33. CALCAREOUS NANNOFOSSILS

33.1. COCCOLITH STRATIGRAPHY LEG 13, DEEP SEA DRILLING PROJECT1

David Bukry, U. S. Geological Survey, La Jolla, California

INTRODUCTION

Leg 13 of the Deep Sea Drilling Project, August-October1970, which began and ended at Lisbon, investigated theMediterranean Sea and adjacent Atlantic Ocean, recovering183 cores at 15 drilling sites (Figure 1). Light-microscopetechniques were used to study the coccoliths of 192samples from these cores. Zonal assignments of cores fromLeg 13 are summarized in Tables 1 and 2.

The majority of samples from the Mediterranean Sea areof Pleistocene or late Pliocene age. None of the Mediter-ranean samples examined are definitely older than middleMiocene, but a few late Jurassic and early Cretaceoussamples were obtained from Site DSDP 120, Cores 2 to 7,west of the Straits of Gibraltar in the Atlantic Ocean. Manyof the Mediterranean samples are turbidite-like sediments,rich in detritus, that contain reworked late Cretaceous andearly Tertiary coccoliths.

The occurrence of Braarudosphaera bigelowi (Gran andBraarud) in Pliocene and Pleistocene samples distinguishesthe Mediterranean assemblages from coeval assemblagesrecovered on previous open-ocean DSDP legs, and itsuggests lower than normal oceanic salinities (<35°/Oo)

OPEN-OCEAN ZONATION OF THE PLIOCENE ANDPLEISTOCENE COMPARED WITH THE ZONATION

AT MEDITERRANEAN SITE DSDP 132

Hole DSDP 132 was drilled on an isolated rise in theTyrrhenian Basin west of Naples (latitude 40° 15.67'N.,longitude 11° 26.46'E., depth 2835 m) in pelagic carbonateooze of Holocene, Pleistocene, Pliocene, and late Mioceneage. As this may provide a useful reference for lateCenozoic stratigraphy, owing to its proximity to classicstage localities in Italy, the ranges of selected coccolithtaxa, as compared with the zonation used for open-oceancoccolith-rich sediments, are illustrated in Table 3.

The Pliocene to Pleistocene interval has been coredrepeatedly in pelagic biogenic sediment by the Deep SeaDrilling Project during the 12 legs prior to coring in theMediterranean Sea. Study of these open-ocean cores hasshown that a series of seven generally defined coccolithzones can be consistently identified. Further, in areas ofhigh biogenic productivity and high diversity, many ofthese zones can be divided into subzones. Publicationspertinent to the development of open-ocean upper Ceno-zoic coccolith zonation include: Boudreaux and Hay, 1969;Bramlette and Riedel, 1954; Bukry, 1971; Bukry andBramlette, 1970; Gartner, 1969; Gartner, 1970; Hay andothers, 1967; Martini and Bramlette, 1963; and Riedel andothers, 1963. With light-microscope study, up to elevenbiostratigraphic units can be identified in the Pliocene toPleistocene interval, based on certain changes in coccolith

1 Publication authorized by the Director, U. S. Geological Survey.

assemblages (such as, specimen size and generic composi-tion) and on the restricted ranges of key species (Table 4).The general characteristics of the biostratigraphic units,beginning with early Pliocene, are as follows:

Ceratolithus tricorniculatm Zone

Ceratolithus amplificus SubzoneThis subzone is characterized throughout by the pres-

