14. Neogene and Quaternary Calcareous Nannofossil Biostratigraphy of the Walvis Ridge1

14. NEOGENE AND QUATERNARY CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY OF THE WALVIS RIDGE1

Ming-Jung Jiang, Robertson Research (U.S.) Inc., Houston, Texas and Stefan Gartner, Department of Oceanography, Texas A&M University, College Station, Texas

ABSTRACT During DSDP Leg 74 in the South Atlantic, 11 holes were drilled at 5 sites (525-529) on the eastern end of Walvis Ridge. The sediments recovered range in age from late Campanian or early Maestrichtian to Holocene. This chapter deals only with the Neogene to Holocene interval. The calcareous nannofossils over this interval have been corroded as well as overgrown, but a precise biostratigraphy is possible at all sites because most of the key index species are present.

INTRODUCTION CALCAREOUS NANNOFOSSIL ZONATION During DSDP Leg 74, 11 holes were drilled at 5 sites Martini's standard Tertiary and Quaternary zonation (525-529) on Walvis Ridge in the South Atlantic near (1971), which is widely used elsewhere, was the starting South Africa (Fig. 1). Sediments ranging in age from basis for the zonation described here. Because of the late Campanian or early Maestrichtian to Holocene scarcity or apparent lack of some of Martini's index fos- were recovered. This chapter deals with the calcareous sils, possibly owing to environmental exclusion of the nannofossils found in the Neogene to Holocene sedi- parent organism or to poor preservation, other species ment from these five sites. The calcareous nannofossils were selected to determine zones. Deviations from Mar- from the Paleogene and the Upper Cretaceous are docu- tinis zonation, necessary for the studied area, are dis- mented by Hélène Manivit in this same volume. cussed in the following. The age and zone assignments Calcareous nannofossils from the Neogene through of the Neogene through Holocene cores based on this Holocene recovered during DSDP Leg 74 are abundant modified zonation are then given in Table 1. at all sites, except for the middle Miocene red clay interval cored at Site 527—the deepest site. Their state of Triquetrorhabdulus carinatus Zone (NN1) preservation, however, is ranked as "moderate" in gen- Definition. Interval from the last occurrence of Helicosphaera rec- eral. Dissolution and recrystallization have progressed ta to the first occurrence of Discoaster druggii above it. Remarks. Because of environmental exclusion, Helicosphaera rec- to such an extent that only solution-resistant or robust ta together with H. perch-nielseniae is present only at Site 526, the forms can be recognized for most of the middle and shallowest site. The last occurrence of Sphenolithus ciperoensis is ten- lower Miocene sections. Fortunately, most of the zonal tatively used to define the base of Zone NN1, i.e., the Oligocene/ markers are present and can be identified with certainty. Miocene boundary, in this study. Other important and solution-resistant species, which become extinct slightly above the last occurrence The main purpose of this chapter is, therefore, to docu- of Sphenolithus ciperoensis, are Dictyococcites bisectus (Dictyococci- ment the biostratigraphic distribution of the calcareous tes abisectus included), aff. D. dictyodus, S. capricornutus, S. del- nannofossils rather than to do a complete taxonomic phix, and Zygrhablithus bijugatus. S. capricornutus and S. delphix study. have very short ranges. Both forms first occur above the last occurrence of S. ciperoensis and become extinct at about the same level as Smear slides of the original unprocessed samples Dictyococcites bisectus, aff. D. dictyodus, and Z. bijugatus. were examined with a light microscope for this study. In Because of the strong overgrowth of discoasters within this inter- order to obtain a precise position of the zonal bounda- val, typical specimens of Discoaster druggii cannot be identified with ries, one sample was taken for each section (150 cm) of a certainty. The first occurrence of an unusual form of discoaster is at core and investigated for its calcareous nannofossil con- the top of Zone NN1. This species is consistently much larger and more robust than the common D. deflandrei specimens in this inter- tent. For some critical intervals, more closely spaced val. It has straight and slightly tapered rays and is documented as Dis- samples were analyzed. Therefore the stratigraphic first coaster sp. aff. D. druggii in this study. and last appearance of the selected species was deter- mined with an accuracy of 150 cm or less for this report. Discoaster druggii Zone (NN2) Checklists of a selected set of species were prepared for Definition. Interval from the first occurrence of Discoaster drug- each site. gii to the last occurrence of Triquetrorhabdulus carinatus. Remarks. The first occurrence of Discoaster sp. aff. D. druggii is used to mark the base of Zone NN2, whereas the first occurrence of Sphenolithus belemnos marks the top of this zone in this study. This Moore, T. C, Jr., Rabinowitz, P. D., et al., Init. Repts. DSDP, 74: Washington (U.S. zone is therefore equivalent to Zone CN1C of Okada and Bukry Govt. Printing Office). (1980).

561 M.-J. JIANG, S. GARTNER

Angola Basin 20° S

-2 25<

-3

30c

35C

i 1 1 1 1 r 20 Time (hr.) Ship Course Track 315° Figure 1. Site locations on the Walvis Ridge in the South Atlantic Ocean for DSDP Leg 74.

The last occurrence of T. cαrinαtus is uncertain, because in some boundary has been identified variously as older, equal to, and younger cases it is difficult to distinguish T. cαrinαtus from an elongate calcite than this datum.) lath in an assemblage with moderate or poor preservation and recrystallization. Reticulofenestrα pseudoumbilicα sample and Cαlcidiscus Sphenolithus heteromorphus Zone (NN5) leptoporus have their first occurrence in this zone. Definition. Interval from the last occurrence of Helicosphαerα αm- pliαpertα to the last occurrence of Sphenolithus heteromorphus. Sphenolithus belemnos Zone (NN3) Remarks. At the boundary of Zones NN4/NN5, i.e., the lower/ Definition. Interval from the last occurrence of Triquetrorhαb- middle Miocene boundary, assemblages of discoaster change signifi- dulus cαrinαtus to the last occurrence of Sphenolithus belemnos. cantly. Discoαster deflαndrei, which is a dominant species in the lower Remarks. The total range of S. belemnos marks Zone NN3 in this Miocene, is replaced abruptly by (overgrown) D. vαriαbilis, although study. Sphenolithus sp. aff. S. belemnos documented in the tables the former persists upward. The first common occurrence of D. vαri- could be small specimens of S. dissimilis. αbilis s. ampl. is therefore used to make the base of Zone NN5 because this datum is easy to recognize (see Bukry, 1973). Helicosphαerα αmpliαpertα Zone (NN4) The top of this zone is also easy to recognize in the studied sites. Definition. Interval from the last occurrence of Sphenolithus belemnos to the last occurrence of Helicosphαerα αmpliαpertα. Remarks. S. heteromorphus first occurs immediately above the ex- Discoαster exilis Zone (NN6) tinction of S. belemnos. Neither gap nor overlap of the ranges of the Definition. Interval from the last occurrence of Sphenolithus two species is observed at the studied sites. The first occurrence of S. heteromorphus to the first occurrence of Discoαster kugleri. heteromorphus may be a good marker for the boundary of Zones Remarks. Because of strong overgrowth of discoasters, typical D. NN3 and NN4 (Bukry, 1972, 1973). kugleri cannot be identified with certainty. The top of Zone NN6 is The index fossil, H. αmpliαpertα, is absent, probably because of therefore placed at the last occurrence of Cyclicαrgolithus floridαnus, ecological exclusion. The first common occurrence of Discoαster vαri- a species which is common within and below this zone (see, e.g., αbilis s. ampl. is tentatively used to mark the top of Zone NN4, i.e., Bukry, 1975). the top of the lower Miocene. (The lower Miocene/middle Miocene Coronocyclus nitescens seems to become extinct within this zone, boundary is for the sake of convenience somewhat arbitrarily placed whereas Triquetrorhαbdulus rugosus has its first occurrence in this at the top of the H. αmpliαpertα Zone, recognizing, however, that the zone.

562 Table 1. Zonal and geologic age assignments of Leg 74 cores, based on calcareous nannofossils in samples from holes at Sites 525-529.

Calcareous Nannofossil Age Zonation (Martini, 1971) 525 525A 525B 526 526A 526B 526C 527 528 528A 529

NN21 Emiliania huxleyi 1-1, 30-32 1-1, top 1-1, 80-82 1-1, 40-41 late 1-2, 30-32 1-1, 101-102 Pleistocene NN20 Gephyrocapsa oceanica 1-1, 20-21 1-1, 28-29 1-1, 150 2-1, 106-107

early NN19 Pseudoemiliania lacunosa 1,CC l.CC 1-2, 80-82 2,CC 1-1, 30-32 1-1, 29-31 1-2, 20-21 1-1, 120-122 1-2, 40-41 3-1, 76-78 3-1,35-36 2-1, 50-51 1,CC 5-3, 19-20 2-6, 40-41 NN18 Discoaster brouweri 3-2, 53-54 3-2, 35-36 2,CC 5-4, 19-20 2,CC 4-1, 75-77 3,CC 6-3, 19-20

late NN17 Discoaster pentaradiatus 4-2, 65-66 3-1, 35-37 NN16 Discoaster surculus 4-3, 65-66 3-1, 50-51 6-3, 111 3-1, 30-31 5-1, 81-83 3-4, 35-37 7-2, 100 5-2, 81-83 4-2, 20-21 Pliocene NN15 Reticulofenestra 1-1, 75-76 1-1, 100 3-4, 50-51 7-3, 40-41 3-2, 30-31 pseudoumbilica 8-2, 86-87 5,CC l.CC 5,CC 11-3, top 4-6, 40-41 NN14 Discoaster asymmetricus 8-3, 3-4 1-2, 75-76 6-1,40-42 11,CC 4,CC 13-2, 63-64 early NN13 Ceratolithus rugosus 3-1, 29-30 1-3, 75-76 6-2, 40-42 13-3, 63-64 12-1. 10-11 2-2, 80-81 NN12 Amaurolithus tricorniculatus 12-1, 54-55 2-3, 80-81 2-1,42-43 13-4, base 4-1, 148-149 14-2, 40-41 5-1, 85-86 2-7, 40-42 7-2, 60-62 14-2, 51-52 NN11 Discoaster quinqueramus 5-1, 60-61 14-2, 100-101 5-2, 85-86 2.CC 7,CC 14.CC 6,CC 24.CC 9,CC 3.CC 13-1, 10 24.CC late NN10 Discoaster calcaris 25-1, 36-37 10-1, 103-104 13-1, 15 25-1, 59-60 28,CC 12-3, 25-26 13-1, 50 25,CC NN9 Discoaster hamatus 29-1, 76-77 12.CC 13-1,63 26-1, 50 32-2, 113-114 14,CC 13-5, 44 27-2, 38-39 NN8 Catinaster coalitus 32-3, 41-42 15-1, 26-27 13-5, 66 27-2, 150 5-1, top 33.CC 15.CC 13-6, 129 27.CC 5.CC NN7 Discoaster kugleri 34-1, 65-66 16-1, 42-43 28-1, 58 middle 36.CC 18-3, 50-51 28.CC NN6 Discoaster exilis 7-1, 84-85 37-1,40-41 18.CC 6-1, 38 Miocene 8-2, 40-41 41,CC 20-2, 78-79 6-6, 100 NN5 Sphenolithus heteromorphus 8-3, 40-41 42-1, 35-36 20-3, 78-79 2-1,0-1 6-6, 150 9,CC 46-1, 60-61 20,CC 3-1,23-24 6,CC NN4 Helicosphaera amptiaperta 10-6, 40-41 46-2, 60-61 21-1, 70-71 3-1, 117 7-1, 65-66 11-1,40-41 48-1, 60-61 8-3, 66 NN3 Sphenolithus belemnos 11-2,40-41 48-1, 100-102 21-2, 70-71 3,CC 8-4, 30-31 11-4,40-41 49-3, 20-21 21, CC 4-3, 110 8-6, 30-31 early NN2 Discoaster druggii 11-5,40-41 49-4, 20-21 22-1, 85-86 4-3, 131 8-7, 30-31 13-4, 40-41 49,CC 4-4,67 9-5, 30-31 NN1 Triquetrorhabdulus carinatus 13-5, 40-41 22-2, 85-86 4-5, 25-26 9-6, 30-31 17-2, 40-41 30.CC 6,CC 13-4, 30-31 Sphenolithus ciperoensis 17,CC 31-1, 57-58 7-1, 10-12 29-1, 20 13-5, 30-31 Oligocene NP25 31.CC 7.CC 30-1, 147 13.CC M.-J. JIANG, S. GARTNER

Discoaster kugleri Zone (NN7) Remarks. The boundary between this zone and the next higher zone is sometimes difficult to recognize because a few specimens re- Definition. Interval from the first occurrence of Discoaster kugleri sembling Discoaster asymmetricus may be found lower. Typically, to the first occurrence of Catinaster coalitus. however, D. asymmetricus is common only in its nominate zone and Remarks. According to the definition, the top of this zone is at the above. first occurrence of C. coalitus. However, in an assemblage with mod- Some five-rayed discoasters found in the NN10 and NN11 zonal erate recrystallization, C. coalitus is difficult to identify, whereas C. interval are very similar to D. asymmetricus of the Pliocene; some, calyculus is still recognizable. In this case, the first occurrence of C. however, have vestigial bifurcation of rays like D. calcaris and are calyculus is used to mark the top of Zone NN7. here included with D. calcaris. Discoaster deßandrei was not recorded above this zone. Discoaster asymmetricus Zone (NN14) Catinaster coalitus Zone (NN8) Definition. Interval from the first occurrence of Discoaster asym- Definition. Interval from the first occurrence of Catinaster coali- metricus to the last occurrence of Amaurolithus tricorniculatus. tus or C. calyculus to the first occurrence of Discoaster hamatus. Remarks. A. delicatus instead of A. tricorniculatus is used to define the top of this zone because the latter species is very rare at the Discoaster hamatus Zone (NN9) studied sites. Definition. Interval from the first occurrence to the last occurrence Reticulofenestra pseudoumbilica Zone (NN15) of Discoaster hamatus. Remarks. D. hamatus in these southeast Atlantic sites is rare and Definition. Interval from the last occurrence pf Amaurolithus much smaller than in other regions. In some cases D. bellus with tricorniculatus to the last occurrence of Reticulofenestra pseudoum- slightly rotated tips (all in the same direction) resembles small D. ha- bilica s. ampl. matus. These two species are probably closely related to each other. Remarks. This zone is easily recognized in the studied sites. In the Both forms have the same first occurrence at the base of Zone NN9; upper part, small specimens of R. pseudoumbilica are typical. The however, D. bellus extends upward to the lower part of Zone NN10. large R. pseudoumbilica becomes extinct somewhat earlier than the D. pentaradiatus and D. neohamatus have their first occurrence in smaller one. Sphenolithus abies (S. neoabies included) has its last oc- the upper part of this zone. Rare to common Minylitha convallis also currence in the upper part of Zone NN15, whereas Pseudoemiliania occur in the upper part of this zone. lacunosa has its first occurrence in the uppermost part of this zone.

