Nannofossils and foraminifers (planktonic and benthic) were examined from core catcher samples at Site 1195 for age assignments (Table T4) and paleoenvironmental interpretation (Table T5). In addition, a number of samples from within selected cores were also studied. Core catcher samples from Hole 1195A generally contained well-preserved calcareous microfossils ranging in age from late Pleistocene to late Mio-cene. Hole 1195B (cored to a depth of 521.2 mbsf) contained a mixture of poorly to well-preserved calcareous microfossils ranging in age from late Pleistocene to early Miocene.
Calcareous nannofossils are generally abundant for the entire sequence recovered at Site 1195. Preservation of nannofossils is good in the upper 10 cores and gradually deteriorates downhole. A succession of Neogene nannofossil datums (Table T4) was recognized throughout the sediment sequence, providing the best biostratigraphic resolution among the sites cored during Leg 194. The biostratigraphy also shows that, unlike other sites, the sequence cored at Site 1195 is virtually complete, with no apparent hiatuses. Detailed shore-based studies of samples from Site 1195 have the potential for recognizing most of the global Neogene nannofossil datums and providing a valuable reference section and possibly detailed biomagnetostratigraphic calibration for the tropics.
The first core catcher sample (Sample 1H-CC) contains abundant Gephyrocapsa, which includes Gephyrocapsa oceanica and various small species of the same genus. Emiliania huxleyi and Pseudoemiliania lacunosa were absent. This suggests that the sample has an age of 0.26-0.46 Ma. Sample 194-1195A-2H-CC contains P. lacunosa but no Calcidiscus macintyrei and can be assigned an age of 0.46-1.7 Ma. C. macintyrei was first encountered in Sample 194-1195A-3H-CC. This sample does not contain discoasters or any large Gephyrocapsa and was dated as 1.7-2.0 Ma.
Two late Pliocene datums (last occurrences [LOs] of Discoaster brouweri = 2.0 Ma and Discoaster pentaradiatus = 2.5 Ma) are located between Samples 194-1195A-3H-CC and 4H-CC. The apparent hiatus is most likely an artifact resulting from the large sample spacing (9.5 m). Similarly, both the LOs of Discoaster surculus (2.6 Ma) and Discoaster tamalis (2.8 Ma) are located between Samples 194-1195A-4H-CC and 5H-CC. Smaller sample spacing may show the sequential occurrences of the two datums, eliminating the appearance of a hiatus within this interval.
The late Pliocene/early Pliocene boundary, generally approximated by the LO of Reticulofenestra pseudoumbilica, is located between Samples 194-1195A-5H-CC and 6H-CC. Both R. pseudoumbilica and Sphenolithus abies are common in the latter sample.
The Miocene/Pliocene boundary, as approximated by the LO of Discoaster quinqueramus, is placed between Samples 194-1195A-8H-CC and 9H-CC, based on the presence of the index species in the latter sample. D. surculus is also present in the latter sample, constraining the sample to an age of 5.6-7.5 Ma.
Nannofossil biostratigraphy for the upper nine cores from Hole 1195B is similar to Hole 1195A. Minor differences observed can be attributed to (1) depth offsets of the cores from the two holes and (2) large sample spacing (9.5 m).
A series of nannofossil datums below Core 194-1195B-9H (Table T4) provides a relatively large number of age-control points for the rest of the sequence. Significant hiatuses are not apparent. More remarkable is that all the Miocene nannofossil datums fall near a straight line when plotted against depth (see "Age Model" for age vs. depth and sedimentation rate plots), further indicating the general stratigraphic completeness of the Miocene interval.
A sample from interval 194-1195B-55X-CC, taken 0.5 cm above the sharp boundary between Units IV and V within the semilithified glauconitic packstone, yielded a few specimens of Cyclicargolithus floridanus and small Reticulofenestra and a specimen that resembles Sphenolithus belemnos or Sphenolithus disbelemnos (a clear identification to either species was not possible because a detrital grain partially blocked the specimen). Either species can constrain the age of the sample to the early Miocene. In the absence of either species, the assemblage can be described as similar to an impoverished middle to lower Miocene assemblage. Another possibly displaced, semilithified sediment sample was taken from the very bottom of the core catcher in Section 194-1195B-55X-CC beneath a piece of limestone defining Unit V, although there is uncertainty as to whether the semilithified sediment was in situ. That sample yielded rare specimens of C. floridanus and small Reticulofenestra, an assemblage that most resembles an impoverished middle to lower Miocene assemblage.
