high abundances with variable preservation. In the lower Miocene through middle Eocene, reworking is common and preservation is moderate to poor, particularly in lowermost Oligocene through middle Eocene samples (Fig. F24). Benthic foraminifers are rare and have good preservation in the upper and lower part of the section; between 43 and 257 mcd (upper Miocene through uppermost lower Eocene), they are common to abundant and have variable preservation because of extensive downslope transport and reworking. Samples from this interval contain common large ostracods and common to abundant echinoid spines.
Examination of calcareous nannofossils and planktonic foraminifers permitted preliminary zonal and stage assignments (Fig. F24; Tables T5, T6, T7, T8). Biochronological ages plotted against depth (mcd) delineate overall sedimentation rates (Fig. F25) (see "Age Model and Mass Accumulation Rates"). Unconformities are present at the Miocene/Pliocene boundary and in the middle Eocene, but the lower Eocene through upper Paleocene section appears to be complete at shipboard biostratigraphic resolution. Benthic foraminifers indicate upper abyssal depths (2000–3000 m) from the middle Eocene through the Pleistocene. The paleodepth could not be ascertained for the early Eocene and was lower bathyal (~1500–2000 m) during the late Paleocene.
Calcareous nannofossil assemblages were examined in core catcher samples from all holes and from additional samples within cores from Hole 1265A (Table T5). Depths and age estimates of key biostratigraphic events are shown in Table T6. Nannofossils are abundant to common through the recovered section and have varying preservation. The Pliocene–Pleistocene assemblages in Cores 208-1265A-1H through 3H and 208-1265B-1H through 3H consist of abundant nannofossils with good preservation. From Core 208-1265A-4H to the bottom of the hole, nannofossil preservation deteriorates and the assemblages show variable degrees of dissolution and overgrowth.
The Pliocene/Pleistocene boundary is placed at 8.5 mcd, between the lowermost occurrence (B) of medium Gephyrocapsa spp. and uppermost occurrence (T) of Discoaster brouweri. Sample 208-1265C-1H-1, 1 cm, contains an upper Pleistocene assemblage of Zone CN14 (NN20). Section 208-1265A-1H-CC contains an upper Pliocene assemblage of Subzone CN12d (NN18). Sections 208-1265A-2H-CC and 3H-CC are placed in lower Pliocene Zone CN11 and Subzone CN10c, respectively. The presence of the upper Miocene ceratolith Nicklithus amplificus in Sample 208-1265A-4H-1, 15 cm, indicates that the Miocene/Pliocene boundary is at ~32.7 mcd within an unconformity spanning a time interval of at least 0.9 m.y. and corresponds to Subzones CN10b through CN9bC.
Within Core 208-1265A-4H, assemblages of some of the Miocene Subzones CN9bB through CN1c (NN11 through NN2) were observed. From 54 to 85 mcd, the regular biostratigraphic succession is disturbed by numerous turbidite layers and intense reworking of lower Miocene and Eocene nannofossils into the middle Miocene assemblages (e.g., in samples from Section 208-1265A-6H-6 and Cores 208-1265A-8H and 7H). From 76 to 128 mcd, the nannofossil assemblages are partially dissolved but contain the lower Miocene biostratigraphic markers Sphenolithus belemnos in Core 208-1265A-9H and Sphenolithus disbelemnos in Cores 208-1265A-11H and 12H, respectively. Abundant placoliths (Cyclicargolithus spp.) and strongly overgrown discoasterids, probably belonging to Discoaster deflandrei gr., are also present. Other lower Miocene markers such as Discoaster druggii and Triquetrorhabdulus carinatus are absent or very rare. The assemblages in this interval do not show intense reworking. The presence of S. disbelemnos in Sections 208-1265A-10H-CC and 11H-CC (107.3–118.6 mcd) and the range of Sphenolithus delphix from Section 208-1265A-12H-CC through Sample 208-1265A-13H-1, 70 cm (129.1–130.6 mcd), and in Core 208-1265B-13H indicate that the O/M boundary is at ~129 mcd.