Discoaster calcaris Zone (NN10) Discoaster surculus Zone (NN16) Definition. Interval from the last occurrence of Discoaster hama- Definition. Interval from the last occurrence of Reticulofenestra tus to the first occurrence of D. quinqueramus. pseudoumbilica to the last ocurrence of Discoaster surculus. Remarks. The composition of discoasters of the assemblage has a Remarks. D. tamalis and D. asymmetricus have their last occur- second major change at the base of this zone, that is, at the base of the rences within this zonal interval. upper Miocene. The common (overgrown) D. variabilis s. ampl. is reduced in numbers, whereas delicate species such as D. brouweri (in- Discoaster pentaradiatus Zone (NN17) cluding large D. neorectus), D. calcaris, and D. neohamatus common- Definition. Interval from the last occurrence of Discoaster sur- ly occur in this zone in our cores. culus to the last occurrence of D. pentaradiatus. Zone NN10 is also characterized by the abundant occurrence of Remarks. This zone is very thin. It was not recognized at several of Minylitha convallis. M. convallis looks like a calcite particle. How- the sites studied. ever, when it occurs abundantly, it is easy to recognize the presence of this species in the assemblages. Discoaster brouweri Zone (NN18) Discoaster quinqueramus Zone (NN11) Definition. Interval from the last occurrence of Discoaster pentaradiatus to the last occurrence of D. brouweri. Definition. Interval from the first to the last occurrence of Disco- aster quinqueramus. Pseudoemiliania lacunosa Zone (NN19) Remarks. Most of the Discoaster quinqueramus (group) specimens identified in this study are of the D. berggrenii type with short rays. Definition. Interval from the last occurrence of Discoaster brou- This latter species is very rare at shallow sites. It is absent at deep sites, weri to the last occurrence of Pseudoemiliania lacunosa. which makes it difficult to differentiate this zone from the superjacent Remarks. Ceratolithus rugosus, Calcidiscus macintyrei, and Hel- and subjacent zones. icosphaera sellii have their last occurrences, whereas Gephyrocapsa The lower part of Zone NN11 is characterized by the presences of caribbeanica and G. oceanica have their first occurrences in the lower D. neohamatus and Minylitha convallis, whereas the upper part is part of this zone. Coccolithus pelagicus is greatly reduced in number characterized by the presences of Amaurolithus spp. The ranges of D. at the base of this zone. neohamatus and A. primus show little overlap. However, these two Calcidiscus macintyrei is much more common at the deeper sites species do co-occur in a few samples. than at the shallower sites. At deeper sites where D. quinqueramus is missing, the last occurrence of A. amplificus is tentatively introduced to mark the top of Gephyrocapsa oceanica Zone (NN20) Zone NN11. This is based on the fact that A. amplificus is restricted to Definition. Interval from the last occurrence of Pseudoemiliania the D. quinqueramus Zone at the shallow sites. lacunosa to the first occurrence of Emiliania huxleyi. Emiliania huxleyi Zone (NN21) Amaurolithus tricorniculatus Zone (NN12) Definition. Interval from the last occurrence of Discoaster quin- Definition. Interval with Emiliania huxleyi. queramus to the first occurrence of Ceratolithus rugosus. Remarks. The boundary between Zones NN20 and NN21 is diffi- Remarks. C. acutus has its first, and Triquetrorhabdulus rugosus cult to determine because E. huxleyi is too small to be identified with has its last, occurrence in this zone. the light microscope with certainty. The recognition of the upper part Typical D. surculus becomes quite common within and above this of this zone is, however, much easier because the nominal species is zone at our sites. extremely abundant there. Ceratolithus rugosus Zone (NN13) SUMMARY OF SITES Definition. Interval from the first occurrence of Ceratolithus rugo- The Neogene and Quaternary calcareous nannofossil sus to the first occurrence of Discoaster asymmetricus. assemblages recovered during DSDP Leg 74 are discussed

564 CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY

in detail as follows: each hole is considered separately, drei and without D. variabilis and D. exilis. The two and the basis for biostratigraphic age assignments is very rare occurrences of S. belemnos in the lower part of documented. Range charts are presented for all holes. this interval are interpreted as due to reworking or mixing during coring. Samples 525A-11-2, 40-41 cm through Hole 525 (29°04.24'S, 02°59.12'E; 525A-11-4, 40-41 cm are typical of the early Miocene water depth: 2467 m) Zone NN3 because of the common occurrence of S. be- Only one surface core, from 0-3.6 meters, was recov- lemnos. Samples 525A-11-5, 40-41 cm through 525A- ered at Hole 525. The core catcher sample from 3.6 me- 13-4, 40-41 cm are assigned to the early Miocene Zone ters sub-bottom contains abundant Pseudoemiliania la- NN2, based on the presence of Discoaster sp. aff. D. cunosa with common Helicosphaera carteri and Calci- druggii and the absence of S. belemnos. Sphenolithus discus leptoporus. Other few to rare species are small sp. aff. S. belemnos, however, might be present in this Gephyrocapsa spp., Rhabdosphaera clavigera, Syraco- interval. sphaera pulchra, Craspedolithus declivus, Scapholithus Samples 525A-13-5, 40-41 cm through 525A-17-2, fossilis, and Ceratolithus rugosus. Gephyrocapsa ocean- 40-41 cm belong to the early Miocene Zone NN1. In this ica may be present; however, no specimens with a com- zonal interval, several biological events occur: Zygrhab- plete bridge were found. This assemblage indicates the lithus bijugatus becomes extinct in Sample 525A-16,CC; early Pleistocene P. lacunosa Zone (NN19). No checklist Dictyococcites bisectus, in Sample 525A-16-1, 40-41 was prepared for this hole because of duplication of the cm; and D. dictyodus, in 525A-15-6, 40-41 cm. Spheno- cored interval at Hole 525A. lithus capricornutus and S. delphix have very short ranges in the lower part of this zone. Only a single speci- Hole 525A (29°04.24'S, 02°59.12'E; men of Helicosphaera recta was found in Sample 525 A- water depth: 2467 m) 15-7, 40-41 cm. It is uncertain whether it is in place or is Hole 525A was drilled with conventional rotary cor- a redeposited specimen. ing. Sediments were not continuously cored above 165.1 Sphenolithus ciperoensis last occurs in 525A-17,CC, meters sub-bottom. Table 2 represents the nannofossil and this point is taken to mark the top of the Oligocene. distribution in this hole. The nannofossil biostratig- The preservation of calcareous nannofossils in Hole raphy is here given for the NN3 through NP25 zonal in- 525A in general is moderate. Dissolution and recrystalli- terval. Nannofossil distribution younger than the NN3 zation increase downhole. Discoasters in Cores 3 through zone for Hole 525A may be compared with that for the 6 are moderate in preservation; however, they are poor nearby Hole 525B given in Table 3. from Core 7 downward. Overgrowth has destroyed many Quaternary sediments were recognized only in Core species characters of discoasters, which makes species 1. The core-catcher sample contains essentially the same identification difficult or impossible. assemblage as that found in Sample 525-l,CC of Hole 525 and is assigned to Zone NN19 of the early Pleisto- Hole 525B (29°04.24S, 02°59.12'E; cene. The only difference is that most of the Gephyro- water depth: 2467 m) capsa species found in this core catcher sample have a Hole 525B was drilled with hydraulic piston coring. complete bridge. Sediments were continuously cored from 0 to 209.4 me- Core 2 has no recovery. ters sub-bottom to compensate for the coring gap in Cores 3 and 4 are early Pliocene in age (Zones NN13- Hole 525A. Table 3 represents the Neogene and Quater- NN12), based on the presence of Reticulofenestra pseu- nary nannofossil distribution in this hole. doumbilica, Sphenolithus abies, Amaurolithus delica- The youngest calcareous nannofossil zone, NN21, of tus, A. primus, A. tricorniculatus, Ceratolithus rugosus, the late Pleistocene was recognized in Samples 525B-1- and C. acutus and the absence of A. amplificus and 1, 20-32 cm and 525B-1-1, 80-82 cm, based on the Discoaster quinqueramus. Cores 5 and 6 are assigned to abundant occurrence of Emiliania huxleyi together with Zone NN11 of the late Miocene, on the basis of the very Gephyrocapsa oceanica. The next zone, NN20, of the rare occurrence of D. quinqueramus. It is worth men- late Pleistocene was encountered in Sample 525B-1-2, tioning that Core 5 contains Amaurolithus species with- 30-32 cm. Then \he first downhole occurrence of Pseu- out D. neohamatus, whereas Sample 525A-6,CC con- doemiliania lacunosa in 525B-1-2, 80-82 cm places this tains D. neohamatus without Amaurolithus species. sample at the top of early Pleistocene Zone NN19. Core 7 through Sample 525A-8-2, 40-41 cm belongs Samples 525B-1,CC and 525B-2-1, 60-61 cm are to the middle Miocene Zone NN6, based on the abundant dominated by small Gephyrocapsa with rare G. oce- occurrence of Cyclicargolithus floridanus with some D. anica and G. caribbeanica. According to Gartner (1977), deflandrei s. ampl. and Coronocyclus nitescens and on this assemblage belongs to the small Gephyrocapsa the absence of Sphenolithus heteromorphus. Sample acme interval which is in the middle part of the Zone 525A-8-2, 40-41 cm through Sample 525A-9,CC are as- NN19. The highest occurrence of Helicosphaera sellii is signed to the middle Miocene Zone NN5, based on the in Sample 525B-2-2, 60-61 cm. Next to it, the highest common presence of S. heteromorphus with some D. occurrence of Calcidiscus macintyrei is in 525B-2-3, variabilis s. ampl. and rare D. exilis. 60-61 cm, and the lowest occurrence of typical G. oce- Core 10 through Sample 525A-11-1, 40-41 cm be- anica and G. caribbeanica is in 525B-2,CC. The early longs to the early Miocene Zone NN4, based on the Pleistocene calcareous nannofossil assemblages in Hole presence of S. heteromorphus with common D. deflan- 525B are essentially the same as those in Holes 525 and

565 Table 2. Nannofossil distribution at Hole 525A, DSDP Leg 74.

S s 3 I S n a 3 iii $ I I E 11111 ti c 2 Overall fjllf• 3 3 ε Preservation 3 3 3 3 3 1 it ?t .11 s 5 3 € •S € -£ 5 5 HUI Depth 1111 3 3 3 3 3 S 1 Other Overall below Core- s s s "ss 1 Disco- Cocco- Abun- Seafloor Section 11111S 1 g s § ill Age asters liths dance (m) (interval in cm) § 3 i a § a, ii E 6 E £ £ c δ <3

525A. Very rare Discoaster brouweri found in this inter- 525B-23-2, 37-38 cm. The lower part is represented by val are interpreted as reworked. the presence of D. neohamatus, which is traced up to Typical, well-preserved D. brouweri with slender long the same sample. Amaurolithus amplificus has a very arms is first encountered in Sample 525B-3-2, 53-54 cm, short range and is restricted to the upper part of Zone which places this sample at the top of Zone NN18 of the NN11. In the lower part of Zone NN11 and downward, late Pliocene. Next, common D. pentaradiatus, the in- slender yet giant D. brouweri (D. neorectus type), to- dex species for Zone NN17 of the late Pliocene, is re- gether with large D. neohamatus and D. variabilis, are corded in 525B-4-2, 65-66 cm. Zone NN17 represents a prominent. very short time interval, because D. surculus, the index The interval between Samples 525B-25-1, 36-37 cm species of Zone NN16 of the late Pliocene, is in Sample and 525B-28,CC belongs to Zone NN10 of the late Mio- 525B-4-3, 65-66 cm. Discoaster asymmetricus and D. cene, based on the absence of both D. quinqueramus tamalis have their highest occurrences in Zone NN16 of and D. hamatus. Discoaster variabilis, large D. neoha- Hole 525B. Also, typical H. carteri gradually gives way matus, and large, slender D. brouweri are still the major downward to a robust form, H. granulata, in this inter- discoaster components in this zone. Minylitha convallis, val. which rarely occurs in the lower part of Zone NN11, be- Typical Reticulofenestra pseudoumbilica (small and comes very abundant throughout the NN10 zonal inter- large forms) abundantly occurs for the first time in val. This species, according to Bukry (1973), commonly Sample 525B-5-2, 81-83 cm, which places this sample in occurs in the middle-late Miocene transitional interval. the top of Zone NN15 of the early Pliocene. Within A form of discoaster with five asymmetrical arms oc- Zone NN15, the highest occurrence of Sphenolithus curs sporadically throughout this interval and its overly- abies is found in 525B-7-2, 39-40 cm, whereas the low- ing NN11 Zone. This form looks much like D. asym- est occurrence of Pseudoemiliania lacunosa is traced metricus of the Pliocene. However, some specimens down to Sample 525B-7-3, 39-40 cm. Helicosphaera with better preservation show vestigial bifurcations. sellii is no longer found below this zone in Hole 525B, This form may be related to the five-rayed D. calcaris but D. variabilis is continuously recorded in the lower and should not be included in D. asymmetricus, with part of this zone and downward. which it does not have a continuous range. Amaurolithus delicatus first appears in Sample 525B- The interval between Samples 525B-29-1, 76-77 cm 8-3, 3-4 cm, which places this sample at the top of Zone and 525B-32-2, 113-114 cm is included in Zone NN9 of NN14 of the early Pliocene. Amaurolithus delicatus and the middle Miocene, based on the total range of D. ha- A. primus are the most common species of the Amauro- matus. Minylitha convallis is still very abundant in the lithus group in this interval and down to the upper Mio- upper part of this zone. It quickly becomes rare down- cene. Typical specimens of A. tricorniculatus are very wards, however, and disappears in the lower part of this rate. The birefringent Ceratolithus rugosus is traced zone. Within the NN9 zonal interval, several biological down to 525B-12-1, 10-11 cm, which places this sample events occur. The small R. pseudoumbilica are no long- at the base of Zone NN13 of the early Pliocene. The er observed within this zone; D. pentaradiatus is not re- NN13/NN14 boundary cannot be defined with certainty corded below Sample 525B-29-2, 76-77 cm; Catinaster in Hole 525B, because the NN14 index species, D. asym- calyculus first appears in 525B-3O-1, 44-45 cm and C. metricus, consistently occurs downward. Discoaster de- coalitus in 525B-32-2, 113-114 cm. Besides D. hamatus, corus is found sporadically within the NN13/NN14 zon- the major discoaster components in this zone are D. al interval and down to Zone NN11 of the late Miocene. variabilis, D. brouweri, D. neohamatus, D. bellus, and The interval between Samples 525B-12-1, 54-55 cm D. calcaris. Some D. signus with long bifurcation of ray and 525B-14-2, 40-41 cm is assigned to Zone NN12 of are also included in the discoaster assemblage. Disco- the earliest Pliocene, based on the absence of both C. aster calcaris, or transitional forms of D. calcaris and rugosus and D. quinqueramus. The highest occurrence D. exilis, do not occur below Zone NN9, but D. neoha- of Triquetrorhabdulus rugosus is recorded in 525B-13- matus is traced down to Sample 525B-31,CC. Discoas- 3, 40-41 cm, and A. bizzarus is found only in 525B-13-1, ter bellus, a form related to and associated with D. 40-41 cm. hamatus, has the same first occurrence as D. hamatus in The highest occurrence of D. quinqueramus is traced 525B-32-2, 113-114 cm. Its highest occurrence, how- up to Sample 525B-14-2, 100-101 cm, which places this ever, is traced up to Sample 525B-28,CC, the base of sample at the top of Zone NN11 (i.e., the top of the up- Zone NN10. per Miocene). Aside from the index species, the calcare- Samples 525B-32-3, 41-42 cm through 525B-33,CC ous nannofossil assemblages in the early Pliocene and belong to Zone NN8 of the middle Miocene, based on the late Miocene are essentially the same. Discoaster the presence of Catinaster species in the absence of D. brouweri, D. surculus, D. pentaradiatus, D. decorus, D. hamatus. The absence of Catinaster species and of Cy- variabilis, and D. intercalcaris are quite common in clicargolithus floridanus places the interval between these intervals. Although D. quinqueramus is very rare Samples 525B-34-1, 65-66 cm and 525B-36,CC in Zone in the upper Miocene of Hole 525B, its occurrence is NN7 of the middle Miocene. Below 525B-31,CC the sufficiently consistent to outline its total range zone. preservation of discoasters suddenly becomes poor, most Zone NN11 can further be divided into two parts. The specimens being overgrown. In the NN7-NN8 zonal in- upper part is characterized by the presence of A. delica- terval and downward, D. variabilis s. ampl. is the only tus and A. primus which is traced down to Sample dominant discoaster species. Moderately preserved D.

