26. nannofossil biostratigraphy, leg 22, …26. nannofossil biostratigraphy, leg 22, deep sea...

26. NANNOFOSSIL BIOSTRATIGRAPHY, LEG 22, DEEP SEA DRILLING PROJECT

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

INTRODUCTION

Calcareous nannofossils were recovered at every sitedrilled during Leg 22. Not all sites, however, yieldedequally good assemblages, and, at some sites only a smallfraction of the interval cored and drilled yielded calcareoussediments. In general, the most representative calcareousnannofossil successions were recovered at the shallowersites, particularly those along the crest of Ninetyeast Ridge(Sites 214, 216, and 217). Poorest recovery of calcareousnannofossils was from the deepest part of the Indian Ocean,in the Wharton Basin east of Ninetyeast Ridge (Sites 211,212, and 213). This is not surprising as the last three sitesare all well below 5000 meters, and one site (212) issituated well below 6000 meters. This same site did yieldcalcareous sediments over much of the interval cored, butthe section is by no means representative. In fact, this sitehas a most unusual history of carbonate deposition in thatall the calcareous sediments seem to have been transportedto this site by currents, and probably none were depositedas normal pelagic sediments from the water column above.One site west of Ninetyeast Ridge (215) also was more than5000 meters deep and only part of the section wascalcareous. Finally, the site drilled on the Bengal Fan (218)yielded calcareous material throughout the interval cored,but because of the large proportion of detrital constituents,the calcareous nannofossils and other pelagic constituentswere diluted to such an extent in some parts of the intervalthat they were only rarely encountered.

NANNOFOSSIL ZONATION

The calcareous nannofossil zonation used during Leg 22is indicated below. With the exception of the Discoasterasymmetricus Zone, all of the zones listed were readilyrecognized in the sediments recovered in the Indian Ocean.Recognition of the Discoaster asymmetricus Zone dependson the identification of Discoaster asymmetricus andCeratolithus tricorniculatus s.l. in an interval where bothspecies may be relatively rare, and hence the zone may goundetected in a preliminary examination. Despite this fact,it has not been excluded from any scheme presented here.Data for constructing the zonal succession and the zonalnames are drawn from all available sources. In choosingfrom among the various zonations, preference was given tozones which are readily recognized in oceanic as well as inhemipelagic sediments. Provincial species, especially thoserestricted to hemipelagic sediments, make poor zonalmarkers in oceanic deposits. Notorious among the latter arethe mid-Tertiary helicopontosphaeras, pentaliths, holo-coccoliths, Ericsonia subdisticha, and some Miocene astero-liths (e.g.,Discoaster kugleri).

The late Neogene zonation Emiliania huxleyi to Discoa-ster quinqueramus is essentially that proposed by Gartner,1969 (see also Gartner, 1973, for a detailed chronology).The remaining Tertiary zones are compiled chiefly fromBramlette and Wilcoxon (1967); Hay et al. (1967); Hay andMohler (1967); Gartner (1969; 1971); Martini and Worsley(1970); Martini (1970; 1971); Roth (1970); and Bukry(1971). Because many of these zones are used in a slightlymodified sense, a brief characterization is given below forall nannofossil zones used in this volume.

Emiliania huxleyi Zone

The interval of occurrence of Emiliania huxleyi: This zonespans somewhat less than 200,000 years.

Gephyrocapsa Zone

The interval from the last occurrence of Pseudoemilianialacunosa to the first occurrence of Emiliania huxleyi.

Pseudoemiliania lacunosa Zone

The interval from the last occurrence of Discoaster brou-weri to the last occurrence of Pseudoemiliania lacunosa.

Discoaster brouweri Zone

The interval from the last occurrence of Discoaster surculusto the last occurrence of Discoaster brouweri The top ofthis zone corresponds very closely to the Pliocene-Pleisto-cene boundary as commonly recognized in deep-sea sedi-ments.

Discoaster surculus Zone

The interval from the last occurrence of Reticulofenestrapseudoumbilica to the last occurrence of Discoastersurculus.

Reticulofenestra pseudoumbilica Zone

The interval from the last occurrence of nonbirefringentceratoliths (chiefly Ceratolithus tricorniculatus and Cerato-lithus primus) to the last occurrence of Reticulofenestrapseudoumbilica. The top of this zone may be difficult todetermine at times because Reticulofenestra pseudoumbil-ica becomes quite rare and may be represented by onlysmall specimens.

577

S. GARTNER

Discoaster asymmetricus Zone

The interval from the first occurrence of Discoasterasymmetricus to the last occurrence of nonbirefringentceratoliths. Discoaster asymmetricus as well as nonbirefrin-gent ceratoliths may be rare in this interval in some types ofpelagic sediment. Consequently, this zone may be difficultto recognize at times.

Discoaster mohleri Zone

The interval from the first occurrence of Discoaster mohlerito the first occurrence of Discoaster multiradiatus.

Heliolithus kleinpelli Zone

The interval from the first occurrence of Heliolithuskleinpelli to the first occurrence of Discoaster mohleri.

Fasciculithus tympaniformis Zone

The interval from the first occurrence of Fasciculithustympaniformis to the first occurrence of Heliolithus klein-pelli.

Cydococcolithina robusta Zone

The interval from the first occurrence of Cydococcolithinarobusta to the first occurrence of Fasciculithus tympanifor-mis. Ellipsolithus macellus and Chiasmolithus bidens firstoccur near the bottom of this zone, and the last-namedspecies enjoys by far the most cosmopolitan distribution ofthe three. Unfortunately, early specimens of this species arefrequently identified as Chiasmolithus danicus with thelight microscope.

