RESULTS

The lower Paleocene is zoned using the high-latitude Antarctic zonal scheme of Wei and Pospichal (1991) (Fig. F3). On the other hand, the number-coded coccolith zonations compiled by Okada and Bukry (1980) and Martini (1971) are used in this report for the mid-Paleocene to Eocene sequences. Although the Okada and Bukry and Martini zonations were developed primarily for the low latitudes, the nannofossil assemblages in the mid-Paleocene and Eocene are, in general, diverse enough to allow application of these schemes. Nevertheless, some of the subzones could not be distinguished and some zones had to be combined, resulting in reduced biostratigraphic resolution.

Site 1135

Site 1135 (59°42.0´S, 84°16.4´E), located on the southern Kerguelen Plateau (Shipboard Scientific Party, 2000b), was rotary cored in a water depth of 1567 m. It penetrated 526 m of upper Pliocene to Upper Cretaceous sediment composed almost entirely of pelagic calcareous ooze and chalk, including an expanded section (238 m thick) of mid-Paleocene to Eocene nannofossil ooze (Fig. F4). Such a section is not well represented in previous coring of high southern latitude sites; in addition, it is remarkably free of the chert that impeded drilling of Paleocene-Eocene sections on the KP during previous ODP Legs 119 and 120 (Schlich, Wise, et al., 1989; Barron, Larsen, et al., 1989). The Cretaceous/Tertiary (K/T) boundary is marked by a hiatus. Preservation is generally poor to moderate (Table T1).

Eocene

Sediments in Samples 183-1135A-3R-1, 131-133 cm (19.70 meters below seafloor [mbsf]), through 7R-6, 100-101 cm (64.60 mbsf), are placed in Subzone CP14a based on the overlap of Reticulofenestra umbilica and Chiasmolithus solitus. Diversity in this zone ranges from 20 to 25 species with abundant to common Coccolithus pelagicus, C. solitus, Chiasmolithus expansus, Chiasmolithus spp., Reticulofenestra spp., Reticulofenestra samodurovii, R. umbilica, Sphenolithus moriformis, and Zygrhablithus bijugatus.

Samples 183-1135A-7R-7, 25-26 cm (65.35 mbsf), through 17R-1, 25-26 cm (151.85 mbsf), are assigned to the combined Discoaster sublodoensis-Nannotetrina quadrata Zones (CP12-CP13). The assemblage is characterized by C. pelagicus, C. solitus, C. expansus, Chiasmolithus spp., Neococcolithes dubius, Neococcolithes minutus, Reticulofenestra spp., R. samodurovii, R. umbilica, S. moriformis, and Z. bijugatus throughout the interval. Reticulofenestra onusta is common to abundant in the upper part of this zone. Discoasters are few to rare in the upper part of the zone, but are few to common in the lower part. No attempt was made to determine the first occurrence (FO) of Nannotetrina fulgens (which separates Zone CP12 from CP13) because it was found only in a few samples and is too rare to be considered a useful datum at this site.

Samples 183-1135A-17R-1, 100-101 cm (152.60 mbsf), through 23R-CC (212 mbsf) are assigned to the combined Discoaster lodoensis-Tribrachyatus orthostylus Zone (CP11-CP10). The interval is normally defined as the FO of D. lodoensis to the FO of D. sublodoensis. Because of the poor preservation, however, the top of the zone is placed at the first common occurrence (FCO) of D. sublodoensis. D. sublodoensis was recorded in Table T1 below its FCO in a few samples down to Sample 183-1135A-21R-5, 100-101 cm (197 mbsf), but those identifications are questionable. The last occurrence (LO) of T. orthostylus is present in Sample 183-1135A-21R-1, 25-26 cm (188.61 mbsf), which places it in the middle of Zone CP11 (50.6 Ma). The assemblage contains abundant C. pelagicus, Coccolithus formosus, C. solitus, N. dubius, N. minutus, Reticulofenestra spp., R. samodurovii, S. moriformis, and Z. bijugatus.