ence of cosmopolitan Ceratolithus tricorniculatus. Thespecies Ceratolithus amplificus is typically restricted to thissubzone; its first occurrence approximates the last occur-rence of Triquetrorhabdulus rugosus, and its last occurrenceapproximates the first occurrence of Ceratolithus rugosus.This stratigraphic sequence is demonstrated in Hole DSDP72, Core 2, and in Hole DSDP 83A, Cores 9A to 11 A. InHole DSDP 82A, Core 9A, a bizarre form of C. tricornicu-latus (having the horn extended into a rod), that occurs inthe lower Pliocene of Italy, is associated with C. amplificus.Typical species of the subzone assemblage include: Cerato-lithus amplificus, C. tricorniculatus, Cyclococcolithinaleptopora, C. macintyrei, Discoaster brouweri, D. penta-radiatus, D. surculus, D. variabilis variabilis, Discolithinajaponica, D. multipora, Helicopontosphaera kamptneri,Reticulofenestra pseudoumbilica, Scyphosphaera globulata,Sphenolithus abies, and S. neoabies. The C. amplificusSubzone is distinguished from the underlying Triquetror-habdulus rugosus Subzone by first occurrence of C.amplificus and last occurrence of T. rugosus.

At Site DSDP 132 the interval from the lower partof Core 16 to Core 21 contains C. tricorniculatus or C.amplificus and lacks Discoaster quinqueramus, a relationindicating assignment of the cores to the Ceratolithustricorniculatus Zone. In Pacific Ocean cores, the extinctionof C. amplificus, an intermediate species considered aprogenitor of C. rugosus and appearing between the firstoccurrences of C. tricorniculatus and C. rugosus, hasformerly been considered to be a convenient guide to theMiocene-Pliocene boundary as lower Pliocene samplesexamined from the Pasquasia-Capodarso and Tabiano sec-tions of Italy show no C. amplificus, only C. tricornicu-latus. In the context of the ranges of these species in SiteDSDP 132, however, the absence of C. amplificus in theterrestrial Italian samples is evidently local, and theformerly Miocene upper C. tricorniculatus Zone—the newC. amplificus Subzone—is now considered lower Pliocene.This designation yields a coccolith identification of theMiocene-Pliocene boundary in open-ocean sediment that ismore consistent with the type and reference sections ofItaly and Site DSDP 132 in the Tyrrhenian Basin. In theabsence of subzonal indicators for the C. tricorniculatusZone, such as C. amplificus or Triquetrorhabdulus rugosus,this designation results in the placement of the Miocene-Pliocene boundary within the C. tricorniculatus Zone.

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DAVID BUKRY

0° 10° 20° 30°Figure 1. Locations of sites cored during DSDP Leg 13 in the Mediterranean Sea and eastern North Atlantic Ocean.

TABLE 1Geologic Age and Zone Assignment of Cores from Holes 120-127 A Based on Coccoliths in Samples Examined

Age

Ple

isto

cene

and

Hol

ocen

eP

lioc

ene

Vlio

cene

Zone Subzone

Emiliania huxleyi

Gephyrocapsa oceanica

Coccolithusdoronicoides

Discoasterbrouweri

Gephyrocapsa caribbeanica

Emiliania annula

Cyclococcolithina macintyrei

Discoaster pentaradiatus

Reticulofenestra pseudoumbilica

Ceratolithus rugosus

Ceratolithus tricorniculatus

Discoaster quinqueramus

Discoaster neohamatus

Discoaster hamatus

Catinaster coalitus

Discoaster exilis

Sphenolithus heteromorphus

DSDP Hole

120

bit

121

1-3

4,7?

7?, 8-9

10-14

19-24

122

1

1

2-3

123

2

3-5

6

124

1

2

2

3

3

4-5

125

1-3

4

4

5-7

125 A

1

1

2-4

5

5

126

1

1

126 A

1?

127

1-10

14-15

18

127A

2-4

818

33.1. COCCOLITH STRATIGRAPHY

TABLE 2Geologic Age and Zone Assignment of Cores from Holes 128-134A Based on Coccoliths in Samples Examined

Age

Plei

stoc

ene

and

Hol

ocen

een

e

o

s

ocen

e

Zone Subzone

Emiliania huxleyi

Gephyrocapsa oceanica

Coccolithus

Discoaster

Gephyrocapsa caribbeanica

Emiliania annula

Cyclococcolithina macintyrei

Discoaster pentaradiatus

Reticulofenestra pseudoumbilica

Ceratolithus ntgosus

Ceratolithus tricorniculatus

Discoaster quinqueramus

Discoaster neohamatus

Discoaster hamatus

Catinqster coalitus

Discoaster exilis

Sphenolithus heteromorphus

DSDP Hole

128

1

2-3

7-11

129

2-3?

