47. SYNTHESIS OF THE LEG 27 BIOSTRATIGRAPHY AND PALEONTOLOGY

47. SYNTHESIS OF THE LEG 27 BIOSTRATIGRAPHY AND PALEONTOLOGY

H. M. Bolli, Geology Department, Swiss Federal Institute of Technology,Zurich, Switzerland

INTRODUCTIONOf the five sites drilled, four (259, 260, 261, and 263)

are situated in deep basins with a much-reduced andstratigraphically incomplete Cenozoic section, analmost nonexistent Upper Cretaceous section, andabout 120 meters to over 600 meters of LowerCretaceous sediments overlying basalt basement. At Site261 the sediments immediately above basement aredated on nannoplankton as Upper Jurassic. Basalt wasreached at three of the four abyssal plain sites, but atSite 263 drilling was terminated for technical reasonsimmediately above basement. Site 262, drilled inrelatively shallow water in the western Timor Trough,penetrated a thick plankton-rich Holocene toPleistocene section and bottomed in shallow-watercalcarenite of Pliocene age.

Figures 1-5 show for each site the distribution andfrequency of the investigated faunal/floral groups andthe ages based on them.

CENOZOICFaunal interpretations and age assignments of the

much-reduced and stratigraphically incompleteCenozoic, ranging from about 70 meters to a maximumof about 170 meters at Sites 259, 260, 261, and 263,posed no particular problems. Detailed faunal studieswere not carried out in the sediments of these sites,which largely consist of turbidites. Except for thePleistocene, the faunas/floras were found to beirregularly distributed, mostly fairly scarce, poor inpreservation and, as a result of reworking andredeposition, often heterogeneous in their composition.At these sites the Quaternary is restricted to the top oneor two cores. At Site 263 the Quaternary is about 100meters thick but only three cores were taken in thisinterval. Notable is an unusual lower Paleoceneplanktonic foraminiferal fauna, consisting of smallglobigerinids of Globigerina eugubina Zone aspect, andof little known, comparatively large quadriserialHeterohelicidae, recovered from Core 4 at Site 263, aninterval in which frequent reworked Cretaceouselements also occur.

The only Paleogene sequence of significant thicknessoccurs at Site 259, where all the lower Eocene and theuppermost Paleocene nannoplankton zones wererecorded in Cores 4-7, with the ages also beingconfirmed by foraminifera.

The only Pliocene-Quaternary sequence studiedpaleontologically in more detail is that of Site 262situated in the Timor Trough. Of the 442 meters drilledand continuously cored, the upper 337.5 meters arePleistocene-Holocene based on planktonic foraminifera,the lower 100 meters, Pliocene. The sequence, except for

the bottom part in which rapid shallowing takes place, isrich in planktonic organisms. Euxinic bottom con-ditions for the Holocene and most of the Pleistocene areindicated by the very rich plankton and the virtualabsence of benthos, the sediment character, and the highcontent of methane in some parts of the section. Thesefeatures compare with those existing in the CariacoTrough, Site 147 of Leg 15, off the north coast ofVenezuela, where euxinic bottom conditions alsoprevail.

The plankton-rich Site 262 Holocene-Pliocene sectionwith the high average sedimentation rate of approx-imately 15-19 cm/1000 yr, was ideal for investigations ofevolutionary trends in planktonic foraminifera. Trendswere investigated in particular for the Globorotaliacrassaform is-tosaensis-truncatulinoides groups ofplanktonic foraminifera, taxa widely used as indexforms in Pliocene-Quaternary biostratigraphy. Thepaper on this subject by Rögl (this volume) is adocumentation of Pliocene/Pleistocene planktonicforaminiferal evolutionary trends and their applicationto biostratigraphy, likely to be of use over wide areaswithin the subtropical/tropical belt. Notable also is thefact that the subdivision of the Quaternary as proposedfor the Caribbean by Bolli and Premoli Silva (1973)could be applied to Site 263, and thus become of morethan only local significance.

Quaternary diatoms at Site 262 were also investigatedin some detail. Like the Radiolaria, they make their firstappearance within the lower part of the Pleistocene(about 250 m below sea floor), indicating a majorecological event at this level, shown also by changes inthe calcareous plankton association. Based on fre-quencies, and changes in the association of taxa, Jouseand Kazarina (this volume) distinguish five zones.Those most extended and rich in diatoms are an upperPleistocene zone (Zone I, Cores 1-11), with anassociation comparable to the Recent Indian Oceanwarm-water diatom flora, and a middle Pleistocene zone(Zone II, Cores 13-25), with an older flora indicatingsomewhat colder water conditions.