Cruciplacolithus tenuis Zone

The interval from the first occurrence of Cruciplacolithustenuis to the first occurrence of Cydococcolithina robusta.In oceanic calcareous oozes the Tertiary record generallydoes not extend below this level, so that sediments of theCruciplacolithus tenuis zone are underlain by Upper Creta-ceous deposits.

Ceratolithus rugosus Zone

The interval from the first occurrence of Ceratolithusrugosus to the first occurrence of Discoaster asymmetricus.

Ceratolithus tricorniculatus Zone

The interval from the last occurrence of Discoaster quin-queramus to the first occurrence of Ceratolithus rugosus.The Miocene-Pliocene boundary falls within this zone.

Discoaster quinqueramus Zone

The interval from the first occurrence of nonbirefringentceratoliths (including but not limited to Ceratolithusprimus) to the last occurrence of Discoaster quinqueramus.

The base of this zone also corresponds closely to the lastoccurrence of Discoaster neohamatus.

Discoaster neohamatus Zone

The interval from the first occurrence of Discoasterneohamatus to the first occurrence of Ceratolithus tricor-niculatus. For practical purposes this is a total range zone asthe last occurrence of Discoaster neohamatus closely corre-sponds to the first occurrence of the genus Ceratolithus.

Discoaster hamatus Zone

The interval from the first occurrence of Discoasterhamatus to the first occurrence of Discoaster neohamatus.

Catinaster coalitus Zone

The interval from the first occurrence of Catinaster coalitusto the first occurrence of Discoaster hamatus.

Discoaster exilis Zone

The interval from the last occurrence of Sphenolithusheteromorphus to the first occurrence of Catinaster coali-tus. This characterization is a poor one because it relies onthe absence of two index species. Cyclicargolithus flo-ridanus and Cyclolithella nitescens both occur within thiszone but do not range to the very top of it. The Discoasterkugleri Zone of other authors corresponds to the top of thiszone, but as Discoaster kugleri is not a cosmopolitan speciesthe zone is not included.

Sphenolithus heteromorphus Zone

The interval from the last occurrence of Sphenolithusbelemnos to the last occurrence of Sphenolithus hetero-morphus. The Helicopontosphaera ampliaperta Zone ofother authors corresponds to the lower part of this zone. Itis not included here because the marker species, Helicopon-tosphaera ampliaperta, generally is not found in oceanic-type pelagic sediments.

Sphenolithus belemnos Zone

The interval of the total range of Sphenolithus belemnos.

Triquetrorhabdulus carinatus Zone

The interval from the first occurrence of Triquetrohabduluscarinatus to the first occurrence of Sphenolithus belemnos.The species Triquetrorhabdulus carinatus seemingly ishighly susceptible to heavy calcification, which makesidentification uncertain. Hence, identification of the zonealso may be difficult.

Sphenolithus ciperoensis Zone

The interval from the first occurrence of Sphenolithusciperoensis to the first occurrence of Triquetrorhabduluscarinatus.

578

NANNOFOSSIL BIOSTRATIGRAPHY

Sphenolithus distentus Zone

The interval from the first occurrence of Sphenolithusdistentus to the first occurrence of Sphenolithusciperoensis.

Sphenolithus predistentus Zone

The interval from the last occurrence of Cyclococcolithinaformosa to the first occurrence of Sphenolithus distentus.

Cyclococcolithina formosa Zone

The interval from the last occurrence of Discoaster bar-badiensis to the last occurrence of Cyclococcolithiniaformosa. The several zones designated for the lowerOligocene interval, all of which are here included in theCyclococcolithinia formosa Zone, are based on provincialspecie (e.g., Helicopontosphaera reticulata, Ericsonia sub-disticha, Cyclococcolithus margaritae) and are of little orno use in open ocean pelagic sediments.

Discoaster barbadiensis Zone

The interval from the last occurrence of Chiasmolithusgrandis to the last occurrence of Discoaster barbadiensis.

Chiasmolithus grandis Zone

The interval from the first occurrence of Reticulofenestraumbilica to the last occurrence of Chiasmolithus grandis.Although Reticulofenestra umbilica is a common, dis-tinctive, and cosmopolitan species, the base of this zonemay be difficult to determine at times on the basis of thisspecies because it evolved gradually from similar but smallerspecies. The separation, therefore, becomes subjective. Inoceanic sediments the first occurrence of Bramletteiusserraculoides closely corresponds to the base of this zone,but this form is not common in hemipelagic sediments.

Nannotetrina alata Zone

The interval from the first occurrence of Nannotetrina alata(=Chiphragmalithus quadratus = Chiphragmalithus alatus)to the first occurrence of Reticulofenestra umbilica.

Discoaster sublodoensis Zone

The interval from the first occurrence of Discoastersublodoensis to the first occurrence of Nannotetrina alata.

Discoaster lodoensis Zone

The interval from the last occurrence of Tribrachiatusorthostylus to the first occurrence of Discoaster sub-lodoensis.

Tribrachiabus orthostylus Zone

The interval from the last occurrence of Discoasterdiastypus to the last occurrence of Tribrachiatusorthostylus.

Discoaster diastypus Zone

The interval of the total range of Discoaster diastypus.

Discoaster multiradiatus Zone

The interval from the first occurrence of Discoastermultiradiatus to the first occurrence of Discoasterdiastypus.

Pre-Tertiary sediments recovered during Leg 22 areassignable to the uppermost four Upper Cretaceous nanno-fossil zones which are characterized as follows.

Nephrolithus frequens Zone

The interval from the first occurrence of Nephrolithusfrequens to the Cretaceous-Tertiary boundary, which ismarked by the disappearance of nearly all Upper Creta-ceous species.

Lithraphidites quadratus Zone

The interval from the first occurrence of Lithraphiditesquadratus to the first occurrence of Nephrolithus frequens.

