BIOSTRATIGRAPHY

Holes 1211A, 1211B, and 1211C comprise apparently complete upper Pleistocene to upper Miocene and upper Oligocene to lower Maastrichtian sequences separated by a condensed interval and at least two unconformities (upper to middle Miocene and lower Miocene to uppermost Oligocene) representing ~20 m.y. of condensed or missing record. High-resolution sampling for both calcareous nannofossil and planktonic foraminiferal biostratigraphy suggests that several key intervals were recovered, including the E/O boundary, the P/E boundary transition, the PETM, and the K/T boundary. The main calcareous nannofossil and foraminiferal datums are summarized in Tables T2 and T3.

Calcareous nannofossils are generally abundant and moderately to well preserved throughout the Cenozoic and Cretaceous sediments of Holes 1211A, 1211B, and 1211C. Planktonic foraminifers exhibit variable preservation and diversity. In particular, preservation is generally poor in samples from the Miocene, Oligocene, and upper Eocene.

Studies of benthic foraminifers were conducted on selected core catcher samples from Holes 1211A and 1211B, and stratigraphic ranges are summarized in Tables T4 and T5. Neogene benthic foraminifers are well preserved and rare to few in abundance; Paleogene and Cretaceous forms are moderately well preserved and rare to few in abundance.

Neogene

The Neogene section ranges from the upper Pleistocene (Subzone CN14b) to the lower-middle Miocene (Zones CN3 and CN4). The Pleistocene to upper Miocene interval appears to be relatively complete. Although a number of zones and subzones have not been recognized, they probably lie within cores. The base of this interval is in Subzone CN9a (upper Miocene), constrained by the FO of Discoaster berggrenii and the FO of Amaurolithus. A lower to middle Miocene interval is present in Core 198-1211A-7H (Samples 198-1211A-7H-2, 10 cm, and 7H-2, 20 cm) based on the presence of Sphenolithus heteromorphus (Zones CN3 and CN4); this interval may be bounded by unconformities. The underlying Oligocene sediment (identified in Sample 198-1211A-17R-2, 86 cm) is assigned to Subzone CP19b.

Paleogene

The Paleogene section ranges in age from late Oligocene (Subzone CN19b) to the K/T boundary and includes the E/O and P/E boundary transitions. The Oligocene is relatively complete, although the Miocene/Oligocene boundary interval is absent, and Zone CP17 (lower Oligocene) was not identified. The uppermost Oligocene sediment analyzed (Sample 198-1211A-17R-2, 86 cm) contains Sphenolithus ciperoensis, which has an LO in Subzone CP19b (25.5 Ma).

The E/O boundary is identified at the LO of Discoaster barbadiensis in Samples 198-1211A-10H-1, 140 cm, and 198-1211B-9H-7, 45 cm. The Eocene is relatively complete with all the CP zones identified. The P/E boundary and PETM interval are rather condensed and may be incomplete. In Hole 1211A, the FO of Discoaster diastypus (Subzone CP9a), LO of Fasciculithus, and FO of Tribrachiatus orthostylus (Subzone CP9b) are all recorded in Sample 198-1211A-13H-6, 1 cm, indicating a condensed or absent Subzone CP9a interval. In Hole 1211B, the FO of Discoaster diastypus (Sample 198-1211B-13H-4, 77 cm) and FO of Tribrachiatus orthostylus (Sample 13H-4, 56 cm) are separated by 21 cm, again suggesting a condensed interval. In Hole 1211C, the interval separating these datums is 100 cm (FO of D. diastypus in Sample 198-1211C-13H-2, 120 cm, and FO of T. orthostylus in Sample 13H-2, 20 cm), indicating a more complete record. The remainder of the Paleocene appears to be relatively complete in all three holes, although sedimentation rates are low (0.5-2.5 m/m.y.) (see "Sedimentation and Accumulation Rates").