Sample 208-1265A-12H-CC through Core 208-1265A-18H are Oligocene, with sediments in the interval from Section 208-1265A-12H-CC through Sample 15H-5, 70 cm, representing the upper Oligocene Subzone CN1a+b and Zone CP19 (NN1–NP24), as indicated by the presence of Sphenolithus ciperoensis and Sphenolithus distentus. Lower Oligocene Zones CP18, CP17, and CP16 (NP23–NP21) were recognized in the interval from Sample 208-1265A-15H-5, 137 cm, through Section 18H-CC. Major components of the assemblages are Dictyococcites spp., Sphenolithus predistentus, Sphenolithus moriformis, Zygrhablithus bijugatus, and Cyclicargolithus spp., with reworked upper Eocene forms. A nannofossil assemblage with abundant Braarudosphaera bigelowii occurs in discrete layers in Sections 208-1265A-15H-2, 15H-4, and 15H-6 (154.9, 157.6, and 161.0 mcd, respectively). Similar "Braarudosphaera layers" occur in coeval sediments in the upper part of Zone CP18 (NP23) at Site 1264.
The major nannofossil events that characterize the Eocene–Oligocene transition were recognized in Cores 208-1265A-18H through the uppermost part of 19H, with the biostratigraphic signal partially blurred by reworking of lower Eocene nannofossils. The boundary between Subzones CP16c and CP16b (NP22/NP21), the T of Ericsonia formosa, is distinct. Rare specimens of Isthmolithus recurvus occur in Zones NP22 and NP21. The highest occurrence of Discoaster saipanensis defines the boundary between Subzone CP16a and Zone CP15 (NP21/NP20) and is recorded between Section 208-1265A-18H-CC and Sample 19H-1, 30 cm, whereas the highest occurrence of Discoaster barbadiensis was difficult to locate because the species is rare and occurs discontinuously. The highest occurrence of D. saipanensis places sediments below ~190 mcd in the uppermost Eocene.
Major components of the diverse Eocene assemblages in Cores 208-1265A-20H through 29H are Chiasmolithus spp., Coccolithus eopelagicus, Dictyococcites spp., Discoaster spp., Ericsonia spp., Reticulofenestra umbilicus, Reticulofenestra dictyoda, Sphenolithus spp., and Z. bijugatus. Dissolution and overgrowth of Discoaster specimens are common and hamper the identification of taxa in some samples. Unconformities are present in the middle Eocene. One unconformity representing at least 3.2 m.y. occurs in Core 208-1265A-20H because the T of Chiasmolithus grandis (37.1 Ma) occurs in Section 208-1265A-20H-3, and the B of Dictyococcites bisectus (38.5 Ma) and the B of Dictyococcites scrippsae (40.3 Ma) both occur in Section 208-1265A-20H-4. Another unconformity, spanning ~7 m.y. of Zones CP14–CP13 (NP16–NP15), occurs in Core 208-1265A-21H between 216.0 and 224.9 mcd.
The lower Eocene zonal boundaries could be recognized (Fig. F24) in Cores 208-1265A-22H through 29H, with the exception of the Zone CP11/CP10 boundary. The marker species of this 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. Lower Eocene assemblages have moderate preservation, consistent reworking of Paleocene taxa, and are dominated by overgrown specimens of Tribrachiatus orthostylus, Sphenolithus radians, Z. bijugatus, and discoasters (e.g., Discoaster lodoensis, Discoaster diastypus, and Discoaster multiradiatus).
