Sediments recovered from the two holes cored at Site 899 provide a discontinuous record from upper Pliocene through Lower Cretaceous. Calcareous nannofossils generally are abundant to very abundant in all the Cenozoic sedimentary sequences and rare to abundant in the Early Cretaceous age sediments. Planktonic foraminifers generally are common to abundant in Hole 899A; however, samples from the deeper Hole 899B were barren or contained few planktonic foraminifers.
The two holes drilled at Site 899, located in the eastern part of the Iberia Abyssal Plain in a water depth of 5291 m, penetrated 562.5 m of sediment. Hole 899A was cored in the interval from 81.5 to 235.5 mbsf, with a total recovery of 51.45 m of sediment, whereas Hole 899B was cored in the interval from 230.5 to 562.5 mbsf, with a recovery of 173.41 m. The calcareous nannofossils define four stratigraphic successions within the Cenozoic sequence; one from the lower Pliocene (Zone NN16 of Martini, 1971) to the lower Pliocene (Zone NN15), a second from the uppermost Miocene (base Zone NN12) to the upper Miocene (Zone NN10), a third from the middle Miocene (NN7) to the lower Oligocene (NP23), and a fourth restricted to the upper Eocene (NP20). A major hiatus representing most of the Paleogene lies within Core 149-899B-15R. Below this level, recovered sediments are Cretaceous in age. Very thin intervals of Lower Cretaceous sediments occur in Cores 149-899B-26R to -37R; these are intercalated with a breccia composed mostly of serpentinized peridotite. This Lower Cretaceous interval corresponds to lithostratigraphic Subunit IVB (see "Lithostratigraphy and Petrology" section, this chapter).
The abundance and preservation of calcareous nannofossils at Site 899 correspond well with the major lithostratigraphic units. Sediments from Unit I (Cores 149-899A-1R to -6R) contain generally very abundant and well-preserved calcareous nannofossils. Unit II (Cores 149-899A-6R to -15R) contains abundant, moderately well-preserved calcareous nannofossils, with some intervals that are barren or contain poorly preserved calcareous nannofossils. Sediments recovered from the top of Unit III to the upper part of Subunit IVA (Intervals 149-899B-15R to -25R) are barren of nannofossils. Finally, the lower part of Subunit IVA (Core 149-899B-26R through Section 149-899B-28R-1) and the breccia from Subunit IVB (Sections 149-899B-28R-1 to 37R-1) contain samples having few, poorly to moderately preserved, calcareous nannofossils, but also contain rare samples having abundant and well-preserved nannofossils. We applied the zonation of Martini (1971) and Sissingh (1977); in most cases, using the primary zonal markers. However, secondary markers, whose biostratigraphic ranges have been recently indicated by Rio et al. (1990) or have been summarized by Perch-Nielsen (1985), were used in a number of instances where abundant reworked specimens occurred or where the primary zonal markers were not present. The biostratigraphy for Site 899 has been summarized in Figure 27.
Intervals 149-899A-1R-2, 44 cm, to -4R-2, 115 cm, contain rare specimens of Discoaster pentaradiatus, Discoaster surculus, and Discoaster brouweri, which suggests a late Pliocene age within Zone NN16. Sample 149-899A-3R-CC has very rare Sphenolithus neoabies. Samples 149-899A-4R-CC, 44 cm, to -5R-3, 49 cm, yielded very abundant Discoaster pentaradiatus and Reticulofenestra ampla, which indicates the lower part of Zone NN16. Samples 149-899A-5R-CC and -6R-1, 86 cm, were placed in Zone NN15 on the basis of few Reticulofenestra pseudoumbilica, common Discoaster tamalis, and common Discoaster asymmetricus.