The K/T boundary is present in Sections 198-1211A-15H-4, 198-1211B-15H-3, and 198-1211C-15H-3. The nannofossil succession is similar to that observed at Site 1210. Sediments bearing common Micula prinsii (Zone CC26; Sample 198-1211B-15H-3, 125 cm) are overlain by a white carbonate interval that has a mixed assemblage at the base, incorporating Cretaceous nannofloras together with common calcisphere fragments (interval 198-1211B-15H-3, 115-120 cm). Above this, smear slides are dominated by fine micrite, minute foraminifers, and abundant calcispheres, with few reworked Cretaceous nannofossil taxa (interval 198-1211B-15H-3, 108 cm, through 15H-2, 90 cm). These samples consistently contain survivor taxa (e.g., species of Lapideacassis, Cyclagelosphaera, and Markalius). The first new Paleocene coccolith taxa include the genus Neobiscutum, recorded in Sample 198-1211B-15H-3, 102 cm, and Cruciplacolithus primus in Sample 198-1211B-15H-3, 62 cm.

Cretaceous

An apparently continuous section of rapidly deposited upper to lower Maastrichtian sediments was recovered at Site 1211. The calcareous nannofossils from this interval are well preserved and the assemblages are diverse. Zones CC26 to CC24 were identified, but the zonal boundaries are somewhat uncertain, due to problems concerning the identification and stratigraphic range of a number of the marker taxa, particularly Micula murus and Reinhardtites levis. The nature of these difficulties will be a focus of postcruise investigations.

Neogene

The Neogene section ranges from upper Pleistocene to upper Mio-cene, with a major unconformity separating the upper Miocene and upper Oligocene. Planktonic foraminifers at Site 1211 are generally moderately preserved. They are abundant to common in the Pleistocene and Pliocene but decline in abundance and preservation through the Mio-cene.

The youngest sediments recovered in Hole 1211A are assigned to the upper part of Zone N22 based on the presence of Truncorotalia truncatulinoides in Sample 198-1211A-1H-CC and on the absence of Truncorotalia tosaensis. The remainder of the Pleistocene sequence (Samples 198-1211A-2H-CC, 198-1211B-1H-CC through 2H-CC, and 198-1211C-1H-CC through 2H-CC) also belongs to Zone N22 and contains common Globigerina bulloides, Globorotalia inflata, Truncorotalia crassaformis, Orbulina universa, Neogloboquadrina dutertrei, Neogloboquadrina pachyderma (dextral), rare to few T. trucatulinoides, and T. tosaensis. They are supplemented by few Globorotalia menardii, Globorotalia tumida, and pulleniatinids. In the Pliocene sediments, the FOs of T. tosaensis, T. crassaformis (Samples 198-1211A-3H-CC, 198-1211B-2H-CC, and 198-1211C-3H-CC), and Sphaeroidinella dehiscens (Samples 198-1211A-5H-CC, 198-1211B-3H-CC, and 198-1211C-4H-CC) permit the differentiation of Zones N21 and N20-N19, respectively. Other useful events are the LOs of Dentoglobigerina altispira (Samples 198-1211A-4H-CC and 198-1211B-4H-CC), Sphaeroidinellopsis seminulina (Samples 198-1211A-5H-CC and 198-1211B-4H-CC), and Globoturborotalita nepenthes (Samples 198-1211A-5H-CC and 198-1211B-5H-CC).

The uppermost Miocene is present in Sample 198-1211B-6H-CC, which contains common G. tumida, Globoconella conoidea, Globoturborotalita nepenthes, and Sphaeroidinellopsis seminulina. This section is assigned to Zone N18 based on the presence of G. tumida and the absence of Sphaeroidinella dehiscens. Although the planktonic assemblage is poorly preserved in Sample 198-1211A-6H-CC, the presence of rare to few taxa such as Dentoglobigerina altispira, "Globigerina" venezuelana, Globoquadrina dehiscens, G. nepenthes, and Globigerinoides extremus and the absence of G. tumida, Globigerinoides conglobatus, and Globorotalia conomiozea are indicative of Subzone N17a.