As at other Leg 208 sites, the nannofossil assemblage at the Paleocene–Eocene transition is characterized by common specimens of Rhomboaster cuspis and Rhomboaster calcitrapa, which provide a distinct nannofossil biostratigraphic signal. Poorly preserved specimens of the Rhomboaster–Tribrachiatus plexus that precede the lowest occurrence of the lowermost Eocene marker T. orthostylus have rare and scattered occurrences in Cores 208-1265A-26H through 29H and are often difficult to recognize because of overgrowth; therefore, they cannot be used to confidently define the boundaries between Subzones CP9b and CP9a (NP11/NP10) and Subzone CP9a and Zone CP8 (NP10/NP9). The lowest occurrence of S. radians in Section 208-1265A-26H-2 (~275.5 mcd) and the lowest occurrence of D. diastypus, the marker of the base of Subzone CP9a in Sections 208-1265A-27H-5 and 27H-6 (~292 mcd), have been used to approximate the boundaries between Subzones CP9b and CP9a (NP11/NP10) and Subzone CP9a and Zone CP8 (NP10/NP9). In the sediments just above the benthic extinction event (BEE) (Sections 208-1265A-27X-2 through 34X-1), the genus Fasciculithus shows a distinct distribution pattern in the uppermost part of its range, with a decrease in relative abundance (between Samples 208-1265A-29H-6, 100 cm, and 29H-7, 15 cm) coincident with an increase in relative abundance of Z. bijugatus just above the BEE, as also observed at Site 1262. The highest occurrence of the genus Fasciculithus is within Section 208-1265A-29H-3.
Paleocene assemblages placed in Zones NP9 and NP8 (CP8 and CP7) are present in the lower part of the record at Site 1265 (Cores 208-1265A-30X through 36X and 208-1265C-5X). The assemblages are generally diverse and moderately preserved and consist mainly of common Discoaster taxa (D. multiradiatus, Discoaster nobilis, and Discoaster mohleri) and Toweius spp., Coccolithus pelagicus, Prinsius spp., Chiasmolithus spp., Cruciplacolithus spp., and Ericsonia spp. Reworked Cretaceous specimens occur in Core 208-1265A-36X. The lowest occurrence of D. multiradiatus, the marker of the base of Zone NP9 (CP8), is between Sample 208-1265A-34X-3, 70 cm, and Section 34X-CC (~340.2 mcd).
Planktonic foraminifers are abundant and generally well preserved in core catcher samples throughout much of the Neogene, but reworking and downslope transport of older microfossils is commonplace in assemblages from the Pliocene through the middle Eocene. Preservation in the Paleogene is highly variable, with middle Eocene through lower Oligocene assemblages exhibiting marked dissolution. Upper Paleocene assemblages from the lowermost part of the section display signs of diagenesis.
Core depths for biochronological datums are reported in Table T7 and incorporated in Figure F25; additional samples from Core 208-1265A-29H were studied through the P/E boundary interval. Shipboard examination of assemblages permitted preliminary determination of the stratigraphic ranges for many Cenozoic planktonic foraminifers (Table T8).
Section 208-1265A-1H-CC (11.1 mcd) contains a typical Pleistocene temperate water fauna. Common species are Globorotalia crassaformis, Globorotalia truncatulinoides, Globorotalia tumida, Globoconella inflata, Globigerinoides ruber, Globigerinoides sacculifer, Globigerinella siphonifera, Hirsutella scitula, and Neogloboquadrina pachyderma (dextral). The Pliocene/Pleistocene boundary, as approximated by the base of Subzone PT1a (2.03 Ma), is placed between Sections 208-1265A-1H-CC (11.1 mcd) and 208-1265B-2H-CC (16.1 mcd) at a depth of ~13.6 mcd.
The presence of Hirsutella margaritae and the absence of Globigerina nepenthes indicate that Section 208-1265A-2H-CC (21.3 mcd) belongs to Zone PL2 (3.88–4.37 Ma). Other taxa common in Section 208-1265A-2H-CC are Dentoglobigerina altispira, Sphaeroidinellopsis spp., Globorotalia tosaensis, G. sacculifer, Globigerinoides extremus, Globigerina bulloides, Orbulina universa, G. inflata, and Globoconella conomiozea. Thus, the upper Pliocene (Zones PL3–PL6) is either confined to a condensed interval within Core 208-1265A-2H or is missing.