Tetralithus nitidus trifidus Zone

The interval from the first occurrence of Tetralithus nitidustrifidus to the first occurrence of Lithraphidites quadratus.

Eiffellithus augustus Zone

The interval from the first occurrence of Broinsonia parcato the first occurrence of Tetralithus nitidus trifidus.

The nannofossil zonal succession in the Indian Ocean,and more specifically, in the equatorial region of theNinetyeast Ridge, is very similar to the nannofossil zonalsuccession found by Bukry (1972) for the North Atlanticsediment recovered on DSDP Leg 12. This seems puzzlingbecause the two areas in question, i.e., the northern NorthAtlantic and the Indian oceans, are separated as much fromone another as is possible. Moreover, one of the areas istropical and the other is cool temperate to subarctic. It istempting to smugly point to this similarity of nannofossilzonal successions as proof of the universality of nannofossilbiostratigraphy, but some of the similarities go beyondthat. This is especially true for some Late Cretaceous andearly Tertiary assemblages. The late Maastrichtian indexspecies Nephrolithus frequens is best known from northernEurope. Worsley and Martini (1970) suggest that thisspecies is a cold water form and, therefore, is absent in lowlatitude late Maastrichtian sediments. On Leg 22 Nephro-lithus frequens was recovered on sites very close to thepresent-day equator, although a Late Cretaceous recon-struction places these same sites at much higher latitudes inthe southern hemisphere. Thus, Nephrolithus frequens, likeseveral modern coccolithophores, probably had a bipolardistribution.

The early Tertiary species, Chiasmolithus danicus, repre-sents a similar case. This form has been reported fromseveral localities, but only specimens from northern Europe

579

S. GARTNER

and from the North Atlantic can be assigned to this speciesunequivocally. In lower Paleocene sediments of the Ninety-east Ridge this species is common, and again the earlyTertiary position of the Indian plate has to be invoked toaccount for the occurrence of this seemingly high latitudeform. A bipolar distribution of this species also seemsreasonable.

Thus, for the Late Cretaceous and early Tertiary thesimilarity of the zonal succession in the North Atlantic andIndian oceans is not at all unreasonable, especially if it iskept in mind that the Tethyan seaway connected the twooceans during Cretaceous and early Tertiary time.

RESULTS AND DISCUSSION

In Figures 1 through 8 are presented checklists of thecalcareous nannofossils recovered at each of the sites drilledduring Leg 22. These checklists have been compiled fromshipboard data and from subsequent examinations. Thelatter were directed primarily at determining the limits ofoccurrence of key index species, so that the biostratigraphicframework for each site could be as accurate as possible.The checklists are by no means comprehensive, althoughthey may be considered as representative of the nanno-fossils contained in a particular sample. In Figure 9 aresummarized the age assignments made on the basis ofcalcareous nannofossils of sediments recovered during Leg22. For additional discussion of the results, the reader isreferred also to the biostratigraphy section of each sitereport.

Four sites (211, 212, 213, and 215) were located belowthe present calcium carbonate compensation depth. Thecalcareous sediments recovered at these sites can beinterpreted to be either allochthonous in origin, i.e., theywere transported to their present location by currents orturbidity flows, or, that at certain times the sites wereabove the calcium carbonate compensation depth. For Site211 an allochthonous origin is suggested by possible currentbedding of the sediment. On the other hand, depositionbelow the lysocline is suggested by the considerablesolution of most nannofossils, though if the probable LateCretaceous high latitude location of this site is taken intoaccount, this considerable solution does not necessarilyrequire deposition at great depth. Moreover, the lowdiversity of the nannofossil assemblage at this site—10species in an interval that normally yields upward of 50species—can be explained, at least partially, by this samehigh latitude location, which is postulated in most LateCretaceous reconstructions of the Indian Ocean. Perhaps amost reasonable explanation for the calcareous nannofossilsrecovered at Site 211 is that they were probably depositedat less than abyssal depths in a high latitude sea and mayhave been redeposited by current action.

For Site 212 the calcareous sediments almost certainlyhave to be allochthonous. Two mechanisms for redeposi-tion are postulated; turbidity currents probably were themajor transporting agency during the last 12 million years(Cores 1 through 10). This is suggested by a general mixingof the sediment, so that the major proportion of the fossilsbecomes younger upward in the section, although there is aconstant and significant proportion of older fossils mixed

Sample

211-12-2, 123 cm211-12-2, 146 cm211-12-3,25 cm211-12, CC211-13-1, 50 cm211-13-1, 80 cm211-13-1, 100 cm ,211-13-1, 120 cm211-13-1, 140 cm211-13, CC211-14-1, 58 cm

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Figure 1. Checklist of calcareous nannofossils recovered atSite 211.

in, but with a notable lack of sorting of the sediment. Priorto that time, redeposition probably was affected chiefly bybottom currents which eroded the calcareous sedimentselsewhere and carried them in suspension as a nepheloidlayer. The short time intervals represented by the consider-able thicknesses of calcareous sediments of early middleMiocene, middle Eocene, and Late Cretaceous age: sortingof the sediments; and selective solution taken collectivelysuggest that all these sediments probably were depositedbelow the regional calcium carbonate compensation depthin a local pocket where for some peculiar reason thebottom waters were nearly saturated with calciumcarbonate.