Paleogene

A major unconformity separates the upper Miocene from the Oligocene sequence drilled in Holes 1211A (interval 198-1211A-7H-CC through 9H-CC), 1211B (interval 198-1211B-6H-CC through 8H-CC), and 1211C (interval 198-1211C-6H-CC through 8H-CC). In general, the Oligocene assemblage shows low diversity and poor preservation. Subdivision of the Oligocene section is difficult, due to the paucity of zonal marker species. The planktonic foraminiferal assemblages are represented mainly by dissolution-resistant taxa such as Catapsydrax dissimilis, Catapsydrax unicavus, "Globigerina" euapertura, Globigerina pseudovenezuelana, Globoquadrina tripartita, Globigerina sellii, and few globorotaloidids. Sample 198-1211A-7H-CC and interval 198-1211B-6H-CC to 7H-CC are tentatively assigned to the upper Oligocene Subzone P21b based on the presence of very rare Paragloborotalia opima and on the absence of chiloguembelinids. The presence of Subbotina angiporoides and the absence of "Globigerina" ampliapertura allow us to assign Sample 198-1211A-8H-CC to lower Oligocene Zone P20-P21a. The underlying Sample 198-1211B-8H-CC yields few "G." ampliapertura, Subbotina angiporoides, S. gortanii, S. praeturritilina, and Globoquadrina tapuriensis and indicates lower Oligocene Zones P19 to P18.

Dissolution and generally poor preservation also characterize the upper Eocene. Sample 198-1211A-9H-6, 118-119 cm, is assigned to Zones P16 to P17 based on the presence of "spines" of Hantkenina, poorly preserved specimens of Hantkenina alabamensis, Pseudohastigerina micra, and Pseudohastigerina naguewichiensis. The assemblage is dominated by dissolution-resistant taxa, including Turborotalia pseudoampliapertura, Globorotaloides suteri, Subbotina eocaena, C. unicavus, and "Globigerina" euapertura. A similar assemblage is present in Sample 198-1211B-9H-CC. Sample 198-1211A-10H-CC, which contains few Globigerinatheka tropicalis, Globigerinatheka index, Globigerinatheka subconglobata, G. senni, subbotinids, common fragments of Globigerinatheka spp., hantkeninids, and turborotalids, is assigned to Zone P14 based on the absence of Globigerinatheka semiinvoluta and "Orbulinoides" beckmanni.

Preservation improves lower in the middle Eocene. Samples 198-1211B-10H-CC and 198-1211C-10H-CC contain a moderately well-preserved assemblage, which includes G. subconglobata, G. senni, Morozovella aragonensis, Acarinina bullbrooki, Igorina broedermanni, Subbotina eocaenica, Subbotina cryptomphala, and Guembelitrioides lozanoi. This assemblage is indicative of the upper part of Zone P10 based on the absence of Morozovella lehneri and Morozovella caucasica.

Samples 198-1211A-11H-CC, 198-1211B-11H-CC, and 198-1211C-11H-CC are characterized by the presence of Morozovella aragonensis, M. caucasica, Igorina broedermanni, Acarinina pentacamerata, Acarinina soldadoensis, Subbotina cryptomphala, Guembelitrioides lozanoi, and Globigerinatheka senni. The absence of Hantkenina, together with the presence of M. caucasica and Acarinina pentacamerata, allows us to assign this assemblage to the lower Eocene Zones P9 to P8. Zone P7 is distinguished from the overlying sediments by the co-occurrence of M. aragonensis, M. formosa, and Subbotina inaequispira and by the absence of Acarinina pentacamerata in Samples 198-1211A-12H-CC and 198-1211B-12H-CC.

Lower Eocene Zone P6 has been recognized in Sample 198-1211B-13H-4, 16-17 cm. Characteristic taxa of Zone P6 include Morozovella subbotinae, Morozovella formosa, Morozovella gracilis, Subbotina velascoensis, and A. soldadoensis in the absence of both M. aragonensis and M. velascoensis.

The LO of Morozovella velascoensis is used to define the P5/P6 zonal boundary, as well as the P/E boundary and lies between Samples 198-1211B-13H-4, 73-74 cm, and 13H-4, 89-90 cm, and between Samples 198-1211A-13H-5, 86-87 cm, and 13H-5, 128-129 cm. The PETM (Zachos et al., 1993) occurs within Zone P5, and the interval is well identified in Sections 198-1211A-13H-6, 198-1211B-13H-4, 198-1211C-13H-2, and 13H-3.

The underlying samples (198-1211A-13H-CC and 198-1211B-13H-CC) contain a diverse and well-preserved assemblage of M. velascoensis, Morozovella occlusa, Morozovella acuta, M. subbotinae, Morozovella aequa, Morozovella pasionensis, Acarinina soldadoensis, Acarinina mckannai, and Acarinina nitida, indicative of Zone P5. Morozovella angulata, Morozovella conicotruncana, Subbotina triloculinoides, Igorina albeari, and Parasubbotina pseudobulloides mark Zone P3 in Sample 198-1211B-14H-CC.