The uppermost occurrence of G. nepenthes (4.37 Ma) is between Sections 208-1265A-2H-CC and 3H-CC at ~26.6 mcd. The presence of Hirsutella cibaoensis, Globorotalia plesiotumida, and G. extremus and the absence of Globorotalia lenguaensis restricts Section 208-1265A-3H-CC (31.9 mcd) to Zones PL1/M14 (4.37–6.0 Ma). Unfortunately, the biostratigraphic position (Section 208-1265A-3H-CC) could not be further refined because of the scarcity of the marker G. tumida and the elimination of Subzone PL1a (Lourens et al., in press).
Section 208-1265A-4H-CC (42.5 mcd) is ascribed to Subzone M13a based on the presence of Neogloboquadrina acostaensis and G. lenguanensis, and the absence of both G. extremus and G. plesiotumida, restricting the age of Section 208-1265A-4H-CC to 8.49–9.89 Ma. The co-occurrence of Paragloborotalia siakensis and G. nepenthes indicates that Section 208-1265A-5H-CC (54.32 mcd) is older than 10.7 Ma but younger than 11.64 Ma. Thus, Section 208-1265A-5H-CC is assigned to Zone M11 of the middle Miocene.
The lowermost occurrence of Fohsella peripheroacuta (14.02 Ma) is between Sections 208-1265A-6H-CC and 7H-CC at ~70.0 mcd. The presence of F. peripheroacuta, Fohsella peripheroronda, Menardella praemenardii, Orbulina spp., Sphaeroidellopsis spp., Globigerina woodi, and Globoconella miozea indicates that Section 208-1265A-6H-CC belongs to Zone M7. Section 208-1265A-7H-CC (~75.0 mcd) is below the lowermost occurrence of Orbulina spp. but above the B of Praeorbulina glomerosa and is assigned to Subzone M5b (14.7–16.2 Ma). Globigerinoides sicanus occurs in Section 208-1265A-8H-CC (85.74 mcd), and its descendant taxa (P. glomerosa and Orbulina suturalis) are absent. This sample is therefore assigned to Subzone M5a, and the B of G. sicanus is between Sections 208-1265A-8H-CC and 9H-CC at ~91 mcd, but the middle Miocene (Subzone M5a through Zone M12) sequence in Cores 208-1265A-6H through 9H contains slumps, making age assignments difficult.
Specimens referable to Catapsydrax dissimilis are present in Section 208-1265A-9H-CC, suggesting that its uppermost occurrence (17.51 Ma) is at ~91 mcd. The overall absence of the marker Globigerinatella insueta from Site 1265 precludes differentiation of Zones M2 and M3, but the presence of Globoquadrina binaiensis (19.08–19.98 Ma) corroborates assigning Section 208-1265A-9H-CC to Zone M2. The apparent juxtaposition of Subzone M5a and Zone M2 at ~91 mcd suggests that the section within Core 208-1265A-9H is condensed. The co-occurrence of Globoquadrina dehiscens and Paragloborotalia kugleri in Sections 208-1265A-10H-CC (107.27 mcd) and 11H-CC (118.63 mcd) places them in Subzone M1b (21.03–21.44 Ma).
The O/M boundary interval includes the lowermost subzone of the Miocene (M1a) and the uppermost zone of the Oligocene (P22). Section 208-1265A-11H-CC is assigned to Subzone M1a based on the presence of P. kugleri and the absence of G. dehiscens. This sample, however, displays extensive reworking as evidenced by the presence of lower Eocene morozovellids. The extreme scarcity of P. kugleri in Section 208-1265A-12H-CC is a strong indication that the O/M boundary is near this sample at ~129 mcd, in agreement with calcareous nannofossil evidence (see "Calcareous Nannofossils"). Section 208-1265A-13H-CC (~140 mcd) contains a typical Zone P22 assemblage of well-preserved Globoquadrina globularis, Globoquadrina tripartita, Globigerina angulisuturalis, and G. ciperoensis and no P. kugleri.
