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14. NEOGENE AND QUATERNARY CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHYOF THE WALVIS RIDGE1

Ming-Jung Jiang, Robertson Research (U.S.) Inc., Houston, Texasand

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 WalvisRidge. The sediments recovered range in age from late Campanian or early Maestrichtian to Holocene. This chapterdeals only with the Neogene to Holocene interval. The calcareous nannofossils over this interval have been corroded aswell as overgrown, but a precise biostratigraphy is possible at all sites because most of the key index species are present.

INTRODUCTIONDuring DSDP Leg 74, 11 holes were drilled at 5 sites

(525-529) on Walvis Ridge in the South Atlantic nearSouth Africa (Fig. 1). Sediments ranging in age fromlate Campanian or early Maestrichtian to Holocenewere recovered. This chapter deals with the calcareousnannofossils found in the Neogene to Holocene sedi-ment from these five sites. The calcareous nannofossilsfrom the Paleogene and the Upper Cretaceous are docu-mented by Hélène Manivit in this same volume.

Calcareous nannofossils from the Neogene throughHolocene recovered during DSDP Leg 74 are abundantat all sites, except for the middle Miocene red clay inter-val cored at Site 527—the deepest site. Their state ofpreservation, however, is ranked as "moderate" in gen-eral. Dissolution and recrystallization have progressedto such an extent that only solution-resistant or robustforms can be recognized for most of the middle andlower Miocene sections. Fortunately, most of the zonalmarkers are present and can be identified with certainty.The main purpose of this chapter is, therefore, to docu-ment the biostratigraphic distribution of the calcareousnannofossils rather than to do a complete taxonomicstudy.

Smear slides of the original unprocessed sampleswere examined with a light microscope for this study. Inorder to obtain a precise position of the zonal bounda-ries, one sample was taken for each section (150 cm) of acore and investigated for its calcareous nannofossil con-tent. For some critical intervals, more closely spacedsamples were analyzed. Therefore the stratigraphic firstand last appearance of the selected species was deter-mined with an accuracy of 150 cm or less for this report.Checklists of a selected set of species were prepared foreach site.

Moore, T. C , Jr., Rabinowitz, P. D., et al., Init. Repts. DSDP, 74: Washington (U.S.Govt. Printing Office).

CALCAREOUS NANNOFOSSIL ZONATION

Martini's standard Tertiary and Quaternary zonation(1971), which is widely used elsewhere, was the startingbasis for the zonation described here. Because of thescarcity or apparent lack of some of Martini's index fos-sils, possibly owing to environmental exclusion of theparent organism or to poor preservation, other specieswere selected to determine zones. Deviations from Mar-tinis zonation, necessary for the studied area, are dis-cussed in the following. The age and zone assignmentsof the Neogene through Holocene cores based on thismodified zonation are then given in Table 1.

Triquetrorhabdulus carinatus Zone (NN1)

Definition. Interval from the last occurrence of Helicosphaera rec-ta to the first occurrence of Discoaster druggii above it.

Remarks. Because of environmental exclusion, Helicosphaera rec-ta together with H. perch-nielseniae is present only at Site 526, theshallowest site. The last occurrence of Sphenolithus ciperoensis is ten-tatively used to define the base of Zone NN1, i.e., the Oligocene/Miocene boundary, in this study. Other important and solution-resis-tant species, which become extinct slightly above the last occurrenceof Sphenolithus ciperoensis, are Dictyococcites bisectus (Dictyococci-tes abisectus included), aff. D. dictyodus, S. capricornutus, S. del-phix, and Zygrhablithus bijugatus. S. capricornutus and S. delphixhave very short ranges. Both forms first occur above the last occur-rence of S. ciperoensis and become extinct at about the same level asDictyococcites bisectus, aff. D. dictyodus, and Z. bijugatus.

Because of the strong overgrowth of discoasters within this inter-val, typical specimens of Discoaster druggii cannot be identified withcertainty. The first occurrence of an unusual form of discoaster is atthe top of Zone NN1. This species is consistently much larger andmore robust than the common D. deflandrei specimens in this inter-val. It has straight and slightly tapered rays and is documented as Dis-coaster sp. aff. D. druggii in this study.

Discoaster druggii Zone (NN2)

Definition. Interval from the first occurrence of Discoaster drug-gii to the last occurrence of Triquetrorhabdulus carinatus.

Remarks. The first occurrence of Discoaster sp. aff. D. druggii isused to mark the base of Zone NN2, whereas the first occurrence ofSphenolithus belemnos marks the top of this zone in this study. Thiszone is therefore equivalent to Zone CN1C of Okada and Bukry(1980).

561

M.-J. JIANG, S. GARTNER

W

Angola Basin

20° S

25<

30c

- 2

- 3

35C

i 1 1 1 1 r20

Time (hr.) Ship Course Track

Figure 1. Site locations on the Walvis Ridge in the South Atlantic Ocean for DSDP Leg 74.

315°

The last occurrence of T. cαrinαtus is uncertain, because in somecases it is difficult to distinguish T. cαrinαtus from an elongate calcitelath in an assemblage with moderate or poor preservation and recrys-tallization. Reticulofenestrα pseudoumbilicα sample and Cαlcidiscusleptoporus have their first occurrence in this zone.

Sphenolithus belemnos Zone (NN3)

Definition. Interval from the last occurrence of Triquetrorhαb-dulus cαrinαtus to the last occurrence of Sphenolithus belemnos.

Remarks. The total range of S. belemnos marks Zone NN3 in thisstudy. Sphenolithus sp. aff. S. belemnos documented in the tablescould be small specimens of S. dissimilis.

Helicosphαerα αmpliαpertα Zone (NN4)

Definition. Interval from the last occurrence of Sphenolithus be-lemnos to the last occurrence of Helicosphαerα αmpliαpertα.

Remarks. S. heteromorphus first occurs immediately above the ex-tinction of S. belemnos. Neither gap nor overlap of the ranges of thetwo species is observed at the studied sites. The first occurrence of S.heteromorphus may be a good marker for the boundary of ZonesNN3 and NN4 (Bukry, 1972, 1973).

The index fossil, H. αmpliαpertα, is absent, probably because ofecological exclusion. The first common occurrence of Discoαster vαri-αbilis s. ampl. is tentatively used to mark the top of Zone NN4, i.e.,the top of the lower Miocene. (The lower Miocene/middle Mioceneboundary is for the sake of convenience somewhat arbitrarily placedat the top of the H. αmpliαpertα Zone, recognizing, however, that the

boundary has been identified variously as older, equal to, and youngerthan this datum.)

Sphenolithus heteromorphus Zone (NN5)

Definition. Interval from the last occurrence of Helicosphαerα αm-pliαpertα to the last occurrence of Sphenolithus heteromorphus.

Remarks. At the boundary of Zones NN4/NN5, i.e., the lower/middle Miocene boundary, assemblages of discoaster change signifi-cantly. Discoαster deflαndrei, which is a dominant species in the lowerMiocene, is replaced abruptly by (overgrown) D. vαriαbilis, althoughthe former persists upward. The first common occurrence of D. vαri-αbilis s. ampl. is therefore used to make the base of Zone NN5 becausethis datum is easy to recognize (see Bukry, 1973).

The top of this zone is also easy to recognize in the studied sites.

Discoαster exilis Zone (NN6)

Definition. Interval from the last occurrence of Sphenolithusheteromorphus to the first occurrence of Discoαster kugleri.

Remarks. Because of strong overgrowth of discoasters, typical D.kugleri cannot be identified with certainty. The top of Zone NN6 istherefore placed at the last occurrence of Cyclicαrgolithus floridαnus,a species which is common within and below this zone (see, e.g.,Bukry, 1975).

Coronocyclus nitescens seems to become extinct within this zone,whereas Triquetrorhαbdulus rugosus has its first occurrence in thiszone.

562

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

Age

Pleistocene

Pliocene

Miocene

late

early

late

early

late

middle

early

Oligocene

Calcareous NannofossilZonation (Martini, 1971)