129 A

3?

130

1-2

3-6

130A

1

131A

4-5

132

1?

2-7

7

8

8-10

11-14

15

15-16

16-26

133

1?

134

3-5

7

134 A

1

Ceratolithus rugosus Zone

This zone is widely identified as the interval from thefirst occurrence of Ceratolithus rugosus tc the last occur-rence of C. tricorniculatus. C. amplificus is usually missingfrom this interval, and in tropical areas Oolithotus antil-larum first occurs at the top of this interval. The assemblageof long-ranging coccoliths is the same as in adjacent zones,but particularly robust specimens of several genera, prob-ably reflecting a general ocean warming, help to distinguishassemblages of this zone, even at high latitudes (DSDPLeg 12).

The assemblages of both this zone and the C. tricornicu-latus Zone at Site DSDP 132 are characterized by thecommon occurrence of a plexus of Scyphosphaera formsand by the sparse occurrence of true ceratoliths. Through-out the lower Pliocene section, Ceratolithus rugosus is rare,but a species of Scyphosphaera with heavily calcified,closely spaced walls that mimics the form of C. rugosus ispresent. Similarly, tilted and broken rims of some discolithsmimic the form of unornamented C. tricorniculatus; thehighest occurrence of true C. tricorniculatus is recorded inSample 132-15-5, 100 cm. Therefore, the C. rugosus Zone,indicated here by the overlapping ranges of C. rugosus andC. tricorniculatus, is restricted to Cores 15 to 16.

Reticulofenestra pseudoumbilica Zone

Sphenolithus neoabies SubzoneThe base of this zone and subzone is recognized by the

disappearance of cosmopolitan Ceratolithus tricorniculatus.The subzone is recognized in tropical areas by the abun-dance of Sphenolithus neoabies and by the lowest commonoccurrences of Oolithotus antillarum, Discoaster asym-metricus, and small Helicopontosphaera sellii. The latterthree species become more common in overlying zonalunits.

Reticulofenestra pseudoumbilica Zone

Discoaster asymmetricus Subzone

The top of this zone and subzone is recognized by aclosely spaced disappearance of Sphenolithus abies, S.neoabies, and large Reticulofenestra pseudoumbilica. Thesubzone is characterized by a marked increase in abundanceof Discoaster asymmetricus and small Helicopontosphaerasellii compared to the underlying Sphenolithus neoabiesSubzone. The lowest sparse occurrence of Discoastertamalis is noted in this subzone. In the upper part of thissubzone and in the overlying Discoaster tamalis Subzone,the last period of Discoaster development is recorded,wherein the common to abundant occurrences of D.asymmetricus, D. tamalis, and D. variabilis decorus serve todistinguish these two subzonal units from other Plioceneintervals.

As Discoaster asymmetricus is rare throughout DSDP132, no subdivision of the short Reticulofenestra pseudo-umbilica Zone is indicated. The last occurrences ofReticulofenestra pseudoumbilica, Sphenolithus abies, andS. neoabies in the top of Core 15, combined with the lastoccurrence of C. tricorniculatus in the bottom of the samecore, delimit this zonal interval. The assemblage containsfew D. asymmetricus, D. brouweri, and tiny H. sellii, andcommon Coccolithus pelagicus, Cyclococcolithina, andScyphosphaera.

Discoaster brouweri ZoneThis zone can be divided into several subzones on the

basis of sequential extinctions of species of Discoaster. Intropical areas the first common occurrences of Emilianiaannula and Rhabdosphaera clavigera are recorded in thiszone.

