Nannofossils and foraminifers were examined from core catcher samples at Site 1194 and from a number of samples and observations within selected intervals. Table T4 details the nannofossil and planktonic datums used for age assignments. Core catcher samples from Hole 1194A (which penetrated to a depth of 160.3 mbsf) generally contained well-preserved calcareous microfossils ranging from the late Pleistocene to late Miocene. Hole 1194B commenced coring at ~110 mbsf to sample the NMP slope. The calcareous microfossils in this hole are low in abundance to barren and poorly preserved, resulting in loosely constrained biostratigraphic age assignments. Microscopic analysis of biogenic constituents >63 µm, including benthic foraminifers, provided data for paleoenvironmental interpretation (Table T5).
Calcareous nannofossils are abundant and moderately well preserved from Core 194-1194A-13H upward and are generally rare and poorly preserved below this core. Upper Pliocene through middle Miocene nannofossils were identified, and nine nannofossil datums were established for age-depth construction (Table T4; see "Age Model" for age vs. depth and sedimentation rate plots). A brief summary of the nannofossil biostratigraphy is given below.
Discoaster brouweri, Discoaster pentaradiatus, and Discoaster surculus were found in Sample 194-1194A-1H-CC. The presence of these taxa in the absence of Sphenolithus abies and Reticulofenestra pseudoumbilica constrains the age of the sample to 2.6-3.8 Ma (late Pliocene). Much of the Pleistocene and part of the upper Pliocene section thus appears to be missing or very condensed at the site.
The upper Pliocene/lower Pliocene boundary is generally approximated by the last occurrence (LO) of R. pseudoumbilica, which is located between Samples 194-1194A-3H-CC and 4H-CC. Both R. pseudoumbilica and S. abies are common in the lower sample, whereas only the latter species is present in the upper sample. This sequence of occurrences is normal in the tropical ocean. The next nannofossil datum recognized is the LO of Amaurolithus spp. (5.6 Ma), between Samples 194-1194A-5H-CC and 6H-CC.
The Miocene/Pliocene boundary, as approximated by the LO of Discoaster quinqueramus, is placed between Samples 194-1194A-7H-CC and 8H-CC, based on the presence of the index species in the latter sample. D. surculus occurs down to Sample 194-1194A-12H-CC and constrains the age of interval 194-1194A-8H-CC to 12H-CC to 5.6-7.5 Ma. Sample 194-1194A-13H-CC contains D. quinqueramus but no D. surculus and thus can be assigned an age range of 7.5-8.6 Ma.
Cyclicargolithus floridanus was first encountered in Sample 194-1194A-14X-1, 48-50 cm, suggesting that this sample is older than 11.9 Ma. A hiatus is thus indicated between this sample and the sample above (194-1194A-13X-CC), coinciding with a major lithologic boundary (see "Lithostratigraphy and Sedimentology"). The upper stratigraphic range of C. floridanus is apparently truncated by this hiatus. With the recognition of the LO of Sphenolithus heteromorphus (13.6 Ma) at a lower stratigraphic level in Hole 1194B (see below), the duration of the hiatus could be constrained to be 3-6 m.y. long.
Samples from Hole 1194B generally contain few to rare nannofossils. A useful datum identified in this hole is the LO of S. heteromorphus between Samples 194-1194B-5R-CC and 9R-CC. The lowest sample from Hole 1194B that enables a relatively useful age determination is Sample 194-1194B-27R-CC, which yielded few nannofossils, including S. heteromorphus, which suggests an age range of 13.6-18.2 Ma. The core catcher samples below this level yielded only rare nannofossils, and the low abundance did not allow a reliable determination of the evolutionary first occurrence of S. heteromorphus.
Planktonic foraminifers were well preserved and highly abundant in Hole 1194A from Samples 194-1194A-1H-CC through 14H-CC, below which the samples were barren of index fossils. The samples in Hole 1194B have low planktonic abundance (generally <10% sample volume), pervasive crystal overgrowths, and species contamination. Because of this, the planktonic foraminifer biostratigraphy is limited to the interval cored in Hole 1194A.