NN21

NN20

NN19

NN18

NN17

NN16

NN15

NN14

NN13

NN12

NN11

NN10

NN9

NN8

NN7

NN6

NN5

NN4

NN3

NN2

NN1

NP25

Emiliania huxleyi

Gephyrocapsa oceanica

Pseudoemiliania lacunosa

Discoaster brouweri

Discoaster pentaradiatus

Discoaster surculus

Reticulofenestrapseudoumbilica

Discoaster asymmetricus

Ceratolithus rugosus

Amaurolithus tricorniculatus

Discoaster quinqueramus

Discoaster calcaris

Discoaster hamatus

Catinaster coalitus

Discoaster kugleri

Discoaster exilis

Sphenolithus heteromorphus

Helicosphaera amptiaperta

Sphenolithus belemnos

Discoaster druggii

Triquetrorhabdulus carinatus

Sphenolithus ciperoensis

525

1,CC

525A

l.CC

3-1, 29-30

4-1, 148-149

5-1, 60-616,CC

7-1, 84-858-2, 40-41

8-3, 40-419,CC

10-6, 40-4111-1,40-41

11-2,40-4111-4,40-41

11-5,40-4113-4, 40-41

13-5, 40-4117-2, 40-41

17,CC

525B

1-1, 30-321-1, 80-82

1-2, 30-32

1-2, 80-823-1, 76-78

3-2, 53-544-1, 75-77

4-2, 65-66

4-3, 65-665-1, 81-83

5-2, 81-838-2, 86-87

8-3, 3-4

12-1. 10-11

12-1, 54-5514-2, 40-41

14-2, 100-10124.CC

25-1, 36-3728,CC

29-1, 76-7732-2, 113-114

32-3, 41-4233.CC

34-1, 65-6636.CC

37-1,40-4141,CC

42-1, 35-3646-1, 60-61

46-2, 60-6148-1, 60-61

48-1, 100-10249-3, 20-21

49-4, 20-2149,CC

526

1-1, 101-1022-1, 106-107

2,CC

526A

1-1, 75-76

1-2, 75-76

1-3, 75-762-2, 80-81

2-3, 80-815-1, 85-86

5-2, 85-869,CC

10-1, 103-10412-3, 25-26

12.CC14,CC

15-1, 26-2715.CC

16-1, 42-4318-3, 50-51

18.CC20-2, 78-79

20-3, 78-7920,CC

21-1, 70-71

21-2, 70-7121, CC

22-1, 85-86

22-2, 85-8630.CC

31-1, 57-5831.CC

526B

1-1, 30-323-1,35-36

3-2, 35-363,CC

4-2, 20-215,CC

526C

1-1, 100l.CC

2-1,42-432-7, 40-42

2.CC3.CC

527

1-1, 29-312-1, 50-51

2,CC

3-1, 35-37

3-1, 50-513-4, 35-37

3-4, 50-515,CC

6-1,40-42

6-2, 40-42

7-2, 60-62

7,CC13-1, 10

13-1, 1513-1, 50

13-1,6313-5, 44

13-5, 6613-6, 129

528

1-1, 20-21

1-2, 20-211,CC

2-1,0-13-1,23-24

3-1, 117

3,CC4-3, 110

4-3, 1314-4,67

4-5, 25-266,CC

7-1, 10-127.CC

528A

1-1, 28-29

1-1, 120-1225-3, 19-20

5-4, 19-206-3, 19-20

6-3, 1117-2, 100

7-3, 40-4111-3, top

11,CC13-2, 63-64

13-3, 63-64

13-4, base14-2, 51-52

14.CC24.CC

25-1, 59-6025,CC

26-1, 5027-2, 38-39

27-2, 15027.CC

28-1, 5828.CC

29-1, 2030-1, 147

529

1-1, top1-1, 40-41

1-1, 150

1-2, 40-412-6, 40-41

2,CC

3-1, 30-31

3-2, 30-314-6, 40-41

4,CC

5-1, top5.CC

6-1, 386-6, 100

6-6, 1506,CC

7-1, 65-668-3, 66

8-4, 30-318-6, 30-31

8-7, 30-319-5, 30-31

9-6, 30-3113-4, 30-31

13-5, 30-3113.CC


Discoaster kugleri Zone (NN7)

Definition. Interval from the first occurrence of Discoaster kuglerito the first occurrence of Catinaster coalitus.

Remarks. According to the definition, the top of this zone is at thefirst occurrence of C. coalitus. However, in an assemblage with mod-erate recrystallization, C. coalitus is difficult to identify, whereas C.calyculus is still recognizable. In this case, the first occurrence of C.calyculus is used to mark the top of Zone NN7.

Discoaster deßandrei was not recorded above this zone.

Catinaster coalitus Zone (NN8)Definition. Interval from the first occurrence of Catinaster coali-

tus or C. calyculus to the first occurrence of Discoaster hamatus.

Discoaster hamatus Zone (NN9)Definition. Interval from the first occurrence to the last occurrence

of Discoaster hamatus.Remarks. D. hamatus in these southeast Atlantic sites is rare and

much smaller than in other regions. In some cases D. bellus withslightly rotated tips (all in the same direction) resembles small D. ha-matus. These two species are probably closely related to each other.Both forms have the same first occurrence at the base of Zone NN9;however, D. bellus extends upward to the lower part of Zone NN10.

D. pentaradiatus and D. neohamatus have their first occurrence inthe upper part of this zone. Rare to common Minylitha convallis alsooccur in the upper part of this zone.

Discoaster calcaris Zone (NN10)Definition. Interval from the last occurrence of Discoaster hama-

tus to the first occurrence of D. quinqueramus.Remarks. The composition of discoasters of the assemblage has a

second major change at the base of this zone, that is, at the base of theupper Miocene. The common (overgrown) D. variabilis s. ampl. isreduced in numbers, whereas delicate species such as D. brouweri (in-cluding large D. neorectus), D. calcaris, and D. neohamatus common-ly occur in this zone in our cores.

Zone NN10 is also characterized by the abundant occurrence ofMinylitha convallis. M. convallis looks like a calcite particle. How-ever, when it occurs abundantly, it is easy to recognize the presence ofthis species in the assemblages.

Discoaster quinqueramus Zone (NN11)Definition. Interval from the first to the last occurrence of Disco-

aster quinqueramus.Remarks. Most of the Discoaster quinqueramus (group) specimens

identified in this study are of the D. berggrenii type with short rays.This latter species is very rare at shallow sites. It is absent at deep sites,which makes it difficult to differentiate this zone from the superjacentand subjacent zones.

The lower part of Zone NN11 is characterized by the presences ofD. neohamatus and Minylitha convallis, whereas the upper part ischaracterized by the presences of Amaurolithus spp. The ranges of D.neohamatus and A. primus show little overlap. However, these twospecies do co-occur in a few samples.

At deeper sites where D. quinqueramus is missing, the last occur-rence of A. amplificus is tentatively introduced to mark the top ofZone NN11. This is based on the fact that A. amplificus is restricted tothe D. quinqueramus Zone at the shallow sites.

Amaurolithus tricorniculatus Zone (NN12)Definition. Interval from the last occurrence of Discoaster quin-

queramus to the first occurrence of Ceratolithus rugosus.Remarks. C. acutus has its first, and Triquetrorhabdulus rugosus

has its last, occurrence in this zone.Typical D. surculus becomes quite common within and above this

zone at our sites.

Ceratolithus rugosus Zone (NN13)Definition. Interval from the first occurrence of Ceratolithus rugo-

sus to the first occurrence of Discoaster asymmetricus.

Remarks. The boundary between this zone and the next higherzone is sometimes difficult to recognize because a few specimens re-sembling Discoaster asymmetricus may be found lower. Typically,however, D. asymmetricus is common only in its nominate zone andabove.

Some five-rayed discoasters found in the NN10 and NN11 zonalinterval are very similar to D. asymmetricus of the Pliocene; some,however, have vestigial bifurcation of rays like D. calcaris and arehere included with D. calcaris.

Discoaster asymmetricus Zone (NN14)Definition. Interval from the first occurrence of Discoaster asym-

metricus to the last occurrence of Amaurolithus tricorniculatus.Remarks. A. delicatus instead of A. tricorniculatus is used to de-

fine the top of this zone because the latter species is very rare at thestudied sites.

Reticulofenestra pseudoumbilica Zone (NN15)Definition. Interval from the last occurrence pf Amaurolithus

tricorniculatus to the last occurrence of Reticulofenestra pseudoum-bilica s. ampl.

Remarks. This zone is easily recognized in the studied sites. In theupper part, small specimens of R. pseudoumbilica are typical. Thelarge R. pseudoumbilica becomes extinct somewhat earlier than thesmaller one. Sphenolithus abies (S. neoabies included) has its last oc-currence in the upper part of Zone NN15, whereas Pseudoemilianialacunosa has its first occurrence in the uppermost part of this zone.

Discoaster surculus Zone (NN16)Definition. Interval from the last occurrence of Reticulofenestra

pseudoumbilica to the last ocurrence of Discoaster surculus.Remarks. D. tamalis and D. asymmetricus have their last occur-

rences within this zonal interval.

Discoaster pentaradiatus Zone (NN17)Definition. Interval from the last occurrence of Discoaster sur-

culus to the last occurrence of D. pentaradiatus.Remarks. This zone is very thin. It was not recognized at several of

the sites studied.

Discoaster brouweri Zone (NN18)

Definition. Interval from the last occurrence of Discoaster penta-radiatus to the last occurrence of D. brouweri.

Pseudoemiliania lacunosa Zone (NN19)Definition. Interval from the last occurrence of Discoaster brou-

weri to the last occurrence of Pseudoemiliania lacunosa.Remarks. Ceratolithus rugosus, Calcidiscus macintyrei, and Hel-

icosphaera sellii have their last occurrences, whereas Gephyrocapsacaribbeanica and G. oceanica have their first occurrences in the lowerpart of this zone. Coccolithus pelagicus is greatly reduced in numberat the base of this zone.

Calcidiscus macintyrei is much more common at the deeper sitesthan at the shallower sites.

Gephyrocapsa oceanica Zone (NN20)Definition. Interval from the last occurrence of Pseudoemiliania

lacunosa to the first occurrence of Emiliania huxleyi.

Emiliania huxleyi Zone (NN21)Definition. Interval with Emiliania huxleyi.Remarks. The boundary between Zones NN20 and NN21 is diffi-

cult to determine because E. huxleyi is too small to be identified withthe light microscope with certainty. The recognition of the upper partof this zone is, however, much easier because the nominal species isextremely abundant there.

SUMMARY OF SITES

The Neogene and Quaternary calcareous nannofossilassemblages recovered during DSDP Leg 74 are discussed

564

CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY

in detail as follows: each hole is considered separately,and the basis for biostratigraphic age assignments isdocumented. Range charts are presented for all holes.

Hole 525 (29°04.24'S, 02°59.12'E;water depth: 2467 m)

Only one surface core, from 0-3.6 meters, was recov-ered at Hole 525. The core catcher sample from 3.6 me-ters sub-bottom contains abundant Pseudoemiliania la-cunosa with common Helicosphaera carteri and Calci-discus leptoporus. Other few to rare species are smallGephyrocapsa spp., Rhabdosphaera clavigera, Syraco-sphaera pulchra, Craspedolithus declivus, Scapholithusfossilis, and Ceratolithus rugosus. Gephyrocapsa ocean-ica may be present; however, no specimens with a com-plete bridge were found. This assemblage indicates theearly Pleistocene P. lacunosa Zone (NN19). No checklistwas prepared for this hole because of duplication of thecored interval at Hole 525A.

Hole 525A (29°04.24'S, 02°59.12'E;water depth: 2467 m)

Hole 525A was drilled with conventional rotary cor-ing. Sediments were not continuously cored above 165.1meters sub-bottom. Table 2 represents the nannofossildistribution in this hole. The nannofossil biostratig-raphy is here given for the NN3 through NP25 zonal in-terval. Nannofossil distribution younger than the NN3zone for Hole 525A may be compared with that for thenearby Hole 525B given in Table 3.