~~567 M.-J. JIANG, S. GARTNER~~

~~Table 3. Nannofossil distribution at Hole 525, DSDP Leg 74. CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY~~

~~Table 3. (Continued).~~

~~569 M.-J. JIANG, S. GARTNER~~

~~Table 3. (Continued).~~

~~570 CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY~~

~~571 M.-J. JIANG, S. GARTNER~~

~~Table 3. (Continued).~~

Overall Preservation ter calyculus ter coalitus ithus acutus ithus cristatus ithus telesmus •ter asymmetricus Depth ithus rugosus o o © o Dictyococcites dictyodus \ urolithus amplificus urolithus delicatus smolithus altus icargolithus floridanus

Other 'urolithus bizzarus ulolithina area •rudosphaera bigelowi idiscus leptoporus idiscus macintyrei nas -.olithus pelagicus s . 1 -.olithus orangensis jnocyclus nitescens •pedolithus declivus Overall below \umlithus tricorniculatus | yococcites bisectus ^3 ^3 (J 1 Disco- Cocco- Abun- Seafloor Core-Section δ maurolithus primus g> "a o 5 -5 o S ricolithus jonesii Cera I o Age Zonation asters liths dance (m) (interval in cm) ε ü G Q <3 ü C ü G c rj rj ü 0 Q * P M A 152.2 36-1, 90-91 C R c R NN7 P M A 36-2, 50-51 C R c R P M A 36-3, 50-51 C R A middle P M A 156.6 36.CC c R A Miocene P M A 156.6 37-1, 40-41 A R A R c P M A 37-2, 40-41 A R A A P M A 37-3, 40-41 A R A A P M A 161.0 37,CC C F A A P M A 161.0 38-1, 29-30 A F F R A P M A 38-2, 29-30 C F F A NN6 P M A 38-3, 29-30 C F C R R A P M A 165.4 38.CC c F C R C P M A 165.4 39-1, 74-75 c F C R R A P M A 39-2, 74-75 c R A R R A P M A 39-3, 74-75 c R A R F A P M A 169.8 39.CC c R C R C P M A 174.2 41,CC c C R F A P M A 174.2 42-1, 35-36 c c R F A P M A 42-2, 35-36 c c R F A P M A 178.6 42, CC c c R C A P M A 178.6 43-1, 58-59 c c R R A P M A 43-2, 58-59 c F R R A P 43.CC F A NN5 M A 183.0 c c P M A 187.4 44.CC P M A 187.4 45-1, 98-99 c c R cf. A P M A 45-2, 117-119 c F R A P M A 45-3, 98-99 c C R A P M A 191.8 45.CC R c R R A P M A 191.8 46-1, 60-61 R c R R A P M A 46-2, 60-61 F c C R A P M A 46-3, 60-61 F c c R A P M A 196.2 46.CC R c F R A P M A 196.2 47-1, 20-21 F R A NN4 c P M A 47-2, 20-21 F C R A P M A 47-3, 20-21 F F R A P M A 200.6 47.CC F F R A P M A 200.6 48-1, 60-61 R C R A early P M A 48-1, 100-102 R F R A Miocene P M A 48-2, 60-61 R F R A P M A 48-3, 60-61 R F R A NN3 P M A 205.0 48.CC R F R A P M A 205.0 49-2, 20-21 R F R A P M A 49-3, 20-21 R F R A P M A 49-4, 20-21 R C A NN2 P M A 49-4, 80-82 F F R A P M A 209.4 49.CC R F R A

Note: For abundance, A = abundant, 10 specimens/field; C = common, 1-10 specimens/field; F = few, 1 specimen/1-10 fields; R = rare, 1 specimen/10 fields; r = very rare, probably due to reworking or contamination (counts at 1000 × magnification). Designations "cf." and "aff." mean that a similar form occurs but no abundance is recorded. For preservation, P = poor; M = moderate; G = good. The dotted line indicates a zonal boundary of uncertainty. a R = Reticulofenestra. exilis is traced upward to Sample 525B-33-1, 45-46 cm, clococcolithus macintyrei are no longer found below Zone NN8, whereas D. deßandrei is recorded up to 525B- this zone. 35,CC of the NN7 Zone. Because of poor preservation The total range of S. heteromorphus, between Sam- or environmental exclusion, typical D. kugleri, the in- ples 525B-42-1, 35-36 cm and 525B-48-1, 60-61 cm, dex species for Zone NN7, was not observed in this hole. represents the NN5 and NN4 zonal intervals. Because of The top of Zone NN6 of the middle Miocene is tenta- the absence of H. ampliaperta, the index species for tively placed in Sample 525B-37-1, 40-41 cm, where the Zone NN4, in Hole 525B, the NN5/NN4 boundary (i.e., first downhole occurrence of C. floridanus is recorded. the middle/early Miocene boundary) cannot be identi- In the NN6 zonal interval, Coronocyclus nitescens has fied with certainty. Tentatively the NN5/NN4 boundary its highest occurrence in 525B-38-3, 29-30 cm, whereas is placed between Samples 525B-46-1, 60-61 cm and Triquetrorhabdulus rugosus has its lowest occurrence in 525B-46-2, 60-61 cm. This is based on the fact that there 525B-39,CC. Discoaster brouweri, D. signus, and Cy- is a significant discoaster assemblage change here. Above

~~572 CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY~~

~~Table 3. (Continued).~~

B• a S S a a s s .§ ü UH C δ I α § g> « S S 3 § - "c s α I s• I I g B. »J i. a -S •~ |3 ε 11i 1 5 o « & 2. S? a © O O m IaJ i j i I ">< S P> ,<3 à S 5 a β Hill -is c>. •^: •T ^ ^ llll! -IU I Illli "S "5 "o "o "5 8 8 8 8 1 ε s s I IllSl ^ B ‰ ‰ Si •a •a a a •a a g -s: -« a a a >, >, js 3; S S S S e ,* PS C\ O, S rC rC Q Q Q Q Q q a; a; a; a; a; a; s;• a; oj ac :=: -sT -? ^ C R ε & S- S A R E ü DO C C c c A R F A F C F C c F C R F C R F A C A R C C R C c C c F R Cc C R R C cf. F F c C F c C C c C F C R C F

~~c C C F C F C C C R R C F F R C R C C Cf. C F C F C F C C C C C C R C C c c c c~~

525B-46-1, 60-61 cm, D. variabilis is one of the domi- Discoaster sp. aff. D. druggii. Discoaster sp. aff. D. nant discoaster species, whereas below 525B-46-2, 60-61 druggii, however, ranges up to the lower part of the cm it suddenly disappears. Discoaster deßandrei is then NN3 Zone. the only dominant discoaster in the assemblage. Rare The preservation of the Neogene and Quaternary cal- specimens of a shallow-water or brackish-water form careous nannofossils at Hole 525B is moderate in gener- Braarudosphaera higelowii are also recorded around the al. Dissolution and recrystallization of placoliths in- middle-early Miocene transition interval. crease downhole. The state of preservation of disco- The interval between Samples 525B-48-1, 100-102 cm asters, however, fluctuates. Most discoasters recovered and 525B-49-3, 20-21 cm is assigned to Zone NN3 of the above Core 30 are moderately preserved. The best-pre- early Miocene, based on the total range of S. belemnos. served discoasters are found in the upper middle and The interval between 525B-49-4, 20-21 cm and 525B- lower upper Miocene interval. However, below Core 31 49,CC is Zone NN2 of the early Miocene in age, based they are so poorly preserved that their diversity becomes on the absence of S. belemnos and the rare presence of very low in the lower middle and lower Miocene.

~~573 M.-J. JIANG, S. GARTNER~~

Hole 526 (30°07.36'S, 03°08.28'E; highest occurrence in Sample 526A-4-3, 15-16 cm in this water depth: 1054 m) zone. Again, the Pliocene/Miocene boundary is not easily Site 526 was the shallowest site drilled during Leg 74. recognized in Hole 526A, because D. quinqueramus, the Hole 526 was drilled with hydraulic piston coring. Only index species for the late Miocene Zone NN11, is very two cores were recovered in this hole, however. Samples rare. After a long search it was found that D. quinque- 526-1-1, 100-102 cm through 526-2-1, 106-107 cm be- ramus consistently occurs between Samples 526A-5-2, long to NN20 Zone of the late Pleistocene. The assem- 85-86 cm and 526A-9,CC. This interval is therefore as- blage includes common Gephyrocapsa oceanica, small signed to Zone NN11. As in Hole 525B, typical A. Gephyrocapsa sp., Calcidiscus leptoporus, Helicosphae- amplificus is restricted to the upper part of this zone. ra carted, Syracosphaera pulchra, and Rhabdosphaera The occurrence of A. delicatus and A. primus, on the clavigera and rare Coccolithus pelagicus, Cricolithus other hand, is traced down to Sample 526A-7,CC, where jonesii, Scapholithus fossilis, Umbilicosphaera mirabi- the highest occurrence of D. neohamatus is recorded. lis, Pontosphaera japonica, and other Pontosphaera sp. Typical Helicosphaera granulata gradually become more Redeposited coccoliths from the Pliocene, Miocene, and important than H. carteri in the late Miocene of Hole Oligocene were also recorded. These are Chiasmolithus 526A. In fact, the two species are very difficult to dif- altus, Cyclicargolithus floridanus, Coronocyclus nites- ferentiate during the late Miocene and early Pliocene. cens, Dictyococcites bisectus, Discoaster deflandrei, They could be the same taxon in different states of Pseudoemiliania lacunosa, Reticulofenestra pseudoum- preservation. Also, in the lower part of this zone, Miny- bilica, and Sphenolithus abies. Core 2 has poor recov- litha convallis occurs abundantly below Sample 526A- ery. The core catcher sample from 6.3 meters sub-bot- 8,CC. tom contains indigenous P. lacunosa and is assigned to The interval between 526A-10-1, 103-104 cm and the NN19 Zone of the early Pleistocene. 526A-12-3, 25-26 cm is attributed to the late Miocene The calcareous nannofossil preservation in Hole 526 Zone NN10, based on the absence of D. quinqueramus is moderate to good. A check list of the nannofossil dis- and D. hamatus. This interval is also characterized by tribution of this hole is given in Table 4. abundant M. convallis, common D. neohamatus, and common D. brouweri with long slender rays (D. rectus Hole 526A (30°07.36'S, 03°08.28'E; type). The highest occurrence of D. bellus is traced up to water depth: 1054 m) Sample 526A-11-3, 30-31 cm in this zone. As in Hole Hole 526A was drilled with hydraulic piston coring. 525B, the same form of discoaster with five asymmetri- Sediments were continuously cored from 28.0 meters cal arms occurs sporadically within the late Miocene süb-bottom down to 228.8 meters (late Eocene). The NN10-NN11 zonal interval of this hole. core recovery in this hole is very good. No significant hi- The interval between 526A-12,CC and 526A-14,CC atuses were recognized through the Neogene. However, belongs to the middle Miocene Zone NN9, based on the the sedimentation rate seems not to be consistent during total range of D. hamatus. Several biological events oc- the Neogene, because some of the calcareous nannofos- cur within this zonal interval, and the pattern of succes- sil zones in this hole are represented by rather short in- sion of these events is comparable to that recorded in tervals. A check list of the Neogene calcareous nanno- Hole 525A. Minylitha convallis is still very abundant in fossil distribution of Hole 526A is given in Table 4. the upper part of this zone, quickly becomes rare down- Three calcareous nannofossil zones are recognized in ward, and disappears in Sample 526A-14-2, 20-21 cm; Core 1. Sample 526A-1-1, 75-76 cm contains abundant the small R. pseudoumbilica are no longer observed Reticulofenestra pseudoumbilica (both small and large within this zonal interval; the lowest occurrence of D. forms), without Amaurolithus species, and is assigned pentaradiatus is traced down to 526A-12,CC; D. neoha- to the NN15 Zone of the early Pliocene. This sample matus extends a little farther down but disappears above also contains Sphenolithus abies, yet without Pseudo- the first occurrence of D. hamatus; rare D. signus are emiliania lacunosa. It is reasonable to place this sample observed within this zone, and Catinaster calyculus has in the lower part of Zone NN15. Sample 526A-1-2, 75- its highest occurrence in Sample 526A-13,CC. However, 76 cm belongs to Zone NN14 of the early Pliocene, D. bellus, a form related to and associated with D. based on the occurrence of both A. delicatus and Dis- hamatus, extends down to Zone NN8 in this hole. coaster asymmetricus. Amaurolithus delicatus has its Sample 526A-15-1, 26-27 cm through 526A-15,CC is highest, and D. asymmetricus has its lowest, occurrence included in Zone NN8 of the middle Miocene, based on in this core sample. Samples 526A-1-3, 75-76 cm through the presence of C. calyculus and the absence of D. ha- 526A-2-2, 80-81 cm contain Ceratolithus rugosus with- matus. Catinaster coalitus, the designated index species out D. asymmetricus and therefore belong to the early for Zone NN8, is very rare in this hole. Next below the Pliocene Zone NN13. absence of both C. calyculus and Cyclicargolithus flori- The interval between 562A-2-3, 80-81 cm and 526A- danus places the interval between Samples 526A-16-1, 5-1, 85-86 cm is included in the earliest Pliocene Zone 42-43 cm and 526A-18-3, 50-51 cm, into Zone NN7 of NN12 based on the absence of C. rugosus and D. quin- the middle Miocene. As in Hole 525B, the preservation queramus. Typical A. tricorniculatus is extremely rare of discoasters becomes poor in the upper part of the in the early Pliocene of Hole 526A; it is found only in middle Miocene. Discoaster brouweri s. ampl. is no Sample 526A-2,CC. Triquetrorhabdulus rugosus has its longer found below the NN8 zonal interval. The over-