Sites 213 and 215 are treated together because theirsedimentary history seems very similar even though theyare on opposite sides of the Ninetyeast Ridge. The upperMiocene to Recent interval is represented by siliceoussediments; the lower Eocene to upper Miocene interval bybarren zeolitic clays; and the lower Eocene to basementinterval is calcareous. At each site the oldest sedimentabove basement is Paleocene in age. Towards the top of thecalcareous interval, solution effects increase. It seemsreasonable that the calcareous sediments at both of thesesites were deposited above the calcium carbonate compen-sation depth, as there is no evidence of slumping orturbidity current deposition. Following the reasoning ofBerger (1972), a likely model is that when the crust at thesetwo sites was formed, it was at a much shallower depth inaccordance with the crustal elevation-sea-floor spreadingmodel of Menard (1969) and of Sclater, Anderson, and Bell(1971); and only after the crust had moved some distancefrom the spreading center, did it subside below the regionalcalcium carbonate compensation depth. If it is assumedthat both sites originated at the average ridge crest elevationof 2700 meters and that subsidence occurred at a rate of1000 meters during the first 10 m.y. and another 1000

580

Sample

212-1-1. top

212-1. CC

212-2-1. 25-26 cm

212-2-4. 47-48 cm

212-2-5. 105-106 cm

21 2-2. CC

21 2-3. CC

212^-1, 21-22 cm

21 2-4. CC

212-5-1.40-41 cm

21 2-5. CC

212-6. CC

21 2-7. CC

212-8-1, 12-13 cm

212-8-2, 3-4 cm

2 1 2-8-3. 5-6 cm

212-8. CC

212-9-1. 97-98 cm

212-9. CC

212-10-1. 23-24 cm

212-10-2. 10-11 cm

212-10-3.6-7 cm

212-10-4, 10-1 1 cm

212-10-5, 12-13 cm

212-10-6, 10-11 cm

212-10. CC

212-11-2, 3-4 cm

212-l l .CC

212-12-2. 1-2 cm

212-12.CC

212-13-2, 1-2 cm

212-13. CC

212-14-2.0-1 cm

212-14.CC

212-15-1. lop

212-15-1. 33-34 cm

212-18.CC

212-19-2. 6-8 cm

212-19.CC

212-20-1. 81-83 cm

212-20. CC

212-21-1.0-2 cm

212-21.CC

21 2-22-2. 0-2 cm

21 2-22. CC

212-23-2. 0-2 cm

21 2-23. CC

212-24. CC

21 2-25. CC

21 2-26. CC

21 2-27. CC

21 2-29. CC

212-31-6.0-1 cm

212-35. CC

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oo Figure 2. Checklist of calcareous nannofossils recovered at Site 212.

S. GARTNER

Sample

213-14-5, 3-4 cm213-14-5, 50-5 lcm213-14-5, 100-101 cm213-14-6, 10-11 cm213-14-6, 50-51 cm213-14-6, 100-101 cm213-14-6, 140-141 cm213-14. CC213-15-1, 120-121 cm213-15-3, 2-3 cm213-15-4, 25-26 cm213-15-4, 70-71 cm213-15-5, 9-10 cm213-15-6, 32-33 cm213-15. CC213-16-1, 89-90 cm213-16-2, 4-5 cm213-16-3, 25-26 cm213-16-4,18-19 cm213-16, CC213-17-1,120 cm

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ides

meg

asty

pus

XX

X

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psol

ithus

dis

tich

us

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psol

ithus

mac

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s

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X

X

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cicu

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s ty

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nifo

rmis

|

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X

Hel

iort

hus

dist

entu

s

X

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nolit

hus

anan

hopu

s

X

X

Sphe

nolit

hus

mor

iform

is

XXX

XX

X

X

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nolit

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ans

XXXXXXXX

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Tow

eius

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ticul

us

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X

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Figure 3. Checklist of calcareous nannofossils recovered at Site 213.

meters during the subsequent 26 m.y. (see Berger, 1972),the approximate depth of the calcium carbonate compensa-tion level at the time when calcareous sediments ceased toaccumulate at these sites can be roughly estimated. Basedon paleontological data, calcareous sediments accumulatedat Site 213 for about 8 m.y. after initial formation of thecrust and at Site 215 for about 11 m.y. Total sedimentthickness at the two sites is the same, and it can probablybe assumed, therefore, that the 300-meter difference indepth at the two sites reflects original irregularities of ridgeelevation when they were formed. Thus, Site 215, whichaccumulated calcareous sediments for about 3 m.y. longerthan Site 213 started out some 300 meters shallower thanthe latter site. If an average of 10 m.y. for the calcareoussediment accumulation period at the two sites (a mostconvenient figure, indeed) is assumed, then it follows thatcalcareous sediments ceased to accumulate when these sitesdropped to a depth of about 3700 meters. Or, putting itanother way, the regional calcium carbonate compensationdepth was at a depth of about 3700 meters about 40 m.y.ago.

It is noteworthy that lower latitude pelagic sediments ofthis same age are characterized by siliceous sediments andby chert, especially in the Atlantic Ocean, a feature lackingat Site 213 and developed weakly at Site 215. Although theabove two sites are now in tropical latitudes, a moresoutherly latitude is implied for these sites in mostreconstructions of the proto-Indian ocean.

Sites 214, 216, and 217 were all drilled along the crestof Ninetyeast Ridge. At all three of these sites presumably acomplete section was penetrated, although continuouscoring was done only at Site 214. A nearly completeTertiary zonal succession can be recognized at Site 214, andof the two zones not recognized, one, the mid-PlioceneDiscoaster asymmetricus Zone, frequently is difficult torecognize elsewhere in pelagic sections. Moreover, themissing zone falls between two cores, and it is entirelypossible that the interval containing this zone was lostduring coring. The second zone not recognized at Site 214is the mid-Oligocene Sphenolithus predistentus Zone. Inthis case the missing zone falls within a core, and itsabsence either represents a hiatus or inadequate develop-ment of the Sphenolithus lineage on which is based therecognition of this zone. At Site 216, and, to a lesserextent, Site 217, this zone is developed. Most of the zonesnot recognized at Sites 216 and 217 correspond to uncoredintervals or to intervals where recovery was poor.