Hole 1195A penetrated through Pliocene sediment to a sufficient depth to reach the Pliocene/Miocene boundary. This interval was repeated in Hole 1195B with a complete sequence of lower Miocene to Pleistocene sediments. The shipboard planktonic foraminifer biostratigraphy is largely founded on Hole 1195B. Planktonic foraminifer abundance and preservation are good downcore to Sample 194-1195B-37X-CC, at which point biostratigraphic resolution becomes less certain as preservation deteriorates.
Sample 194-1195A-1H-CC contains Globorotalia truncatulinoides and Pulleniatina finalis, which places the sample in the middle of Zone N22 and younger. Globorotalia tosaensis was absent; thus, the sample must represent an age younger than its LO datum at the base of Pt 1b. Sample 194-1195A-4H-CC contains Globigerinoides fistulosus, Globigerinoides extremus, and G. tosaensis. Globorotalia miocenica is absent, and G. truncatulinoides is present; however, there is a marked decline in species number from Samples 194-1195A-3H-CC to 4H-CC. This may indicate some downhole contamination in Sample 194-1195A-4H-CC rather than it being placed within the datum range of G. truncatulinoides. In summary, Sample 194-1195A-4H-CC most likely represents the interval between the first occurrence (FO) of G. truncatulinoides and the LO of G. miocenica (i.e., a zonal assignment at the N21/N22 boundary); thus, the Pleistocene/Pliocene boundary occurs between Samples 194-1195A-3H-CC and 4H-CC.
Samples 194-1195A-6H-CC through 8H-CC contain Sphaeroidinella dehiscens, Globigerina nepenthes, Globorotalia margaritae, Globorotalia cibaoensis, and Dentoglobigerina altispira, which places these samples in Zones N20 and N19. Sample 194-1195A-9H-CC was assigned to Zone N18 based on the absence of S. dehiscens and the continued presence of Globorotalia tumida. The Pliocene/Miocene boundary, therefore, lies between these two core catcher samples.
Samples 194-1195B-1H-CC and 2H-CC contain G. truncatulinoides, G. tosaensis, and P. finalis, confining the samples to Pt 1a. G. extremus is absent in Sample 194-1195B-2H-CC and present in Sample 3H-CC, which places the Pleistocene/Pliocene boundary between these samples. The continued presence of G. fistulosus in Sample 194-1195B-4H-CC places this sample in Zone N21. Sample 194-1195B-9H-CC was placed within the lower part of Zone N19 based on the occurrence of G. nepenthes and S. dehiscens, even though specimens of G. tumida were present. Sample 194-1195B-10H-CC contains G. cibaoensis but no S. dehiscens or G. tumida and represents, therefore, the uppermost Zone N17. Therefore, the base of Zone N18, which approximates the Pliocene/Miocene boundary, must occur within Sample 194-1195B-9H-CC or 10H-CC.
Samples 194-1195B-10H-CC through 25X-CC were assigned to the extensive Zones N17 and N16 that comprise the late Miocene. These zones can be largely assigned using a combination of the occurrences of Globorotalia plesiotumida (FO datum lies in the middle of Zone N16) and Neogloboquadrina acostaensis (FO marks the base of Zone N16). Sample 194-1195B-26X-CC is assigned to Zones N14-N15 based on the presence of the Globorotalia siakensis-mayeri lineage. The late/middle Miocene boundary bisects Zone N15 and thus probably lies within Core 194-1195B-26X. The LO datum of Globorotalia peripheroacuta occurs between Samples 194-1195B-28X-CC and 29X-CC, thus marking a possible Zone N12/N11 boundary. Although this lineage would be used to define the late middle Miocene, this group is rare in abundance, and in many cases, surface denudation precludes accurate identification. The Orbulina taxa share a common FO datum marking the Zone N8/N9 boundary, which can be placed between Samples 194-1195B-35X-CC and 36X-CC. Globigerinoides sicana, Praeorbulina curva, and Praeorbulina transitoria occurrences were also used to assign a number of samples, such as 194-1195B-35X-CC through 40X-CC, to Zones N8-N9. The exact position of the early/middle Miocene boundary at the base of Zone N8 could not be defined.