574 CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY grown D. variabilis becomes the only dominant discoas- Hole 526A is the shallowest (1054 m), both forms spo- ter species in the lower part of the middle Miocene. The radically occur in the upper Oligocene of this hole. Also first downhole occurrence of D. deflandrei is recorded Braarudosphaera bigelowii, a hemipelagic form, occurs in the lower part of Zone NN7. Discoaster kugleri, the fairly consistently in the late Oligocene and the earliest true index for Zone NN7, is not found in Hole 526A, Miocene of this hole. however. The preservation of the Neogene calcareous nanno- The top of the middle Miocene Zone NN6 is tentative- fossils recovered in Hole 526A is much the same as that ly placed in Sample 526A-18,CC, where the first down- in Hole 525B. Assemblages in general are moderately hole occurrence of C. floridanus is recorded. Calcidis- preserved. Dissolution and recrystallization of placo- cus macintyrei is no longer recorded below this zone. liths increase downhole. Discoasters are moderately pre- Also in the NN6 zonal interval, Coronocyclus nites- served in the Pliocene and the uppermost Miocene. How- cens has its highest occurrence in 526A-19-3, 40-41 cm, ever, from the middle Miocene on they become so whereas Triquetrorhabdulus rugosus has its lowest oc- strongly overgrown that species identification is some- currence in 526A-18,CC. times difficult. Though no significant hiatus is found in the early middle, and early Miocene of Hole 526A, the sediment Hole 526B (30°07.36'S, 03°08.28'E; interval represented by Zone NN5 through Zone NN2 is water depth: 1054 m) very thin in this hole. The total range of S. heteromor- Hole 526B was drilled with hydraulic piston coring. phus places the interval between Samples 526A-20-3, Sediments were continuously cored from 6.3 down to 78-79 cm and 526A-21-1, 70-71 cm, into Zones NN5 28.3 meters sub-bottom. The main purpose of this hole and NN4. Next, the total range of S. belemnos limits the was to recover the coring gap between Holes 526 and interval between Samples 526A-21-2, 70-71 cm and 526A. The calcareous nannofossil distribution of this 526A-21,CC to Zone NN3 of the early Miocene. In hole is given in Table 4. 526A-22-1, 85-86 cm, S. belemnos is absent. The lowest Samples 526B-1-1, 30-32 cm through 526B-3-1, 35- occurrence of Discoaster sp. aff. D. druggii assigns this 36 cm belong to the early Pleistocene Zone NN19, based sample to Zone NN2 of the early Miocene. on the consistent presence of Pseudoemiliania lacunosa. Helicosphaera ampliaperta is absent and the NN5/ Gephyrocapsa oceanica and G. caribbeanica are abun- NN4 boundary (i.e., the middle/early Miocene bound- dant in this interval, except in the lowest part, in 526B- ary) is recognized in this hole by a sudden discoaster as- 3-1, 35-36 cm. Samples 526B-3-2, 35-36 cm through semblage change recorded between Samples 526A-20,CC 526B-3,CC contain Discoaster brouweri and are assigned and 526A-21-1, 70-71 cm. In 526A-20,CC and above, to the late Pliocene Zone NN18. No G. oceanica, G. ca- D. variabilis is the only dominant discoaster species, ribbeanica, D. pentaradiatus, or D. surculus were ob- whereas in 526A-21-1, 70-71 cm and below, no D. vari- served in this short interval. Sample 526B-4-2, 20-21 cm abilis is observed. Discoaster deflandrei becomes the on- through 526B-5,CC are included in the early Pliocene ly dominant discoaster species. Helicosphaera obliqua Zone NN15, based on the common and persistent occur- occurs sporadically between 526A-20,CC and 526A-21- rence of Reticulofenestra pseudoumbilica. Because of 2, 70-71 cm. the common presence of P. lacunosa without Spheno- The long interval between Samples 526A-22-2, 85-86 lithus abies, this interval is no older than the upper part cm and 526A-30,CC is assigned to Zone NN1 of the ear- of Zone NN15. Zones NN17 and NN16 are apparently liest Miocene, based on the absence of Discoaster sp. missing. It is uncertain whether they are absent because aff. D. druggii and S. ciperoensis. Sphenolithus sp. aff. of a minor hiatus or because of too large a sampling in- S. belemnos (= S. dissimilisl) appears sporadically with- terval. in this zonal interval. In the upper part of this zone, The calcareous nannofossils in Hole 526B are moder- R. pseudoumbilica and Calcidiscus leptoporus are still ately preserved. quite common. However, both forms become atypical downward and disappear in the lower part of this zone. Hole 526C (30°07.36'S, 03°08.28'E; In the lower part of this zone, Zygrahablithus bijugatus water depth: 1054 m) has its highest occurrence in Sample 526A-28-2, 44-45 Hole 526C was drilled with conventional rotary cor- cm. Dictyococcites bisectus and D. aff. D. dictyodus, ing. A short sediment interval was tentatively cored to on the other hand, are not found above 526A-28-3, determine the Pliocene-Miocene transition at Site 526. 44-45 cm. Also S. delphix and S. carpricornutus have The calcareous nannofossil distribution for this hole is very short ranges and are restricted to the lower part of given on Table 4. Zone NN1 in this hole. Samples 526C-1-1, 100 cm through 526C-1,CC belong The top of the Oligocene is placed in Sample 526A- to the upper part of the early Pliocene Zone NN15, based 31-1, 57-58 cm, where the highest occurrences of H. rec- on the presence of Reticulofenestra pseudoumbilica and ta and S. ciperoensis are recorded. In the late Oligocene Pseudoemiliania lacunosa, without Sphenolithus abies of this hole, several new species are encountered. These and Amaurolithus sp. The sediments recovered in Core are Chiasmolithus altus, Ericsonia fenestrata, and H. 1 probably are not in place because Core 1 has a poor re- perch-nielseniae. Helicosphaera recta and H. perch-niel- covery. Samples 526C-2-1, 42-43 cm through 526C-2-7, seniae are hemipelagic species. They are very rarely 40-42 cm have an early Pliocene Zone NN12 age, based found at other sites of DSDP Leg 74. However, because on the absence of Discoaster asymmetricus, Ceratolith-

575 all -: III 1 I 1 | I „ I I 1 3 „ a I I I a 11 1 I 111 Overall 3S333g^tl|| ^^|| 3| |?li *~™*» Depth Illllllllllllllllllillil Other Overall below isià^•il^^δilllli^oi•SlSl^ Disco- Cocco- Abun- Seafloor Sample llilllll-i l'|§§§^l§ool I I, I, K Age Zonation asters liths dance (m) (interval in cm) XXtX^^iülJüljölSljδüüüüijIJüüü Holes 526-526B

~~M A 0.0 526-1-1, 101-102 A R R R~~

late NN20 M A 1.9 l.CC A r R r r r M A 1.9 2-1, 106-107 c R R M A 6.3 2.CC c R M A 6 3 Pleistocene 526B-1-1, 30-32 c R Pleistocene ear]y Nm9 M A 10.7 l.CC c R M A 15.1 2.CC c R R M A 15.1 3-1,35-36 A r F r late NN18 M M A 3-2,35-36 Q~~R F R N " M M A 19.5 3.CC A R p M M A 19.5 4-2,20-21 C~~jj p r M M A 4-2, 110-112 c R p r M M A 23.9 4,CC c R p N.5 M M A 23.9 5-1,20-21 c R F M M A 5-2,20-21 c C r M M A 5-3, 20-21 c R R M M A 28.3 5.CC C R R R M M A 28.0 526A-1-1, 75-76 C R R R R NN14 M M A 1-2, 75-76 R C R R R M M A 1-3,75-76 R R C R R NN13 M M A 32.4 l.CC R R C R R

Püocene M M A 32.4 2-1,80-81 R C R R R early M M A 2-2,80-81 R C R R y M M A 2-3,80-81 R R C R R R M M A 36.8 2.CC p R R c R R M M A 36.8 3-1, 65-66 F R C R R M M A 3-2, 65-66 F R C F R M M A 3-3,65-66 R R c R R R NN12 M M A 41.2 3.CC R R C R cf F F M M A 41.2 4-1, 15-16 R C R F R M M A 4-2, 15-16 R R C F R M M A 4-3, 15-16 R R C C R M M A 45.6 4.CC R R C C R M M A 45.6 5-1,85-86 R R C R R M M A 5-2,85-86 ~R R^ C F R M M A 5-3, 85-86 R R C F M M A 50.0 5iCC__ R R R C C R M M A 50.0 6-1,80-81 R F R C C R M M A 6-2, 80-81 R C F M M A 6-3, 120-122 R R C F R M M A 54.4 6.CC R R C F R M M A 54.4 7-1, 7-8 R R C C R M M A 7-2,7-8 R R C C R NN11 M M A 7-3,7-8 R C C M M A 58.8 7.CC R C A R M M A 58.8 8-1,46-47 C A R M M A 8-2, 46-47 C A M M A 8-3, 46-47 C A R late M M A 63.2 8,CC A A R A M M A 63.2 9-1, 6-7 C A R M M A 9-2, 6-7 A A R M M A 9-3, 6-7 A C R M M A 67.6 9,CC A A_ __R M M A 67.6 10-1, 103-104 C F M M A 10-2, 103-104 C C R M M A 10-3, 13-14 A A R M M A 72.0 10.CC A C R M M A 72.0 11-1, 30-31 C C R M M A 11-2,30-31 C C R M M A 11-3,30-31 C C R NN10 M M A 76.4 11,CC C F R M M A 76.4 12-1, 25-26 C R F R P M A 12-2, 25-26 C F F P M A 12-3,25-26 ç p R P M A 80.8 12.CC A C R P M A 80.8 13-2, 30-31 C C R P M A 13-3, 30-31 C C R

~~NN9 P M A 85.2 13.CC C R R C R P M A 85.2 14-1, 20-21 C R C P M A 14-2, 20-21 A R C F P M A 14-3, 20-21 C R C R P M A 89.6 14.CC ç R ç__ R P M A 89.6 15-1, 26-27 C R F R~~

~~NN8 P M A 15-2,30-32 R C R C R P M A 15-3,26-27 C R R F R P M A 94.0 15.CC ç R ç__ __R . P M A 94.0 16-1, 42-43 C C R I I P | M I A 1 | 16-2, 42-43 C^ F^ R~~

~~576 CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY~~

~~Table 4. (Continued). ill a 2 sail i. | •§ I - J s ? i s 111 I 311 „ 11 g 1111 i iliüLi IhüjifllijltliiitfU liftii IllIflii I s*δδδSδδδδδδδδδδδδδiiHHJl!lll|ffiiiitilititttiilt3i~~

AFC RR FR RR r CFC RRrrRRr FR AACF rRR FR AACR RRrRRr F AACR RFrRRr F R FAR RRCrRR FR ACAR RRR F _r r R R R A rRR R R r F R A r R R F R C F__A R_R C R RR F RARR F RR RRR FR RAFFRR F RR RRR R FACAR F FR FFR R RACARR F FR FFR R RACARRR F RR RRR F RFCAR R RR RRR F FFCARR R RR RFR C RRARRRR R RR FC F RAARRFR R R CC F RAARRF R CC R RRAARFF R R RRR R RCARRF R FR F RCARRRR R R CCR F RAARRR R R CCR C RAARFR F R CFR F RAARRR R R FFR F RAARRR F F FFR F RAARRRR F R C cf. R C F RAARRRC F R FRF F RAARRF R R RRR F RAARFF R aff. R RRF F RAARFC R aff. R Fcf. RF RI RAARRF R R R cf, R R cf. R cf. R A A R R R R F R ~R F cT R R A A R R RF RR F cf. R RAARRR aff. R R R R R F R aff. A F R R F RR FR F R R aff. A C R C R RRRF RR R aff. A A R RR RRF RR R aff. A A R R F R RRRF RR R aff. A A R R F R RR RRRF RR R aff. A A R R C R RR FRRF RR RCARF R RR FRF R RAAF R R RRR C RF RAARF RR F RRRF RF RAARF R C FRRF F RAARF RR aff. C FRRC F RAARF R aff. C RRRC R CA F RR F RRRCR RF FACF R F RRRRCR RF ARCCRRF RR aff. R R F R cf. R C R FF ARAA RC RR aff. C R R R cf. R C R R_ _F jK C C C R F FR FR F CRCAF RR F RR FR RF ARAF R aff. C FR C FC ARRARF R C FR F RF ARCAR R aff. C RRF R A A A R R R RR FR R AARR R RF RR CR RF AA R RR RF RRRCR R A A cf. R R aff. R R R F R R R A R A A cf. R R R RRR RR F RR A ACRF RR aff. R R R R RFR F A A R R R F R R R F~~R ~R T £ F Tl RR RR F RR FA R RR RR RRRF R FARF R FR RRF R CAC R RR RR R R FAC R R FRRF RRAF R RR R FR RR AF R R R R R C R R_ _F A R_F R R R F R R A F K " RR FR RF RAC RR R FRRR AF R I* F R R^ A^ F^ R R FR R RARF RR : I F R| R| R I A 1 F_ I [_R

~~577 M.-J. JIANG, S. GARTNER~~

~~Table 4. (Continued).~~

~~I Si orangensis pelagicus s.l .~~

c us declivus leptoporus alyculus thus floridanus macintyrei u s amplificus us bizzarus us delicatus us primus na area haera bigelowii •oalitus i acutus ! cristatus i rugosus i telesmus tus altus jonesii 'ithus leptoporus Overall us tricomiculatus 'ithus macintyrei \ Preservation 3 •g Depth "5 | nocyclt urolith urolith urolith tlolithi, discus raster c tolithw tolithw tolithw olithus cargoli Other Overall below urolith 1 % laster c tolithw olithus I I Disco- Cocco- Abun- Seafloor Sample 1 5 5 5 s Calci Calci Coro Cycli