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DAVID BUKRY

TABLE 3Occurrence of Selected Coccolith Species in Samples from Site DSDP 132, with Geologic Age and Zonal Assignment*

Age

ene

| H

oloc

ene

Plei

stoc

Plio

cene

Lat

eoc

ene

Ear

ly P

li

Upper Cenozoic Coccoliths

Zone/Subzone

E. huxleyi (?)

G. oceanica

C. doronicoidesG. caribbeanicaE. annula

D. brouweriC. macintyrei

D. pentaradiatus

D. tamalis

R. pseudoumbilica

C. rugosus

C. tricorniculatusC. amplificus

DSDP Sample

132-1-1, 142 cm132-2-1, 149 cm132-3-1, 144 cm132-4-1, 143 cm132-5-1, 140 cm132-6-1, 120 cm132-7-1, 140 cm132-7-4, 138 cm132-7-5, 140 cm132-8-3, 140 cm132-8-6, 140 cm132-9-2, 140 cm132-10-1, 140 cm132-11-1, 140 cm132-12-1, 140 cm132-13-1, 140 cm132-14-2, 83 cm132-15-1, 140 cm132-15-4, 100 cm132-15-5, 100 cm132-16-1, 140 cm132-16-3, 100 cm132-16-5, 100 cm132-17-3, 100 cm132-18-4, 100 cm132-19-1, 140 cm132-20-4, 100 cm132-21-1, 100 cm

Sphe

nolit

hus

abie

sC

erat

olith

us tr

icor

nicu

latu

sR

etic

ulof

enes

tra

pseu

doum

bilic

aD

isco

aste

r su

rcul

usSc

ypho

spha

era

cf. i

nter

med

ia

X

XX XX XX X

X XX X

X X X XX X

X X XX X X XX X X XX X X XX X X XX X X X XX X X X X

Dis

coas

ter

brou

wer

iC

yclo

cocc

oUth

ina

mac

inty

rei

Hel

icop

onto

spha

era

kam

ptne

riSp

heno

lithu

s ne

oabi

esD

isco

aste

r pe

ntar

adia

tus

XXXXXXXX

X XX X

X X XX X XX X XX X X XX X X XX X XX X XX X X

X X X XX X X X

X X X X XX X X X X

X X X XX X X XX X X XX X X X XX X X X XX X X

Cer

atol

ithus

am

plifi

cus

Dis

coas

ter

vari

abili

s va

riab

ilis

Dis

coas

ter a

sym

met

ricu

sC

erat

olith

us r

ugos

usH

elic

opon

tosp

haer

a se

llii

X

X

XXXXXX

X XX X X

X XX XX X X

X XX X

XX XX

XX

X X X

Dis

coas

ter

tam

alis

Coc

coU

thus

dor

onic

oide

sE

mili

ania

ann

ula

Bra

arud

osph

aera

big

elow

iR

habd

osph

aera

cla

vige

ra

XXX XX X X X

X XX X X X

X X XX X

X X XX X XX X XX X XX X X XX

X X X XX XX

Syra

cosp

haer

a hi

stri

caG

ephy

roca

psa

cf. c

arib

bean

ica

Rha

bdos

phae

ra

styl

ifera

Gep

hyro

caps

a oc

eani

caE

mili

ania

hux

leyi

XX X

X XXX XX X

XX X X XX X X

XXXX

aTaxa are arranged by first occurrence; those occurring in the deepest sample are arranged by last occurrence in this hole.

Discoaster tamalis Subzone

This subzone is defined at the base by the lastoccurrences of Reticulofenestra pseudoumbilica, Spheno-lithus abies, and S. neoabies. The top can be recognized bythe last occurrence of Discoaster variabilis decorus intropical areas, or by the last common occurrence of D.tamalis in tropical and temperate areas. Assemblages of thissubzone are characterized in many areas by the restrictedoccurrence of D. variabilis decorus and the commonoccurrence ofD. tamalis and/), asymmetricus.