Quaternary sediments were recognized only in Core1. The core-catcher sample contains essentially the sameassemblage as that found in Sample 525-l,CC of Hole525 and is assigned to Zone NN19 of the early Pleisto-cene. The only difference is that most of the Gephyro-capsa species found in this core catcher sample have acomplete bridge.

Core 2 has no recovery.Cores 3 and 4 are early Pliocene in age (Zones NN13-

NN12), based on the presence of Reticulofenestra pseu-doumbilica, Sphenolithus abies, Amaurolithus delica-tus, A. primus, A. tricorniculatus, Ceratolithus rugosus,and C. acutus and the absence of A. amplificus andDiscoaster quinqueramus. Cores 5 and 6 are assigned toZone NN11 of the late Miocene, on the basis of the veryrare occurrence of D. quinqueramus. It is worth men-tioning that Core 5 contains Amaurolithus species with-out D. neohamatus, whereas Sample 525A-6,CC con-tains D. neohamatus without Amaurolithus species.

Core 7 through Sample 525A-8-2, 40-41 cm belongsto the middle Miocene Zone NN6, based on the abundantoccurrence of Cyclicargolithus floridanus with some D.deflandrei s. ampl. and Coronocyclus nitescens and onthe absence of Sphenolithus heteromorphus. Sample525A-8-2, 40-41 cm through Sample 525A-9,CC are as-signed to the middle Miocene Zone NN5, based on thecommon presence of S. heteromorphus with some D.variabilis s. ampl. and rare D. exilis.

Core 10 through Sample 525A-11-1, 40-41 cm be-longs to the early Miocene Zone NN4, based on thepresence of S. heteromorphus with common D. deflan-

drei and without D. variabilis and D. exilis. The twovery rare occurrences of S. belemnos in the lower part ofthis interval are interpreted as due to reworking or mix-ing during coring. Samples 525A-11-2, 40-41 cm through525A-11-4, 40-41 cm are typical of the early MioceneZone NN3 because of the common occurrence of S. be-lemnos. Samples 525A-11-5, 40-41 cm through 525A-13-4, 40-41 cm are assigned to the early Miocene ZoneNN2, based on the presence of Discoaster sp. aff. D.druggii and the absence of S. belemnos. Sphenolithussp. aff. S. belemnos, however, might be present in thisinterval.

Samples 525A-13-5, 40-41 cm through 525A-17-2,40-41 cm belong to the early Miocene Zone NN1. In thiszonal interval, several biological events occur: Zygrhab-lithus bijugatus becomes extinct in Sample 525A-16,CC;Dictyococcites bisectus, in Sample 525A-16-1, 40-41cm; and D. dictyodus, in 525A-15-6, 40-41 cm. Spheno-lithus capricornutus and S. delphix have very shortranges in the lower part of this zone. Only a single speci-men of Helicosphaera recta was found in Sample 525 A-15-7, 40-41 cm. It is uncertain whether it is in place or isa redeposited specimen.

Sphenolithus ciperoensis last occurs in 525A-17,CC,and this point is taken to mark the top of the Oligocene.

The preservation of calcareous nannofossils in Hole525A in general is moderate. Dissolution and recrystalli-zation increase downhole. Discoasters in Cores 3 through6 are moderate in preservation; however, they are poorfrom Core 7 downward. Overgrowth has destroyed manyspecies characters of discoasters, which makes speciesidentification difficult or impossible.

Hole 525B (29°04.24S, 02°59.12'E;water depth: 2467 m)

Hole 525B was drilled with hydraulic piston coring.Sediments were continuously cored from 0 to 209.4 me-ters sub-bottom to compensate for the coring gap inHole 525A. Table 3 represents the Neogene and Quater-nary nannofossil distribution in this hole.

The youngest calcareous nannofossil zone, NN21, ofthe late Pleistocene was recognized in Samples 525B-1-1, 20-32 cm and 525B-1-1, 80-82 cm, based on theabundant occurrence of Emiliania huxleyi together withGephyrocapsa oceanica. The next zone, NN20, of thelate Pleistocene was encountered in Sample 525B-1-2,30-32 cm. Then \he first downhole occurrence of Pseu-doemiliania lacunosa in 525B-1-2, 80-82 cm places thissample at the top of early Pleistocene Zone NN19.

Samples 525B-1,CC and 525B-2-1, 60-61 cm aredominated by small Gephyrocapsa with rare G. oce-anica and G. caribbeanica. According to Gartner (1977),this assemblage belongs to the small Gephyrocapsaacme interval which is in the middle part of the ZoneNN19. The highest occurrence of Helicosphaera sellii isin Sample 525B-2-2, 60-61 cm. Next to it, the highestoccurrence of Calcidiscus macintyrei is in 525B-2-3,60-61 cm, and the lowest occurrence of typical G. oce-anica and G. caribbeanica is in 525B-2,CC. The earlyPleistocene calcareous nannofossil assemblages in Hole525B are essentially the same as those in Holes 525 and

565

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

Age

OverallPreservation

Disco-asters

OtherCocco-

liths

OverallAbun-dance

Depthbelow

Seafloor(m)

Core-Section

(interval in cm)

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525A. Very rare Discoaster brouweri found in this inter-val are interpreted as reworked.

Typical, well-preserved D. brouweri with slender longarms is first encountered in Sample 525B-3-2, 53-54 cm,which places this sample at the top of Zone NN18 of thelate Pliocene. Next, common D. pentaradiatus, the in-dex species for Zone NN17 of the late Pliocene, is re-corded in 525B-4-2, 65-66 cm. Zone NN17 represents avery short time interval, because D. surculus, the indexspecies of Zone NN16 of the late Pliocene, is in Sample525B-4-3, 65-66 cm. Discoaster asymmetricus and D.tamalis have their highest occurrences in Zone NN16 ofHole 525B. Also, typical H. carteri gradually gives waydownward to a robust form, H. granulata, in this inter-val.

Typical Reticulofenestra pseudoumbilica (small andlarge forms) abundantly occurs for the first time inSample 525B-5-2, 81-83 cm, which places this sample inthe top of Zone NN15 of the early Pliocene. WithinZone NN15, the highest occurrence of Sphenolithusabies is found in 525B-7-2, 39-40 cm, whereas the low-est occurrence of Pseudoemiliania lacunosa is traceddown to Sample 525B-7-3, 39-40 cm. Helicosphaerasellii is no longer found below this zone in Hole 525B,but D. variabilis is continuously recorded in the lowerpart of this zone and downward.

Amaurolithus delicatus first appears in Sample 525B-8-3, 3-4 cm, which places this sample at the top of ZoneNN14 of the early Pliocene. Amaurolithus delicatus andA. primus are the most common species of the Amauro-lithus group in this interval and down to the upper Mio-cene. Typical specimens of A. tricorniculatus are veryrate. The birefringent Ceratolithus rugosus is traceddown to 525B-12-1, 10-11 cm, which places this sampleat the base of Zone NN13 of the early Pliocene. TheNN13/NN14 boundary cannot be defined with certaintyin Hole 525B, because the NN14 index species, D. asym-metricus, consistently occurs downward. Discoaster de-corus is found sporadically within the NN13/NN14 zon-al interval and down to Zone NN11 of the late Miocene.

The interval between Samples 525B-12-1, 54-55 cmand 525B-14-2, 40-41 cm is assigned to Zone NN12 ofthe earliest Pliocene, based on the absence of both C.rugosus and D. quinqueramus. The highest occurrenceof Triquetrorhabdulus rugosus is recorded in 525B-13-3, 40-41 cm, and A. bizzarus is found only in 525B-13-1,40-41 cm.

The highest occurrence of D. quinqueramus is tracedup to Sample 525B-14-2, 100-101 cm, which places thissample at the top of Zone NN11 (i.e., the top of the up-per Miocene). Aside from the index species, the calcare-ous nannofossil assemblages in the early Pliocene andthe late Miocene are essentially the same. Discoasterbrouweri, D. surculus, D. pentaradiatus, D. decorus, D.variabilis, and D. intercalcaris are quite common inthese intervals. Although D. quinqueramus is very rarein the upper Miocene of Hole 525B, its occurrence issufficiently consistent to outline its total range zone.Zone NN11 can further be divided into two parts. Theupper part is characterized by the presence of A. delica-tus and A. primus which is traced down to Sample

525B-23-2, 37-38 cm. The lower part is represented bythe presence of D. neohamatus, which is traced up tothe same sample. Amaurolithus amplificus has a veryshort range and is restricted to the upper part of ZoneNN11. In the lower part of Zone NN11 and downward,slender yet giant D. brouweri (D. neorectus type), to-gether with large D. neohamatus and D. variabilis, areprominent.

The interval between Samples 525B-25-1, 36-37 cmand 525B-28,CC belongs to Zone NN10 of the late Mio-cene, based on the absence of both D. quinqueramusand D. hamatus. Discoaster variabilis, large D. neoha-matus, and large, slender D. brouweri are still the majordiscoaster components in this zone. Minylitha convallis,which rarely occurs in the lower part of Zone NN11, be-comes very abundant throughout the NN10 zonal inter-val. This species, according to Bukry (1973), commonlyoccurs in the middle-late Miocene transitional interval.A form of discoaster with five asymmetrical arms oc-curs sporadically throughout this interval and its overly-ing NN11 Zone. This form looks much like D. asym-metricus of the Pliocene. However, some specimenswith better preservation show vestigial bifurcations.This form may be related to the five-rayed D. calcarisand should not be included in D. asymmetricus, withwhich it does not have a continuous range.