Age Catii Catii Cera, Cych Cych Angi Zonation asters liths dance (m) (interval in cm) Amaurolith 1 A ma I C Q ü 8 Q Q ò 1 Holes 526-526B (Cont.) P M A 16-3, 42-43 C C R mirtHlp P M A 98.4 16.CC C C R 1111UU1C P M A 98.4 17-1, 40-41 c F R NN7 P M A 17-2, 40-41 c C R P M A 17-3, 40-41 c C R Miocene P M A 102.8 17.CC R C F R P M A 102.8 18-1, 50-51 C F F P M A 18-2, 50-51 C R r C R P M A 18-3, 50-51 C C R F P M A 107.2 18.CC A R r A F C P M A 107.2 19-1,40-41 C F F C P M A 19-2, 40-41 C R C F C NN6 P M A 19-3, 40-41 c F R F C P M A 111.6 19.CC c R R C C P M A 111.6 20-1, 78-79 c R C R F C P M A 20-2, 78-79 c F R F C p NN5 M A 20-3, 78-79 c C R F C P M A 116.0 20.CC c C R C A NN4 P M A 116.0 21-1, 70-71 R C C R A P M A 21-2. 70-71 C C R A NN3 P M A 21-3, 70-71 C C R A P M A 120.4 21.CC C C R R A NN2 P M A 120.4 22-1, 85-86 C A R A P M A 22-2, 85-86 C A R A P M A 22-3, 85-86 C F R A P M A 124.8 22.CC C C R A P M A 124.8 23-2, 46-47 F C R A P < M A 23-3, 46-47 F c R A P M A 129.2 23.CC F A R R A P M A 129.2 24-1, 35-36 F C R A P M A 24-2, 35-36 F A R A P M A 24-3, 35-36 R A R R A P M A 133.6 24,CC F A R R A P M A 133.6 25-2, 54-55 R C R A P M A 25-3, 54-55 R C R A P M A 138.0 25, CC R C R R A r early P M A 138.0 26-2, 40-41 R C R A P M A 26-3, 40-41 R F R R A r r NN1 P M A 142.4 26.CC Cf. C R R A P M A 142.4 27-1,48-49 cf. r C R A P M A 27-2, 48-49 cf. C R A P M A 27-3, 48-49 cf. C R A P M A 146.8 27.CC C R A P M A 146.8 28-1,44-45 cf. C R A P M A 28-2, 44-45 cf. C R A P M A 28-3, 44-45 C R A R R P M A 151.2 28.CC cf. C R R A R R P M A 151.2 29-1, 30-31 cf. F R A R R P M A 29-2, 30-31 C R R A R R P M A 29-3, 30-31 R C R A R R P M A 155.6 29,CC C R A R R P M A 155.6 30-1, 36-37 cf. C R R A R R P M A 30-2, 36-37 R C R R A R R P M A 30-3, 36-37 R C R A R R P M A 160.0 30.CC R C R A R R P M A 160.0 31-1, 57-58 R c R A F R Oligo. late NP25 P M A 31-2, 57-58 R c R A F R P M A 31-3, 57-58 R c R A C R p M A 164.4 31.CC R F c R A C Hole 526C

NN15 M M A 33.0 1-1, 100 c R R r M M A 42.5 1,CC A R M M A 42.5 2-1, 42-43 R R R A R M M A 2-2, 42-43 R R R A R F Pliocene early M M A 2-3, 42-43 R R R C R NN12 M M A 2-4, 42-43 R R C F M M A 2-5, 40-42 cf. R R A R C M M A 2-6, 40-42 cf. R R R C R M M A 2-7, 40-42 R R C C M M A 52.0 2,CC R R R Mio. late NN11 M M A 52.0 3-1, 30-31 R R R cC F G G A 56.5 3,CC R R C F Note: For abundance, A = abundant, 10 specimens/field; C = common, 1-10 specimens/field; F = few, 1 specimen/1-10 fields; R = rare, 1 specimen/10 fields; r = very rare, probably due to reworking or contamination (counts at 1000 × magnification). Designations "cf." and "aff." mean that a similar form occurs but no abundance is recorded. For preservation, P = poor; M = moderate; G = good. a R = Reticulofenestra.

~~578 CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY~~

Table 4. (Continued). lIliilHulllliiiLllliillliiiiltlllhtillltlElll! i^i^l^lllll^lli^^l*1!^ I § § biitiff-s^f•|'glifiiiiiilii•§.ε 2 | i Q S il8illi8iilsii88S'8ji•|' i' tl•§ l i i § §i'i>||'3|,|.l•§.•§.SS§JJ§J|g,|,S•εi

F RR RA R RR C R R A R R R F R R A R R R R R R R R A R F R R A R R C R A R R R FR RR RA R R R FR RF RARF R F R R__R A R F It F CR R RARF R R F RF RAR R• R F RR ARC R R FR R RARF R cf. R R F R A F cf. cf. R F R R R A C F I* R A F F F RAR R R F F R R A It R F R C R_R R A C C R C R R AC C C R R RARCR R_C_ R R A II C R R^ R F A C R C R A A R C R R A C R C R R A C R F R A C R C R R A C R C R R A C R C R R A C R C R R R A F R C R R A aff. C R C R F aff. C R F R R R F aff. C R r F R A aff. C R F R R R A aff. C R R R A aff. C F R C C R C R r R C C R r C R R C R r C R R R C R r C R r R C aff. C R F R r F C F F R R C R r F R R cf. C R R F R cf. C R F R R cf. C R C R cf. C R R C R R cf. RRCRR C R C R R C R R R C R F R R F C R C R R F R R C R RRRR CF C R R It C R F F R R R R R C R I? F R RRR RFRF C RRR RCRF C R R R F R R It R C

RR RRR rR RFARRR F R R R R R R_ F R A RRR F R FFR R RARRR R R FFR C FARRF F R RRR F RARF R R RFRF R FARRRC R R FRF R RARRRC R R RRR R RARF RR FRF RR RRARRC RR R F R C R__R R A F It R Cl C R R cf. A F R R R [ R| R R F R R cf. A R C R

~~579 M.-J. JIANG, S. GARTNER~~

us rugosus, and D. quinqueramus. The assemblage re- 50-51 cm in this zone. Also, H. carteri gradually gives corded in this interval includes Amaurolithus delicatus, way to H. granulata within this zonal interval. A. primus, Coccolithus pelagicus, Calcidiscus leptop- The early Pliocene Zone NN14 is recognized only in orus, D. broweri, D. pentaradiatus, D. surculus, D. va- Samples 527-6-1, 40-42 cm, where D. asymmetricus and riabilis, Helicosphaera carteri, Pontosphaera sp., R. Amaurolithus delicatus co-occur. The interval between pseudoumbilica, Rhabdosphaera clavigera, Scapholith- 527-6-2, 40-42 cm and 527-7-2, 60-62 cm is included in usfossilis, Scyphosphaera spp., Sphenolithus abies, and the early Pliocene NN13-NN14 zonal interval, based on Syracosphaera pulchra. Triquetrorhabdulus rugosus has the presence of Ceratolithus acutus and Ceratolithus sp. its highest occurrence in Sample 526C-2-4, 42-43 cm in cf. C. rugosus and on the absence of D. asymmetricus this zonal interval. and A. amplificus. Zones NN13 and NN12 remain un- Samples 526C-2,CC through 526C-3.CC contain D. differentiated, because the lowest occurrence of the quinqueramus and Amaurolithus sp. and belong to the poorly preserved C. rugosus is difficult to determine in upper part of the late Miocene Zone NN11. Rare A. am- this interval. Typical A. tricorniculatus is not found, plificus are recorded only in 526C-3-1, 30-31 cm. but A. bizzarus has its highest occurrence in Sample The calcareous nannofossils in Hole 526C are moder- 527-7-2, 60-62 cm in the lower part of this zonal inter- ately preserved. val. Discoaster quinqueramus is missing in Hole 527. The Hole 527 (28°02.49S, 01°45.80'E; Pliocene/Miocene boundary is tentatively located in water depth: 4428 m) Sample 527-7,CC, where the highest occurrence of A. Site 527 is the deepest site drilled during Leg 74. The amplificus is recognized. The interval between 527-7,CC hole was drilled with conventional rotary coring. Sedi- and 527-12,CC contains A. primus, A. delicatus, and A ments were cored from the top down to the Maestrich- amplificus and belongs to the upper part of Zone NN11. tian of the Upper Cretaceous. A major depositional hia- Small R. pseudoumbilica and A. bizzarus do not extend tus was encountered between Samples 527-13,CC and down to the lower part of this interval. Below Core 11, the top of Core 527-14. The missing section includes the red clay gradually becomes dominant. This corresponds lower part of the middle Miocene through the upper Oli- to a minor assemblage change or, more specifically, to a gocene. The calcareous nannofossils were studied above preservational change. Well-preserved D. calcaris, D. the major hiatus for this hole. The results are document- variabilis, D. pentaradiatus, and D. brouweri become ed on Table 5. Special attention was given to the red clay abundant, and dissolution and fragmentation of other interval just above the hiatus, where the calcareous nan- coccoliths become more significant. Because of dissolu- nofossil assemblages change very abruptly. tion, neither H. granulata nor H. carteri is recorded Samples 527-1-1, 29-31 cm through 527-2-1, 50-51 below Core 11, and Sphenolithus abies is no longer pres- cm are Pleistocene in age. Because the entire interval ent below Core 12. contains common Pseudoemiliania lacunosa and Calci- Core 13 has very good recovery, but the red clay is discus macintyrei with rare Helicosphaera sellii, it is in- mostly barren of calcareous nannofossils. By selective cluded in the lower part of the earliest Pleistocene Zone sampling of light-colored calcareous mottles in the clay, NN19. Gephyrocapsa oceanica and G. caribbeanica are common to abundant nannofossil assemblages were dis- not recorded below 527-1-6, 29-31 cm. Calcidiscus mac- covered. The entire Core 13 was therefore investigated intyrei is rare at other shallower sites but is quite com- with very closely spaced samples. The results reveal that mon at this deeper site. these light-colored calcareous mottles scattered within The upper Pliocene is very thin in Hole 527. The late the red clay are in-place materials. Core 13 contains sev- Pliocene Zone NN18 is recognized only in Sample 527- eral calcareous nannofossil zones. Section 527-13-1, 2,CC, based on the presence of Discoaster brouweri. top, to Section 527-13-1, 10 or 15 cm could belong to the Very rare and poorly preserved D. pentaradiatus in this lower part of Zone NN11. The lowest occurrence of A. sample are interpreted as reworked. Sample 527-3-1, primus is traced down to Section 527-13-1, 5 cm, where- 35-37 cm belongs to the late Pliocene Zone NN17, based as the highest occurrence of D. neohamatus is recorded on the indigenous occurrence of D. pentaradiatus within 527-13-1, 10 cm. Abundant Minylitha convallis occur out D. surculus. Coccolithus pelagicus becomes numeri- throughout this interval and downward. cally significant in the nannofossil assemblage in this The NN10/NN11 boundary is difficult to determine. sample and downward. The interval between Samples The interval between Sections 527-13-1, 15 to 20 cm and 527-3-1, 50-51 cm and 527-3-4, 35-37 cm is included in 527-13-1, 50 cm could belong to the late Miocene Zone the late Pliocene Zone NN16, based on the presence of NN10. The assemblages are characterized by the enrich- D. surculus without Reticulofenestra pseudoumbilica. ment of very well-preserved D. brouweri, D. neohama- Discoaster tamalis has its highest occurrence in this zone tus, D. calcaris, and D. variabilis, with rare D. bellus. in Hole 527. Other important species present are exclusively solution- The interval between Samples 527-3-4, 50-51 cm and resistant forms, such as R. pseudoumbilica (large), Cal- 527-5,CC is assigned to the early Pliocene Zone NN15, cidiscus macintyrei, M. convallis, and Triquetrorhabdu- based on the common to abundant occurrence of R. lus rugosus. pseudoumbilica. Pseudoemiliania lacunosa (typical and The interval between Sections 527-13-1, 63 cm and atypical) occurs throughout this zonal interval, whereas 527-13-5, 44 cm is assigned to the middle Miocene Zone Sphenolithus abies has its highest occurrence in 527-5-3, NN9, based on the total range of D. hamatus. The main