Section 1265A-14H-CC (150.38 mcd) is assigned to Subzone P21b based on the co-occurrence of G. angulisuturalis, G. ciperoensis, Globoquadrina selli, and G. tripartita. The presence of abundant Chiloguembelina cubensis at 162.34 mcd indicates that the lower/upper Oligocene boundary is between Sections 208-1265A-14H-CC and 15H-CC at ~156 mcd.
Preservation declines dramatically downhole, and the assemblage in Section 208-1265A-16H-CC consists largely of shell fragments. This foraminiferal "hash" does, however, contain a few thick-shelled specimens of Subbotina angiporoides, indicating an age >30 Ma. Section 208-1265A-16H-CC (171.54 mcd) is tentatively assigned to Zone P19. Preservation improves in Section 208-1265A-17H-CC (182.69 mcd), which contains rare "Globigerina" ampliapertura and Pseudohastigerina spp. but also numerous reworked specimens of Globigerinatheka spp., Acarinina spp., and Morozovella spp. Hence, Section 208-1265A-17H-CC is assigned to Zone P18.
The E/O boundary record suffers from extensive reworking and severe dissolution and spans Zones P18–P16 (Sections 208-1265A-17H-CC through 19H-CC; 182.7–204.1 mcd). Section 208-1265A-17H-CC contains a lowermost Oligocene (Zone P18) assemblage. The assemblage in Section 208-1265A-18H-CC (190.0 mcd) is poorly preserved and contains abundant spines of Hantkenina spp., as well as thick-shelled Globigerinatheka spp. that are likely reworked. It also contains extremely rare specimens of poorly preserved Turborotalia cerroazulensis cunialensis, which is indicative of a latest Eocene age. Consequently, the E/O boundary is placed within Core 208-1265A-18H and likely coincides with the lithologic change at 191.0 mcd (see "Subunit IIB," in "Unit II" in "Description of Lithostratigraphic Units" in "Lithostratigraphy"). Sections 208-1265A-18H-CC and 19H-CC are assigned to Zone P16 based largely upon the abundance of Globigerinatheka spp. and hantkeninid spines, although this interval has been extensively reworked. Other faunal elements of Section 208-1265A-19H-CC include S. angiporoides, Subbotina linaperta, Pseudohastigerina spp., and Hantkenina alabamensis.
An incomplete Eocene record was recovered in Cores 208-1265A-19H through 29H. Acarininid diversity is high in Section 208-1265A-20H-CC (~212 mcd), which contains Acarinina bullbrooki, Acarinina spinuloinflata, Acarinina topilensis, Acarinina rohri, and Acarinina crassata. Also preserved in this sample are "Globigerinatheka" senni, Globigerinatheka index, Globigerinatheka subconglobata, Morozovella spinulosa, H. alabamensis, and Subbotina inaequispira. The general absence of the marker Orbulinoides beckmanni precludes identification of Zone P13, hindering differentiation of Zones P12 and P14, so Section 208-1265A-20H-CC is loosely assigned to Zones P12–P14. A P12/P14 zonal boundary designation for Section 208-1265A-20H-CC suggests that the middle/upper Eocene boundary may be incomplete (Fig. F24).
A more significant unconformity separates Sections 208-1265A-20H-CC and 21H-CC (Fig. F24). Section 208-1265A-21H-CC (225.43 mcd) contains abundant well-preserved Morozovella aragonensis/Morozovella caucasica, as well as Subbotina lozanoi, "G." senni, and assorted acarininids (e.g., A. bullbrooki and A. spinuloinflata). This assemblage typifies Zone P9/P10, which corresponds to the lower/middle Eocene boundary (~49 Ma). Thus, both the upper and lower boundaries of the middle Eocene are marked by unconformities, which is in agreement with calcareous nannofossil data (see "Calcareous Nannofossils"). Section 208-1265A-22H-CC (238 mcd) is assigned to Zone P9 and contains an assemblage similar to that found in Section 21H-CC, although less well preserved.