Pulleniatina primalis, Sphaeroidinella dehiscens, and Globorotalia truncatulinoides were found in Sample 194-1194A-1H-2, 45 cm. These taxa, coupled with the absence of Globorotalia tosaensis and its LO datum, constrain the sample to Zone N23. Both Dentoglobigerina altispira and Sphaeroidinellopsis seminulina are last observed in Sample 194-1194A-2H-CC; thus, their LO datums occur between Samples 1H-CC and 2H-CC. Both datums mark the Zone N20/N21 boundary. Sample 194-1194A-1H-CC contains Globigerinoides extremus, Globorotalia pseudomiocenica, and S. dehiscens, whose datums infer a Zone N19 age. This implies the presence of a condensed Pleistocene to upper Pliocene sequence within the first core. Zone N19 extends to Sample 194-1194A-4H-CC, where the presence of Globorotalia plesiotumida, S. dehiscens, and Globorotalia margaritae, together with the absence of Globigerina nepenthes, confirm this zonal assignment. In addition, the first occurrence (FO) datum of Globorotalia puncticulata is observed between Samples 194-1194A-6H-2, 80 cm, and 6H-5, 80 cm. This datum approximates the middle of Zone N19 and thus strengthens the zonal assignment.
Sample 194-1194A-5H-CC contains both G. margaritae and Globorotalia tumida and lacks S. dehiscens, implying a Zone N18 age. Samples 194-1194A-6H-CC through 8H-CC contain G. nepenthes and Neogloboquadrina acostaensis in addition to the aforementioned taxa and thus can also be assigned to Zone N18. Sample 194-1194A-9H-CC represents the base of Zone N18, as specimens of G. margaritae and Globorotalia cibaoensis were observed. The presence of N. acostaensis, G. plesiotumida, and Globorotalia lenguaensis in Sample 194-1194A-10H-CC indicates an age near the top of Subzone N17a. Sample 194-1194A-13H-CC, the last sample from Hole 1194A, was observed to contain G. extremus and G. plesiotumida, whose FO datums indicate an early Zone N17 age. Cores 194-1194A-14X through 20X were barren of planktonic foraminifer index species and therefore could not be assigned to a zone.
Many of the samples from this hole contain reworked planktonic foraminifers, making age assignments difficult. Samples 194-1194B-3R-CC through 8R-CC are devoid of index fossils and are not ascribed to a particular range zone. Sample 194-1194B-9R-CC contains a mixed zonation assemblage of planktonic foraminifers, including Globigerina druryi (Zones N15-N7) and Neogloboquadrina mayeri (Zones N14-N4). The lack of additional index fossils makes this sample difficult to assign to a specific zone. Samples 194-1194B-10R-CC through 14R-CC are also difficult to assign to a specific zone, as these samples contain rare planktonic foraminifers that do not constitute a viable assemblage for zone assignments.
Globigerinoides trilobus and Globigerinoides sicanus are present in Sample 194-1194B-16R-CC, which is tentatively assigned to Zones N8-N9. Samples 194-1194B-17R-CC, 20R-CC, 21R-CC, and 22R-CC contain G. sicanus, N. mayeri, Globoquadrina dehiscens, Globigerinella obesa, and Praeorbulina transitoria, but the successive samples did not produce a clear age-diagnostic fauna. Sample 194-1194B-27R-CC contains specimens of Globigerinoides immaturus, G. dehiscens, Globigerinella praesiphonifera, and Globigerina ciperoensis and can be placed in the range of Zone N4b-N5. Samples 194-1194B-31R-CC through 33R-CC lack age-diagnostic taxa.
The sand-sized fraction of Sample 194-1194A-1H-CC (4.6 mbsf) is overwhelmingly dominated by very small planktonic foraminifers (Table T5). A minor sand- and fine gravel-sized fraction of siliciclastic material is also present. Small bryozoan colonies and bivalves are rare in this fraction. Benthic foraminifers are rare but include conspicuous nodosarids and agglutinated specimens indicating a bathyal depositional environment. The sand-sized fractions of Samples 194-1194A-2H-CC (14.4 mbsf) through 6H-CC (52.6 mbsf) appear bimodal, visually predominated by adult globigerinid planktonic foraminifers but with a substantial component of very small planktonic foraminifers and planktonic debris. The relative proportions of coarser and finer planktonic fractions varies among samples, possibly indicating changes in current winnowing. Benthic foraminifers are generally rare, and the species present indicate bathyal depths of deposition. Gray or blackened grains become increasingly common downward and are significant components of Samples 194-1194A-9H-CC (80.8 mbsf) through 13H-CC (117.4 mbsf). The proportions of very fine sand-sized debris vary from sample to sample; the source appears to be broken planktonic foraminiferal tests. These hemipelagic sediments with some reworked components make up lithologic Unit II (see "Lithostratigraphy and Sedimentology").