~~580 CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY~~

components of the assemblage are not greatly different rocapsa caribbeanica and G. oceanica are abundant from those of the overlying Zone NN10. Discoaster bel- throughout this interval. lus and the transitional form between D. calcaris and D. The interval between Core 2, top, and Section 528-3-1, exilis become more significant in this zone. Discoaster 117 cm belongs to the NN5-NN4 zonal interval of the neohamatus and D. pentaradiatus were no longer recov- Miocene, based on the total range of Sphenolithus het- ered below Section 527-13-1, 83 cm. Well-preserved Cat- eromorphus. The assemblage includes Coccolithus pe- inaster coalitus and C. calyculus, on the other hand, lagicus, Cyclicargolithusfloridanus, Calcidiscus leptop- first appear below Section 527-13-3, 83 cm. Minylitha orus, Discoaster deflandrei, D. exilis, D. variabilis, S. convallis is still abundant in the upper part of this zone heteromorphus, and S. moriformis. Discoaster exilis but becomes rare and disappears in the lower part. and other Discoaster species are common only above Sections 527-13-5, 66 cm to 527-13-6, 129 cm are in- Sample 528-3-1, 23-24 cm, whereas D. deflandrei be- cluded in the middle Miocene Zone NN8, based on the comes consistently abundant below Section 528-3-1, 117 occurrence of C. coalitus and C. calyculus and on the cm. The NN5/NN4 boundary (i.e., the middle/early absence of D. hamatus. Well-preserved D. exilis and D. Miocene boundary) is therefore located in Section 528- variabilis with rare D. brouweri are the main discoaster 3-1 between 23-24 cm and 117 cm. Within Zone NN5, components in this interval. Typical D. kugleri, how- sediments derived from slumping and reworking were ever, is not recorded. recognized. The reworked species indicate an age rang- Samples 527-13-7, 40-41 cm and 527-13,CC are bar- ing from the early Oligocene to middle Eocene. The as- ren of calcareous nannofossils. These represent the ex- semblage recovered in Sample 528-2,CC is typical of the treme of the red clay development. Next, the interval middle Eocene Zone NP 14. between 527-14-1, 28-29 cm and 527-14-3, 28-29 cm The interval between 528-3,CC and Section 528-4-3, (or lower) contains an assemblage completely different. 110 cm is included in the early Miocene Zone NN3, based Among the species included are Coccolithus pelagicus, on the total range of S. belemnos. Next below, the inter- D. deßandrei, D. tanii, Dictyococcites bisectus, Sphe- val between Sections 528-4-3, 31 cm and 528-4-4, 67 cm nolithus moriformis, H. compacta, and S. predistentus, is the early Miocene Zone NN2, based on the absence of which indicates the early Oligocene Zone NP23. Because typical S. belemnos and the rare presence of Discoaster of reworking or mixing, rare species ranging from Eo- sp. aff. D. druggii. cene to earliest Oligocene were also observed in the up- The long interval between Samples 528-4-5, 25-26 cm per part of this interval. They are R. umbilica, D. sai- and 528-6,CC belongs to the early Miocene Zone NN1, panensis, D. barbadiensis, and Cyclococcolithus formo- based on the absence of Discoaster sp. aff. D. druggii sus. and S. ciperoensis. In this zonal interval Calcidiscus lep- Except for the pure red clay interval, the abundant toporus becomes atypical. It eventually disappears in Neogene and Quaternary coccoliths and the Neogene the lower part of this zone. Also, Reticulofenestrapseu- discoasters recovered in Hole 527 are moderately to doumbilica is not recorded below 528-4,CC. In the poorly preserved. Dissolution and fragmentation of pla- lower part of this zone, Dictyococcites bisectus has its coliths and recrystallization of discoasters increase down- highest occurrence in Sample 528-6-1, 40-41 cm, and hole. Below Core 11, where the red clay lithology be- aff. Dictyococcites dictyodus has its highest occurrence comes more dominant, dissolution and fragmentation in 528-6-2, 40-41 cm. Sphenolithus delphix has a very increase. Species not resistant to dissolution disappear short stratigraphic range and is restricted to the lower from the assemblages. The solution-resistant discoasters part of Zone NN1. Sphenolithus capricornutus was not become enriched and appear well preserved. Core 13 recorded in Hole 528. represents the extreme of this phenomenon, because the The top of the Oligocene is placed in Sample 528-7-1, well-preserved discoasters are so enriched that they dom- 10-12 cm, where the highest occurrence of S. ciperoen- inate entire assemblages. sis is recorded. The first downhole appearance of Chi- asmolithus altus is found in 528-7-2, 30-32 cm, where Hole 528 (28°31.49'S, 02°19.44'E; rare Ericsonia fenestrata are observed. Perhaps because water depth: 3800 m) of the depth of the site, Helicosphaera recta and H. Hole 528 was drilled with conventional rotary coring. perch-nielseniae are not recovered in the upper Oligo- Core 1 sampled the topmost layer of the sediment. Con- cene of Hole 528. tinuous cores were taken from 122.0 meters sub-bottom. The preservation of calcareous nannofossils in Core 1 Quaternary and Neogene calcareous nannofossils were is moderate. In the Miocene and upper Oligocene inter- recovered in the six cores of this hole. A checklist of val, the state of preservation becomes moderate to poor. these Quaternary and Neogene calcareous nannofossils Dissolution and overgrowth are so extensive that small is given in Table 6. coccoliths are totally eliminated, and discoasters and Core 1 is Pleistocene in age. Sample 528-1-1, 20-21 other solution-resistant coccoliths are strongly over- cm belongs to the late Pleistocene Zone NN20, based on grown. the occurrence of Gephyrocapsa caribbeanica and G. oceanica and on the absence of Pseudoemiliania lacu- Hole 528A (28°31.16'S; 02°18.97E; nosa. Then the interval between 528-1-2, 20-21 cm and water depth: 3815 m) 528-1,CC is included in the early Pleistocene Zone Hole 528A was drilled with hydraulic piston coring. NN19, based on the occurrence of P. lacunosa. Gephy- Sediments were continuously cored from 0 to 130.5 me-

~~581 M.-J. JIANG, S. GARTNER~~

~~Table 5. Nannofossil distribution at Hole 527, DSDP Leg 74.~~

3 | dictyodus j us s.l . 'ificus trus ~δ 3 rniculatus igelowi 3 3 nsis cens 1 >ridanus ptoporus tacintyrei tricus 3 •a & 8 -3! 6 | 3 decli trico delic area litus •5 prim 8 Sf a '8 I 1 Overall I 3 S. if 1SS 18 • §1 Preservation ! 1 Depth Core- || | nocyclus cargolith Other Overall below Section urolithus urolithus urolithus tlolithina rudospha taster cal taster cot tolithus a tolithus cristat tolithus n tolithus ti olithus oi edolithus >lithusjoi •3 ! Disco- Cocco- Abun- Seafloor •« 1 (interval mauroiithus 1 mauroiithus I § S g g § 1 g .3 a •a •a a" Crict Age Zonation asters liths dance (m) in cm) × 1 (J Cj δ C

~~582 CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY~~

Table 5. (Continued). J «iii ^ fit xl j ? 8 ill i >li ft till i h« ill U l fill ii»"*iUHn|fJi flltii IK} ft 111 if 1 I I f!Ill|{f111 flllhüülilli lllilII l!llllltllli 1111111!1111 iiifiiiül? IIMU itlllllll !I lllülll CCCF R AFR FR F R A R R R C RAFRR R CRC RAF RR RFF R RARR RR RFC RAF R C C R A F R R R C R A R R_ A I* r C^ R A E I* C R A F C R R r R R R C r F R R F R R C F RCFR C RC R C F R r CR R R A R C C F R C AFR F RCFR CR ARC C RRCF FR RAFA R FCF FR CRARr F FCF RF RCCA R RFF RF RFA R RCCR RF FAr R RRR F FCAR R C R R^ _F R F C A II II c c R j* c A ç FFR F RCAC R CAF F CCC R CCF R CCF R CCR F RCAC R RCCR F CAC R RFCR F CCR R CCR F ACF R RCR R RAFF R R R C F R A_F R R FCF R ARR R RCCR A R R CCC R A R C F C R R A R CCC R A R cf. C F C R A R C F C R A R ACF R A R cf. F F C A R R C C R A R R R C R C A FA C A A C A A C R A A C R AC C R C A C R A A F R cf. R A AC R r_ R_ _R_ jA _ A_ _^C_ __E r F A " "A C R r F A AC R r F A AC R r R A AC R F R A AC R R F R A A A R R cf. R R j\ A A^ It RRR A C A R F R R A C C R FRRRA CC R F R A C C R r F A C C R r R F A C C R r R R cf. cf. A F C R F, C C R r F R R C R C R R R C^ Ji C R F C C ' R C C C r C C C R C C^ C R

~~C R R R R C R R R R F R C RRR C F C R R C R R~~

~~583 Table 6. Nannofossil distribution at Hole 528, DSDP Leg 74.~~

1% 1 I I § E •a J. I. .a 1 « ^ ε g "§ I ü f 1 5 S .1 •s. a | a * c ^ O β «3 Overall 1 II S | fe •§ I a 1111 Preservation | $,§ Depth Core- 3 1 1 I 3 II -§ Other Overall below Section 8 §I .3 i 11 111 * i: : a: as a, è 8 3 o 8 δ 1 I Disco- Cocco- Abun- Seafloor (interval o, 6, s; If Age asters liths dance (m) in cm) II <5 O 5; IJf? ito Ic/y Ion Hfc è Ni (3

Note: For abundance, A = abundant, 10 specimens/field; C common, 1-10 specimens/field; F = few, 1 specimen/1 10 fields; R = rare, 1 specimen/10 fields; r = very rare, probably due to reworking or contamination (counts at 1000 x magnification). Species looked for but not found: Amaurolithus amplificus, A, bizzarus, A. delicatus, A. primus, A. tricorniculatus, Angulolithina area, Braarudosphaera bigelowi, Catinaster calyculus, C. coalitus, Ceratolithus acutus, C. rugosus, C. telesmus, Craspedodiscus declivus, Discoaster asymmetricus, D. bellus, D. brouweri, D. cakaris, D. decorus, D. hamatus, D. intercalcaris, D. neohamatus, D. penta radiatus, D. quinqueramus, D. surculus, D. tamalis, Hayasterperplexus, Helkosphaera granulata, H. obliqua, H. perch-nietseniae, H. recta, H. sellii, Minylitha convallis, R. pseudoumbüica (small), Scyphosphaera spp., Sphenolithus abies, S. capricornulus, Triquetrorhabdulus rugosus. Designation "cf." means that a similar form occurs but no abundance is recorded. For preservation, P = poor; M = moderate; G = good. Shaded area indicates slumping. a R. = Reticulofenestra. CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY ters sub-bottom to recover the interval of coring gap of amplificus. Discoaster variabilis first appears in the low- Hole 528. A major hiatus was observed between Sample er part of Zone NN15 and suddenly becomes important 528A-28,CC and Core 528A-29, top. The entire lower in the assemblage in this zone. Miocene and the lower part of the middle Miocene are The Miocene top is tentatively placed in Sample 528A- missing in this hole, which is not compatible with Hole 14,CC, where the highest occurrence of typical A. am- 528. A checklist of the calcareous nannofossil distribu- plificus is recorded. Because of the depth of the site, D. tion of the entire Hole 528A is given in Table 7. quinqueramus, index species for the late Miocene Zone Sample 528A-1-1, 28-29 cm is assigned to the late NN11, is extremely rare in the upper Miocene of this Pleistocene Zone NN20, based on the common occur- hole. The interval between 528A-14,CC and 528A-23,CC rence of Gephyrocapsa oceanica and G. caribbeanica in belongs to the upper part of the late Miocene Zone NN11 the absence of Pseudoemiliania lacunosa. The presence because of the consistent presence of Amaurolithus sp. of Emiliania huxleyi in this sample is not confirmed. and the absence of D. neohamatus. Discoaster surculus, Samples 528A-1-1, 120-122 cm through 528A-5-3, 19- A. bizzarus, and H. granulata (dissolution effect?) do 20 cm belong to the early Pleistocene Zone NN19, based not extend down to the lower part of this interval, on the presence of P. lacunosa together with G. oceanica whereas Triquetrorhabdulus rugosus first occurs spo- and G. caribbeanica. Calcidiscus macintyrei, a species radically in this interval. Small R. pseudoumbilica are no younger than 1.51 m.y. (Gartner, 1977), is present still common to abundant in this entire interval. They throughout this interval. are, however, no longer recorded below Core 23. The interval between Samples 528A-5-4, 19-20 cm The interval between Sample 528A-24-1, 70-71 cm and 528A-6-3, 19-20 cm is assigned to the late Pliocene and 528A-25,CC is included in the lower part of the late Zone NN18, based on the few to common occurrences Miocene Zone NN11 or Zone NN10, based on the ab- of Discoaster brouweri. Gephyrocapsa oceanica and G. sence of Amaurolithus sp. and D. hamatus. Discoaster caribbeanica are not present in this zone. The rare oc- neohamatus and Minylitha convallis have their highest currence of D. pentaradiatus in this interval is interpret- occurrences in Sample 528A-24-1, 70-71 cm. This entire ed as redeposited because of their poor preservation. interval is characterized by the common presence of M. Helicosphaera granulata becomes common in this zonal convallis, D. variabilis, and D. brouweri with long slen- interval of Hole 528A. The interval between Sections der rays, together with D. neohamatus. Discoaster bel- 528A-6-3, 111 cm and 528A-7-2, 100 cm belongs to the lus has it highest occurrence in 528A-25-3, 59-60 cm in late Pliocene Zone NN16, based on the occurrence of D. this interval. Because of the scarcity of D. quinquera- surculus together with D. pentaradiatus and D. brouweri mus, the NN11/NN10 boundary can not be identified in this interval. Discoaster tamalis and D. asymmetricus with certainty in this hole. have their highest occurrences in the lower part of the The total range of D. hamatus, recorded from Sec- zone. Zone NN17 apparently is not developed in this tion 528A-26-1, 50 cm to Sample 528A-27-2, 38-39 cm, hole. It is unclear whether this represents a minor hiatus, places this interval into the middle Miocene Zone NN9. whether the sampling intervals are not close enough, or Minylitha convallis remains very abundant in the upper whether the marker species were excluded from this area. part of this interval and disappears in the underlying The interval from Sample 528A-7-3,40-41 cm to Sec- Zone NN8. Discoaster pentaradiatus is missing below tion 528A-11-3, top, is assigned to the early Pliocene Sample 528A-26-1, 50 cm. Discoaster neohamatus has Zone NN15 because of the presence of Reticulofenestra its lowest occurrence and Catinaster calyculus has its pseudoumbilica in the absence of Amaurolithus delica- highest occurrence in the same core, in Sample 528A-26- tus. Both large and small R. pseudoumbilica are traced 3, 54-56 cm. Discoaster bellus, on the other hand, has up to Sample 528A-7-3, 40-41 cm, whereas Sphenolith- the same lowest occurrence as D. hamatus in Core 27 in us abies has its highest occurrence in Sample 528A-10, Sample 528A-27-2, 38-39 cm. CC, in the lower part of Zone NN15. Pseudoemiliania Sample 528A-27-2, 150 cm to Sample 528A-27,CC is lacunosa is present throughout this zonal interval. It is, included in the middle Miocene Zone NN8, based on the however, atypically small in the lower part of this zone occurrence of C. calyculus and C. coalitus in the absence and is not recorded in the underlying zone. of D. hamatus. Discoaster variabilis, D. exilis, and rare The interval between Samples 528A-11,CC and 528A- D. brouweri are the main discoaster components in this 13-2, 63-64 cm is included in the early Pliocene Zone interval. Discoaster exilis is not observed above this NN14, based on the co-occurrence of D. asymmetricus zone in this hole. The interval between Sample 528A-28- and A. delicatus. Discoaster tamalis has its lowest oc- 1,58 cm and Sample 528A-28,CC is assigned to the mid- currence in this zone. The single Sample 528A-13-3, dle Miocene Zone NN7, based on the absence of C. caly- 63-64 cm is assigned to the early Pliocene Zone NN13, culus and C. coalitus. Other species components are al- based on the presence of Ceratolithus rugosus in the ab- most identical to the overlying Zone NN8, except for the sence of D. asymmetricus. In the same sample, rare A. first downhole occurrence of D. deflandrei in this inter- tricorniculatus and the highest occurrence of A. biz- val. Typical D. kugleri, the index species for Zone NN7, zarus are recorded. is absent. Some specimens of Coronocyclus nitescens The interval between Section 528A-13-4, base, and and Cyclicargolithus floridanus were found in Sample Sample 528A-14-2, 51-52 cm represents the Pliocene/ 528A-28,CC, which might indicate an age of the middle Miocene Zone NN12 transition, based on the absence of Miocene Zone NN6 or the fact of reworking from inter- the Pliocene Ceratolithus sp. and the typical Miocene A. vals of older age.