Section 208-1265A-23H-CC (~250 mcd) contains a well-preserved assemblage with a suite of morozovellids including Morozovella subbotinae, Morozovella gracilis, Morozovella lensiformis, M. aragonensis, and Morozovella aequa. The presence of transitional forms linking M. aragonensis to ancestral M. lensiformis indicates that this sample can be assigned to Zone P7. The absences of A. spinuloinflata and A. bullbrooki distinguish Section 208-1265A-23H-CC from overlying samples.
Assemblages in Samples 208-1265B-25H-1, 66 cm, and 25H-1, 78 cm, across a distinctive clay layer at ~257.3 mcd indicate that the uppermost occurrence of "large" (>150 µm) biserial planktonic species and the zonal boundary between Subzone P6b and Zone P7 may be correlative with this layer. Thus, Sample 208-1265B-25H-1, 66 cm (257.3 mcd), is assigned to Zone P7 and Sample 208-1265B-25H-1, 78 cm (257.4 mcd), is assigned to Subzone P6b. Section 208-1265A-24H-CC (~261.0 mcd) is also assigned to Subzone P6b based on the absence of M. aragonensis and the presence of Morozovella marginodentata, M. gracilis/Morozovella formosa morphotypes, and "large" biserial taxa.
Sections 208-1265A-25H-CC through 27H-CC (272.0–295.0 mcd) contain well-preserved assemblages that are typical of Subzone P6a. Some of the more common species are M. subbotinae, M. gracilis, M. aequa, Acarinina soldadoensis, Acarinina coalingensis, Igorina broedermanni, Subbotina triangularis, Subbotina velascoensis, and Globanomalina planoconica. Diminutive high-spired acarininids tentatively ascribed to Acarinina chascanona and "large" biserial forms are also present.
This critical boundary interval is confined to Zone P5 between Sections 208-1265A-28H-CC and 29H-CC. Additional samples were taken from Core 208-1265A-29H to increase stratigraphic resolution across the P/E boundary at ~315.8 mcd. The top of Zone P5 could only be approximated because of the overall scarcity of M. velascoensis. Section 208-1265A-28H-CC (~306 mcd) contains a well-preserved, diverse assemblage composed of assorted morozovellids, acarininids, subbotinids, globanomalinids, igorinids, and "large" biserial species. Preservation declines downhole from 315.24 to 315.81 mcd. Carbonate content decreases, and planktonic foraminiferal shells are mostly fragmentary and diminutive. Preservation improves immediately below the P/E boundary clay layer (315.86–316.44 mcd) as diversity and shell sizes increase within these uppermost Paleocene assemblages. No P/E boundary "excursion" taxa were seen within this series of samples. Section 208-1265A-29H-CC (~317 mcd) contains a diverse, well-preserved assortment of morozovellids, acarininids, subbotinids, globanomalinids, and igorinids.
Preservation throughout the upper Paleocene is variable but generally declines downhole. Sections 208-1265A-29H-CC through 31H-CC are assigned to Zone P5. The assemblages are dominated by acarininids, although members of the genera Globanomalina and Morozovella are common. Globanomalina pseudomenardii has its uppermost occurrence (delimiting the zonal boundary between Subzone P4c and Zone P5; 55.9 Ma) between Sections 208-1265A-31H-CC and 32H-CC at ~324 mcd. The lowermost Section 208-1265A-35X-CC at ~355 mcd is from a chalky interval that belongs to Subzone P4a. The assemblage contains G. pseudomenardii, Acarinina subsphaerica, Acarinina nitida, Acarinina mckannai, Igorina tadjikistanensis, M. velascoensis, Morozovella acutispira, and Morozovella acuta.
All core catcher samples from Holes 1265A and 1265D were semiquantitatively investigated for benthic foraminifers. In addition, samples were studied from the mudline and from intervals in Hole 1265B that were not recovered in Hole 1265A and across the P/E boundary in Hole 1265C (Table T9).