The interval between Samples 525B-29-1, 76-77 cmand 525B-32-2, 113-114 cm is included in Zone NN9 ofthe middle Miocene, based on the total range of D. ha-matus. Minylitha convallis is still very abundant in theupper part of this zone. It quickly becomes rare down-wards, however, and disappears in the lower part of thiszone. Within the NN9 zonal interval, several biologicalevents occur. The small R. pseudoumbilica are no long-er observed within this zone; D. pentaradiatus is not re-corded below Sample 525B-29-2, 76-77 cm; Catinastercalyculus first appears in 525B-3O-1, 44-45 cm and C.coalitus in 525B-32-2, 113-114 cm. Besides D. hamatus,the major discoaster components in this zone are D.variabilis, D. brouweri, D. neohamatus, D. bellus, andD. calcaris. Some D. signus with long bifurcation of rayare also included in the discoaster assemblage. Disco-aster calcaris, or transitional forms of D. calcaris andD. exilis, do not occur below Zone NN9, but D. neoha-matus is traced down to Sample 525B-31,CC. Discoas-ter bellus, a form related to and associated with D.hamatus, has the same first occurrence as D. hamatus in525B-32-2, 113-114 cm. Its highest occurrence, how-ever, is traced up to Sample 525B-28,CC, the base ofZone NN10.

Samples 525B-32-3, 41-42 cm through 525B-33,CCbelong to Zone NN8 of the middle Miocene, based onthe presence of Catinaster species in the absence of D.hamatus. The absence of Catinaster species and of Cy-clicargolithus floridanus places the interval betweenSamples 525B-34-1, 65-66 cm and 525B-36,CC in ZoneNN7 of the middle Miocene. Below 525B-31,CC thepreservation of discoasters suddenly becomes poor, mostspecimens being overgrown. In the NN7-NN8 zonal in-terval and downward, D. variabilis s. ampl. is the onlydominant discoaster species. Moderately preserved D.

567


Table 3. Nannofossil distribution at Hole 525, DSDP Leg 74.

Table 3. (Continued).


569



570


571



Age

middleMiocene

earlyMiocene

Zonation

NN7

NN6

NN5

NN4

NN3

NN2

OverallPreservation

Disco-asters

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Depthbelow

Seafloor(m)

152.2

156.6156.6

161.0161.0

165.4165.4

169.8174.2174.2

178.6178.6

183.0187.4187.4

191.8191.8

196.2196.2

200.6200.6

205.0205.0

209.4

Core-Section(interval in cm)

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525B-46-1, 60-61 cm, D. variabilis is one of the domi-nant discoaster species, whereas below 525B-46-2, 60-61cm it suddenly disappears. Discoaster deßandrei is thenthe only dominant discoaster in the assemblage. Rarespecimens of a shallow-water or brackish-water formBraarudosphaera higelowii are also recorded around themiddle-early Miocene transition interval.

The interval between Samples 525B-48-1, 100-102 cmand 525B-49-3, 20-21 cm is assigned to Zone NN3 of theearly Miocene, based on the total range of S. belemnos.The interval between 525B-49-4, 20-21 cm and 525B-49,CC is Zone NN2 of the early Miocene in age, basedon the absence of S. belemnos and the rare presence of

Discoaster sp. aff. D. druggii. Discoaster sp. aff. D.druggii, however, ranges up to the lower part of theNN3 Zone.

The preservation of the Neogene and Quaternary cal-careous nannofossils at Hole 525B is moderate in gener-al. Dissolution and recrystallization of placoliths in-crease downhole. The state of preservation of disco-asters, however, fluctuates. Most discoasters recoveredabove Core 30 are moderately preserved. The best-pre-served discoasters are found in the upper middle andlower upper Miocene interval. However, below Core 31they are so poorly preserved that their diversity becomesvery low in the lower middle and lower Miocene.

573



Site 526 was the shallowest site drilled during Leg 74.Hole 526 was drilled with hydraulic piston coring. Onlytwo cores were recovered in this hole, however. Samples526-1-1, 100-102 cm through 526-2-1, 106-107 cm be-long to NN20 Zone of the late Pleistocene. The assem-blage includes common Gephyrocapsa oceanica, smallGephyrocapsa sp., Calcidiscus leptoporus, Helicosphae-ra carted, Syracosphaera pulchra, and Rhabdosphaeraclavigera and rare Coccolithus pelagicus, Cricolithusjonesii, Scapholithus fossilis, Umbilicosphaera mirabi-lis, Pontosphaera japonica, and other Pontosphaera sp.Redeposited coccoliths from the Pliocene, Miocene, andOligocene were also recorded. These are Chiasmolithusaltus, Cyclicargolithus floridanus, Coronocyclus nites-cens, Dictyococcites bisectus, Discoaster deflandrei,Pseudoemiliania lacunosa, Reticulofenestra pseudoum-bilica, and Sphenolithus abies. Core 2 has poor recov-ery. The core catcher sample from 6.3 meters sub-bot-tom contains indigenous P. lacunosa and is assigned tothe NN19 Zone of the early Pleistocene.

The calcareous nannofossil preservation in Hole 526is moderate to good. A check list of the nannofossil dis-tribution of this hole is given in Table 4.

Hole 526A (30°07.36'S, 03°08.28'E;water depth: 1054 m)

Hole 526A was drilled with hydraulic piston coring.Sediments were continuously cored from 28.0 meterssüb-bottom down to 228.8 meters (late Eocene). Thecore recovery in this hole is very good. No significant hi-atuses were recognized through the Neogene. However,the sedimentation rate seems not to be consistent duringthe Neogene, because some of the calcareous nannofos-sil zones in this hole are represented by rather short in-tervals. A check list of the Neogene calcareous nanno-fossil distribution of Hole 526A is given in Table 4.

Three calcareous nannofossil zones are recognized inCore 1. Sample 526A-1-1, 75-76 cm contains abundantReticulofenestra pseudoumbilica (both small and largeforms), without Amaurolithus species, and is assignedto the NN15 Zone of the early Pliocene. This samplealso contains Sphenolithus abies, yet without Pseudo-emiliania lacunosa. It is reasonable to place this samplein the lower part of Zone NN15. Sample 526A-1-2, 75-76 cm belongs to Zone NN14 of the early Pliocene,based on the occurrence of both A. delicatus and Dis-coaster asymmetricus. Amaurolithus delicatus has itshighest, and D. asymmetricus has its lowest, occurrencein this core sample. Samples 526A-1-3, 75-76 cm through526A-2-2, 80-81 cm contain Ceratolithus rugosus with-out D. asymmetricus and therefore belong to the earlyPliocene Zone NN13.

The interval between 562A-2-3, 80-81 cm and 526A-5-1, 85-86 cm is included in the earliest Pliocene ZoneNN12 based on the absence of C. rugosus and D. quin-queramus. Typical A. tricorniculatus is extremely rarein the early Pliocene of Hole 526A; it is found only inSample 526A-2,CC. Triquetrorhabdulus rugosus has its

highest occurrence in Sample 526A-4-3, 15-16 cm in thiszone.

Again, the Pliocene/Miocene boundary is not easilyrecognized in Hole 526A, because D. quinqueramus, theindex species for the late Miocene Zone NN11, is veryrare. After a long search it was found that D. quinque-ramus consistently occurs between Samples 526A-5-2,85-86 cm and 526A-9,CC. This interval is therefore as-signed to Zone NN11. As in Hole 525B, typical A.amplificus is restricted to the upper part of this zone.The occurrence of A. delicatus and A. primus, on theother hand, is traced down to Sample 526A-7,CC, wherethe highest occurrence of D. neohamatus is recorded.Typical Helicosphaera granulata gradually become moreimportant than H. carteri in the late Miocene of Hole526A. In fact, the two species are very difficult to dif-ferentiate during the late Miocene and early Pliocene.They could be the same taxon in different states ofpreservation. Also, in the lower part of this zone, Miny-litha convallis occurs abundantly below Sample 526A-8,CC.

The interval between 526A-10-1, 103-104 cm and526A-12-3, 25-26 cm is attributed to the late MioceneZone NN10, based on the absence of D. quinqueramusand D. hamatus. This interval is also characterized byabundant M. convallis, common D. neohamatus, andcommon D. brouweri with long slender rays (D. rectustype). The highest occurrence of D. bellus is traced up toSample 526A-11-3, 30-31 cm in this zone. As in Hole525B, the same form of discoaster with five asymmetri-cal arms occurs sporadically within the late MioceneNN10-NN11 zonal interval of this hole.

The interval between 526A-12,CC and 526A-14,CCbelongs to the middle Miocene Zone NN9, based on thetotal range of D. hamatus. Several biological events oc-cur within this zonal interval, and the pattern of succes-sion of these events is comparable to that recorded inHole 525A. Minylitha convallis is still very abundant inthe upper part of this zone, quickly becomes rare down-ward, and disappears in Sample 526A-14-2, 20-21 cm;the small R. pseudoumbilica are no longer observedwithin this zonal interval; the lowest occurrence of D.pentaradiatus is traced down to 526A-12,CC; D. neoha-matus extends a little farther down but disappears abovethe first occurrence of D. hamatus; rare D. signus areobserved within this zone, and Catinaster calyculus hasits highest occurrence in Sample 526A-13,CC. However,D. bellus, a form related to and associated with D.hamatus, extends down to Zone NN8 in this hole.

Sample 526A-15-1, 26-27 cm through 526A-15,CC isincluded in Zone NN8 of the middle Miocene, based onthe presence of C. calyculus and the absence of D. ha-matus. Catinaster coalitus, the designated index speciesfor Zone NN8, is very rare in this hole. Next below theabsence of both C. calyculus and Cyclicargolithus flori-danus places the interval between Samples 526A-16-1,42-43 cm and 526A-18-3, 50-51 cm, into Zone NN7 ofthe middle Miocene. As in Hole 525B, the preservationof discoasters becomes poor in the upper part of themiddle Miocene. Discoaster brouweri s. ampl. is nolonger found below the NN8 zonal interval. The over-

574


grown D. variabilis becomes the only dominant discoas-ter species in the lower part of the middle Miocene. Thefirst downhole occurrence of D. deflandrei is recordedin the lower part of Zone NN7. Discoaster kugleri, thetrue index for Zone NN7, is not found in Hole 526A,however.