At each of the above three sites shoaling can berecognized as basement is approached. It appears that at thetime of formation of the crust at these sites, the crest ofNinetyeast Ridge was at or near sea level. It is of interest,therefore, that members of the family Braarudosphaeradaeare sparce in the early Tertiary sediments at Site 214. Atthis site Paleocene and lower Eocene sediments weredeposited in what is interpreted to be a lagoonal orshelf-like environment. Elsewhere, as in California (Sullivan,

582

NANNOFOSSIL BIO STRATIGRAPHY

1964, 1965), sediments of this age and bathymetric rangecontain diverse assemblages of pentaliths, and the same istrue of lower, middle, and upper Eocene sediments else-where (Bouché, 1962; Levin and Joerger, 1967; Bramletteand Sullivan, 1961; Bybell and Gartner, 1972). It may besignificant that all of the lower Tertiary nannofloras withdiverse pentalith assemblages are from regions which had asubtropical to temperate climate, while all of the Ninety-east Ridge sites, including Site 214, probably originated atrelatively higher latitudes or were under the influence ofhigh latitude oceanic conditions.

For Sites 216 and 217, no clear ecological inferences canbe made from the oldest calcareous nannofossils abovebasement. It is unclear whether the low diversity recordedis due entirely to the scarcity of nannofossils in thesamples, or whether it also is attributable to shallow waterconditions or high latitude.

The nannofossils from Site 218 are precisely what mightbe expected in an open ocean area that receives a great dealof clastic sediment. The normal pelagic contribution isdiluted by the clastic sediments being transported to theocean floor by turbid flows and in suspension. Thus theabundance of nannofossils is related inversely to grain sizeand directly to carbonate content. In the case of Site 218,sufficient nannofossils were recovered to permit adequatebiostratigraphic determinations.

CRETACEOUS-TERTIARY BOUNDARY

At Sites 216 and 217 on Ninetyeast Ridge the Creta-ceous-Tertiary boundary was penetrated, and at Site 216relatively undisturbed sediment was recovered across thisboundary (Figure 10). The sediment above about 103 cm isuniform in texture, and color changes are gradational.Between 103 and 114 cm light buff to white chalkfragments, mottled and covered with green specks, float ina matrix of faintly and irregularly banded brownish graychalk. Below about 107 cm the white chalk fragments lackthe green specks, are irregular in size, and flattenedhorizontally. Below 130 cm the dark bands make up aneven smaller proportion, and the white chalk fragmentsbecome more massive. Nannofossil assemblages from aselected sample in the vicinity of the Cretaceous-Tertiaryboundary are as follows.

22-216-23-2; 108 cm; brownish-buff chalk

Chiasmolithus danicus, Cruciplacolithus helis, Micula sp.,Makalius reinhardti, Zygodiscus sigmoides, Cribrosphaerellasp., Markalius astroporus, numerous small and somemedium-sized placoliths variously assigned to the generaEricsonia, Biscutum, Marlkalius, Coccolithus. Predom-inantly Danian assemblage with some Maastrichtiancontaminants.

109 cm; dark layer in chalk

Cuiciplacolithus helis, Markalius reinhardti, Zygodiscussigmoides, Chiasmolithus danicus, Watznaueria barnesae,many small unidentifiable placolith as at 108 cm. Predomi-nantly Danian assemblage with some Maastrichtiancontaminants.

110 cm; white chalk fragment covered with fine greenlayer, in brownish-buff chalk

Micula sp., Watznaueria barnesae, Arkhangelskiellacymbiformia, Cylindralithus gallicus, Lithraphidites quad-ratus, Cretarhabdus sp., Prediscosphaera cretacea, muchunidentifiable debris. Maastrichtian assemblage.

117 cm; dark layer in brownish-buff chalk

Zygodiscus sigmoides, Chiasmolithus danicus, Micula sp.,Lithraphidites quadratus, Cruciplacolithus helis, Arkhan-gelskiella cymbiformis, Markalius astroporus, Markaliusreinhardti, Prediscosphaera cretacea, numerous small,unidentifiable placoliths. Predominantly Danian assemblagewith some Maastrichtian contaminants.

139 cm; white chalk in mottled interval

Micula sp., Watznaueria barnesae, Lithraphidites quad-ratus, Arkhangelskiella cymbiforms, Nephrolithus frequens,Cretarhabdus sp., much unidentifiable debris. Late Maas-trichtian assemblage.

The sediments above 103 cm consist largely of unidenti-fiable debris with predominantly Danian age nannofossilsadmixed with very few Maastrichtian specimens. Thematrix and bands below 103 cm have a similar compositionand age. The nannofossils indicate that the Danian agesediment at this site is not the oldest known Tertiaryalthough it is early Danian (M.N. Bramlette, personalcommunication). The white chalk fragments below 103 cmalso consist chiefly of unidentifiable debris and contain lateMaastrichtian nannofossil assemblages, including Nephro-lithus frequens and Cylindralithus gallicus. Thus, on theNinetyeast Ridge, as seemingly everywhere in the marinerealm, the youngest Cretaceous sediments are separated bya hiatus from the oldest Tertiary sediments.

Some novel and ingenious explanations have beenoffered for the widespread occurrence of this hiatus. In thisparticular instance the evidence seems to indicate thatduring the interval of nondeposition the chemistry of theocean water in this region was such as to favor lithificationof the late Maastrichtian sediments. It is obvious from thesedimentary structures in the core that the Maastrichtiansediments were relatively firm at the time when calcareoussediments again started to accumulate in early Danian time.Some solution of Maastrichtian chalk no doubt occurredduring the interval represented by the hiatus, but the age ofthe highest Maastrichtian sediment indicates that relativelylittle material was lost. Indeed, most of the hiatus repre-sents nondeposition rather than solution. According toWorsley's (1971) model of the terminal Cretaceous eventthe relatively short duration of noncarbonate deposition atSite 216 would require that the site be located at arelatively shallow depth. This seems to be borne out by thelate Maastrichtian age of the oldest pelagic sediments abovebasement recovered at this site and the fact thatimmediately above basement the sediment indicates alagoonal or shallow shelf environment.