In the absence of the tropical guide species Discoastervariabilis decorus, the last common occurrence of Disco-aster tamalis in Sample 132-11-2, 140 cm is used todetermine the top of the D. tamalis Subzone. The assem-blages are dominated by placoliths with only few Cerato-lithus rugosus, D. asymmetricus, D. brouweri, D.pentaradiatus, D. surculus, andD. tamalis.

Discoaster brouweri Zone

Discoaster pentaradiatus Subzone

The top of this subzone is determined by the lastoccurrence of Discoaster pentaradiatus. Discoaster surculusgenerally becomes extinct at or just below this level. Thebottom of the subzone is determined by the highestoccurrence of D. variabilis decorus or by the highestcommon occurrence of D. tamalis. The occurrence ofCeratolithus rugosus, CoccoUthus doronicoides, Cyclococ-coUthina leptopora, C. macintyrei, Discoaster brouweri, D.pentaradiatus, D. surculus, Helicopontosphaera kamptneri,and H. sellii with early forms of Emiliania annula andRhabdosphaera clavigera is characteristic.

This unit is limited at DSDP 132 by the last occurrenceof Discoaster pentaradiatus in Sample 132-10-5, 140 cm;the last D. surculus is in 132-10-6, 140 cm, and the last/).

820

33.1. COCCOLITH STRATIGRAPHY

TABLE 4Typical Ranges of Zonal Guide Fossils in Open-Ocean Sediment

Coccoliths

Age

Holocene

Pleistocene

LatePliocene

EarlyPliocene

LateMiocene

Zone Subzone

Emiliania huxleyiGephyrocapsa oceanica

Coccolithusdoronicoides

Discoasterbrouweri

Reticulofenestrapseudoumbilica

Gephyrocapsa caribbeanica

Emiliania annulaCyclococcolithina macintyrei

Discoaster pentaradiatusDiscoaster tamalisDiscoaster asymmetricus

Sphenolithus neoabiesCeratolithus rugosusCeratolithustricorniculatus

Ceratolithus amplificus

Triquetrorhabdulus rugosus

Triq

uetr

orha

bdul

us r

ugos

us

Cer

atol

ithus

am

plifi

cus

Cer

atol

ithus

rug

osus

1

Cer

atol

ithus

tric

orni

cula

tus

Dis

coas

ter

asym

met

ricu

s

\i

1

R e

ticu

lofe

nest

ra p

seud

o um

bilic

a

Sphe

nolit

hus

neoa

bies

Dis

coas

ter

tam

alis

1

I

Dis

coas

ter

vari

abüi

s de

coru

s

i

1

Dis

coas

ter

surc

ulus

Dis

coas

ter

pent

arad

iatu

s

Dis

coas

ter

brou

wer

i

Cyc

loco

ccol

ithin

a m

acin

tyre

i

i

Gep

hyro

caps

a ca

ribb

eani

ca

Gep

hyro

caps

a oc

eani

ca

Em

ilian

ia h

uxle

yi

1•

tamalis in 132-11-2, 140 cm. The assemblage containsCoccolithus doronicoides, C. pelagicus, Cyclococcolithinamacintyrei, Discolithina japonica, Helicopontosphaerakamptneri, H. sellii, Rhabdosphaera clavigera, R. procera,and Scyphosphaera apsteinii.

Discoaster brouweri Zone

Cyclococcolithina macintyrei Subzone

This unit is defined at the base by the absence ofDiscoaster pentaradiatus and D. surculus, which occurbelow. Discoaster brouweri, showing maximum down-bending of rays, and Discoaster triradiatus are the onlycommon discoasters. Discoaster asymmetricus may occurrarely. The most prominent coccoliths in tropical areas areCeratolithus rugosus, Coccolithus doronicoides, Cyclococ-colithina macintyrei, Emiliania annula, and Helicoponto-sphaera sellii. The appearance or increased abundance ofCoccolithus pelagicus near the top of this subzone istypical. In most areas, the top can be recognized by anabrupt reduction in the abundance of D. brouweri, C.macintyrei, and C. rugosus.