Samples 183-1135A-25R-1, 25-26 cm (228.75 mbsf), through 25R-2, 100-101 cm (231 mbsf), are placed in the Discoaster binodosus Subzone (CP9b) based on the co-occurrence of T. orthostylus and Tribrachyatus contortus. This subzone marks the greatest diversification of sphenoliths at Site 1135; S. moriformis, Sphenolithus primus, Sphenolithus radians, and Sphenolithus editus are all common to abundant. The FOs of C. expansus and Chiasmolithus grandis are present in this subzone as well as the LO of Chiasmolithus bidens. The assemblage is characterized by abundant to common Chiasmolithus spp., Toweius spp., and Z. bijugatus. No Reticulofenestra spp. were observed in this zone.

Paleocene/Eocene Boundary

The Paleocene/Eocene boundary at Site 1135 is marked by an unconformity that is present between Samples 183-1135A-25R-3, 25-26 cm (231.75 mbsf), and 25R-2, 100-101 cm (231.0 mbsf), and spans Subzone CP9a (NP10). This unconformity was identified by the absence of the basal Eocene Tribrachiatus bramlettei and the presence of T. contortus and T. orthostylus as well as Fasciculithus spp. and Prinsius bisulcus in Sample 183-1135A-25R-2, 100-101 cm (231.0 mbsf). The Fasciculithus and Prinsius species are thought to be reworked. The FOs of T. contortus and T. orthostylus co-occur, indicating that the sample belongs to Subzone CP9b. Sample 183-1135A-25R-2, 25-26 cm (230.25 mbsf), contains the lower Eocene species Discoaster barbadiensis and S. editus.

Paleocene

The uppermost Paleocene Discoaster multiradiatus Zone (CP8) encompasses Samples 183-1135A-25R-3, 25-26 cm (231.75 mbsf), through 26R-CC (241.61 mbsf), which extends down to the FO of the marker D. multiradiatus. The assemblage is characterized by abundant C. bidens, C. pelagicus, D. multiradiatus, Fasciculithus tympaniformis, P. bisulcus, S. primus, Toweius eminens, and Z. bijugatus.

The Discoaster nobilis Zone (CP7) is missing. Either the marker is not present in this section or there is a hiatus that separates Sample 183-1135A-26R-CC (241.61 mbsf) from Sample 27R-1, 25-26 cm (247.95 mbsf), or the zone is present in the 6-m gap between samples.

The Discoaster mohleri Zone (CP6) is recorded in Sample 183-1135A-27R-1, 25-26 cm (247.95 mbsf), where the FO of D. mohleri is noted. The assemblage is characterized by abundant to common Chiasmolithus danicus, C. pelagicus, F. tympaniformis, Fasciculithus magnicordis, Fasciculithus clinatus, Neochiastozygus perfectus, Neochiastozygus junctus, P. bisulcus, Prinsius martinii, S. primus, T. eminens, and Z. bijugatus.

Similarly, Sample 183-1135A-27R-1, 100-101 cm (248.70 mbsf), is the only sample that contains the marker species Heliolithus kleinpellii; thus, it is assigned to the zone of that name (CP5). The assemblage is characterized by common to abundant C. pelagicus, C. danicus, F. tympaniformis, and P. bisulcus.

The F. tympaniformis Zone (CP4) is assigned to Samples 183-1135A-27R-2, 25-26 cm (249.45 mbsf), through 27R-CC (252.45 mbsf). The assemblage consists of abundant to common C. pelagicus, Prinsius dimorphosus, Thoracosphaera spp., C. danicus, C. bidens, P. bisulcus, P. martinii, S. primus, and Toweius pertusus.

For the lower Paleocene we used the high-latitude Antarctic zonation scheme of Wei and Pospichal (1991) (Fig. F3). The bottom of Zone CP4, defined as the FO of F. tympaniformis, roughly correlates to the middle of the C. bidens Zone (NA6) of Wei and Pospichal. The lower portion of the C. bidens Zone (NA6) and all of the P. martinii Zone (NA5) is missing. This hiatus is marked by the apparent FOs of F. tympaniformis, P. martinii, and C. bidens all in the same sample (183-1135A-27R-CC [252.45 mbsf]).

Sample 183-1135A-28R-1, 25-26 cm (257.55 mbsf), is assigned to the one-sample-long C. danicus Zone (NA4). The zone is based on the FO of C. danicus through the FO of P. martinii. The assemblage consists of C. pelagicus, Cruciplacolithus tenuis, Placozygus sigmoides, P. dimorphosus, Thoracosphaera operculata, Thoracosphaera spp., Cruciplacolithus primus, and C. danicus.