In many samples, benthic foraminifers are rare compared to planktonic foraminifers, with the exception of those in the lowermost Eocene, where the assemblages have suffered strong dissolution. In addition, benthic foraminifers are more common in many samples between 43 and 257 mcd (Sections 208-1265A-4H-CC and 23H-CC) (Table T9). In these samples, preservation is extremely variable and very large thick-walled specimens are broken and/or abraded, whereas small thin-walled specimens are well preserved. Many of these samples contain reworked planktonic and/or benthic foraminifers, and the benthic faunas indicate downslope transport. Typical indicators of downslope transport are abundant large siphonodosariid species (e.g., Siphonodosaria pomuligera), large nodosariids, large specimens of Oridorsalis umbonatus, Globocassidulina subglobosa, Vulvulina spinosa, and Plectofrondicularia paucicostata (Table T9). The latter species has been recorded as Plectofrondicularia lirata in the upper Eocene at several South Atlantic DSDP sites to the east and west of the Mid-Atlantic Ridge over a large depth range and may represent downslope transport at many of these sites (Tjalsma, 1983; Clark and Wright, 1984). At Site 1265, the species occurs in foraminiferal turbidites in the upper Eocene through Miocene.
Benthic foraminiferal assemblages from Site 1265 indicate deposition at upper abyssal depths (2000–3000 m) in samples from above 238 mcd (Cores 208-1265B-1H through 208-1265A-22H; middle Eocene and younger), although for some samples paleodepths could not be determined because of downslope transport (Table T9). Paleodepths could not be estimated for samples between 250 and 275 mcd (Section 208-1265A-23H-CC through Sample 34X-1, 27–28 cm; lower Eocene) because benthic foraminifers are not reliable depth indicators for that period (Müller-Merz and Oberhänsli, 1991). Samples below 275 mcd (upper Paleocene) were deposited at lower bathyal depths (~1500–2000 m).
Benthic foraminiferal assemblages between 0 and 2 mcd (Samples 208-1265B-1H-1, 0–2 cm, and 208-1265A-1H-1, 0–2 cm) contain assemblages with common Epistominella exigua, Cassidulina laevigata, G. subglobosa, Cibicidoides wuellerstorfi, Cibicidoides mundulus, O. umbonatus, and Pyrgo spp., with few specimens of the Uvigerina peregrina group, Pullenia spp., Bulimina rostrata, Bolivinita pseudothalmanni, and Gyroidinoides spp., and rare Hoeglundina elegans; in contrast to Site 1264, Osangularia culter is absent. 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 ~3000 and 4000 m (Schmiedl et al., 1997). At these depths, bottom waters are derived from northern sources (North Atlantic Deep Water), as indicated by the common presence of C. wuellerstorfi. The common occurrence of E. exigua indicates seasonally fluctuating primary productivity in the overlying waters.
Assemblages in samples between 4 and 65 mcd (Sections 208-1265B-1H-CC and 208-1265A-6H-CC) resemble those in the upper samples but lack E. exigua and contain pleurostomellid and siphonodosariid species in addition to those listed (Table T9). C. wuellerstorfi has its lowest occurrence between Sections 208-1265A-6H-CC and 7H-CC (65 and 75 mcd), which is several millions of years before its first appearance at Site 1264. This first appearance is close in time to the first appearance of the species in the Atlantic Ocean at ~13.7 Ma (e.g., Thomas, 1986; age recalculated to the timescale of Leg 208). Samples between 43 and 65 mcd commonly contain evidence of downslope transport and/or reworking (Table T9).
Assemblages between 75 and 198 mcd (Sections 208-1265A-7H-CC through 208-1265B-19H-CC) resemble the assemblages in the higher samples but lack C. wuellerstorfi and contain long-lived abyssal to lower bathyal taxa such as Cibicidoides spp., O. umbonatus, Pullenia spp., and Siphonodosaria spp. Typical middle Miocene and younger taxa (e.g., Bulimina exilis, B. rostrata, B. pseudothalmanni, and Sigmoilopsis schlumbergeri) have their lowermost appearances in this interval, and pre-middle Miocene taxa (e.g., Anomalinoides spissiformis, Nonion havanense, and Bolivinoides huneri) have their uppermost appearances. Many samples contain evidence of downslope transport and/or reworking (Table T9). The reworked specimens are generally derived from middle bathyal (600–1000 m) or greater depths.