In Sample 149-899A-6R-CC, the occurrence of Triquetrorhabdulus rugosus and Amaurolithus delicatus and the absence of Discoaster quinqueramus indicate the uppermost Miocene (Zone NN12). The Pliocene/Miocene boundary was correlated with the highest occurrence (HO) of Triquetrorhabdulus rugosus, which occurs in the lower part of Zone NN12. However, according to the foraminiferal data (see below), the age of Sample 149-899A-6R-CC may be slightly younger and has been assigned to the upper part of Zone NN12, which represents the lowermost Pliocene. An early Pliocene hiatus within Core 149-899A-6R has been estimated to represent at least 1.50 Ma from the HO of Triquetrorhabdulus rugosus to the lowest occurrence (LO) of Discoaster tamalis. Intervals 149-899A-7R-1, 52 cm, to -8R-CC contain few Amaurolithus delicatus and Discoaster quinqueramus, which indicates Subzone NN11b. Amaurolithus primus markers were observed in Sample 149-899A-7R-1, 52 cm, at the top of Zone NN11b. Sample 149-899A-9R-3, 71 cm, contains common Sphenolithus abies and rare Sphenolithus verensis, but lacks Discoaster loeblichii and can be assigned to Subzone NN11a. Rare Discoaster loeblichii occur in Sample 149-899A-9R-CC and indicate the upper part of Zone NN10. Samples 149-899A-10R-l, 58cm, and -10R-CC contain few Discoaster prepentaradiatus and rare Discoaster neohamatus, but lack Discoaster hamatus. This interval was assigned to the lower part of Zone NN10. Samples 149-899A-11R-1, 118cm, and -11R-CC contain very rare Discoaster deflandrei, rare Cyclicargolithus floridanus, Discoaster exilis, D. kugleri, and D. moorei, and few Triquetrorhabdulus rugosus. This assemblage indicates the lower part of Zone NN7 and also that a major unconformity lies between the middle Miocene Zone NN7 and the upper Miocene Zone NN10. On the basis of the presence of Cyclicargolithus floridanus in Sample 149-899A-11R-1, 118 cm, and the absence of Discoaster hamatus in Sample 149-899A-10R-CC, the unconformity may represent an age of at least 2.9 Ma. The LO of Calcidiscus macintyrei (10.0 µm, circular) was in Sample 149-899A-11R-1, 118 cm. Intervals 149-899A-13R-CC, 7 cm, to -13R-CC were assigned to Zone NN6, as indicated by the presence of rare Triquetrorhabdulus rugosus and Calcidiscus premacintyrei and common Cyclicargolithus floridanus. Sphenolithus heteromorphus occurs in Sample 149-899A-14R-CC, which places this sample in Zone NN5. Intervals 149-899A-15R-3, 125 cm, to -16R-CC were placed in the lower Miocene Zone NN4 on the basis of the presence of few Sphenolithus heteromorphus (Sample 149-899A-15R-3, 140 cm), rare Sphenolithus dissimilis and Helicosphaera ampliaperta, rare to few Calcidiscus leptoporus, sporadic occurrence of Calcidiscus premacintyrei, and abundant Discoaster deflandrei. Rare Cretaceous, rare lower Miocene, and very abundant Eocene reworked specimens occur repeatedly throughout this interval. The resedimented sequences deposited during the early Miocene may correspond to an increase during this time of contour current sedimentation (lithostratigraphic Subunit IIB; see "Lithostratigraphy and Petrology" section, this chapter).
Sample 149-899B-1R-3, 1 cm, contains rare Calcidiscus premacintyrei, Discoaster moorei, and Discoaster variabilis, and few Calcidiscus leptoporus. This assemblage has been assigned to the lower Miocene Zone NN4 and has an assemblage of calcareous nannofossils similar to that in Core 149-899A-16R. Sample 149-899B-1R-3, 36 cm, contains Sphenolithus belemnos and Sample 149-899B-2R-2, 36 cm, contains Sphenolithus dissimilis, Discoaster druggii, and Calcidiscus leptoporus, but lacks Triquetrorhabdulus carinatus. This interval can be assigned to the lower Miocene Zone NN3. Intervals 149-899B-2R-CC to -4R-6, 18 cm, can be assigned to the lower Miocene Zone NN2 by the presence of Triquetrorhabdulus carinatus. The underlying sequence, from Samples 149-899B-4R-CC to -6R-CC, yielded various assemblages corresponding to Zone NN1. Helicosphaera recta occurs in Sample 149-899B-4R-CC, and Sphenolithus ciperoensis has its HO in Sample 149-899B-5R-6, 16 cm. Rare Cyclicargolithus abisectus, few Clausicoccus fenestratus and Zygrhablithus bijugatus, and common Reticulofenestra bisecta also indicate Zone NN1 but, due to reworked material, no biostratigraphic events have been defined.