The upper Pliocene Cyclococcolithina macintyrei Sub-zone of DSDP 132 (Cores 8 to 10) is characterized bysparse Discoaster brouweri and D. triradiatus; commonCoccolithus pelagicus, Cyclococcolithina macintyrei, Rhab-dosphaera clavigera, Discolithina, and Scyphosphaera.Emiliana annula and Helicopontosphaera sellii are sparse inthe lower part of the interval but become more commontoward the top. Braarudosphaera bigelowi is sparselypresent through the interval.

In the upper part of the interval, Discoaster occurrenceis discontinuous; none are noted in Sample 132-8-5, 140 cmand above. The sparse occurrence of Discoaster in the upper

Pliocene of DSDP 132 is similar to the relation encounteredat high latitudes in the Atlantic Ocean (DSDP Leg 12),where discoasters, though common in the warm-waterlower Pliocene, are rare in the cool-water upper Pliocene. Intropical open-ocean sediment (DSDP Leg 7), discoasters areabundant through the entire Pliocene.

Coccolithus doronicoides Zone

Emiliania annula Subzone

This unit is characterized by the common occurrences ofCoccolithus doronicoides, C. pelagicus, Cyclococcolithinaleptopora, Emiliania annula, and Helicopontosphaera sellii,and by the absence of species of Discoaster and Gephyro-capsa. Ceratolithus rugosus is replaced by C. cristatus in thisinterval, and Cyclococcolithina macintyrei is replaced bysmall C. leptopora, although in some areas C. macintyreipersists through this interval in small numbers. The base ofthe subzone is defined by an abrupt reduction in theabundances of D. brouweri, C. macintyrei, and C. rugosus.The first occurrence of Gephyrocapsa caribbeanica is usedto distinguish the top of this subzone.

The last common occurrence of Discoaster brouweri is inDSDP 132, Core 9. Rare specimens occur in the lower partof Core 8. The interval in Core 8 above the last occurrenceof discoasters contains common Cyclococcolithina macin-tyrei but no ceratoliths and is assigned to the Coccolithusdoronicoides Zone. The common occurrence of Helico-pontosphaera sellii through the C. doronicoides Zone andthe dominance of this species over H. kamptneri arecharacteristic of oceanic assemblages. This relation occurshere in Cores 7 and 8. Emiliania annula abundance isvariable, being greatest in Sample 132-8-1, 137 to 140 cm.Small Gephyrocapsa sp. cf. G. caribbeanica occur through

821

DAVID BUKRY

Core 7 and allow division of the Coccolithus doronicoidesZone into lower and upper subzones at DSDP 132.

Coccolithus doronicoides Zone

Gephyrocapsa caribbeanica SubzoneThe assemblage of the upper subzone of the C.

doronicoides Zone is similar to that of the E. annulaSubzone, but the first appearance and common occurrenceof Gephyrocapsa caribbeanica below the first appearance ofG. oceanica is used to define this unit.

Gephyrocapsa oceanica ZoneThis unit is defined at the base by the first occurrence of

G. oceanica. Assemblages of the zone are characterized byCeratolithus cristatus, Cyclococcolithina leptopora,Gephyrocapsa aperta, G. caribbeanica, G. oceanica, Helico-pontosphaera kamptneri H. sellii absent or rare] ,Rhabdo-sphaera clavigera, and Scapholithus sp. The top of this unitis based, in light-microscope study, on the occurrence aboveof a great abundance of EmiUania huxleyi, a small (2 to 3micron) faint oval coccolith.