The C. tenuis Subzone (NA3; CP1b) encompasses Samples 183-1135A-28R-1, 100-101 cm (258.30 mbsf), through 28R-2, 100-101 cm (259.80 mbsf), and is based on the FO of C. tenuis through the FO of C. danicus. The assemblage consists of abundant to common C. pelagicus, C. tenuis, P. sigmoides, P. dimorphosus, T. operculata, and Thoracosphaera spp., plus Hornibrookina teuriensis, which are few to common.

Site 1136

Site 1136 (59°39.1´S, 84°50.1´E), rotary cored in a water depth of 1931 m, is located ~30 km east of Site 1135 on the Southern Kerguelen Plateau (Shipboard Scientific Party, 2000c). At Site 1136, a 128-m-thick sedimentary section of middle Eocene to upper Albian sediments was recovered (Fig. F5). There is an expanded upper-lower to lower-middle Eocene section of calcareous ooze and chalk. Preservation is poor to moderate (Table T2).

Eocene

The topmost Sample 183-1136A-2R-1, 58-59 cm (5.28 mbsf), is placed in the Discoaster bifax Subzone (CP14a), as it contains the FO of R. umbilica plus C. solitus, whose LO marks the Subzone CP14a/CP4b boundary. The assemblage is characterized by abundant to common C. solitus, C. pelagicus, N. dubius, N. minutus, Reticulofenestra spp., and Z. bijugatus.

Samples 183-1136A-2R-2, 25-26 cm (6.45 mbsf), to 3R-2, 100-101 cm (16.90 mbsf), are placed in the Chiasmolithus gigas Subzone (CP13b), defined by the total range of C. gigas. The assemblage consists of common to abundant C. expansus, C. solitus, C. formosus, C. pelagicus, N. dubius, N. minutus, R. onusta, R. samodurovii, Reticulofenestra spp., S. moriformis, and Z. bijugatus.

The Discoaster strictus Subzone (CP13a) comprises Samples 183-1136A-3R-2, 100-101 cm (18.40 mbsf), through 4R-2, 100-101 cm (26.40 mbsf), and ranges from the FO of N. fulgens through the FO of C. gigas. The zone is characterized by common to abundant C. expansus, C. solitus, C. formosus, C. pelagicus, N. dubius, N. minutus, R. onusta, R. samodurovii, Reticulofenestra spp., S. moriformis, and Z. bijugatus. There is an increase in the abundance and diversity of discoasters overall as compared to the zones above. This may indicate that the oceans at this time were warmer than during the previous interval (Pospichal and Wise, 1990b)

The D. sublodoensis Zone (CP12) is assigned to Samples 183-1136A-4R-3, 25-27 cm (27.15 mbsf), through 5R-4, 25-26 cm (38.15 mbsf). Discoaster abundance increases in the assemblage, indicating warmer surface ocean temperatures during the early middle Eocene as compared with the late middle Eocene. The assemblage is characterized by common to abundant C. expansus, C. grandis, C. solitus, C. formosus, C. pelagicus, Coronocyclus prionion, D. binodosus, Discoaster kuepperi, D. lodoensis, Discoaster praebifax, N. dubius, N. minutus, R. samodurovii, Reticulofenestra spp., S. moriformis, and Z. bijugatus.

Zones D. lodoensis (CP11) and T. orthostylus (CP10) are combined here because the marker species that separates them, Toweius crassus, is reported here out of its reported range. This combined zone encompasses Samples 183-1136A-5R-4, 100-101 cm (38.90 mbsf), to 6R-7, 25-26 cm (52.05 mbsf). Defined by the FO of D. lodoensis at its base and the FO of D. sublodoensis at its top, this interval has common to abundant C. bidens, C. solitus, C. pelagicus, D. binodosus, D. kuepperi, N. dubius, N. minutus, Reticulofenestra spp., S. moriformis, S. radians, Thoracosphaera spp., Toweius spp., and Z. bijugatus. Also noted in this zone was the LO of T. orthostylus between Samples 183-1136A-6R-1, 100-101 cm (43.80 mbsf), and 6R-1, 25-26 cm (43.05 mbsf).