No generally accepted agreement exists on where toplace the Pliocene/Pleistocene boundary based onplanktonic microorganisms. A number of authors useGloborotalia truncatulinoides truncatulinoides as an in-dex. Others base it on the first evolutionary appearanceof this taxon at approximately 1.8 m.y. Others prefer tohave it somewhat higher, at a level where the percentageof G. truncatulinoides tosaensis and G. truncatulinoidestruncatulinoides reach 50% each.

Based on calcareous nannoplankton, thePliocene/Pleistocene limit is determined by someauthors to be where Discoaster abundance including D.brouweri decreases markedly at about 2.5 m.y. Ac-

993

H. M. BOLLI

Frequency of specimens:

• abundant; O common; * frequent; X rare; — absent;

blank: not investigated.

Depth

(tn)

O.Q- 8,0

8.0-17.5

17.5-27.0

27.0-36.5

36.5-46.0

46.0-55.5

55.5-65.0

65.0- 74.5

74.5- 84.0

84.0- 93.5

93.5-103.0

103.0-112.5

112.5-,122.0

122.0-131.5

131.5-141.0

141.0-150.5

150.5-160.0

160.0-159.5

169.5-179.0

179.0-188.5

188.5-198.0

198.0-207.5

207.5-217.0

217.0-226.5

226.5-236.0

236.0-245.5

245.5-255.0

255.0-264.5

264.5-274.0

274.0-283.5

283.5-293.0

293.0-302.5

302.5-304.3

Core

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

Foraminifera

Bent

Aren.

-

X

X

X

X

X

-

-

-

X

X

X

o

**X

X

X

X

X

X

X

X

X

X

X

•k

•k

*

ionic

Calc.

X

*

*

*

*

-

-

-

X

X

X

o*

*-------------

---

Plankt.

•

-

X

*

*

*

-

-

-

X

O

O

•

O

oo-------------

---

Quaternary

L. Eocene

Upper

Paleocene

E,_ s_

5 oTO U_

•O u

o

&

ε

_ o

!£ «j

< : • ^

Nannoplankton

•

-

•

O

O

oo--

n••

•ooX

X

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Quaternary

L. Eocene

Upper

Paleocene

Middle

Albian

Radioiaria

X

X

X

O

O

X

X

X

X

X

O

X

X

O

X

X

X

Quaternary

3O

<uIQJß<US-o

Dinoflagellates

-

-

-

-

-

-

•

O•

•

•

•

•

•

•

O

•

X

OX

Upper

Aptian

LowerAptian

Pollen/Spores

1O

-P

2

a>a.

cit)

§o+J

(O

Q.

§o<u

Calcisphae-rulidae

-

-

O

•

O

X

O

•

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Ostracods

-

-

X

O

X

X

X

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

ICO

e-»

o•pcrα

<

Molluscs

-

-

-

X

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Albian

FishDebris

X

X

*

*

X

X

X

X

X

-

X

X

*

-

-

X

X

-

-

X

X

X

X

-

X

-

-

-

-

Figure 1. Distribution, age, and frequency of investigated fossils, Site 259.

cording to those authors Discoaster does not becomeextinct at this level, but continues in a much reduced andirregular way because of cooling. Shortly after the firstappearance of G. truncatulinoides truncatulinoides theretakes place again a slight and short lived increase, afterwhich the genus becomes finally extinct.

At Site 262, G. truncatulinoides truncatulinoides firstappear in Core 36, CC at 337.5 meters, the sharpdecrease in Discoaster peak with D. brouweri falls withinCore 44 at 407 meters, with a weak reappearance ofDiscoaster in Cores 33 and 32. The position of thePliocene/Pleistocene boundary at Site 262 thus variesconsiderably, depending on which of the above criteriais applied. Based on nannoplankton, it lies within Core44 and on G. truncatulinoides truncatulinoides at the baseof Core 36, a difference of some 70 meters.