583

Figure 4. (Continued).


REFERENCES

Berger, W. H., 1972. Deep sea carbonates: Dissolutionfacies and age-depth constancy: Nature, v. 236, p. 392-395.

Bouché, P. M., 1962. Nannofossiles calcaires du Lutetiandubassin de Paris: Rev. Micropaleontologie, v. 5, p. 75-103.

Bramlette, M. N. and Sullivan, F. R., 1961. Cocco-lithophorids and related nannoplankton of the earlyTertiary in California: Micropaleontology, v. 7, p.129-188.

Bramlette, M. N., and Wicoxon, J. A., 1967. Middle tertiarycalcareous nannoplankton of the Cipero section,Trinidad W. I.: Tulane Studies Geol., v. 5, p. 93-131.

Bukry, D., 1971. Cenozoic calcareous nannofossils from thePacific Ocean: San Diego Soc. Nat. Hist. Trans., v. 16, p.303-327.

, 1972. Further comments on coccolith stratig-raphy, Leg 12, Deep Sea Drilling Project. In Laughton,A. S., Berggren, W. A., et al., Initial Reports of the DeepSea Drüüng Project, Volume XII: Washington (U. S.Government Printing Office), p. 1071-1083.

Bybell, L. and Gartner, S., 1972. Provincialism amongmid-Eocene calcareous nannofossils: Micropaleontology,v. 18, p. 319-336.

Gartner, S., 1969. Correlation of Neogene planktonicforaminifer and calcareous nannofossil zones: Gulf CoastAssoc. Geol. Soc. Trans., v. 19, p. 585-599.

, 1971. Calcareous nannofossils from the JOIDESBlake Plateau cores, and revision of Paleogene nanno-fossil zonation: Tulane Studies Geol. PaleontoL, v. 8, p101-121.

, 1973. Absolute chronology of the Late Neogenecalcareous nannofossil succession in the EquatorialPacific: Geol. Soc. Am. Bull., v. 84, p. 2021-2034.

Hay, W. W. and Mohler, H. P., 1967. Calcareous nanno-plankton from early Tertiary rocks at Pont Labau,France, and Paleocene early Eocene correlations: J.PaleontoL, v. 41, p. 1505-1541.

Hay, W. W., Mohler, H. P., Roth, H. P., 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., v. 17, p. 428-480.

Levin, H. L. and Joerger, A. P., 1967. Calcareous nanno-plankton from the Tertiary of Alabama: Micropaleon-tology^. 13, p. 163-182.

Martini, E., 1970. Standard Paleogene calcareous nanno-plankton zonation: Nature, v. 226, p. 560-561.

, 1971. Standard Tertiary and Quaternary calcar-eous nannoplankton zonation: Plank. Conf., 2nd, Rome,1970, Proc, p. 739-785.

Martini, E. and Worsley, T. T., 1970. Standard Neogenecalcareous nannoplankton zonation: Nature, v. 225, p.289-290.

Menard, H. W., 1969. Elevation and subsidence of oceaniccrust: Earth Planet. Sci. Lett., v. 6, p. 275-284.

Roth, P. H., 1970. Oligocene calcareous nannoplanktonbiostratigraphy: Ecolog. Geol. Helv., v. 63, p. 799-881.

Sclater, J. G., Anderson, R. N., and Bell, M. L., 1971. Theelevation of ridges and the evolution of the CentralEastern Pacific: J. Geophys. Res., v. 76, p. 7888.

Sullivan, F. R., 1964. Lower Tertiary nannoplankton fromthe California Coast Ranges-I Paleocene: Calif. Univ.Pubs. Geol. Sci., v. 53, p. 163-227.

, 1965. Lower Tertiary nannoplankton from theCalifornia Coast Ranges—II Eocene: Calif. Univ. Pubs.Geol. Sci., v. 53, p. 1-75.

Worsley, T. R., 1971. The terminal Cretaceous event:Nature, v. 230, p. 318-320.

Worsley, T. and Martini, E., 1970. Late Maastrichtiannannoplankton provinces: Nature, v. 225, p. 1242-1243.

587

S. GARTNER

Sample

215-9-3, 130-131 cm215, CC215-10-1, 104-105 cm215-10-2, 30-33 cm215-10-3, 42-43 cm215-10-3, 105-106 cm215-10, CC215-11-1, 30-31 cm215-11-2, 4-5 cm215-11-2, 80-81 cm215-11-3, 2-3 cm215-11-3, 89-90 cm215-11, CC215-12-1, 19-20 cm215-12, CC215-13-2, 4-5 cm215-13-2, 97-98 cm215-13-3, 90-91 cm215-13, CC215-14-1, 12-13 cm215-14-4, 2-3 cm215-14-4, 91-92 cm215-14-5, 2-3 cm215-14-5, 90-91 cm215-14, CC215-15-1, 112-113 cm215-15-4, 20-21 cm215-15, CC215-16-1, 99-100 cm215-16-4, 2-3 cm215-16-4, 90-91 cm215-16, CC215-17-1, 90 cm215-17-1,106 cm215-17-1, 110 cm215-17, CC