The Pleistocene zonal assemblages of DSDP 132, in thisand adjacent zones, are distinguished from open-oceanassemblages by the presence throughout of Braarudo-sphaera bigelowi, a marginal-marine species, and by theabsence of Ceratolithus cristatus, a fully marine species.Gephyrocapsa caribbeanica, the most temperature-tolerantspecies of Gephyrocapsa, occurs commonly through thePleistocene cores. The warm-water species G. oceanicaoccurs most commonly at the top of Core 7, considered thelower part of the Gephyrocapsa oceanica Zone. Occur-rences in higher cores are sparse and discontinuous.

EmiUania huxleyi Zone

This zone, the highest coccolith zone recognized, ischaracterized by the overwhelming dominance of EmiUaniahuxleyi. This species cannot be definitely identified by lightmicroscopy, but dominance of small coccoliths at the topof oceanic-sediment sections in conjunction with narrow-rimmed specimens of Helicopontosphaera kamptneri gen-

erally results in the identification of E. huxleyi whenelectron-microscope study is carried out.

Sample 132-1-1, 142 to 143 cm contains abundantlEmiliania huxleyi and some small, narrow-rimmed Helico-pontosphaera kamptneri, with Coccolithus pelagicus, Cyclo-coccolithina leptopora, and Gephyrocapsa sp. cf. G.caribbeanica.

REFERENCES

Boudreaux, J. E. and Hay, W. W., 1969. Calcareousnannoplankton and biostratigraphy of the late Pliocene-Pleistocene-Recent sediments in the Submarex cores.Revistà Espahola de Micropaleontologia. 1, 249.

Bramlette, M. N. and Riedel, W. R., 1954. Stratigraphicvalue of discoasters and some other microfossils relatedto recent coccolithophores./. Paleontology. 28, 403.

Bukry, D., 1971. Coccolith stratigraphy Leg 7, Deep SeaDrilling Project. Initial Reports of the Deep Sea DrillingProject, Volume VII. Washington (U.S. GovernmentPrinting Office).

Bukry, D. and Bramlette, M. N., 1970. Coccolith agedeterminations Leg 3, Deep Sea Drilling Project. InitialReports of the Deep Sea Drilling Project, Volume III.Washington (U.S. Government Printing Office). 589.

Gartner, S., Jr., 1969. Correlation of Neogene planktonicforaminifer and calcareous nannofossil zones. Gulf CoastAssoc. Geol. Soc. Trans. 19, 585.

, 1970. Coccolith age determinations Leg 3,Deep Sea Drilling Project. Initial Reports of the DeepSea Drilling Project, Volume III. Washington (U.S.Government Printing Office). 613.

Hay, W. W., Mohler, H., Roth, P. H., Schmidt, R. R. andBoudreaux, J. E., 1967. Calcareous nannoplanktonzonation of the Cenozoic of the Gulf Coast andCaribbean-Antillean area, and transoceanic correlation.Gulf Coast Assoc. Geol. Soc. Trans. 17,428.

Martini, E. and Bramlette, M. N., 1963. Calcareous nanno-plankton from the experimental Mohole drilling. /.Paleontology. 37,845.

Riedel, W. R., Bramlette, M. N. and Parker, F. L., 1963."Pliocene-Pleistocene" boundary in deep-sea sediments.Science. 140, 1238.

33.2. CALCAREOUS NANNOFOSSIL AGE DETERMINATIONS,DEEP SEA DRILLING PROJECT, LEG 13

Stefan Gartner, Jr., Rosenstiel School of Marine and Atmospheric Science,University of Miami, Miami, Florida

This paper contains age determinations made on a suiteof samples from the cores collected during Leg 13 of theDeep Sea Drilling Project. With the exception of Site 120 inthe eastern North Atlantic, all samples containing nanno-fossils are Neogene in age. The samples from Site 120 weredated approximately, based on meager literature available

for the Jurassic and lower Cretaceous calcareous nanno-fossils. Inconsistency in the results obtained by the severalworkers who have studied this interval, lack of rigorousnomenclature, and the absence of nannoconids in thesamples, make the ages assigned to Samples 13-120-2-1; 70cm and 13-120-7-1; 33-34 cm mere estimates.

822