Samples 183-1136A-7R-1, 25-26 cm (52.35 mbsf), through 7R-2, 100-101 cm (54.60 mbsf), are assigned to the D. binodosus Subzone (CP9b). Defined as the FO of T. orthostylus (base) through the FO of D. lodoensis (top), this zone is relatively short and is characterized by abundant to common C. bidens, C. consuetus, C. solitus, C. pelagicus, D. binodosus, D. kuepperi, N. dubius, S. moriformis, S. radians, T. crassus, Toweius spp., and Z. bijugatus.

Site 1138

Site 1138 (53°33.1´S, 75°58.5´E), rotary cored in a water depth of 1141 m, is located on the central Kerguelen Plateau (Shipboard Scientific Party, 2000d). About 698 m of sediment was recovered, and the age ranges from Pleistocene to Late Cretaceous (Fig. F6). Six lithologic units are recognized at this site, one of which, Unit 3 (265.9-601.9 mbsf), was examined in this study. It consists of upper Oligocene to mid-Campanian foraminifer-bearing chalk with scattered chert nodules in the lower section. There is a possibly complete K/T boundary section located in Core 183-1138A-52R (see "Isotopic Analysis"). This site provides an excellent chance to investigate environmental and biotic changes at high latitudes across this boundary (Table T3).

Eocene

The Isthmolithus recurvus Subzone (CP15b) encompasses Samples 183-1138A-36R-5, 25-26 cm (339.25 mbsf), through 37R-2, 25-26 cm (344.34 mbsf). The FO of I. recurvus provides a well-documented datum for the base of the subzone (Wei and Wise, 1990; Wei, 1992). The top of the subzone is missing because of an unconformity between Samples 183-1138A-36R-5, 25-26 cm (339.25 mbsf), and 36R-4, 100-101 cm (337.75 mbsf). Sample 183-1138A-36R-5, 25-26 cm (339.25 mbsf), is of Eocene age, whereas Sample 36R-4, 100-101 cm (337.75 mbsf), is of early Oligocene age, based on the large number of Chiasmolithus altus relative to Chiasmolithus oamaruensis (Wei and Wise, 1990).

Subzone CP15b is characterized by abundant to common C. oamaruensis, C. pelagicus, I. recurvus, Reticulofenestra spp., Reticulofenestra bisecta, R. umbilica, and Thoracosphaera spp. The FO of Reticulofenestra oamaruensis is also noted in this subzone. Discoasters are almost completely absent. The only discoasters present are overgrown six-rayed forms that cannot be identified to species level.

Samples 183-1138A-37R-2, 100-101 cm (345.1 mbsf), through 37R-3, 100-101 cm (346.6 mbsf), are assigned to the C. oamaruensis Subzone, which extends from the LO of C. grandis to the FO of I. recurvus. The assemblage consists of abundant to common C. oamaruensis, Coccolithus formosa, C. pelagicus, Reticulofenestra spp., R. bisecta, R. umbilica, and Thoracosphaera spp. Other nannofossils include few to rare Blackites spinosus, Discoaster spp., R. onusta, R. samodurovii, S. moriformis, and Z. bijugatus.

Samples 183-1138A-37R-4, 25-26 cm (347.35 mbsf), through 37R-6, 100-101 cm (351.1 mbsf), belong to the Discoaster saipanensis Subzone (CP14b), defined by the LO of C. solitus at its base and the LO of C. grandis at the top. The FO of R. bisecta (38.0 Ma) is present within this subzone. The LO of C. solitus is reported above the FO of R. bisecta on the KP (this paper) and on the Falkland Plateau (Mostajo and Wise, 1983) (see "Discussion" for further detail). The assemblage consists of common to abundant Chiasmolithus spp., C. formosus, C. pelagicus, Reticulofenestra spp., R. bisecta, R. samodurovii, R. umbilica, S. moriformis, and Thoracosphaera spp.

The D. bifax Subzone (CP14a) is assigned to sediments of Samples 183-1138A-37R-CC (351.94 mbsf) through 43R-1, 100-101 cm (401.4 mbsf), based on the first common occurrence (FCO) of R. umbilica and presence of C. solitus. The top of the subzone is defined by the LO of C. solitus, and the base of the subzone is defined by the FO of R. umbilica. The base of this subzone is somewhat uncertain because of the nature of the species definition of R. umbilica (see "Discussion" for further details). The assemblage consists of abundant to common C. solitus, C. formosus, C. pelagicus, Discoaster spp., Discoaster deflandrei, five- and six-rayed Discoaster spp., Reticulofenestra spp., R. onusta, R. samodurovii, R. umbilica, S. moriformis, Thoracosphaera spp., and Z. bijugatus.