The top of the middle Miocene Zone NN6 is tentative-ly placed in Sample 526A-18,CC, where the first down-hole occurrence of C. floridanus is recorded. Calcidis-cus macintyrei is no longer recorded below this zone.Also in the NN6 zonal interval, Coronocyclus nites-cens has its highest occurrence in 526A-19-3, 40-41 cm,whereas Triquetrorhabdulus rugosus has its lowest oc-currence in 526A-18,CC.

Though no significant hiatus is found in the earlymiddle, and early Miocene of Hole 526A, the sedimentinterval represented by Zone NN5 through Zone NN2 isvery thin in this hole. The total range of S. heteromor-phus places the interval between Samples 526A-20-3,78-79 cm and 526A-21-1, 70-71 cm, into Zones NN5and NN4. Next, the total range of S. belemnos limits theinterval between Samples 526A-21-2, 70-71 cm and526A-21,CC to Zone NN3 of the early Miocene. In526A-22-1, 85-86 cm, S. belemnos is absent. The lowestoccurrence of Discoaster sp. aff. D. druggii assigns thissample to Zone NN2 of the early Miocene.

Helicosphaera ampliaperta is absent and the NN5/NN4 boundary (i.e., the middle/early Miocene bound-ary) is recognized in this hole by a sudden discoaster as-semblage change recorded between Samples 526A-20,CCand 526A-21-1, 70-71 cm. In 526A-20,CC and above,D. variabilis is the only dominant discoaster species,whereas in 526A-21-1, 70-71 cm and below, no D. vari-abilis is observed. Discoaster deflandrei becomes the on-ly dominant discoaster species. Helicosphaera obliquaoccurs sporadically between 526A-20,CC and 526A-21-2, 70-71 cm.

The long interval between Samples 526A-22-2, 85-86cm and 526A-30,CC is assigned to Zone NN1 of the ear-liest Miocene, based on the absence of Discoaster sp.aff. D. druggii and S. ciperoensis. Sphenolithus sp. aff.S. belemnos (= S. dissimilisl) appears sporadically with-in this zonal interval. In the upper part of this zone,R. pseudoumbilica and Calcidiscus leptoporus are stillquite common. However, both forms become atypicaldownward and disappear in the lower part of this zone.In the lower part of this zone, Zygrahablithus bijugatushas its highest occurrence in Sample 526A-28-2, 44-45cm. Dictyococcites bisectus and D. aff. D. dictyodus,on the other hand, are not found above 526A-28-3,44-45 cm. Also S. delphix and S. carpricornutus havevery short ranges and are restricted to the lower part ofZone NN1 in this hole.

The top of the Oligocene is placed in Sample 526A-31-1, 57-58 cm, where the highest occurrences of H. rec-ta and S. ciperoensis are recorded. In the late Oligoceneof this hole, several new species are encountered. Theseare Chiasmolithus altus, Ericsonia fenestrata, and H.perch-nielseniae. Helicosphaera recta and H. perch-niel-seniae are hemipelagic species. They are very rarelyfound at other sites of DSDP Leg 74. However, because

Hole 526A is the shallowest (1054 m), both forms spo-radically occur in the upper Oligocene of this hole. AlsoBraarudosphaera bigelowii, a hemipelagic form, occursfairly consistently in the late Oligocene and the earliestMiocene of this hole.

The preservation of the Neogene calcareous nanno-fossils recovered in Hole 526A is much the same as thatin Hole 525B. Assemblages in general are moderatelypreserved. Dissolution and recrystallization of placo-liths increase downhole. Discoasters are moderately pre-served in the Pliocene and the uppermost Miocene. How-ever, from the middle Miocene on they become sostrongly overgrown that species identification is some-times difficult.

Hole 526B (30°07.36'S, 03°08.28'E;water depth: 1054 m)

Hole 526B was drilled with hydraulic piston coring.Sediments were continuously cored from 6.3 down to28.3 meters sub-bottom. The main purpose of this holewas to recover the coring gap between Holes 526 and526A. The calcareous nannofossil distribution of thishole is given in Table 4.

Samples 526B-1-1, 30-32 cm through 526B-3-1, 35-36 cm belong to the early Pleistocene Zone NN19, basedon the consistent presence of Pseudoemiliania lacunosa.Gephyrocapsa oceanica and G. caribbeanica are abun-dant in this interval, except in the lowest part, in 526B-3-1, 35-36 cm. Samples 526B-3-2, 35-36 cm through526B-3,CC contain Discoaster brouweri and are assignedto the late Pliocene Zone NN18. No G. oceanica, G. ca-ribbeanica, D. pentaradiatus, or D. surculus were ob-served in this short interval. Sample 526B-4-2, 20-21 cmthrough 526B-5,CC are included in the early PlioceneZone NN15, based on the common and persistent occur-rence of Reticulofenestra pseudoumbilica. Because ofthe common presence of P. lacunosa without Spheno-lithus abies, this interval is no older than the upper partof Zone NN15. Zones NN17 and NN16 are apparentlymissing. It is uncertain whether they are absent becauseof a minor hiatus or because of too large a sampling in-terval.

The calcareous nannofossils in Hole 526B are moder-ately preserved.

Hole 526C (30°07.36'S, 03°08.28'E;water depth: 1054 m)

Hole 526C was drilled with conventional rotary cor-ing. A short sediment interval was tentatively cored todetermine the Pliocene-Miocene transition at Site 526.The calcareous nannofossil distribution for this hole isgiven on Table 4.

Samples 526C-1-1, 100 cm through 526C-1,CC belongto the upper part of the early Pliocene Zone NN15, basedon the presence of Reticulofenestra pseudoumbilica andPseudoemiliania lacunosa, without Sphenolithus abiesand Amaurolithus sp. The sediments recovered in Core1 probably are not in place because Core 1 has a poor re-covery. Samples 526C-2-1, 42-43 cm through 526C-2-7,40-42 cm have an early Pliocene Zone NN12 age, basedon the absence of Discoaster asymmetricus, Ceratolith-

575

a l l -: I I I1 I 1 | I „ I I 1 3 „ a I I I a 11 1 I 111

Overall 3 S 3 3 3 g ^ t l | | ^ ^ | | 3 | | ? l i

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Disco- Cocco- Abun- Seafloor Sample l l i l l l l l - i l ' | § § § ^ l § o o l I I , I , KAge Zonation asters liths dance (m) (interval in cm) X X t X ^ ^ i ü l J ü l j ö l S l j δ ü ü ü ü i j I J ü ü ü

Holes 526-526BM 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 rM A 1.9 2-1, 106-107 c R RM A 6.3 2.CC c R

Pleistocene M A 6 3 526B-1-1, 30-32 c RPleistocene e a r ] y N m 9 M A 1 0 . 7 l.CC c R

M A 15.1 2.CC c R RM 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 rM M A 4-2, 110-112 c R p rM M A 23.9 4,CC c R p

N . 5 M M A 23.9 5-1,20-21 c R FM M A 5-2,20-21 c C rM M A 5-3, 20-21 c R RM M A 28.3 5.CC C R R RM 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 RM M A 1-3,75-76 R R C R R

N N 1 3 M M A 32.4 l.CC R R C R RPüocene 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 Ry 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 RM M A 36.8 3-1, 65-66 F R C R RM M A 3-2, 65-66 F R C F RM 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 FM M A 41.2 4-1, 15-16 R C R F RM M A 4-2, 15-16 R R C F RM M A 4-3, 15-16 R R C C RM M A 45.6 4.CC R R C C RM M A 45.6 5-1,85-86 R R C R RM M A 5-2,85-86 ~R R ^ C F RM M A 5-3, 85-86 R R C FM M A 50.0 5 i C C _ _ R R R C C RM M A 50.0 6-1,80-81 R F R C C RM M A 6-2, 80-81 R C FM M A 6-3, 120-122 R R C F RM M A 54.4 6.CC R R C F RM M A 54.4 7-1, 7-8 R R C C RM M A 7-2,7-8 R R C C R

NN11 M M A 7-3,7-8 R C CM M A 58.8 7.CC R C A RM M A 58.8 8-1,46-47 C A RM M A 8-2, 46-47 C AM M A 8-3, 46-47 C A R

late M M A 63.2 8,CC A A R AM M A 63.2 9-1, 6-7 C A RM M A 9-2, 6-7 A A RM M A 9-3, 6-7 A C RM M A 67.6 9,CC A A _ __RM M A 67.6 10-1, 103-104 C FM M A 10-2, 103-104 C C RM M A 10-3, 13-14 A A RM M A 72.0 10.CC A C RM M A 72.0 11-1, 30-31 C C RM M A 11-2,30-31 C C RM M A 11-3,30-31 C C R

NN10 M M A 76.4 11,CC C F RM M A 76.4 12-1, 25-26 C R F RP M A 12-2, 25-26 C F FP M A 12-3,25-26 ç p RP M A 80.8 12.CC A C RP M A 80.8 13-2, 30-31 C C RP M A 13-3, 30-31 C C R

N N 9 P M A 85.2 13.CC C R R C RP M A 85.2 14-1, 20-21 C R CP M A 14-2, 20-21 A R C FP M A 14-3, 20-21 C R C RP M A 89.6 14.CC ç R ç _ _ RP M A 89.6 15-1, 26-27 C R F R

N N 8 P M A 15-2,30-32 R C R C RP M A 15-3,26-27 C R R F RP 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 Ĉ F̂ R

576



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A A C F r R R FRA A C R R R r R R r FA A C R R F r R R r F RF A R R R C r R R FRA C A R R R R F

_r r R R R A r R R RR r F R A r R R FR C F__A R _ R CR R R F R A R R F

R R R R R F R R A F F R R FR R R R R R F A C A R FF R F F R R R A C A R R FF R F F R R R A C A R R R FR R R R R F R F C A R RR R R R R F F F C A R R RR R R F R C R R A R R R R RR R F C F R A A R R F R R

