NANNOFOSSIL RESULTS

A total of 32 smear slides were examined from Hole 1207A (Cores 198-1207A-18H to 24X, excluding Core 22X, which had no recovery) and 45 from Hole 1207B (Cores 198-1207B-2R through 28R, except Cores 7R [no recovery] and 25R to 27R [chert without adhering calcareous material]). The majority of these nannofossil ooze samples contained moderately well preserved, highly abundant nannofloras. Samples with poor preservation are generally those comprising scrapings from chert pieces. These were analyzed from chert intervals, where core recovery was very low, and the only calcareous material available for analysis was that adhering to the chert (e.g., lower Campanian–middle Coniacian of Hole 1207B; Sections 198-1207B-10R-CC to 19R-CC).

Nannofossil range charts for these holes are shown in Tables T1 and T2. From these, it can be seen that Hole 1207A ranges from upper (Subzones UC15d^TP–UC15e^TP) to lower (Subzones UC14d^TP–UC15a^TP) Campanian (equivalent to CC22a–CC22c to CC18c–CC19b), terminating in chert, whereas Hole 1207B is upper Campanian (Subzones UC15d^TP–UC15e^TP; CC22a–CC22c) to uppermost Albian–lower Cenomanian (Subzones UC0a–UC1a; CC9a–CC9c) (see Bown, this volume, for the Lower Cretaceous succession in this hole). The absence of certain Campanian marker species (Eiffellithus parallelus, Misceomarginatus pleniporus, and Bukryaster hayi) from both holes is discussed below (see "Discussion").

In Hole 1207B, biostratigraphic application was hampered from the pre-Campanian to the upper Coniacian (Subzones UC14c^TP–UC11b; CC18b–CC14; Sections 198-1207B-10R-CC to 14R-CC) by poorly preserved assemblages from the ooze scrapings from chert pieces, in which only the more robust taxa were present. In the upper–middle Coniacian (Subzone UC11a–Zone UC10; CC18b–CC14; Sections 198-1207B-15R-CC to 19R-CC), Lithastrinus grillii was absent, so the UC10/UC11 (CC14/CC15) zonal boundary could not be determined. Zone UC9 (upper Coniacian–middle Turonian; CC13b) appears to be missing, due to very low core recovery combined with the absence from the region, or very sporadic occurrence, of the marker taxa (Broinsonia parca expansa, Zeugrhabdotus biperforatus, and Lithastrinus septenarius). A hiatus is not necessarily indicated at this level. Subzones UC8b and UC8a (Sections 198-1207B-20R-CC to 21R-CC; CC13a–CC12) could not be separated because the marker species (Lucianorhabdus quadrifidus) is absent from the region. The concentration of first and last occurrences in Section 198-1207B-21R-CC may indicate a hiatus, resulting in the loss of sediments comprising Zone UC7–Subzone UC3d (lower Turonian–upper Cenomanian; CC11–CC10a). The last occurrence (LO) of Staurolithites gausorhethium is lower than expected, so Subzones UC3b and UC3c (in CC10a; upper–middle Cenomanian; Section 198-1207B-21R-CC) cannot be separated. Subzones UC2c–UC2b (in CC9c) are missing and Subzones UC1b–UC2a (in CC9c) are indistinguishable because of the presence of a condensed section. The absence from the region of a number of consecutive marker taxa (Corollithion kennedyi, Calculites anfractus, and Hayesites albiensis) means that Subzones UC1a–UC0b (CC9c–CC9b; lower Cenomanian–uppermost Albian; Section 198-1207B-24R-CC) cannot be separated.

Only one hole was drilled at Site 1208; 43 samples were examined for nannofossils (Cores 198-1208A-36X to 41X; Core 42X had low recovery because of chert, which resulted in termination of the hole). Preservation was generally moderate; nannofossil abundance was generally high. Table T3 shows the nannofossil stratigraphic distributions. The succession is upper (Subzones UC15e^TP–UC15d^TP; CC22c–CC22a) to lower (Subzones UC14c^TP–UC14b^TP; CC18b) Campanian. Subzones UC15d^TP–UC15e^TP, UC14d^TP–UC15a^TP, and UC14b^TP–UC14c^TP could not be differentiated due to the respective absences of the subzonal markers E. parallelus (from this site), M. pleniporus, and B. hayi (from this region) (see "Discussion").