Planktonic foraminifers identified in Samples 194-1195B-43X-CC through 57X-CC were not diagnostic for establishing an early Miocene biostratigraphic framework. As with previous sites during Leg 194, abundances were very low and test alteration levels were high. Within these samples, index species (G. sicana, Catapsydrax dissimilis, and Globorotalia birnageae) were either tentatively identified, or more commonly, samples would contain nonindex species of extended ranges (e.g., Globoquadrina dehiscens, Globoquadrina venezuelana, and Globorotalia bella). Globigerina ciperoensis was also cautiously identified at the base of the hole in Sample 194-1195B-57X-CC. This may indicate a sample age (in the upper portion of its range Zones P20-N5) of Zones N4-N5. This datum is not included in the age vs. depth plot (see "Age Model") because the identification is not certain.
Microscopic analysis of biogenic constituents, particularly the diverse and often abundant benthic foraminifers, provide data for paleoenvironmental interpretation of the sediment sequence at Site 1195 (Table T5).
The sand-sized fraction of Samples 194-1195A-1H-CC (4.70 mbsf) through 9X-CC (80.9 mbsf) are overwhelmingly dominated by planktonic foraminifers (Table T5). Benthic foraminifers are rare to common and often include conspicuous Cibicidoides, nodosarids, and agglutinated specimens, indicating a bathyal depositional environment. Fifty percent or fewer of the grains were brown in color. The relative proportions of coarser and finer planktonic fractions varies among samples, possibly indicating changes in current winnowing. These samples represent lithologic Unit I and Subunit IIA (see "Lithostratigraphy and Sedimentology") and indicate a hemipelagic, current-influenced environment.
Samples 194-1195B-1H-CC (8.4 mbsf) through 10H-CC (94.1 mbsf) represent lithologic Unit I and Subunit IIA (see "Lithostratigraphy and Sedimentology") and are very similar to those described for this interval in Hole 1195A (Table T5). Samples 194-1195B-11R-CC (103.5 mbsf) and 21H-CC (198.9 mbsf) (lithologic Subunits IIB and IIC) are also overwhelmingly dominated by planktonic foraminifers but differ somewhat in that brown and black grains are generally rare to occasionally common but never as abundant as higher in the section. Benthic foraminifers indicate that all of these samples represent hemipelagic sediments deposited at upper bathyal water depths.
In Samples 194-1195B-22H-CC (207.4 mbsf) through 47X-CC (446.2 mbsf), planktonic foraminifers continue to be abundant in the coarse sand fractions but neritic debris becomes increasingly important, particularly very fine bioclastic material with minor quartz and occasionally slightly larger reworked bioclasts that include small specimens of larger benthic foraminifers. Glauconite grains and infill are rare to common in most samples. Based on these neritic components, a distal periplatform depositional environment at outer neritic depths is interpreted.
Beginning in Sample 194-1195B-48X-CC (458.0 mbsf), glauconite, quartz, and neritic debris substantially increase downcore. In Sample 194-1195B-49X-CC (463.5 mbsf), glauconite, quartz, and blackened grains predominate and remain important through Sample 194-1195B-54X-CC (513.1 mbsf). These samples, which are part of lithologic Unit IV (see "Lithostratigraphy and Sedimentology"), are interpreted as representing a proximal periplatform depositional environment in outer neritic water depths. Sample 194-1195B-55X-CC (517.7 mbsf) contains a gold-colored limestone, which contains abundant larger benthic foraminifers. These foraminifers are tentatively identified as nummulitids, discocyclinids, and Heterostegina spp., which may be late Eocene in age. This gold-colored limestone has a lithified contact with a black grainstone that contains abundant Lepidocyclina, which, along with nannofossils in the surrounding sediment, indicate lower Miocene deposition. Confirmation of the age and depositional environment of the gold limestone will require detailed thin section analysis.