The Coccolithus staurion Subzone (CP13c) encompasses Samples 183-1138A-43R-2, 25-26 cm (402.15 mbsf), through 43R-4, 100-101 cm (405.9 mbsf). This subzone ranges from the LO of C. gigas to the FO of R. umbilica. The assemblage consists of abundant to common C. solitus, C. formosus, C. pelagicus, Discoaster spp., six-rayed Discoaster spp., D. praebifax, Reticulofenestra spp., R. onusta, R. samodurovii, R. umbilica, and Z. bijugatus.

Samples 183-1138A-43R-5, 25-26 cm (406.65 mbsf), through 45R-CC (422.8 mbsf) are assigned to the C. gigas Subzone (CP13b). This subzone is defined by the total range of C. gigas. The assemblage is made up of mostly abundant to common C. expansus, C. grandis, C. solitus, C. formosus, C. pelagicus, Discoaster spp., six-rayed Discoaster spp., N. fulgens, N. dubius, Reticulofenestra spp., R. onusta, R. samodurovii, and Z. bijugatus.

Sample 183-1138A-46R-1, 25-26 cm (429.55 mbsf), is assigned to the Discoaster strictus Subzone (CP13a). This subzone is defined at its base by the FO of N. fulgens and at its top by the FO of C. gigas. The assemblage consists of C. solitus, C. formosus, C. pelagicus, N. dubius, Reticulofenestra spp., R. onusta, R. samodurovii, and Z. bijugatus.

Samples 183-1138A-46R-CC (430.38 mbsf) through 47R-CC (441.92 mbsf) are assigned to the D. sublodoensis Zone (CP12). This zone extends from the FO of D. sublodoensis (base) to the FO of N. fulgens (top). The assemblage is characterized by abundant to common C. solitus, C. formosus, C. pelagicus, Discoaster spp., D. binodosus, D. kuepperi, D. sublodoensis, Reticulofenestra spp., and Z. bijugatus.

There is a hiatus between Samples 183-1138A-47R-CC (441.92 mbsf) and 48R-1, 25-26 cm (448.85 mbsf), that spans Zones CP10 and CP11. Samples 183-1138A-48R-1, 25-26 cm (448.85 mbsf), through 48R-1, 100-101 cm (449.6 mbsf), are assigned to the D. binodosus Subzone (CP9b). The assemblage is composed mostly of abundant to common Chiasmolithus spp., C. pelagicus, D. kuepperi, Discoaster spp., Toweius spp., T. crassus, and Z. bijugatus.

Paleocene/Eocene Boundary

The Paleocene/Eocene boundary is represented by a hiatus between Samples 183-1138A-48R-1, 100-101 cm (449.60 mbsf), and 48R-2, 25-26 cm (450.35 mbsf). The boundary is usually placed at the base of Subzone CP9a (NP10) based on the FO of T. bramlettei, which was not observed at this site. Sample 183-1138A-48R-1, 100-101 cm (449.60 mbsf), contains the early Eocene species T. orthostylus, whose FO marks the base of Subzone CP9b (NP11). The next sample below, Sample 183-1138A-48R-2, 25-26 cm (450.35 mbsf), contains a Paleocene assemblage with D. multiradiatus, F. tympaniformis, and P. bisulcus.

Paleocene

Samples 183-1138A-48R-2, 25-26 cm (450.35 mbsf), through 48R-CC (457.3 mbsf) are assigned to the D. multiradiatus Zone, CP8 (NP9). The FO of D. multiradiatus, which is common throughout the zone, marks the Zone CP7/CP8 boundary. Diversity is relatively high, with abundant to common C. bidens, C. pelagicus, Coccolithus spp., F. tympaniformis, P. bisulcus, S. primus, T. pertusus, Toweius tovae, Toweius spp., and Z. bijugatus.

Samples 183-1138A-49R-1, 25-26 cm (458.45 mbsf), through 49R-1, 100-101 cm (459.20 mbsf), are assigned to the combined D. nobilis-D. mohleri Zone (CP7-CP6). This interval ranges from the FO of D. mohleri through the FO of D. multiradiatus. The FO of D. nobilis is normally used to separate Zone CP6 from CP7, but was not observed in this interval. The assemblage consists of C. bidens, C. consuetus, Coccolithus spp., F. tympaniformis, Heliolithus spp., Heliolithus kleinpellii, P. bisulcus, T. eminens, and T. pertusus.