A total of 16 smear slides were examined from Hole 1209A (Cores 198-1209A-25H to 28X, where the hole terminates) and 39 from Hole 1209C (Cores 198-1209C-16H to 22H; there was no recovery from Core 23X, where the hole terminated). Preservation was moderate and abundance high virtually throughout. Tables T4 and T5 illustrate the nannofossil stratigraphic distributions. The Hole 1209A succession is upper Maastrichtian (Subzones UC20d^TP–UC20b^TP; CC26b–CC25c). Hole 1209C is upper Maastrichtian to around the Maastrichtian/Campanian boundary (Subzone UC20c^TP–Zone UC17; CC26a–CC23b). Stratigraphic difficulties were encountered in Hole 1209C in differentiating between Zone UC18–Subzone UC20a^TP, due to the absence of Reinhardtites levis from and the higher than expected first occurrence (FO) of Lithraphidites quadratus at this location (see "Discussion" ). The uppermost Maastrichtian is present in Hole 1209A, as evidenced by the presence of Micula prinsii and Ceratolithoides ultimus. Bown (in press) presents the complete K/T interval boundary nannofossil data from this site.

The MME lies between Sections 198-1209C-21H-1, 125 cm, and 21H-3, 128 cm (279.15–282.18 meters below seafloor [mbsf]) (Frank et al., 2005). This interval contains the LO of Zeugrhabdotus bicrescenticus and lies above the LOs of Cribrocorona echinus and Tranolithus orionatus, in the undifferentiated Zone UC18–Subzone UC20a^TP (CC24–CC25b).

A total of 23 samples were analyzed from Hole 1210A (Cores 198-1210A-24H to 27H, where the hole terminates), 3 of which are interpreted as Danian (Samples 198-1210A-24H-4, 38 cm, 40 cm, and 44 cm), based on the presence of frequent and consistently occurring calcispheres and small foraminifer fragments. A total of 112 samples were examined from Hole 1210B (Cores 198-1210B-24H to 42H, where the hole terminates). Preservation is generally moderate and nannofossil abundance high throughout this relatively chert-free succession.

Tables T6 and T7 show the nannofossil distributions for these holes. Hole 1210A is upper Maastrichtian (Subzones UC20d^TP–UC20b^TP; CC26b–CC25c), whereas Hole 1210B is upper Maastrichtian–lower Campanian (Subzones UC20d^TP–UC15b^TP; CC26b–CC20). Hole 1210B contains the only succession that records the expected sequence of consecutive FOs of L. quadratus and Micula murus (bases of Subzones UC20a^TP and UC20b^TP, respectively) in Core 198-1210B-26H. However, the succession is similar to other sites of this age in that the bases of Zone UC19 (LO of R. levis) and Subzone UC15e^TP (FO of E. parallelus) cannot be distinguished (see "Discussion"). The uppermost Maastrichtian is present in Holes 1210A and 1210B, as illustrated by the presence of both M. prinsii and C. ultimus. The complete K/T boundary interval nannofossil data from this site are presented in Bown (in press).

Hole 1210B contains the MME between Sections 198-1210B-28H-5, 72 cm, and 28H-6, 52 cm (262.92–264.22 mbsf), with a further layer of inoceramid prisms at 261.48 mbsf (Frank et al., 2005). The LO of Z. bicrescenticus lies below the single layer of prisms but above the MME interval proper. The MME lies above the LOs of C. echinus and T. orionatus, in the undifferentiated Zones UC18–UC19 (CC24–CC25a).

A total of 22 smear slides were examined from Hole 1211A (Cores 198-1211A-15H to 18H, in which the hole terminates) and 5 from Hole 1211C (Core 198-1211C-15H, in which the hole terminates). In general, preservation was moderate and nannofossil abundance high throughout.

The nannofossil stratigraphic distributions are shown in Tables T8 and T9. Hole 1211A is uppermost Maastrichtian (Subzone UC20d^TP) to upper–lower Maastrichtian (Subzone UC20a^TP–Zone UC18; CC26b to CC25b–CC24), whereas Hole 1211C is uppermost Maastrichtian (Subzone UC20d^TP; CC26b). The apparently reversed FOs of M. murus and L. quadratus in the Maastrichtian are discussed below, along with the absence of R. levis, which means that Zone UC18–Subzone UC20a^TP (lower–upper Maastrichtian; Core 198-1211A-18H) cannot be differentiated (see "Discussion"). The uppermost Maastrichtian is present in Hole 1211A, based on the presence of both M. prinsii and C. ultimus. The complete K/T boundary interval nannofossil data from this site are presented in Bown (in press).