Sample 198-1211B-14H-CC contains Praemurica uncinata, Praemurica inconstans, Parasubbotina varianta, Morozovella praeangulata, Globoanomalina compressa, and Parasubbotina pseudobulloides. This interval is assigned to lower Paleocene Zone P2 based on the absence of M. angulata and M. conicotruncata.

The interval containing Zone P1 at Site 1211 was not observed in core catcher samples. However, several samples taken across the K/T boundary permit the recognition of the Parvularugoglobigerina eugubina Zone (Zone P) in the interval between Samples 198-1211A-15H-4, 88-89 cm, and 15H-5, 0-1 cm. The boundary between the lowermost Paleocene and the uppermost Maastrichtian is clearly bioturbated, and careful sampling of burrows yields an identifiable biostratigraphy. Few well-preserved Paleocene taxa indicative of the P Zone, including P. eugubina, Parvularugoglobigerina extensa, and woodringinids, are underlain by a rich assemblage dominated by minute Guembelitria indicative of Zone P0. The Paleocene components are clearly confined to burrows. The highest Cretaceous assemblages are present in Samples 198-1211A-15H-4, 147-148 cm, and 198-1211B-15H-3, 119-120 cm.

Cretaceous

In general, Cretaceous planktonic foraminifers recovered at Site 1211 are abundant and well preserved. However, the uppermost Cretaceous assemblages are significantly affected by dissolution with few whole specimens. Nevertheless, the presence of large-sized Cretaceous taxa such as Abathomphalus mayaroensis, Globotruncana stuarti, Globotruncana linneiana, Contusotruncana contusa, Pseudoguembelina costulata, Pseudoguembelina excolata, and Pseudoguembelina hariaensis, as well as the small taxa, including Schackoina cenomana, Schackoina multispinata, Globigerinelloides subcarinatus, Globotruncanella havanensis, and Globotruncanella petaloidea, indicate that these assemblages belong to the upper Maastrichtian Abathomphalus mayaroensis Zone (Zone KS31).

The underlying Upper Cretaceous interval (Samples 198-1211A-16H-6 and 16H-CC, and 198-1211B-16H-CC through 17H-CC) is characterized by moderately to well-preserved planktonic foraminiferal assemblages yielding Abathomphalus mayaroensis, Abathomphalus intermedius, Contusotruncana contusa, Racemiguembelina fructicosa, Pseudotextularia elegans, P. excolata, P. hariaensis, Globotruncanita stuarti, Globotruncana stuartiformis, Globotruncana orientalis, G. linneiana, Heterohelix rajagopalani, and rugoglobigerinids, as well as rare Globotruncanita angulata and Gublerina cuvillieri. Based on the presence of Abathomphalus mayaroensis, this interval is also assigned to the upper Maastrichtian A. mayaroensis Zone (KS31).

Samples 198-1211A-17H-CC through 18H-CC yield common Contusotruncana contusa and Racemiguembelina fructicosa in the absence of Abathomphalus mayaroensis, indicating that this interval belongs to the mid-Maastrichtian C. contusa-R. fructicosa Zone (upper KS30). Other species occurring in this interval are Contusotruncana patelliformis, Globotruncana bulloides, G. linneiana, G. stuarti, G. stuartiformis, Rugotruncana subcircumnodifer, associated with rare Gansserina gansseri and Gansserina wiedenmayeri, and common pseudoguembelinids and rugoglobigerinids. The lowest part of Hole 1211B (Sections 198-1211B-18H-CC through 19H-CC) is assigned to the lower Maastrichtian-upper Campanian Gansserina gansseri Zone (lower KS30) based on the absence of C. contusa and R. fructicosa and the presence of few G. gansseri together with Contusotruncana fornicata, Globotruncana bulloides, and globigerinelloidids.

Benthic foraminifers were examined in selected core catcher samples of Holes 1211A and 1211B. They are well preserved and rare to few in abundance in the Neogene. The Paleogene through Cretaceous section contains moderately preserved benthic foraminifers that are generally rare to few in abundance. Benthic foraminifers are relatively abundant in the upper Miocene, in the E/O boundary interval, and near the K/T boundary, due to dissolution of planktonic foraminifers.