As at Site 1135, the H. kleinpellii Zone (CP5) is represented in only one sample, 183-1138A-49R-2, 25-26 cm (459.95 mbsf). The zone is defined by the FO of H. kleinpellii at the base and the FO of D. mohleri at the top. The assemblage is similar to that at Site 1135, consisting of abundant to common C. bidens, C. danicus, F. tympaniformis, H. kleinpellii, H. universus, P. sigmoides, P. bisulcus, and P. martinii. The only noticeable difference is that Site 1138 has more common Heliolithus than Site 1135, perhaps a function of the lower latitude of Site 1135.

The F. tympaniformis Zone (CP4) spans Samples 183-1138A-49R-2, 100-101 cm (460.70 mbsf), through 49R-CC (461.69 mbsf). Defined by the FO of F. tympaniformis at the base and the FO of H. kleinpellii at the top, the assemblage is similar to that of Site 1135, consisting of C. bidens, C. danicus, Coccolithus spp., F. magnicordis, F. tympaniformis, N. perfectus, P. sigmoides, P. bisulcus, P. martinii, Thoracosphaera spp., and T. pertusus.

Samples 183-1138A-50R-1, 25-26 cm (467.75 mbsf), through 50R-CC (470.43 mbsf) are assigned to the C. bidens Zone (NA6) of the high-latitude Antarctic zonation scheme of Wei and Pospichal (1991), defined by the FO of C. bidens through the LO of H. teuriensis. It also encompasses the FO of T. pertusus, the FO of P. bisulcus, and the LO of P. dimorphosus. The assemblage consists of abundant to common C. bidens, C. danicus, C. pelagicus, P. sigmoides, P. bisulcus, P. dimorphosus, P. martinii, T. operculata, Thoracosphaera spp., and T. pertusus.

The P. martinii Zone (NA5), which was not present at Site 1135, consists of one sample, 183-1138A-51R-1, 25-26 cm (477.35 mbsf). The assemblage includes abundant to common C. danicus, C. pelagicus, P. dimorphosus, P. martinii, T. operculata, and Thoracosphaera spp.

The subjacent C. danicus Zone (NA4), represented by only one sample at Site 1135, here encompasses Samples 183-1138A-51R-1, 100-101 cm (478.10 mbsf), through 51R-4, 100-101 cm (482.60 mbsf). The assemblage consists of abundant to common C. danicus, C. pelagicus, Cruciplacolithus edwardsii, P. dimorphosus, T. operculata, and Thoracosphaera spp., with rare to few Markalius inversus, Biscutum constans, and reworked Cretaceous taxa. Site 1138 contrasts with Site 1135 by having much fewer H. teuriensis and fewer Chiasmolithus and Cruciplacolithus throughout this zone.

Samples 183-1138A-52R-1, 3 cm (486.72 mbsf), through 52R-3, 4 cm (489.73 mbsf), are assigned to the C. tenuis Zone (NA3). The assemblage consists of abundant C. pelagicus, C. tenuis, P. sigmoides, P. dimorphosus, and reworked Cretaceous taxa. Few to rare B. constans, C. edwardsii, C. primus, Cyclagelosphaera reinhardti, M. inversus, Neocrepidolithus cruciatus, N. fossus, Neocrpidolithus neocrassus, and Thoracosphaera spp. are also present in this zone. In contrasting the assemblages of Site 1135 and Site 1138, we find that H. teuriensis, along with species of Cruciplacolithus, P. sigmoides, and Thoracosphaera spp., are all more abundant at the higher-latitude Site 1135.

The H. teuriensis Zone (NA2) is represented in Samples 183-1138A-52R-3, 10-11 cm (489.80 mbsf), through 52R-3, 29-29 cm (489.99 mbsf). The FO of H. teuriensis marks the base of the zone, and the top is defined by the FO of C. tenuis. The assemblage consists of common reworked Cretaceous taxa, few P. sigmoides and Thoracosphaera spp., and rare B. constans, H. teuriensis, M. inversus, N. neocrassus, and Neocrepidolithus spp.