~~585 M.-J. JIANG, S. GARTNER~~

~~Table 7. Nannofossil distribution at Hole 528A, DSDP Leg 74.~~

t II111 n 11 ^ 11 u i f 11 i 11 i 11 ^ Overall 3a33j?|tEf|»S5-|J;||^||s|^ Other Overall below Section ^aaaa•lδlδ^llsSSSloos^^.S^^IS Disco- Cocco- Abun- Seafloor (interval Illllglli^^llgδlδδlg•g•RSsjáJ

~~Age Zon. asters liths dance (m) in cm) •^^^xXTβaOOüOOüOUOUOOüU~~

NπsI1, M M A 55.7 13-4, base R R R C R* F F M M A 55.7 14-2,51-52 cf. R R C_R F__ _R r M M A 60.1 14.CC R F R C R C M M A 60.1 15-1, 50-51 RRRRcf. AR R R r M M A 15-2, 50-51 R R R A R R R M M A 15-3, 50-51 RRRR CR R R M M A 64.5 15,CC RRRR AR R R M M A 64.5 16-1,80-81 R R R C R R R M M A 68.9 16.CC R R R C R F R M M A 68.9 17-1, 80-81 R R C R R F M M A 73.3 17.CC F R C R R M M A 73.3 18-1, 20-21 RRFRR CR R R M M A 77.7 18,CC R F R C R R r M M A 77.7 19-2, 20-21 R R R A R F

~~NNn M M A 19-3,20-21 R R R C F R M M A 82.1 19.CC R F R C R F R M M A 86.5 20.CC R R R C R R late M M A 86.5 21-1, 118-119 R R R C F C R Miocene ] | M | M | A | 90.9 | 21,CC | R R F | C R [ C R~~

~~586 CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY~~

~~Table 7. (Continued).~~

~~i i 11 i .ilJll.-i•βic Jliirifiüliiiliitisilllilltiiill I αi !iriiiiil||}|||||||51 liillll iliii il ü ! i 11111 i 111111111!i!!!!!!!!11!111111111111111 H I i I~~

C A F C R F R II R_ AAFC R RRF FR C A R C R R R CCCC RAF FR AAFC F R R FFAC FAF RR R C C R A R R AC FAF F C C F A F R F C C R A F R ACCC CAFR CR ARCC FAF F ARC RAR RR R F R R A F RF RARRR F R C R A F R C r R F A F C R ARFC RAF C L r R F_ _R R A R R R F F R A R C F r R F FAF C C FF FARR C F r FF FAFR C _F r F _F R A F R C F RR RF FARRR C F RRrr FR RAR F F RRR F RAFRR C F R F RAR C _R A R R F _F R_A R R C C RCCF FF RARFR C C CCF FF RACCR F F CFF FF RARFRR C F FFR RR RACR F F CCF R RCAR C F FFF RF RCARR C C RCF RF RCAR F F FCF F RCA R F FFR F RRFA F R FFR F RFAR R R RFF R RFRA R R RRR R FA R R RR F RRRA R F RFF F RCRARR R F RCF C RFARR R F CF C RFRARR R _F R C F R F R F C A R R F F RFCRR F RCARR R F RCRR F RCARF F R FCRR F RCARR R R FFRR F RAARC R _R F F R C RCA R C R _R C C R F R AC C_ R F FRC F ARC R JF R F R C F R A F R F cf. F R C R A R R CrFrC R AR R R FCR R AR R F FFF F ARR R C CCC R AR R F CCC R ARR R F FCC R A R R RFC R A cf. R R R Rcf. FRC R AARR RR R CFF F AAR R F CCF R R A cf. R R F R R C AAR R R F C AAR R cf. AC AAR R cf. C C AAR R cf. F F cf. A cf. F R R R I F| R C | | | cf. A cfj F |

~~587 M.-J. JIANG, S. GARTNER~~

~~Table 7. (Continued).~~

3 .8 3 1 1 ε Overall 3 i Preservation 1 thus acutus thus cristatus thus rugosus thus telesmus tyococcites dictyodus cus macintyrei ter bellus occites bisectus ~>lithus amplificus ilithus primus ilithus tricorniculatus Hthina area losphaera bigelowi ter calyculus ter coalitus thus pelagicus s.l . thus orangensis cyclus nitescens Golithus declivus hus jonesii "golithus ßoridanus Depth Core- ilithus bizzarus "δ o

c: .o o o ca oli to! tol Other Overall below Section 3 3 § tas % "δ c ilit o 3 1 •• •S 25-2, 59-60 c c M M A 25-3, 59-60 c R c R M M A 108.5 25,CC c c R M M A 108.5 26-1, 50 c R F R M M A 26-2, 54-56 c c F NN9 M M A 112.9 26-3, 54-56 c R R c C M M A 112.9 27-1, 38-39 C R R c F M M A 27-2, 38-39 c R R c R M M A 27-2, 150 c R F R c NN8 M M A 27-3, 38-39 c R F R c M P A 117.3 27.CC c F R F M P A 117.3 28-1, 58 c C r NN7 M P A 28-1, 108 c c P P A 121.7 28.CC c R c R C P M A 121.7 29-1, 20

Note: For abundance, A = abundant, 10 specimens/field; C = common, 1-10 specimens/field; F = few, 1 specimen/1 10 fields; R = rare, 1 specimen/10 fields; r = very rare, probably due to reworking or contamination (counts at 1000 × magnification). Designation "cf." means that a similar form occurs but no abundance is recorded. For preservation, P = poor; M = moderate; G = good. The dotted line indicates a zonal boundary of uncertainty. a R = Reticulofenestra.

A sharp assemblage change occurs between Sample crystallization of placoliths increase downhole, whereas 528A-28,CC and Section 528A-29-1, 20 cm. The inter- discoasters in this interval show moderate overgrowth. val between 528A-29-1, 20 cm and 528A-30-1, 147 cm is Below Sample 528A-23,CC, where the color of the typical of the late Oligocene Zone NP25, based on the sediments changes sharply, the state of preservation of consistent presence of S. ciperoensis. Other components nannofossils also deteriorates significantly. Most species in the assemblage are Coccolithus pelagicus, Coronocy- are strongly etched or fragmented. Small specimens are clus nitescens, Cyclicargolithus floridanus, Dictyococci- totally eliminated. By contrast, the discoasters remain tes bisectus, Discoaster deflandrei, S. moriformis, Zyg- unaffected or show a slight increase in number. Preser- rahablithus bijugatus, and rare Chiasmolithus altus. vation improves in Core 28, where large placoliths and Next, a few S. distentus, recorded in Sample 528A-30, discoasters show moderate overgrowth. CC, place this sample in the late Oligocene Zone NP 24. The nannofossils from the upper Oligocene of this Obviously a major hiatus occurs in the interval between hole show moderate to poor preservation. Both discoas- 528A-28,CC and 528A-29-1, 20 cm. The entire early ters and coccoliths show strong overgrowth. Miocene and part of the middle Miocene are missing. This result, however, is not comparable to the same Hole 529 (28°55.83'S, 02°46.08E; depth interval in Hole 528. Another possibility is that water depth: 3035 m) the entire late Oligocene in Cores 29 and 30 is reworked Only one hole was drilled at Site 529. Hole 529 was material because of slumping, which occurs in the drilled with conventional rotary coring. Though this NN6-NN7 zonal interval of the middle Miocene. This hole is located between Sites 525 and 528, the sedimen- problem cannot be resolved, because no further cores tary sequence recovered in the Neogene and Quaternary were taken in this hole. does not show a transition between the two. A hiatus oc- The preservation of calcareous nannofossils recov- curs between Cores 4 and 5, where the lower Pliocene is ered in Hole 528A ranges from moderate to poor. The underlain by the middle Miocene. Three apparent slump Pleistocene to upper Miocene sediment in general yield deposits were observed in the Neogene and Quaternary moderately preserved nannofossils. Dissolution and re- interval: one occurs in the early Pleistocene (NN19), one

~~588 CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY~~

~~Table 7. (Continued).~~

Hi B• -a -s •£? δ g l•S Li 5 5 § o. .j; II 3 .a δ• 8 s as sjfc. ill 3 i —5 αS uβ s«a .2 5 S 3 3 3 S-1 •g JS JB -SJ -SJ .8 § al 8 a 1 III I I i I! ε 5 •s ΛW .H* ΛU ΛU l! 33 a; ft; ft: ft: fi £ S R F cf. A C F F cf. A C R R R cf. A cf. F R C R cf. A cf. R R R cf. A C F cf. R cf. A F F F cf. A F F C cf. A C R R R C R cf. F A A R R A A R R A F R A C R A C R A R C R C R R F R C F R F F R C cf. cf. R R cf. R cf. R cf. F A R C C

in the upper part of the early Miocene, and one in the or whether it is contained in the interval within adjacent basal Miocene. Table 8 represents the Neogene and Qua- samples. ternary calcareous nannofossil distribution of Hole 529. The interval between Samples 529-3-1, 30-31 cm and Section 529-1-1, top, through Sample 529-1-1, 40-41 529-4-6, 40-41 cm is included in the early Pliocene Zone cm contains abundant Emiliania huxleyi, with some NN15, based on the abundance of Reticulofenestrapseu- Gephyrocapsa oceanica, and belongs to the latest Pleis- doumbilica (both large and small forms). Pseudoemilia- tocene Zone NN21. Section 529-1-1, 150 cm contains nia lacunosa is still quite common in this interval. Disco- abundant Gephyrocapsa caribbeanica and G. oceanica, asters recorded in this zone are D. brouweri, D. pentara- without Pseudoemiliania lacunosa and E. huxleyi, and diatus, D. surculus, D. tamalis, D. asymmetricus, D. va- belongs to the late Pleistocene Zone NN20. The top of riabilis, and D. intercalcaris. The next sample, 529-4,CC, the early Pliocene Zone NN19 is located in Sample 529- belongs to the early Pliocene Zone NN14, based on the 1-2, 40-41 cm, where the highest occurrence of P. presence of Amaurolithus delicatus. Sphenolithus abies lacunosa is recorded. Zone NN19 extends down to Sam- has its highest occurrence in this sample, too. At other ple 529-2-6, 40-41 cm. Within Zone NN19, the subinter- sites of DSDP Leg 74 S. abies extends upward to the val between Sections 529-1-2, 73 cm and 529-2-2, 150 lower part of zone NN15, and therefore a minor hiatus cm, however, consists of redeposited sediment. The nan- (or a sampling gap?) is inferred between Samples 529-4-6, nofossil assemblages recovered from this interval are 40-41 cm and 529-4,CC. middle Pliocene (NN14-NN16). Core 5 has very poor recovery. Samples from Section The upper Pliocene is very thin in Hole 529. Zone 1 and the core catcher contain Catinaster calyculus and NN18 is recorded only in Sample 529-2,CC, where the C. coalitus and belong to the middle Miocene Zone highest occurrence of Discoaster brouweri is found. Ge- NN8. Other important species included in the assemblage phyrocapsa oceanica and G. caribbeanica are not found are Coccolithus pelagicus, Craspedolithus declivus (? = in Core 2. The next sample, 529-3-1, 30-31 cm, belongs Cyclococcolithus rotulá), Calcidiscus leptoporus, D. to the late Pliocene Zone NN16, based on the occur- brouweri (the uppermost sample only), D. variabilis, rence of D. surculus with D. pentaradiatus and D. Helicosphaera granulata, R. pseudoumbilica (large form asymmetricus. Zone NN17 is apparently missing. It is only), S. abies, and Triquetrorhabdulus rugosus. Obvi- uncertain whether this zone is cut out by a minor hiatus ously, a major hiatus occurs between Core 4 and the top

~~589 M.-J. JIANG, S. GARTNER~~

~~Table 8. Nannofossil distribution at Hole 529, DSDP Leg 74. CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY~~

~~Table 8. (Continued). M.-J. JIANG, S. GARTNER~~

Table 8. (Continued). leptoporus macintyrei us tricorniculatus us amplificus us delicatus us bizzarus jonesii s telesmus ithus floridanus na area coccites dictyodus 'haera bigelowi calyculus coalitus s rugosus hus altus s pelagicus s.l . ? orangensis 'us nitescens ites bisectus asymmetricus Overall •us primus 'hus declivus Preservation •s: •g •g o Depth Core- 1 "δ I £0 ;ter | tolithus acutus tolithus cristatus tolithu tolithu

~~| idiscus idiscus taster i taster i •olithw vococc Dictyo Other Overall below Section 3 ilolithi <3 11.8 o 1~~

~~Disco - Cocco- Abun- Seafloor (interval I ict. isc | S3 α 5 c <~ 1 I I 1 I o cβ Age Zonation asters liths dance (m) in cm) l 1 1G G <3 G G G G ü Q G O G~~

Note: For abundance, A = abundant, 10 specimens/field; C = common, 1-10 specimens/field; F = few, 1 specimen/1-10 fields; R = rare, 1 specimen/10 fields; r = very rare, probably due to reworking or contamination (counts at 1000 × magnification). Designations "cf." and "aff." mean that a similar form occurs but no abundance is recorded. For preservation, P = poor; M = moderate; G = good. Shaded areas indicate slumping. a R = Reticulofenestra. of Core 5. The sediment representing the interval from The interval between Samples 529-7-1, 65-66 cm and Zone NN9 through most the NN14 is missing. 529-8-3, 66 cm is attributed to the early Miocene Zone Another significant assemblage change occurs in Core NN4, based on the co-occurrence of S. heteromorphus 6. Sections 529-6-1, 38 cm through 529-6-6, 100 cm are with common D. deflandrei. Discoaster exilis and D. assigned to the middle Miocene Zone NN6, based on the variabilis are no longer present in this interval. Within abundant occurrence of Cyclicargolithus floridanus.Al - the NN4 zone, the short interval between Section 529- so, Coronocyclus nitescens, D. deflandrei, and/λ exilis 7-5, 114 cm and Sample 529-8-2, 30-31 cm consists of have their first downhole occurrence in this zonal in- redeposited sediments. The nannofossil assemblage re- terval. Calcidiscus macintyrei, on the other hand, does corded from this subinterval indicates early Miocene not occur below this zone. Zone NN7 is not observed in Zone NN3, based on the occurrence of S. belemnos in Hole 529, probably because of the poor recovery for the absence of S. heteromorphus. (The possibility that Core 5. this inferred redeposited sequence was induced by cor- The highest occurrence of S. heteromorphus is traced ing cannot be precluded, because the site was cored by up to Section 529-6-6, 150 cm. The interval between Sec- rotary drilling rather than hydraulic piston coring.) tion 529-6-6, 150 cm and Sample 529-6,CC is included The interval between Samples 529-8-4, 30-31 cm and in the middle Miocene Zone NN5, based on the occur- 529-8-6, 30-31 cm is assigned to the early Miocene Zone rence of 5. heteromorphus with common D. exilis and NN3, based on the total range of S. belemnos. The in- D. variabilis. Though D. deflandrei is present in this interval between Samples 529-8-7, 30-31 cm and 529-9-5, terval, it is quantitatively insignificant. 30-31 cm is the early Miocene Zone NN2, based on the

~~592 CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY~~

~~Table 8. (Continued).~~

3 1 I : So Q .8 g 1 &a •S : 1 & II •ST ü •SS S > "i S ||| I 3 <* § III fc Vt =s 8 =a s .8 5 I •s I Λ :~ a in ε 'C •§ -ë 1 1 55> o 11iI l 113 fi S. 8. | a I 3 3 3 3 3 il1 I S *! * "S g 11 ll Hill o o o o £ J•a a •a •a a 1 & a] et; « 8 &t t it H sj o aff. aff. aff. aff.