Chi

asm

olith

us b

iden

s

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

XX

X

X

X

X

X

X

X

X

X

X

Chi

asm

olith

us

calif

orni

cus

X

X

X

X

X

X

X

Chi

asm

olith

us c

onsu

etus

X

X

X

X

X

X

X

X

X

X

X

X

Chi

asm

olith

us e

ogra

ndis

X

X

X

X

X

X

X

X

Chi

asm

olith

us g

rand

is

X

X

X

Cru

cipl

acol

ithus

ten

uis

X

X

X

X

X

X

X

X

X

X

Cyc

loco

ccol

ithin

a ro

bust

a

X

X

X

X

X

X

X

X

X

X

X

X

Dis

coas

ter

oran

eus

X

Dis

coas

ter

dias

typu

sX

X

X

X

X

X

X

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coas

ter

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icul

aris

X

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X

X

X

X

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s

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coas

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ter

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s

X

X

X

X

X

X

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X

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coas

ter

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tus

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X

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coas

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ides

kue

pper

i

X

X

X

Dis

coas

tero

ides

meg

asty

pus

X

X

X

X

X

X

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ithus

dis

tichu

s

X

X

X

X

X

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psol

ithus

mac

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s

X

X

X

X

X

X

X

Fas

cicu

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s m

itreu

s

X

X

X

X

Fas

cicu

lithu

s ty

mpa

nifo

rmis

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

Hel

iolit

hus

klei

npel

li

X

X

X

X

X

X

X

X

X

Hel

iolit

hus

ried

eli

X

X

X

X

X

X

X

Hel

iolit

hus

conc

innu

s

X

Hel

iolit

hus

dist

entu

s

X

Loph

odol

ithus

na

scen

s

X

X

Mar

kaliu

s as

trop

orus

X

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nolit

hus

anar

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us

X

X

X

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nolit

hus

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ans

X

X

X

X

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eius

bis

ulcu

s

X

X

X

X

X

X

X

X

X

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cra

ticul

us

X

X

X

X

X

X

X

X

X

X

X

X

X

X

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s

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

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X

X

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rach

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s

X

X

X

X

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us s

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oide

s

X

X

X

X

X

X

X

X

X

X

X

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X

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X

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X

X

X

X

X

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habl

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bi

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tus

X


588



589

S. GARTNER


590



591

S. GARTNER


592



593

S. GARTNER


594



595

Age m. y. Nannofossil Zone

Pleistocene

Miocene

Oligocene

Eocene

Paleocene

g Maastrichtian

8u

U Campanian3

^ ^ ^ _ Emiliania luixleyi Zone

"Xs^^^^-v^ Gepliyrocapsa oceanica Zone

- 5 ^ Λ \ Λ \ \ \ ^ Pseudoemiliania lacunosa Zone

VVvVxV Discoaster brouweri Zone

\ \ \ \ \. Discoaster surculus Zone

—\ \ \ \ \ Reticulofenestra pseudoumbilica Zone

\ \ \ \ Discoaster asyminetricus Zone

\ \ \ Ceratolitluts rugosus Zone

\ \ Ceratolithus triconüculatus Zone

\ Discoaster quinqueramus Zone

—20- Discoaster neohamatus Zone

Discoaster hamatus Zone

\ Catinaster coalitus Zone

\ Discoaster e.xilis Zone

\ Splienolithus heteromorplius Zone

\ Splienolithus belenmos Zone

\ Triquetrorliabdiilus rarinatus Zone

Splienolithus ciperoensis Zone

— 35- Splienolithus distentus Zone

Splienolithus predistentus Zone

"** • - ^ ^ Cyclococcolithina fonnosa Zone

Discoaster barbadiensis Zone

^^~ Chiasmolithus grandis Zone

— 45—^^ Nannotetrina alata Zone

Discoaster sublodoensis Zone

' Discoaster lodoensis Zone

Tribrachiatus orthostylus Zone

Discoaster diastypus Zone

Discoaster multiradiatus Zone

Discoaster mohleri Zone

Heliolithus kleinpelli Zone

-60— Fasciculithus tympaniformis Zone

Cvclococcolithina robusta Zone

Cruciplacolithus helis Zone

Nephrolithus frequens Zone

Lithraphidites quadratus ZoneT I T t V,U VVJ 'CA 7

Eiffellithus augustus Zone

211

12-2 to 12, CC

13-1 to 14-2

212

1-1

to

10-1

10-2 to 15-1

18-2 to 27, CC

29-CCto35,CC

213

14-5 to 14-6

14-6 to 15, CC16-1 to 16. CC

17-1

214

1-1 to 1-2

1-3 to 1-5

1-6 to 3-2

3-3 to 4-1

4-2 to 6-3

64 to8.CC

9-1 to9.CC

10-1 to 10-5

10-6 to 13-3

13-5 to 17-1

17-2 to 17-6

17-CC to 18.CC

19-1 to 20, CC

21-1 to 22-1

22-2 to 23-2

23-2 to 24-1

24-1 to 25, CC

26-1 to 26-6

26-CC to 27-6

27-CC to 28, CC

29-2 to 31-4

31-5 to 32. CC

33-1 to 33, CC

34-1 to 35-4

35. CC

to

36-2

36-4

37-1

37-CC to 41, CC

215

9-3 to9,CC

10-1 to 11-2

11-3 to 13-2

13-3 to 14-4

14-5 to 17-1

17-1 to 17, CC

216

1-1 to 1-3

14 lo 1-6

ICC

2-1 to 24

2-5 to 2, CC

3-1 to3,CC

4-1

4-2 to 4, CC

5-1

5-2 to

8.CC

9-1 to 10, CC

1 1-1 to 14. CC

15-1

15-2 to 15-3

15-CC to 17-1

17-2 to 18-1

19-CC to 20-3

20-CC to 21, CC

22-1

to

23-2

23-3 to 35,CC

2I6A

1-CC to 2,CC

3,CC

4,CC

5.CC

6,CC

217

1-1

1-2 lo 1-3

14 to l.CC

2-1 to 2.CC

3-1 to 3.CC

4-1 to 4, CC

5-1

to

64

6-5 to 6-6

6,CC

7-1 to 8-1

8-2 to 9-1

9-2 to

9-5

9-6

0-1 to 10, CC

12-1

12-CC to 14, CC

15-1

15-CC to 16-6

16,CCto

24, CC

25-1 to 28-6

29-1 to 36

217A

13-1 to 14. CC

218

1-1 to l.CC

2-1 to 4, CC

5-CC to 8, CC

11, CC

12-CC to 15.CC

16-CC to 23, CC

25, CC

26, CC

Figure 9. Summary correlation chart based on calcareous nannofossils of sites drilled on Leg 22, DSDP.


i

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I

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Figure 10. Core photograph across Cretaceous-Tertiary Boun-dary at Site 216, Sample 32-2, 61-150 cm.