Between 85 and 87 mcd (lower part of Core 208-1265-8H), benthic foraminiferal assemblages contain high relative abundances (>75%) of small smooth-walled bolivinid species, as in coeval sediments at Site 1264. These occurrences reflect an unusual event in benthic foraminiferal faunas at ~18 Ma, which was recognized in the eastern Atlantic and western Indian Oceans and is called the high abundance of bolivinids event (Smart and Murray, 1994; Smart and Ramsay, 1995).
Nuttallides truempyi has its uppermost occurrence in Section 208-1265A-19H-CC (204 mcd). Samples between 204 and 249 mcd (Sections 208-1265A-19H-CC through 23H-CC) contain typical species-rich upper abyssal middle–upper Eocene assemblages, with N. truempyi, Bulimina semicostata, Cibicidoides praemundulus, Cibicidoides grimsdalei, O. umbonatus, Gyroidinoides spp., A. spissiformis, N. havanense, and common Siphonodosaria spp. as well as unilocular, laevidentalinid, and pleurostomellid taxa. Evidence for downslope transport is present throughout this interval (Table T9).
Samples 208-1265A-25H-1, 66–67 cm, through 29H-7, 65–66 cm (257–317 mcd), contain much less species rich assemblages, 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 rare Aragonia aragonensis and 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 are rare to common, as are specimens of unilocular, laevidentalinid, and pleurostomellid taxa. Two samples in relatively clay rich intervals at 257.3 mcd (Sample 208-1265B-25H-1, 65–66 cm) and 277.4 mcd (Sample 208-1265A-26H-3, 55–56 cm) contain assemblages with a relatively low species richness and common to abundant Clinapertina and Abyssamina spp.
In the lowermost part of this interval (315.4–315.8 mcd; Samples 208-1265A-29H-7, 30–31 cm, through 29H-7, 65–66 cm, and Section 208-1265D-4H-CC), species richness is extremely low and long-lived unilocular and laevidentalinid taxa are absent. Abundant taxa are Abyssamina quadrata, B. kugleri, O. umbonatus, and N. truempyi. The lowermost samples in this interval contain minute specimens of N. truempyi, T. selmensis, O. umbonatus, B. kugleri, B. simplex, and A. quadrata; most are dominated by N. truempyi and one by O. umbonatus. Similar assemblages have been described from immediately after the P/E BEE on Walvis Ridge (Müller-Merz and Oberhänsli, 1991; Thomas and Shackleton, 1996).
The BEE occurs between Samples 208-1265A-29H-7, 65–66 cm, and 29H-7, 70–71 cm (315.81 and 315.86 mcd), and between Sections 208-1265D-4H-CC and 5H-CC. At Site 1265, a few very small specimens of species that usually become extinct at the BEE are present in the lower few samples above the event (Bulimina thanetensis and Paralabamina lunata) (Table T9). The specimens are small and thin walled like the other species in the assemblage and show no signs of reworking.
Samples from below the BEE through the bottom of the hole (317–355 mcd) contain typical extremely species rich Paleocene lower bathyal through abyssal assemblages with Stensioeina beccariiformis, P. lunata, Paralabamina hillebrandti, Pullenia coryelli, large thick-walled species of Gyroidinoides such as G. beisseli, G. globosa, and G. quadrata, and large agglutinant taxa (e.g., Clavulinoides spp., Marssonella oxycona, and Gaudryina pyramidata). Aragonia velascoensis is rare at Site 1265. As at Site 1263 and in contrast with Site 1262, lower bathyal indicator species such as Alabamina creta, Bolivinoides delicatulus, Coryphostoma midwayensis, and Neoflabellina semireticulata are present, but they are less common than at Site 1263, indicating lower bathyal depths (1500–2000 m).