~~aff. aff. aff.~~

~~C R C R C R C R~~

absence of S. belemnos and the presence of Discoaster posited sediments from the latest Oligocene/earliest sp. aff. D. druggii. Sphenolithus sp. aff. S. belemnos Miocene boundary. (? = S. dissimilis), however, still occurs sporadically. Re- The top of the Oligocene is placed in Sample 529-13- ticulofenestra pseudoumbilica, on the other hand, is no 5, 30-31 cm, where the highest occurrence of S. cipero- longer recorded below the upper part of this zonal inter- ensis is recorded. A little downward, the highest occur- val in this hole. rence of Chiasmolithus altus is found in Sample 529-13- The long interval between Samples 529-11-2, 30-31 6, 30-31 cm, whereas the highest occurrence of Ericso- cm and 529-13-4, 30-31 cm is included in the early Mio- nia fenestrata is located in 529-13-7, 30-31 cm. Prob- cene zone NN1, based on the absence of Discoaster sp. ably because of the depth of site, neither Helicosphaera aff. D. druggii and 5. ciperoensis. Calcidiscus leptopor- recta nor H. perch-nielseniae are recovered in the late us is not recorded below the upper part of this interval. Oligocene of Hole 529. In the lower part of this interval, Dictyococcites bisectus The preservation of the calcareous nannofossils re- aff. D. dictyodus and Zygrahablithus bijugatus have covered in Hole 529 is generally moderate. Dissolution their highest occurrences in Sample 529-12-1, 30-31 cm. and recrystallization of placoliths increase downhole. Sphenolithus delphix and S. capricornutus have very Discoasters are moderately preserved in the Pliocene. short ranges and are restricted to the lower part of Zone However, they show overgrowth in the entire Miocene, NN1 in Hole 529. In the upper part of the NN1 zonal in- so that their recognizable diversity is very low within terval, Dictyococcites bisectus, D. dictyodus, and Z. bi- that interval. jugatus, together with rare S. ciperoensis, consistently REMARKS ON SELECTED CALCAREOUS occur between Sample 529-10-2, 30-31 cm and Section NANNOFOSSIL TAXA 529-11-2, 110 cm. Such a nannofossil distribution sug- Most of the calcareous nannofossil species present in this study are gests that this short sub-interval is represented by rede- well documented elsewhere and need no discussion. The state of pre-

593 M.-J. JIANG, S. GARTNER servation of the calcareous nannofossils is only moderate, which dic- Discoaster sp. aff. D. druggii Bramlette and Wilcoxon, 1967 tates a broader species concept during identification. This is especially Discoaster exilis Martini and Bramlette, 1963 true for the early to middle Miocene (NN1-NN9) discoasters. Over- Discoaster hamatus Martini and Bramlette, 1963 growth rather than dissolution has strongly affected the primary Discoaster intercalcaris Bukry, 1971 characters of this group of fossils, which has made precise identifica- Discoaster neohamatus Bukry and Bramlette, 1969 tion at the species level uncertain. Discoaster pentaradiatus Tan, 1927 Amaurolithus amplificus (Bukry) Gartner and Bukry, 1975 Remarks. This taxon may include its earlier form Discoaster pre- Amaurolithus bizzarus (Bukry) Gartner and Bukry, 1975 pentaradiatus Bukry and Percival, 1971 Amaurolithus delicatus Gartner and Bukry, 1975 Discoaster quinqueramus Gartner, 1969 Amaurolithus primus (Bukry and Percival) Gartner and Bukry, 1975 Remarks. Discoaster berggrenii Bukry, 1971, is included with D. Amaurolithus tricorniculatus (Gartner) Gartner and Bukry, 1975 quinqueramus in this study. Angulolithina area Bukry, 1973 Discoaster signus Bukry, 1971 Braarudosphaera bigelowi (Gran and Braarud) Deflandre, 1947 Discoaster surculus Martini and Bramlette, 1963 Catinaster calyculus Martini and Bramlette, 1963 Remarks. This taxon includes Discoaster icarus Stradner, 1972, or Catinaster coalitus Martini and Bramlette, 1963 D. pseudovariabilis Bukry and Worsley, 1971. Typical D. sur- Ceratolithus acutus Gartner and Bukry, 1974 culus is most common in the Pliocene, whereas D. icarus and Ceratolithus cristatus Kamptner, 1954 D. pseudovariabilis are typically present in the upper Miocene Ceratolithus rugosus Bukry and Bramlette, 1968 includes Ceratolithus interval. separatus Bukry, 1979 Discoaster tamalis Kamptner, 1967 Ceratolithus telesmus Norris, 1965 Discoaster variabilis Martini and Bramlette, 1963, s. ampl. Chiasmolithus altus Bukry and Percival, 1971 Remarks. This taxon includes Coccolithus pelagicus (Wallich) Schiller, 1930 s. ampl. Discoaster aulakos Gartner, 1967 Remarks. Coccolithus miopelagicus Bukry, 1971, is included with Discoaster bollii Martini and Bramlette, 1963 C. pelagicus s. ampl. Coccolithus miopelagicus is, however, Discoaster challenged Bramlette and Riedel, 1954 much larger and is restricted to the middle and early Miocene. Discoaster divaricatus Hay, 1967 Coronocyclus nitescens (Kamptner) Bramlette and Wilcoxon, 1967 in- Discoaster kugleri Martini and Bramlette, 1963 cludes Coronocyclus serratus Hay, Mohler and Wade, 1966 Discoaster loeblichii Bukry, 1971 Coccolithusip.) orangensis Bukry, 1971 Discoaster moorei Bukry, 1971 Cricolithus jonesii Cohen, 1965 Discoaster pansus (Bukry and Percival) Bukry, 1973 Craspedolithus declivus (Kamptner) Nishida, 1970 Discolithina ovata Levin and Joerger, 1967 Remarks. Cyclococcolithus rotula Kamptner, 1956, could be in- includes Discolithina segmentata Bukry and Percival, 1971 cluded with the same taxon. Emiliania huxleyi (Lohmann) Hay and Mohler, 1967 Cyclicargolithus floridanus(Rot h and Hay) Bukry, 1971 Gephyrocapsa caribbeanica Boudreaux and Hay, 1967 Calcidiscus leptoporus (Murray and Blackman) Kamptner, 1954 Gephyrocapsa oceanica Kamptner, 1943 Remarks. Coccolithus radiatus Kamptner, 1955 might be included Remarks. This taxon may include Gephyrocapsa lumina Bukry, in this taxon. Typical Calcidiscus leptoporus first occurs in the 1973 and G. omega Bukry, 1973. These two forms are, how- NN2-NN3 zonal interval of DSDP Leg 74. Many circular ever, very rare in the samples studied. forms which look like small C. leptoporus, however, occur in Gephyrocapsa spp. (small) the Oligocene/Miocene boundary interval. Some other forms Remarks. Gephyrocapsa aperta Kamptner, 1963, could be the which are elliptical and occur in the Oligocene/Miocene dominant form of this group. boundary interval could be reworked Striatococcolithus pacifi- Hay aster perplexus (Bramlette and Riedel) Bukry, 1973 canus Bukry, 1971, though superficially they look like C. lep- Helicosphaera carteri (Wallich) Kamptner, 1954 toporus in the light microscope. includes Helicopontosphaera kamptneri Hay and Mohler, 1967 Calcidiscus macintyrei Bukry and Bramlette, 1969 Remarks. This taxon includes Helicosphaera wallichi (Lohmann) Dictyococcites bisectus (Hay, Mohler, and Wade) Bukry and Percival, Okada and Mclntyre, 1977, of the Quaternary. 1971. Helicosphaera granulata (Bukry and Percival) Jafar and Martini, 1975 Remarks. Dictyococcites abisectus (Muller) Bukry and Percival, Remarks. Because of dissolution and recrystallization, Helico- 1971, with a central opening, is considered as a later form of D. sphaera carteri can appear like H. granulata and may be identi- bisectus and is included with that same taxon here, fied as this taxon. This is especially the case in the Miocene in- aff. Dictyococcites dictyodus (Deflandre and Fert) Martini, 1969 is the terval. For this same reason H. intermedia Martini, 1965, and same as Reticulofenestra lockeri Muller, 1970 H. euphratis (Haq) Jafar and Martini, 1975, are included with Discoaster asymmetricus Gartner, 1969 H. granulata. Discoaster bellus Bukry and Percival, 1971 Helicosphaera obliqua Bramlette and Wilcoxon, 1967 Discoaster brouweri Tan, 1927 Helicosphaera perch-nielseniae (Haq) Jafar and Martini, 1975 Remarks. Discoaster triradiatus Tan, 1927, D. blackstockae Bukry, Helicosphaera recta (Haq) Jafar and Martini, 1975 1973, D. neorectus Bukry, 1971, D. brouweri rutellus Gartner, Helicosphaera recta (Haq) Jafar and Martini, 1975 1967, andZ>. braarudii Bukry, 1973, are included with D. brou- Helicosphaera sellii (Bukry and Bramlette) Jafar and Martini, 1975 weri because, owing to poor preservation or to general scarcity, Minylitha convallis Bukry, 1973 these similar species cannot be consistently identified or used Pontosphaera japonica (Takayama) Nishida, 1971 for biostratigraphy. Pontosphaera spp. Discoaster calcaris Gartner, 1967 Pseudoemiliania lacunosa (Kamptner) Gartner, 1969 Discoaster decorus Bukry, 1971 Reticulofenestra pseudoumbilica (Gartner) Gartner, 1969 Discoaster deflandrei Bramlette and Riedel, 1954, s. ampl. Rhabdosphera calvigera Murray and Blackman, 1898 Remarks. Because of heavy overgrowth of the discoasters in the includes Rhabdosphaera stylifera Lomann, 1902 middle and lower Miocene, identification of a number of spe- Scapholithus fossilis Deflandre, 1954 cies is impractical. Forms common in the lower Miocene (and Scyphosphaera spp. less common in middle Miocene) which may be included in Remarks. Various forms of Scyphosphaera were found during this Discoaster deflandrei s. ampl. are study. They are especially common in the lower Pliocene and Discoaster adamanteus Bramlette and Wilcoxon, 1967 the uppermost Miocene intervals of Site 525. Species of this Discoaster calculosus Bukry, 1971 genus are not resistant to dissolution; therefore they are very Discoaster druggii Bramlette and Wilcoxon, 1967 rare or even missing in the same interval of other sites (deeper Discoaster nephados Hay, 1967 sites). Detailed taxonomic work of this genus is not attempted Discoaster soundersii Hay, 1967 in this study. Members of this group are documented as Scy- Discoaster trinidadensis Hay, 1967 phosphaera spp.

~~594 CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY~~

Sphenolithus abiβs Deflandre, 1954 Discoaster barbadiensis Tan, 1927 Remarks. Sphenolithus neoabies Bukry and Bramlette, 1969, is in- Discoaster lodoensis Bramlette and Riedel, 1954 cluded with S. abies. Discoaster sublodoensis Bramlette and Sullivan, 1961 Sphenolithus belemnos Bramlette and Wilcoxon, 1967 Discoaster tanii Bramlette and Riedel, 1954 Remarks. Species documented as aff. Sphenolithus belemnos in Ericsonia sp. cf. E. fenestrata (Deflandre and Fert) Stradner, 1968 the tables could be S. dissimilis Bukry and Percival, 1971. Neococcolithes dubius (Deflandre and Fert) Black, 1967 Sphenolithus capricornutus Bukry and Percival, 1971 Reticulofenestra umbilica (Levin) Martini and Ritzkowski, 1968 Sphenolithus ciperoensis Bramlette and Wilcoxon, 1967 Sphenolithus distentus (Martini) Bramlette and Wilcoxon, 1967 Sphenolithus heteromorphus Deflandre, 1953 Sphenolithus predistentus Bramlette and Wilcoxon, 1967 Sphenolithus moriformis (Brönnimann and Stradner) Bramlette and Sphenolithus radians Deflandre, 1952 Wilcoxon, 1967 Wiseorhabdus inversus (Bukry and Bramlette, 1969) Bukry, 1981 Remarks. Sphenolithus conicus Bukry, 1971, is included in the same taxon. Differentiation between S. abies and S. morifor- ACKNOWLEDGMENTS mis is in fact very difficult in the middle Miocene interval. We thank Drs. D. Bukry and B. U. Haq for reviewing this manu- Sphenolithus distentus (Martini) Bramlette and Wilcoxon, 1967 script and for offering many helpful comments. Sphenolithus delphix Bukry, 1973 Syracosphaera pulchra Lehmann, 1902 REFERENCES Thoracosphaera spp. Bukry, D., 1972. Coccolith stratigraphy—Leg 14, Deep Sea Drilling Remarks. Species of this genus occur sporadically throughout the Project. In Hayes, D. E., Pimm, A. C, et al., Init. Repts. DSDP, Neogene and Quaternary. They are more common in younger 14: Washington (U.S. Govt. Printing Office), 487-494. sediments. Detailed taxonomic study of this group is not attempted in this study. , 1973. Low-latitude coccolith biostratigraphic zonation. In Triquetrorhabdulus carinatus Martini, 1965 Edgar, N. T., Saunders, J. B., et al., Init. Repts. DSDP, 15: Washington (U.S. Govt. Printing Office), 685-703. Triquetrorhabdulus milowii Bukry, 1971 _, 1975. Coccolith and silicoflagellate stratigraphy, north- Remarks. This species seems to occur in the lower Miocene of the studied area. Strong overgrowth, however, makes identifica- western Pacific Ocean, Deep Sea Drilling Project Leg 32. In Lar- tion of this species difficult. son, R. L., Moberly, R., et al., Init. Repts. DSDP, 32: Washington Triquetrorhabdulus rugosus Bramlette and Wilcoxon, 1967 (U.S. Govt. Printing Office), 677-701. Umbilicosphaera mirabilis Lohmann, 1902 Gartner, S., 1977. Calcareous nannofossil biostratigraphy and revised Zygrahablithus bijugatus (Deflandre) Deflandre, 1959 zonation of the Pleistocene. Mar. Micropaleont., 2:1-25. Martini, E., 1971. Standard Tertiary and Quaternary calcareous nan- Various reworked species were found also in some intervals. They nofossil zonation. In Farinacci, A. (Ed.), Proc. II Plankt. Conf. are Roma 1970 (Vol. 2): Rome (Edizione Tecnoscienza), 739-785. Chiasmolithus grandis (Bramlette and Riedel) Radomski, 1968 Okada, H., and Bukry, D., 1980. Supplementary modification and Chiphragmalithus sp. introduction of code number to the low-latitude coccolith bio- Cydococcolithus formosus Kamptner, 1963 stratigraphic zonation (Bukry, 1973, 1975). Mar. Micropaleont. Cydococcolithus gammation (Bramlette and Sullivan) Sullivan, 1964 5:321-325.

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