R C C F R A A R R FR C C R R R A A R F F RR R R R R R C A R R F R

F R F R C A R R R R RR C C R F R A A R R R RR C C R C R A A R F R FR C F R F R A A R R R RR F F R F R A A R R R FF F F R F R A A R R R R FR C cf. R C F R A A R R R C FR F R F F R A A R R F RR R R R F R A A R F F R

aff. R R R F F R A A R F C Raff. R F c f . R F R I R A A R R F R

R R cf, R R cf. R cf. R A A R R R RF R ~R F cT R R A A R RRF R R F cf. R R A A R R R

aff. R R R R R F R aff. A F R R FRR F R F R R aff. A C R CR R R R F R R R aff. A A RR R R R F R R R aff. A A R R FR R R R F R R R aff. A A R R F RR R R R R F R R R aff. A A R R C RR R F R R F R R R C A R F RR R F R F R R A A F RR R R R C R F R A A R F RRF R R R F R F R A A R F RC F R R F F R A A R F RR

aff. C F R R C F R A A R F Raff. C R R R C R C A F RR

F R R R C R R F F A C F RF R R R R C R R F A R C C R R F RR

a f f . R R F R c f . R C R F F A R A A R C RRaff. C R R R cf. R C R R_ _F jK C C C R

F F R F R F C R C A F RRF R R F R R F A R A F R

a f f . C F R C F C A R R A R F RC F R F R F A R C A R R

a f f . C R R F R A A A R RR R R F R R A A R R R

RF RR CR RF A A R RRR F R R R C R R A A cf. R R

aff. R R R F R R R A R A A cf. R R RR R R R R F R R A A C R F RR

aff. R R R R R F R F A A R R RF R R R F~~R ~R T £ F TlRR R R F RR F A R RRR R R R R F R F A R F RF R R R F R C A C RR R R R R R F A C R

R F R R F R R A F RRR R FR RR A F RR R R R C R R_ _F A R _ F RR R F R R A F K "R R F R R F R A C RRR F R R R A F R

I* F R R̂ Â F̂ R RF R R R A R F RR

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577



Age

Holes 526-526B(Cont.)

Miocene

Oligo.

Hole 526C

Pliocene

Mio.

mirtHlp1111UU1C

early

late

early

late

Zonation

NN7

NN6

NN5

NN4

NN3

NN2

NN1

NP25

NN15

NN12

NN11

OverallPreservation

Disco-asters

PPPPPPPPPPPPPPPPpPPPPPPPPPPP <PPPPPPPPPPPPPPPPPPPPPPPPPPPPPPp

MMMMMMMMMMMG

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MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM

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Depthbelow

Seafloor(m)

98.498.4

102.8102.8

107.2107.2

111.6111.6

116.0116.0

120.4120.4

124.8124.8

129.2129.2

133.6133.6

138.0138.0

142.4142.4

146.8146.8

151.2151.2

155.6155.6

160.0160.0

164.4

33.042.542.5

52.052.056.5

Sample(interval in cm)

16-3, 42-4316.CC17-1, 40-4117-2, 40-4117-3, 40-4117.CC18-1, 50-5118-2, 50-5118-3, 50-5118.CC19-1,40-4119-2, 40-4119-3, 40-4119.CC20-1, 78-7920-2, 78-7920-3, 78-7920.CC21-1, 70-7121-2. 70-7121-3, 70-7121.CC22-1, 85-8622-2, 85-8622-3, 85-8622.CC23-2, 46-4723-3, 46-4723.CC24-1, 35-3624-2, 35-3624-3, 35-3624,CC25-2, 54-5525-3, 54-5525, CC26-2, 40-4126-3, 40-4126.CC27-1,48-4927-2, 48-4927-3, 48-4927.CC28-1,44-4528-2, 44-4528-3, 44-4528.CC29-1, 30-3129-2, 30-3129-3, 30-3129,CC30-1, 36-3730-2, 36-3730-3, 36-3730.CC31-1, 57-5831-2, 57-5831-3, 57-5831.CC

1-1, 1001,CC2-1, 42-432-2, 42-432-3, 42-432-4, 42-432-5, 40-422-6, 40-422-7, 40-422,CC3-1, 30-313,CC

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a R = Reticulofenestra.

578



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F I* R A FF F R A R R RF F R R A It R F R

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579


us rugosus, and D. quinqueramus. The assemblage re-corded in this interval includes Amaurolithus delicatus,A. primus, Coccolithus pelagicus, Calcidiscus leptop-orus, D. broweri, D. pentaradiatus, D. surculus, D. va-riabilis, Helicosphaera carteri, Pontosphaera sp., R.pseudoumbilica, Rhabdosphaera clavigera, Scapholith-usfossilis, Scyphosphaera spp., Sphenolithus abies, andSyracosphaera pulchra. Triquetrorhabdulus rugosus hasits highest occurrence in Sample 526C-2-4, 42-43 cm inthis zonal interval.

Samples 526C-2,CC through 526C-3.CC contain D.quinqueramus and Amaurolithus sp. and belong to theupper part of the late Miocene Zone NN11. Rare A. am-plificus are recorded only in 526C-3-1, 30-31 cm.

The calcareous nannofossils in Hole 526C are moder-ately preserved.

Hole 527 (28°02.49S, 01°45.80'E;water depth: 4428 m)

Site 527 is the deepest site drilled during Leg 74. Thehole was drilled with conventional rotary coring. Sedi-ments were cored from the top down to the Maestrich-tian of the Upper Cretaceous. A major depositional hia-tus was encountered between Samples 527-13,CC andthe top of Core 527-14. The missing section includes thelower part of the middle Miocene through the upper Oli-gocene. The calcareous nannofossils were studied abovethe major hiatus for this hole. The results are document-ed on Table 5. Special attention was given to the red clayinterval just above the hiatus, where the calcareous nan-nofossil assemblages change very abruptly.

Samples 527-1-1, 29-31 cm through 527-2-1, 50-51cm are Pleistocene in age. Because the entire intervalcontains common Pseudoemiliania lacunosa and Calci-discus macintyrei with rare Helicosphaera sellii, it is in-cluded in the lower part of the earliest Pleistocene ZoneNN19. Gephyrocapsa oceanica and G. caribbeanica arenot recorded below 527-1-6, 29-31 cm. Calcidiscus mac-intyrei is rare at other shallower sites but is quite com-mon at this deeper site.

The upper Pliocene is very thin in Hole 527. The latePliocene Zone NN18 is recognized only in Sample 527-2,CC, based on the presence of Discoaster brouweri.Very rare and poorly preserved D. pentaradiatus in thissample are interpreted as reworked. Sample 527-3-1,35-37 cm belongs to the late Pliocene Zone NN17, basedon the indigenous occurrence of D. pentaradiatus with-out D. surculus. Coccolithus pelagicus becomes numeri-cally significant in the nannofossil assemblage in thissample and downward. The interval between Samples527-3-1, 50-51 cm and 527-3-4, 35-37 cm is included inthe late Pliocene Zone NN16, based on the presence ofD. surculus without Reticulofenestra pseudoumbilica.Discoaster tamalis has its highest occurrence in this zonein Hole 527.

The interval between Samples 527-3-4, 50-51 cm and527-5,CC is assigned to the early Pliocene Zone NN15,based on the common to abundant occurrence of R.pseudoumbilica. Pseudoemiliania lacunosa (typical andatypical) occurs throughout this zonal interval, whereasSphenolithus abies has its highest occurrence in 527-5-3,

50-51 cm in this zone. Also, H. carteri gradually givesway to H. granulata within this zonal interval.

The early Pliocene Zone NN14 is recognized only inSamples 527-6-1, 40-42 cm, where D. asymmetricus andAmaurolithus delicatus co-occur. The interval between527-6-2, 40-42 cm and 527-7-2, 60-62 cm is included inthe early Pliocene NN13-NN14 zonal interval, based onthe presence of Ceratolithus acutus and Ceratolithus sp.cf. C. rugosus and on the absence of D. asymmetricusand A. amplificus. Zones NN13 and NN12 remain un-differentiated, because the lowest occurrence of thepoorly preserved C. rugosus is difficult to determine inthis interval. Typical A. tricorniculatus is not found,but A. bizzarus has its highest occurrence in Sample527-7-2, 60-62 cm in the lower part of this zonal inter-val.

Discoaster quinqueramus is missing in Hole 527. ThePliocene/Miocene boundary is tentatively located inSample 527-7,CC, where the highest occurrence of A.amplificus is recognized. The interval between 527-7,CCand 527-12,CC contains A. primus, A. delicatus, and Aamplificus and belongs to the upper part of Zone NN11.Small R. pseudoumbilica and A. bizzarus do not extenddown to the lower part of this interval. Below Core 11,red clay gradually becomes dominant. This correspondsto a minor assemblage change or, more specifically, to apreservational change. Well-preserved D. calcaris, D.variabilis, D. pentaradiatus, and D. brouweri becomeabundant, and dissolution and fragmentation of othercoccoliths become more significant. Because of dissolu-tion, neither H. granulata nor H. carteri is recordedbelow Core 11, and Sphenolithus abies is no longer pres-ent below Core 12.

Core 13 has very good recovery, but the red clay ismostly barren of calcareous nannofossils. By selectivesampling of light-colored calcareous mottles in the clay,common to abundant nannofossil assemblages were dis-covered. The entire Core 13 was therefore investigatedwith very closely spaced samples. The results reveal thatthese light-colored calcareous mottles scattered withinthe red clay are in-place materials. Core 13 contains sev-eral calcareous nannofossil zones. Section 527-13-1,top, to Section 527-13-1, 10 or 15 cm could belong to thelower part of Zone NN11. The lowest occurrence of A.primus is traced down to Section 527-13-1, 5 cm, where-as the highest occurrence of D. neohamatus is recordedin 527-13-1, 10 cm. Abundant Minylitha convallis occurthroughout this interval and downward.