Oligocene assemblages were observed from Samples 149-899B-7R-2, 79 cm, to -13R-4, 62 cm, and represent continuous deposition from Zones NP23 to NP25. The assemblages observed are similar to those observed at Sites 897 and 898. Samples 149-899B-7R-2,79 cm, to -9R-CC contain rare Pontosphaera enormis, few Helicosphaera recta, common Sphenolithus ciperoensis, Cyclicargolithus abisectus, and Reticulofenestra bisecta, indicating the upper Oligocene Zone NP25. The HO of Sphenolithus distentus, Sphenolithus predistentus, and Helicosphaera compacta is in Sample 149-899B-10R-1, 83 cm, and this defines the top of Zone NP24. The interval from here to Sample 149-899B-11R-4, 134 cm, is also from Zone NP24. Intervals 149-899B-12R-2, 141 cm, and -13R-4, 63 cm, were assigned to Zone NP23 on the basis of the presence of Sphenolithus predistentus and the absence of Sphenolithus ciperoensis. The LO of Sphenolithus distentus and Coronocyclus nitescens is recorded in Sample 149-899B-13R-2, 127 cm. Zones NP22 and NP21 were not observed between Samples 149-899B-13R-2, 127 cm (Zone NP23), and -13R-CC (NP20). According to the sediment accumulation rate during this period (about 9 m/m.y.) and according to the biostratigraphic time scale (see Table 1 in "Explanatory Notes" chapter, this volume), an unconformity lies between the HO of Sphenolithus distentus (33.1 Ma) and the LO of Discoaster saipanensis (35.6 Ma) and represents 2.5 Ma of missing sediment. The Eocene/Oligocene boundary (35.4 Ma) must be located just above Sample 149-899B-13R-CC.
Intervals 149-899B-13R-CC to -15R-1, 4 cm, were assigned to Zone NP19/20. Sample 149-899B-13R-CC contains rare Discoaster saipanensis, Discoaster barbadiensis, and Cyclococcolithus formosus, and few Reticulofenestra hillae and Reticulofenestra umbilica. Sample 149-899B-15R-1, 4 cm, contains Isthmolithus recurvus and can be assigned an age not older than zone NP19/20. Below this level, no more fossiliferous calcareous claystones were observed in the Cenozoic sequence.
Drilling in Hole 899B recovered a sequence from Upper Cretaceous to Lower Cretaceous from Sample 149-899B-15R-3, 147-149 cm, to Core 149-899B-37R. From Section 149-899B-15R-1 (upper Eocene) to Sample 149-899B-16R-4, 21 cm no calcareous nannofossils were observed, but a Cretaceous age was indicated by the planktonic foraminifers for Sample 149-899B-15R-3, 147 cm, which was barren of calcareous nannofossils. From Sample 149-899B-16R-4, 21 cm, to -26R-1, 85 cm, only serpentinized peridotite was recovered.
The first datable lithology in Subunit IVA occurs in Sample 149-899B-26R-1, 85 cm. This sample and Sample 149-899B-29R-1, 22 cm, were assigned to the Aptian Zone CC7 on the basis of Rucinolithus irregularis, Micrantholithus hoschulzii, and Micrantholithus obtusus. Sample 149-899B-27R-1, 65 cm, and Section 149-899B-28R-1 contain moderately well-preserved calcareous nannofossils, which may yield good ages after more detailed analyses.
The lowermost sample of Hole 899B (149-899B-35R-1, 99 cm) in Subunit IVB having calcareous claystone yielded a common and well-preserved assemblage. This sample was assigned to the lower Barremian, as indicated by rare Rucinolithus terebrodentarius, Markalius ellipticus, Calcicalathina oblongata, Tranolithus pseudoangustus, Calcicalathina aff. C. oblongata, Micrantholithus hoschulzii, Micrantholithus obtusus, few Microstaurus chiastus, Reinhardtites praesisyphus, Nannoconus globulus, Nannoconus ligius, Nannoconus steinmanii, and common Nannoconus spp. and by the absence of Rucinolithus irregularis. Also present in this sample were rare Cruciellipsis cuvillieri, Seetonia colligata, and Zeugrhabdotus erectus, which may indicate a late Hauterivian age, but the presence of a specimen of Conusphaera mexicana minor, indicated the presence of reworked sediments. According to Bralower et al. (1989), Conusphaera mexicana minor has a stratigraphic range restricted to the Tithonian. This interpretation is also supported by the composition of this sample, a claystone with reworked basalt clasts (see Table 12 and the "Lithostratigraphy and Petrology" section, this chapter), and by the highly deformed nature of this interval. Other samples from Subunit IVB (149-899B-32R-1, 5 cm; -33R-1, 13 cm) contain few and poorly preserved calcareous nannofossils that exhibit severe dissolution.
Planktonic foraminifers in core-catcher samples from Holes 899A and 899B were examined to establish preliminary ages for the sediments. The number of planktonic foraminifers was generally low, with more planktonic foraminifers present in Hole 899A than in Hole 899B. Many of the samples were barren or yielded a low-diversity planktonic foraminiferal assemblage having moderate preservation (Table 13). Similar patterns were observed in the benthic foraminiferal assemblages.