597

S. GARTNER

APPENDIX INannofossil species identified in sediment recovered

during Leg 22 (listed in Alphabetical order).

Ahmullerella octoradiataArkhangelskiella cymbiformis

Biantholithus sparsusBiscutum sp.Braarudosphaera bigelowiBramletteius serraculoidesBroinsonia parca

Cambylosphaera delaCatinaster calyculusCatinaster coalitusCeratolithus amplificu sCeratolithus cristatusCeratolithus primusCeratolithus rugosusCeratolithus tricorniculatusChiasmolithus altusChiasmolithus bidensChiasmolithus californicusChiasmolithus consuetusChiasmolithus danicusChiasmolithus eograndisChiasmolithus expansusChiasmolithus gigasChiasmolithus grandisChiasmolithus oamaruensisChiasmolithus solitusChiasmolithus titusChiastozygus cuneatusChiphragmalithus acanthodesCoccolithus miopelagicusCoccolithus pelagicusCretarhabdus conicusCretarhabdus crenulatusCretarhabdus decorusCribrosphaerella ehrenbergiCruciplacolithus staurionCruciplacolithus tenuisCyclicargolithus floridanusCyclicargolithus mansmontiumCyclicargolithus reticulatusCyclococcolithina formosaCyclococcolithina gammationCyclococcolithina leptoporaCyclococcolithina macintyreiCyclococcolithina robustaCyclolithella nitescensCylindralithus gallicusCylindralithus serratus

Dictiococcites abisectusDiscoaster araneusDiscoaster asymmetricusDiscoaster barbadiensisDiscoaster bellusDiscoaster berggreniDiscoaster binodosusDiscoaster brouweriDiscoaster calculosusDiscoaster challengeriDiscoaster deflandreiDiscoaster diastypusDiscoaster druggiDiscoaster exilisDiscoaster hamatusDiscoaster lenticularisDiscoaster lodoensisDiscoaster loeblichiDiscoaster mirusDiscoaster mohleriDiscoaster moorei

Discoaster multiradiatusDiscoaster neohamatusDiscoaster neorectusDiscoaster ornatusDiscoaster pentaradiatusDiscoaster quinqueramusDiscoaster saipanensisDiscoaster sublodoensisDiscoaster surculusDiscoaster tamalisDiscoaster taniDiscoaster variabilis decorusDiscoaster variabilis pansusDiscoasteroides kuepperiDiscoasteroides megastypusDiscolithina japonica

Eiffellithus augustusEiffellithus turriseiffeliEllipsolithus distichusEllipsolithus macellusEmiliania huxleyi

Fasciculithus MiliFasciculithus mitreusFasciculithus tympaniformis

Gephyrocapsa apertaGephyrocapsa caribbeanicaGephyrocapsa oceanica

Hayella situliformisHelicopontosphaera bramletteiHelicopontosphaera compactaHelicopontosphaera granulataHelicopontosphaera heezeniHelicopontosphaera kamptneriHelicopontosphaera rectaHelicopontosphaera wallichiHeliolithus kleinpelliHeliolithus riedeliHeliorthus concinnusHeliorthus distentusHeliorthus fallax

Isthmolithus recurvus

Kamptnerius magnificus

Leptodiscus larvalisLithraphidites carniolensisLithraphidites quadratusLophodolithus nescensLucianorhabdus cayeuxi

Markalius astroporusMicrohabdulus decoratusMicula decussata

Nannotetrina alataNephrolithus frequens

Oolithotus antillarumOrthorhabdus serratus

Peritrachelina sp.Prediscosphaera cretaceaPrediscosphaera spinosaPseudoemiliania lacunosa

Reticulofenestra hillaeR eticu lofenestra pseudou mb ilicaReticulofenestra samoduroviReticulofenestra scissuraReticulofenestra umbilicaRhabdolithina regularisRhabdolithina splendensRhabdosphaera claviger

Scyphosphaera amphoraSphenolithus abies

598


Sphenolithus anarrhopus Tetralithus quadratusSphenolithus belemnos Thoracosphaera oblongaSphenolithus capricornutus Toweis bisulcusSphenolithus ciperoensis Toweius craticulusSphenolithus distentus Toweius eminensSphenolithus furcatolithoides Tribrachiatus orthostylusSphenolithus heteromorphus Triquetrorhabdulus carinatusSphenolithus moriformis Triquetrorhabdulus milowiSphenolithus obtusus Triquetrorhabdulus rugosusSphenolithus pacificusSphenolithus predistentus Umbilicosphaera mirabilisSphenolithus pseudoradiansSphenolithus radians Watznaueria barnesaeSphenolithus spiniger

Zygodiscus elegansTetralithus aculeus Zygodiscus sigmoidesTetralithus mums Zygodiscus spiralisTetralithus nitidus nitidus Zygrhablithus bijugatusTetralithus nitidus trifidus Zygrhablithus bijugatus crassus

599

26. nannofossil biostratigraphy, leg 22, …26. nannofossil biostratigraphy, leg 22, deep sea...

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