The NN10/NN11 boundary is difficult to determine.The interval between Sections 527-13-1, 15 to 20 cm and527-13-1, 50 cm could belong to the late Miocene ZoneNN10. The assemblages are characterized by the enrich-ment of very well-preserved D. brouweri, D. neohama-tus, D. calcaris, and D. variabilis, with rare D. bellus.Other important species present are exclusively solution-resistant forms, such as R. pseudoumbilica (large), Cal-cidiscus macintyrei, M. convallis, and Triquetrorhabdu-lus rugosus.

The interval between Sections 527-13-1, 63 cm and527-13-5, 44 cm is assigned to the middle Miocene ZoneNN9, based on the total range of D. hamatus. The main

580


components of the assemblage are not greatly differentfrom those of the overlying Zone NN10. Discoaster bel-lus and the transitional form between D. calcaris and D.exilis become more significant in this zone. Discoasterneohamatus and D. pentaradiatus were no longer recov-ered below Section 527-13-1, 83 cm. Well-preserved Cat-inaster coalitus and C. calyculus, on the other hand,first appear below Section 527-13-3, 83 cm. Minylithaconvallis is still abundant in the upper part of this zonebut becomes rare and disappears in the lower part.

Sections 527-13-5, 66 cm to 527-13-6, 129 cm are in-cluded in the middle Miocene Zone NN8, based on theoccurrence of C. coalitus and C. calyculus and on theabsence of D. hamatus. Well-preserved D. exilis and D.variabilis with rare D. brouweri are the main discoastercomponents in this interval. Typical D. kugleri, how-ever, is not recorded.

Samples 527-13-7, 40-41 cm and 527-13,CC are bar-ren of calcareous nannofossils. These represent the ex-treme of the red clay development. Next, the intervalbetween 527-14-1, 28-29 cm and 527-14-3, 28-29 cm(or lower) contains an assemblage completely different.Among the species included are Coccolithus pelagicus,D. deßandrei, D. tanii, Dictyococcites bisectus, Sphe-nolithus moriformis, H. compacta, and S. predistentus,which indicates the early Oligocene Zone NP23. Becauseof reworking or mixing, rare species ranging from Eo-cene to earliest Oligocene were also observed in the up-per part of this interval. They are R. umbilica, D. sai-panensis, D. barbadiensis, and Cyclococcolithus formo-sus.

Except for the pure red clay interval, the abundantNeogene and Quaternary coccoliths and the Neogenediscoasters recovered in Hole 527 are moderately topoorly preserved. Dissolution and fragmentation of pla-coliths and recrystallization of discoasters increase down-hole. Below Core 11, where the red clay lithology be-comes more dominant, dissolution and fragmentationincrease. Species not resistant to dissolution disappearfrom the assemblages. The solution-resistant discoastersbecome enriched and appear well preserved. Core 13represents the extreme of this phenomenon, because thewell-preserved discoasters are so enriched that they dom-inate entire assemblages.


Hole 528 was drilled with conventional rotary coring.Core 1 sampled the topmost layer of the sediment. Con-tinuous cores were taken from 122.0 meters sub-bottom.Quaternary and Neogene calcareous nannofossils wererecovered in the six cores of this hole. A checklist ofthese Quaternary and Neogene calcareous nannofossilsis given in Table 6.

Core 1 is Pleistocene in age. Sample 528-1-1, 20-21cm belongs to the late Pleistocene Zone NN20, based onthe occurrence of Gephyrocapsa caribbeanica and G.oceanica and on the absence of Pseudoemiliania lacu-nosa. Then the interval between 528-1-2, 20-21 cm and528-1,CC is included in the early Pleistocene ZoneNN19, based on the occurrence of P. lacunosa. Gephy-

rocapsa caribbeanica and G. oceanica are abundantthroughout this interval.

The interval between Core 2, top, and Section 528-3-1,117 cm belongs to the NN5-NN4 zonal interval of theMiocene, based on the total range of Sphenolithus het-eromorphus. The assemblage includes Coccolithus pe-lagicus, Cyclicargolithusfloridanus, Calcidiscus leptop-orus, Discoaster deflandrei, D. exilis, D. variabilis, S.heteromorphus, and S. moriformis. Discoaster exilisand other Discoaster species are common only aboveSample 528-3-1, 23-24 cm, whereas D. deflandrei be-comes consistently abundant below Section 528-3-1, 117cm. The NN5/NN4 boundary (i.e., the middle/earlyMiocene boundary) is therefore located in Section 528-3-1 between 23-24 cm and 117 cm. Within Zone NN5,sediments derived from slumping and reworking wererecognized. The reworked species indicate an age rang-ing from the early Oligocene to middle Eocene. The as-semblage recovered in Sample 528-2,CC is typical of themiddle Eocene Zone NP 14.

The interval between 528-3,CC and Section 528-4-3,110 cm is included in the early Miocene Zone NN3, basedon the total range of S. belemnos. Next below, the inter-val between Sections 528-4-3, 31 cm and 528-4-4, 67 cmis the early Miocene Zone NN2, based on the absence oftypical S. belemnos and the rare presence of Discoastersp. aff. D. druggii.

The long interval between Samples 528-4-5, 25-26 cmand 528-6,CC belongs to the early Miocene Zone NN1,based on the absence of Discoaster sp. aff. D. druggiiand S. ciperoensis. In this zonal interval Calcidiscus lep-toporus becomes atypical. It eventually disappears inthe lower part of this zone. Also, Reticulofenestrapseu-doumbilica is not recorded below 528-4,CC. In thelower part of this zone, Dictyococcites bisectus has itshighest occurrence in Sample 528-6-1, 40-41 cm, andaff. Dictyococcites dictyodus has its highest occurrencein 528-6-2, 40-41 cm. Sphenolithus delphix has a veryshort stratigraphic range and is restricted to the lowerpart of Zone NN1. Sphenolithus capricornutus was notrecorded in Hole 528.

The top of the Oligocene is placed in Sample 528-7-1,10-12 cm, where the highest occurrence of S. ciperoen-sis is recorded. The first downhole appearance of Chi-asmolithus altus is found in 528-7-2, 30-32 cm, whererare Ericsonia fenestrata are observed. Perhaps becauseof the depth of the site, Helicosphaera recta and H.perch-nielseniae are not recovered in the upper Oligo-cene of Hole 528.

The preservation of calcareous nannofossils in Core 1is moderate. In the Miocene and upper Oligocene inter-val, the state of preservation becomes moderate to poor.Dissolution and overgrowth are so extensive that smallcoccoliths are totally eliminated, and discoasters andother solution-resistant coccoliths are strongly over-grown.

Hole 528A (28°31.16'S; 02°18.97E;water depth: 3815 m)

Hole 528A was drilled with hydraulic piston coring.Sediments were continuously cored from 0 to 130.5 me-

581



Age

earlyPleisto.

latePliocene

early

lateMiocene

middleMiocene

earlyOligo.

Zonation

NN19

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NN16

NN15

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NN12

NN11

NN10

NN9

NN8

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NP23

OverallPreservation

Disco-asters

MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG

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Depthbelow

Seafloor(m)

0.0

9.09.0

18.51.8.5

28.028.0

37.537.5

47.047.0

56.556.5

66.066.0

75.575.585.089.594.594.5

104.0104.0

113.5113.5

123.0

Core-Section(intervalin cm)

1-1, 29-311-2, 29-311-3, 29-311-4, 29-311-5, 29-311-6, 29-31l.CC2-1,40-422-1, 50-512.CC3-1, 35-373-1, 50-513-2, 35-373-3, 35-373-4, 35-373-4, 50-513,CC4-1, 30-314-2, 20-224.CC5-1, 50-515-2, 50-515-3, 50-515.CC6-1,40-426-2, 40-426-3, 40-426-4, 40-426-5, 40-426-6, 40-426-7, 40-426,CC7-1, 100-1017-2, 60-627,CC8-1, 64-668-2, 64-668-3, 64-668-4, 64-668-5, 64-668.CC9-1, 40-429,CC11-1, 37-3911,CC12-1, 59-6112-2, 59-6112-3, 52-5312-4, 59-6112-5, 59-6112.CC13-1, top13-1, 513-1, 1013-1, 1513-1, 2013-1, 2513-1, 3013-1, 3513-1, 4013-1, 5013-1, 6313-1, 7413-1, 8313-1, 9613-1, 11013-1, 13213-2, 8813-3, 8313-5, 1413-5, 4413-5, 6613-5, 98-9913-6, 7713-6, 12913-7, 40-4113.CC14-1, 28-2914-1, 3414-2, 28-2914-2, 11814-3, 28-29

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a R = Reticulofenestra.

582



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583


Age

OverallPreservation

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ters sub-bottom to recover the interval of coring gap ofHole 528. A major hiatus was observed between Sample528A-28,CC and Core 528A-29, top. The entire lowerMiocene and the lower part of the middle Miocene aremissing in this hole, which is not compatible with Hole528. A checklist of the calcareous nannofossil distribu-tion of the entire Hole 528A is given in Table 7.

Sample 528A-1-1, 28-29 cm is assigned to the latePleistocene Zone NN20, based on the common occur-rence of Gephyrocapsa oceanica and G. caribbeanica inthe absence of Pseudoemiliania lacunosa. The presenceof Emiliania huxleyi in this sample is not confirmed.Samples 528A-1-1, 120-122 cm through 528A-5-3, 19-20 cm belong to the early Pleistocene Zone NN19, basedon the presence of P. lacunosa together with G. oceanicaand G. caribbeanica. Calcidiscus macintyrei, a speciesno younger than 1.51 m.y. (Gartner, 1977), is presentthroughout this interval.