Neogene

In Samples 198-1211A-1H-CC through 5H-CC and 198-1211B-1H-CC through 5H-CC, the Pleistocene to Pliocene benthic assemblages are represented by diverse taxa including Anomalinoides globulosus, Oridorsalis tener, cibicidoidids, gyroidinoidids, Pyrgo lucernula, Pyrgo murrhina, uvigerinids, and agglutinated species (Eggerella bradyi and Martinottiella sp.). Uvigerina is one of the characteristic genera of the Neogene but is poorly preserved and very rare in Hole 1211B. The upper Miocene interval represented in Sample 198-1211A-6H-CC is characterized by the benthic foraminifers A. globulosus, Gyroidinoides girardanus, O. tener, P. lucernula, P. murrhina, and abundant Stilostomella subspinosa.

Neogene benthic foraminifer assemblages indicate paleowater depths in the upper abyssal zone (2000-3000 m) based on the presence of A. globulosus, cibicidoidids (Cibicidoides mundulus and Cibicidoides wuellerstorfi), Pyrgo murrhina, P. lucernula, and uvigerinids (Uvigerina hispida, Uvigerina hispidocostata, and Uvigerina senticosa) (Pflum et al., 1976; Woodruff, 1985; van Morkhoven et al., 1986).

Paleogene

The Oligocene interval (Samples 198-1211A-7H-CC, 9H-CC, and 198-1211B-6H-CC through 8H-CC) yields benthic assemblages that are generally dominated by large and abundant stilostomellids (Orthomorphina spp., Stilostomella abyssorum, Stilostomella gracillima, Stilostomella subspinosa, and Stilostomella spp.). Other components include Bolivina huneri, Globocassidulina subglobosa, and Vulvulina spinosa. Near the E/O boundary (Samples 198-1211A-9H-CC and 198-1211B-8H-CC), buliminids (Bulimina elongata, Bulimina impendens, Bulimina jarvisi, and Bulimina semicostata) also characterize the benthic assemblages.

B. jarvisi, B. semicostata, Clinapertina complanata, Nuttallides truempyi, Oridorsalis umbonatus, and stilostomellids represent the Eocene benthic assemblages (Samples 198-1211A-10H-CC through 12H-CC and 198-1211B-11H-CC and 12H-CC). In Samples 198-1211A-11H-CC and 198-1211B-11H-CC and 12H-CC, benthic foraminifers are rare and small. Sample 198-1211A-12H-CC contains abundant Aragonia aragonensis and Chrysalogonium spp.

Samples 198-1211A-13H-CC and 198-1211B-13H-CC and 14H-CC contain benthic assemblages characterized by the species Conorbinoides hillebrandti, Nuttallides truempyi, Oridorsalis umbonatus, Aragonia ouezzanensis, Aragonia velascoensis, Buliminella grata, Dentalina spp., Lenticulina spp., and agglutinated taxa (Marssonella trochoides and Spiroplectammina jarvisi). Paleogene benthic assemblages are indicative of upper abyssal depths (2000-3000 m).

Cretaceous

Sections 198-1211A-15H-CC through 18H-CC and 198-1211B-15H-CC through 19H-CC contain benthic assemblages that are generally dominated by trochospiral calcareous taxa (Nuttallides truempyi, Oridorsalis umbonatus, Osangularia plummerae, and Sliterella lobulata), Aragonia ouezzanensis, A. velascoensis, Dentalina spp., Lenticulina spp., and Pyramidina szajnochae. Although rare, the agglutinated species including Gaudryina pyramidata, Marssonella trochoides, and Spiroplectammina jarvisi also characterize the benthic assemblages of this interval.

Upper Cretaceous trochospiral calcareous benthic foraminifers indicate abyssal paleowater depths (>2500 m; after Nyong and Olsson, 1984) in nannofossil Zones CC25 and CC26. The presence of A. velascoensis in nannofossil Zone CC24 is indicative of lower bathyal to uppermost abyssal paleowater depth (1500-2500 m depth, according to Nyong and Olsson, 1984), suggesting a general deepening trend through the Maastrichtian.