Samples 194-1194A-14X-CC (119.4 mbsf) through 20X-CC (161.0 mbsf), representing lithologic Unit III (see "Lithostratigraphy and Sedimentology"), are dominated by small bryozoan colonies, fragments of bryozoan branches, echinoid fragments, benthic foraminifers, and sometimes quartz or glauconite grains (Table T5). In Sample 194-1194A-16X-CC (132.9 mbsf), the prevalence of Amphistegina hauerina and Amphistegina radiata, both of intermediate robustness, indicate middle neritic water depths of ~30-50 m. In addition, the lack of rounding of the Amphistegina specimens, along with Lepidocyclina specimens that show minimal breakage and well-preserved surface detail, indicate relatively limited transport. The bryozoan and larger foraminiferal bioclastic sands appear similar to modern sediments described from middle neritic depths on the west Australian shelf by James et al. (1999). In Samples 194-1194A-18X-CC (145.5 mbsf) and 20X-CC, the sediments are finer and more poorly preserved.
Samples 194-1194B-2R-CC (119.6 mbsf) through 8R-CC (177.2 mbsf) represent lithologic Unit III (see "Lithostratigraphy and Sedimentology") and are similar to those described for this interval in Hole 1194A (Table T5). In particular, the distinctive A. hauerina-A. radiata foraminiferal assemblage was found in Sample 194-1194B-4R-CC, indicating middle neritic water depths of ~30-50 m. Samples 194-1194B-7R-CC (167.6 mbsf) and 8R-CC (177.2 mbsf) are heavily recrystallized fine sands that may represent transport into outer neritic depths.
Samples 194-1194B-9R-CC (177.6 mbsf) and 10R-CC (191.4 mbsf), at the top of lithologic Unit IV (see "Lithostratigraphy and Sedimentology"), are characterized by mud and a few ostracode shells. The depositional environment is unknown. Samples 194-1194B-11R-CC (197.9 mbsf) and 15R-CC (238.4 mbsf) are characterized by mud and fine- to medium-sized bioclastic fragments consisting of bryozoan, echinoid fragments, and benthic foraminifers, which are interpreted as representing proximal periplatform deposition at outer neritic water depths. Samples 194-1194B-16R-CC (244.9 mbsf) through 22R-CC (303.9 mbsf) are characterized by fine bioclastic debris that contains both neritic (bryozoan, echinoid, and benthic foraminifers) and pelagic (whole and broken planktonic foraminifers) components. A distal periplatform depositional environment at upper bathyal water depths is tentatively interpreted for this interval (Table T5). Sediments are highly recrystallized, and preservation is generally poor throughout this unit.
Samples 194-1194B-30R-CC (388.8 mbsf) through 33R-CC (417.5 mbsf), which occur in lithologic Subunit VB (see "Lithostratigraphy and Sedimentology"), are dominated by poorly preserved fine bioclastic material with minor quartz and reworked bioclasts that include larger benthic foraminifers. Based on these latter components, a proximal periplatform depositional environment at outer neritic depths is interpreted.
Sample 194-1194B-34R-CC (421.0 mbsf) is a larger benthic foraminifer-dominated grainstone (Table T5). White, relatively fresh-appearing specimens, as well as pyrite and glauconite-infilled Lepidocyclina and Miogypsina and either Operculina or Cycloclypeus are abundant. Additional thin sections are needed to determine the range of taxa present. A platform depositional environment at middle neritic depths is interpreted based on the presence of these taxa and their relatively flat morphologies. This sample is representative of the base of lithologic Subunit VB (see "Lithostratigraphy and Sedimentology").
Microscopic analysis of the sand-sized sediment constituents from Site 1194 reveal that sediments of neritic origin are significant components of lithologic Units III through V (see "Lithostratigraphy and Sedimentology"). The larger benthic foraminiferal grainstones of lithologic Unit V represent sedimentation in inner to middle neritic depths shortly after flooding of the basement. Sediments of Unit V generally indicate deepening-upward conditions. Although constituents are relatively poorly preserved, the presence of quartz and larger benthic foraminifers in Subunit VB are indicative of middle to outer neritic paleodepths. The abundance of planktonic foraminifers, coupled with the benthic foraminiferal assemblage, indicates probable upper bathyal depths in a distal periplatform depositional environment for Subunit VA. These depositional conditions continued through the deposition of Subunit IVB, whose neritic component is predominantly in the mud to very fine sand fractions. Medium sand-sized fragments of neritic bryozoan, echinoid, and foraminiferal components are prevalent in most of Subunit IVA, indicating greater proximity to the neritic source of bioclasts and thus a proximal periplatform depositional setting. Subunit IVA also represents a shallowing-upward trend that culminates in middle to inner neritic water depths in Unit III.
Biogenic constituents of nannoplankton and planktonic foraminiferal origin totally dominate lithologic Units I and II. Bathyal benthic foraminifers are a rare but conspicuous component. Differences in sorting and breakage of the planktonic foraminiferal tests among samples within these units are indicative of the influence of an active current regime.