The interval between Samples 528A-5-4, 19-20 cmand 528A-6-3, 19-20 cm is assigned to the late PlioceneZone NN18, based on the few to common occurrencesof Discoaster brouweri. Gephyrocapsa oceanica and G.caribbeanica are not present in this zone. The rare oc-currence of D. pentaradiatus in this interval is interpret-ed as redeposited because of their poor preservation.Helicosphaera granulata becomes common in this zonalinterval of Hole 528A. The interval between Sections528A-6-3, 111 cm and 528A-7-2, 100 cm belongs to thelate Pliocene Zone NN16, based on the occurrence of D.surculus together with D. pentaradiatus and D. brouweriin this interval. Discoaster tamalis and D. asymmetricushave their highest occurrences in the lower part of thezone. Zone NN17 apparently is not developed in thishole. It is unclear whether this represents a minor hiatus,whether the sampling intervals are not close enough, orwhether the marker species were excluded from this area.

The interval from Sample 528A-7-3,40-41 cm to Sec-tion 528A-11-3, top, is assigned to the early PlioceneZone NN15 because of the presence of Reticulofenestrapseudoumbilica in the absence of Amaurolithus delica-tus. Both large and small R. pseudoumbilica are tracedup to Sample 528A-7-3, 40-41 cm, whereas Sphenolith-us abies has its highest occurrence in Sample 528A-10,CC, in the lower part of Zone NN15. Pseudoemilianialacunosa is present throughout this zonal interval. It is,however, atypically small in the lower part of this zoneand is not recorded in the underlying zone.

The interval between Samples 528A-11,CC and 528A-13-2, 63-64 cm is included in the early Pliocene ZoneNN14, based on the co-occurrence of D. asymmetricusand A. delicatus. Discoaster tamalis has its lowest oc-currence in this zone. The single Sample 528A-13-3,63-64 cm is assigned to the early Pliocene Zone NN13,based on the presence of Ceratolithus rugosus in the ab-sence of D. asymmetricus. In the same sample, rare A.tricorniculatus and the highest occurrence of A. biz-zarus are recorded.

The interval between Section 528A-13-4, base, andSample 528A-14-2, 51-52 cm represents the Pliocene/Miocene Zone NN12 transition, based on the absence ofthe Pliocene Ceratolithus sp. and the typical Miocene A.

amplificus. Discoaster variabilis first appears in the low-er part of Zone NN15 and suddenly becomes importantin the assemblage in this zone.

The Miocene top is tentatively placed in Sample 528A-14,CC, where the highest occurrence of typical A. am-plificus is recorded. Because of the depth of the site, D.quinqueramus, index species for the late Miocene ZoneNN11, is extremely rare in the upper Miocene of thishole. The interval between 528A-14,CC and 528A-23,CCbelongs to the upper part of the late Miocene Zone NN11because of the consistent presence of Amaurolithus sp.and the absence of D. neohamatus. Discoaster surculus,A. bizzarus, and H. granulata (dissolution effect?) donot extend down to the lower part of this interval,whereas Triquetrorhabdulus rugosus first occurs spo-radically in this interval. Small R. pseudoumbilica arestill common to abundant in this entire interval. Theyare, however, no longer recorded below Core 23.

The interval between Sample 528A-24-1, 70-71 cmand 528A-25,CC is included in the lower part of the lateMiocene Zone NN11 or Zone NN10, based on the ab-sence of Amaurolithus sp. and D. hamatus. Discoasterneohamatus and Minylitha convallis have their highestoccurrences in Sample 528A-24-1, 70-71 cm. This entireinterval is characterized by the common presence of M.convallis, D. variabilis, and D. brouweri with long slen-der rays, together with D. neohamatus. Discoaster bel-lus has it highest occurrence in 528A-25-3, 59-60 cm inthis interval. Because of the scarcity of D. quinquera-mus, the NN11/NN10 boundary can not be identifiedwith certainty in this hole.

The total range of D. hamatus, recorded from Sec-tion 528A-26-1, 50 cm to Sample 528A-27-2, 38-39 cm,places this interval into the middle Miocene Zone NN9.Minylitha convallis remains very abundant in the upperpart of this interval and disappears in the underlyingZone NN8. Discoaster pentaradiatus is missing belowSample 528A-26-1, 50 cm. Discoaster neohamatus hasits lowest occurrence and Catinaster calyculus has itshighest occurrence in the same core, in Sample 528A-26-3, 54-56 cm. Discoaster bellus, on the other hand, hasthe same lowest occurrence as D. hamatus in Core 27 inSample 528A-27-2, 38-39 cm.

Sample 528A-27-2, 150 cm to Sample 528A-27,CC isincluded in the middle Miocene Zone NN8, based on theoccurrence of C. calyculus and C. coalitus in the absenceof D. hamatus. Discoaster variabilis, D. exilis, and rareD. brouweri are the main discoaster components in thisinterval. Discoaster exilis is not observed above thiszone in this hole. The interval between Sample 528A-28-1,58 cm and Sample 528A-28,CC is assigned to the mid-dle Miocene Zone NN7, based on the absence of C. caly-culus and C. coalitus. Other species components are al-most identical to the overlying Zone NN8, except for thefirst downhole occurrence of D. deflandrei in this inter-val. Typical D. kugleri, the index species for Zone NN7,is absent. Some specimens of Coronocyclus nitescensand Cyclicargolithus floridanus were found in Sample528A-28,CC, which might indicate an age of the middleMiocene Zone NN6 or the fact of reworking from inter-vals of older age.

585


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

t II111 n 11 ̂ 11 u i f 11 i 11 i 11 ̂Overall 3 a 3 3 j ? | t E f | » S 5 - | J ; | | ^ | | s | ^

Other Overall below Section ^ a a a a • l δ l δ ^ l l s S S S l o o s ^ ^ . S ^ ^ I S

Disco- Cocco- Abun- Seafloor (interval I l l l l g l l i ^ ^ l l g δ l δ δ l g • g • R S s j á JAge Zon. asters liths dance (m) in cm) • ^ ^ ^ x X T β a O O ü O O ü O U O U O O ü U < j Q β Q Q

late Pleisto. NN20 M A 0.0 1-1,28-29 A R R cf. RM A 1-1, 120-122 A R R R RMA 1-2, 28-29 C cf. R R cf.M A 2.9 l.CC A R FM A 2.9 2-1, 40-41 RM A 2-2, 40-41 C R R R RM A 2-3,40-41 C R cf.M A 7.3 2,CC A R RM A 7.3 3-1, 40-41 A R R cf.

early N I N l y M A 3-2,40-41 A R R R RPleisto. M A 3-3, 40-41 A R

M A 11.7 3.CC A R R RM A 11.7 4-1, 38-39 A R R RM A 4-2, 38-39 C R RM A 4-3, 38-39 C RM A 4-3, 130 A RM A 16.1 4.CC A R R FM A 16.1 5-2, 19-20 A R RM A 5-3,19-20 C R It

M M A 5-4, 19-20 C R RM M A 20.5 5.CC A R R R C

NN18 M M A 20.5 6-1, 111 A CM M A 6-2, 111 A R C R

late M M A 6-3,19-20 A R CPliocene M M A 6-3, 111 A R R C R

M M A 24.9 6.CC A R CNN16 M M A 24.9 7-1, 40-41 C R F R

M M A 7-2, 40-41 A R C RG M A 7-2,100 A R II CM M A 7-3, 40-41 A R R C R RM M A 29.3 7.CC A R R C R FM M A 29.3 8-1, 40-41 A R C R FM M A 8-2, 40-41 A R F R RM M A 8-3, 40-41 A R R C R RM M A 33.7 8.CC A R R C R FM M A 33.7 9-1, 100-101 ' A R F R F

NN15 M M A 9-2, 100-101 C R R F R FM M A 9-3, 100-101 r C R R R R RM M A 38.1 9.CC r A F R R R RM M A 38.1 10-1,89-90 C R R R FM M A 10-2, 89-90 C R R R R R R

e a r l y M M A 10-3, 89-90 C R R R R RPliocene M M A 42.5 10.CC A F R R R R F

M M A 42.5 11-1,40-41 A R R R R R FM M A 11-2,40-41 A R R R R R FM M A 11-3, top C R R R _ __R _FM M A 46.9 11,CC R C R R R R RM M A 46.9 12-2, 40-41 C R R R F F

NN14 M M A 51.3 12.CC F A R R R R RM M A 51.3 13-1,63-64 R A R RM M A 13-2,63-64 R R C R R R R _ _ R It

NN13 M M A 13-3,63-64 R F R R C R R R It

N π s I 1 , M M A 55.7 13-4, base R R R C R* F FM M A 55.7 14-2,51-52 cf. R R C_R F _ _ _R rM M A 60.1 14.CC R F R C R CM M A 60.1 15-1, 50-51 R R R R c f . A R R R rM M A 15-2, 50-51 R R R A R R RM M A 15-3, 50-51 R R R R C R R RM M A 64.5 15,CC R R R R A R R RM M A 64.5 16-1,80-81 R R R C R R RM M A 68.9 16.CC R R R C R F RM M A 68.9 17-1, 80-81 R R C R R FM M A 73.3 17.CC F R C R RM M A 73.3 18-1, 20-21 R R F R R C R R RM M A 77.7 18,CC R F R C R R rM M A 77.7 19-2, 20-21 R R R A R F

N N n M M A 19-3,20-21 R R R C F RM M A 82.1 19.CC R F R C R F RM 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 RMiocene ] | M | M | A | 90.9 | 21,CC | R R F | C R [ C R

586



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_R A R R F _ F R _ A R R CC R C C F F F R A R F R CC C C F F F R A C C R FF C F F F F R A R F R R CF F F R R R R A C R FF C C F R R C A R CF F F F R F R C A R R CC R C F R F R C A R FF F C F F R C A RF F F R F R R F A FR F F R F R F A R RR R F F R R F R A RR R R R R F A RR R R F R R R A RF R F F F R C R A R R RF R C F C R F A R R RF C F C R F R A R R R

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calcareous nannofossil zonation · 2007. 5. 3. · calcareous nannofossil zonation martini's...

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