The Biantholithus sparsus Zone (NA1) encompasses Samples 183-1138A-52R-3, 40-42 cm (490.11 mbsf), through 52R-3, 127 cm (490.95 mbsf), which is unusually long for this zone (84 cm) relative to other Southern Ocean sites. The zone is defined as the FO of B. sparsus to the FO of H. teuriensis. The FO of B. sparsus is used to approximate the K/T boundary. This boundary was placed at Section 183-1138A-52R-3, 127 cm (490.95 mbsf), by the Shipboard Scientific Party (2000d) at a dramatic color change in Core 52R from a white chalk to a greenish clayey chalk (Fig. F7). The FO of B. sparsus was observed in Sample 183-1138A-52R-3, 70 cm (490.41 mbsf), some 57 cm above the color change. A stable isotopic analysis across this boundary supports this conclusion, although this is at odds with the conclusion from paleomagnetic stratigraphy (see "Discussion"). The assemblage is characterized by abundant to common reworked Cretaceous taxa with rare to common B. constans, M. inversus, N. neocrassus, P. sigmoides, and Thoracosphaera spp.

Samples 183-1138A-52R-3, 129 cm (490.99 mbsf), through 52R-4, 10-11 cm (491.31 mbsf), just below the K/T boundary are assigned a late Maastrichtian age. Preservation is poor at the boundary, but as one moves down the section preservation improves significantly. The nannofossil assemblage is dominated by Prediscosphaera stoveri, which makes up ~30% of the assemblage (Table T4). Other taxa found were Arkhangelskiella cymbiformis, Eiffellithus turriseiffelii, Kamptnerius magnificus, Nephrolithus frequens, Prediscosphaera cretacea, and Zygodiscus spiralis.

A bulk carbonate isotopic analysis across the K/T boundary in Core 183-1138A-52R is presented in Figure F8 along with some nannofossil datums. Samples 183-1138A-52R-4, 100-102 cm (492.21 mbsf), through 52R-4, 25-27 cm (491.46 mbsf), show an average ¹³C value of 2.25. The interpreted K/T boundary is placed at a color change at interval 183-1138A-52R-3, 127-128 cm (490.97 mbsf) (Fig. F7) (see "Discussion"). ¹³C values decrease across the boundary to 1.75 and continue to decrease until a low of 1.20 in Sample 183-1138A-52R-2, 127-128 cm (489.48 mbsf), is reached in Zone NA3 (CP1b, NP2). The overall decrease in ¹³C is ~1.05 through this interval. Samples above interval 183-1138A-52R-2, 127-128 cm (489.48 mbsf), show a recovery of ¹³C back to previous values of >2 (see Table T5).

Linear sedimentation rates, uncorrected for compaction, were calculated for the Paleogene section of each site and plotted with best-fit lines. Sedimentation rates for Hole 1135A are based on 13 nannofossil age estimates (Table T6). Sedimentation rates vary from 1.7 to 15.7 m/m.y. (Fig. F9). Apparently, low sedimentation rates for the upper and lower Paleocene are a product of hiatuses spanning Zones NA5, NA6, and CP7 (see Table T1). Linear sedimentation rates for Hole 1136A are based on seven nannofossil age estimates (Table T7). Sedimentation rates average 5.1 m/m.y. throughout the Eocene (Fig. F10). Linear sedimentation rates for Hole 1138A are based on 19 nannofossil age estimates (Table T8). Sedimentation rates vary from 1.7 to 9.2 m/m.y. (Fig. F11). Low sedimentation rates in the lower and upper Eocene can be attributed to hiatuses in those sections (Table T3).

At Sites 1135 and 1138, the lower Paleocene sedimentation rates are approximately the same (1.7 m/m.y.). This shows that sedimentation on the KP was similar in the southern and central areas. Both sites also show hiatuses in the lower upper Paleocene where marker species are missing or exceedingly rare.

Sites 1135, 1136, and 1138 all exhibit an unconformity at the Paleocene/Eocene boundary. At Sites 1135 and 1136, only the topmost section of the upper Paleocene and the lowermost Eocene is missing. At Site 1136, the unconformity below the Eocene spans the entire Paleocene and extends into the Cretaceous. Sediments of early to middle Eocene age are characterized by high sedimentation rates at all three sites (between 9 and 15 m/m.y.). Unfortunately, only Site 1138 has any upper Eocene sediment; therefore, we cannot compare the upper Eocene here with any other sites in this study (Fig. F12).