Sample 149-899A-1R-CC is characterized by the presence of relatively common Globorotalia inflata and the absence of Globorotalia truncatulinoides and Globorotalia tosaensis. This sample has been tentatively assigned to Zone N21, which is of late Pliocene age. Samples 149-899A-2R-CC and -3R-CC contain no zonal markers. Samples 149-899A-4R-CC and -5R-CC are characterized by the presence of Globorotalia puncticulata and the absence of Globorotalia inflata and Globorotalia margaritae margaritae, indicating that they can be assigned to the upper part of Zone N19, which is of late early to early late Pliocene age. Sample 149-899A-6R-CC contains Globorotalia merotumida and Globorotalia crassaformis crassaformis and can be assigned to the early part of Zone N19, which is of early Pliocene age. This sample also contains Globorotalia margaritae margaritae, Globigerina nepenthes, and Sphaeroidinellopsis seminulina. Abyssal and reworked shallow-water benthic foraminifers were present in all these samples.
Samples 149-899A-7R-CC and -8R-CC are characterized by the presence of Neogloboquadrina pachyderma and Globigerina nepenthes and the absence of Globorotalia crassaformis s.l., indicating that these two samples can be assigned to Zones N16/N17, which are of late Miocene age. Although Zone N18 was not identified, calcareous nannofossil evidence does not support an unconformity between Samples 149-899A-6R-CC and -7R-CC. Sample 149-899A-9R-CC contains only Globigerina nepenthes, which has a long range from Zone N14 to the early part of Zone N19. As Zone N17 had already been reached in Sample 149-899A-7R-CC, this sample was interpreted to be somewhere in Zones N14 to N17, which are of late middle to late Miocene age. Sample 149-899A-10R-CC contains Globorotalia nepenthes, Globorotalia conoidea, Globoquadrina dehiscens, and Sphaeroidinellopsis disjuncta and can also be placed in Zones N14 to N17. Few abyssal benthic foraminifers were present in these samples.
Samples 149-899A-11R-CC and -13R-CC have an assemblage similar to that in Sample 149-899A-10R-CC. These samples also contain Globorotalia mayeri, but Globigerina nepenthes is absent. This interval can be assigned to Zones N9 to N13, which are of middle Miocene age. Sample 149-899A-14R-CC is characterized by the presence of Globorotalia scitula scitula and the absence of Globigerina nepenthes and also can be placed in Zones N9 to N13. The presence of only thick-shelled planktonic foraminifers from Samples 149-899A-7R-CC to -13R-CC points to a high degree of dissolution in this interval. Radiolarians and silicoflagellates also were common in Intervals 149-899A-11R-CC to -14R-CC.
Sample 149-899A-15R-CC is characterized by the presence of Catapsydrax stainforthi and absence of Catapsydrax dissimilis. It can be assigned to the N7 zone, which is of late early Miocene age. Also present in this sample are Globorotalia altispira altispira, G. altispira globosa, Globorotalia mayeri and Globorotalia siakensis. Although Zone N8 was not identified in the core-catcher samples, calcareous nannofossil evidence does not support an unconformity between Samples 149-899A-14R-CC and -15R-CC. Sample 149-899A-16R-CC is barren of planktonic foraminifers.
Samples 149-899B-1R-CC and -4R-CC are barren of planktonic foraminifers. Samples 149-899B-2R-CC and -3R-CC contain very rare planktonic foraminifers, none of which can be used as a zonal marker. Sample 149-899B-5R-CC is marked by the presence of Globorotalia kugleri and Globigerinoides spp. Globorotalia kugleri defines the "N4" zone, which is of latest Oligocene to early Miocene age. Sample 149-899B-6R-CC does not contain G. kugleri, but Globigerinoides spp. are still present. This sample belongs to the upper part of Zone P22, which is of late Oligocene age. Radiolarians and silicoflagellates also are common in these samples.
Samples 149-899B-7R-CC, -8R-CC, -10R-CC, -11R-CC, -12R-CC, -13R-CC, -14R-CC, and 15R-CC are barren of planktonic foraminifers. Sample 149-899B-9R-CC contains very rare planktonic foraminifers, none of which is a zonal marker. Samples 149-899B-13R-CC and -14R-CC contain only arenaceous benthic foraminifers (Bathysiphon spp., Glomospira charoides, Glomospira spp., Cyclammina spp., Haplophragmoides spp., and Recurvoides spp.) and ichthyoliths.
Sample 149-899A-15R-3, 147-149 cm, contains Globotruncana orientalis and Globotruncana lineana, indicating that it belongs between the Globotruncanita elevata Zone and the lower part of the Gansserina gansseri Zone, which are of Campanian to early Maastrichtian age (Robaszynski et al., 1984). Other species found in this sample are Archeoglobigerina cretacea, Hedbergella holmdenensis, and Marginotruncana marginata.