Isolated inoceramid prisms are present in Section 198-1211A-18H-2 (~157.0 mbsf, from the original core descriptions in Bralower, Premoli Silva, Malone, et al., 2002), although Frank et al. (2005) do not consider these to be representative of the MME. However, these isolated prisms lie at/immediately above the LO of Z. bicrescenticus and above the LOs of C. echinus and T. orionatus in undifferentiated Zone UC18–Subzone UC20a^TP (CC24–CC25b), as at previous sites.

Two samples were analyzed from Hole 1212A (Cores 198-1212A-12H to 13H; flow-in was a problem below the samples analyzed from Section 13H-1, and coring terminated in this core) and 63 from Hole 1212B (Cores 198-1212B-11H to 25H, except for 16H, which had no recovery; the hole terminates in chert). Preservation and nannofossil abundance were generally moderate and high, respectively.

The nannofossil stratigraphic distributions are shown in Tables T10 and T11. The two samples from Hole 1212A were uppermost Maastrichtian (Subzone UC20d^TP; CC26b). Hole 1212B contains the uppermost Maastrichtian (Subzone UC20d^TP; CC26b) to the lower Cenomanian (Subzones UC2c–UC1b; in CC9c). The uppermost Maastrichtian is present in both holes, indicated by the presence of M. prinsii. C. ultimus was not present in the samples analyzed, however. The complete K/T nannofossil succession is presented in Bown (in press). The reversed FOs of M. murus and L. quadratus in the Maastrichtian and the absence/nonutility of a number of Maastrichtian (R. levis) and Campanian (E. parallelus and Uniplanarius sissinghii) marker species are discussed below. The oldest Campanian preserved here appears to lie above a mid-Campanian to lower Coniacian hiatus (Subzone UC15a^TP–Zone UC10; CC19–CC14), as indicated by a concentration of FOs in Section 198-1212B-24H-6 between 1 and 30 cm. Below this, Subzones UC9a–UC9c could not be separated because of the sporadic occurrence of Z. biperforatus and/or the absence from the region of B. parca expansa. Another hiatus was identified in Section 198-1212B-24H-6 between 30 and 30.5 cm, as indicated again by the concentration of FOs/LOs at 30.5 cm, effectively removing Subzones UC8b–UC3c (CC10b–CC13a; middle Turonian–upper Cenomanian). This condensed section resulted in the compression of Subzones UC3a–UC3b, rendering them indistinguishable from one another. Subzones UC2c–UC1b (lower Cenomanian) also could not be differentiated; some events were higher than expected (FOs of Cylindralithus sculptus and Gartnerago segmentatum) or lower than expected (FO of Helicolithus anceps) or the marker taxa were absent from this site (Zeugrhabdotus xenotus) or the region (C. kennedyi and C. anfractus).

Isolated inoceramid prisms were found in Sample 198-1212B-18H-1, 94–96 cm (144.64 mbsf, from initial core descriptions in Bralower, Premoli Silva, Malone, et al., 2002), although these were not considered to constitute the MME proper (Frank et al., 2005). The prism layer lies at/immediately above the LOs of T. orionatus and C. echinus but below the LO of Z. bicrescenticus. This is apparently older than at Site 1211, lying at the base of undifferentiated Zone UC18–Subzone UC20a^TP (CC24–CC25b).

Seven smear slides were analyzed from Core 198-1213A-7R; below this core, chert was predominant. The nannofloras were generally poorly preserved resulting in the loss of many taxa, although abundance was high. The stratigraphic distribution is shown in Table T12, but the ages assigned (upper–lower Campanian to lower Coniacian–lower Turonian; Subzones UC15e^TP–UC15b^TP to UC9c–UC8a; CC22c–CC20 to CC13b–CC12) are of very low resolution due to the loss of many marker taxa.

Figure F2 shows the correlation between the sites and gives an overview of the occurrence of chert in relation to the biostratigraphy.