MESOZOIC

With few exceptions, the faunas and floras of theMesozoic are poor, monotonous, and often of inferiorpreservation. Over long intervals it was therefore dif-ficult to arrive, on paleontological grounds, atreasonably accurate and reliable age assignments. Inview of the importance of obtaining accurate ages of theMesozoic sections, in particular their basalt partsoverlying basaltic basement, special efforts were un-dertaken to arrive at biostratigraphic results. Allmicrofaunas and floras thought to offer information onage and ecology were therefore investigated. Theyinclude planktonic and benthonic foraminifera,calcareous nannoplankton, radiolaria, dinoflagellates,pollen/spores, ostracods, and molluscs. Fish debris was

994

SYNTHESIS, BIOSTRATIGRAPHY AND PALEONTOLOGY

Depth(m)

0.0- 8.0

44.0- 53.5

91.5-101.0

129.5-139.0

158.0-167.5

177.0-186.5

196.0-205.5

215.0-224.5

234.0-243.5

253.5-253.0

253.0-262.5

262.5-272.0

272.0-281.5

281.5-291.0

291.0-300.5

300.5-310.0

310.0-319.5

319.5-322.5

Core

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

Foraminifera

Benthonic

Aren.

X

X

X

-

X

oX

X

*

*

X

X

X

X

X

X

X

Calc.

X

X

X

X

X

-

-

-

ooo-------

Plankt.

O

•

X

•

*

-

-

O

•

•

-

-

-

-

-

-

-

Quaternary

L. Pliocene

not olderM. Mioc.not olderM. Olig.not youngerMaestr.noù olderConiacian

J3 *

=D ~*"*

'. 01

Σ ;5

-Q i—

•― a.

Lower

Albian

to

? Upper

Aptian

Nannoplankton

y

o

oo----o

ooooooX

•

•

Quaternary

not older

L. Pliocene

M.-U. Mioc.

not olderM. Oligocene

Middle

Albian


% abundant; O common; * frequent; x


Radiolaria

X

X

-

X

X

-

•

*

*

O

•

•

X

•k

•

•

•

Quaternary

oα><j

4J

01s-o

Dinoflagellates

Pollen/

Spores

Calcisphae-

rulidae

-

*

-

-

-

X

X

X

X

-

X

-

-

-

'•àrt; — absent

Ostracods

-

-

-

-

*

O

X

-

-

-

-

-

-

-

° J

Molluscs

-

-

-

*

*

-

-

-

-

-

-

-

-

Albian

FishDebris

-

•k

O

•

X

X

X

X

-

X

X

-

X

-

-

o


also noted and indicated for future reference, but wasnot investigated here. Arenaceous foraminifera arepresent in almost all examined Mesozoic samples butare sparse in number and composed mostly of primitivegenera.

Except at Site 263, Radiolaria are frequent in mostLower Cretaceous cores. Because of their poor preserva-tion and the limited information available on theirdistribution in the Lower Cretaceous, Radiolaria didnot offer much stratigraphic information for the InitialReport. The Leg 27 Radiolaria are described andfigured by Renz (this volume).

Other microfossils, like calcareous foraminifera,nannoplankton, palynomorphs, ostracods, and in par-ticular molluscs, were found restricted often to onlyshort intervals. The sporadic appearance of many of themore valuable biostratigraphic fossils such asplanktonic foraminifera, nannoplankton, anddiagnostic calcareous benthonic foraminifera made ac-curate age assignments of the sediments often difficultor tentative, particularly for those sediments im-mediately overlying basement.

Upper Cretaceous sediments are completely absent atSites 259 and 263, and only occur in much reducedthickness at Site 260, Core 6; and Site 261, Cores 5-8.These sediments consist of zeolite clays thought to havebeen laid down below the lysocline. They contain anarenaceous foraminiferal fauna of unusual appearance,the tests of which are very small, the walls thin, finegrained or almost homogeneous, and the surfacesmooth. Faunas like this have previously been recoveredonly in some deep-water clays of Leg 20 in the Pacific,where they occur with Upper Cretaceous Radiolaria.

Based on its distribution at Site 261, this arenaceousfauna which is diverse in genera and species, many of

them new, can be subdivided there into an upper and alower assemblage. The upper assemblage alone is pre-sent in Core 6 of Site 260 and also in Leg 20 of thePacific.

The Site 260 arenaceous fauna is accompanied byplanktonic foraminifera of ?Albian, Cenomanian, andnot older than Coniacian age. Because of itsheterogeneous composition, it is considered reworked orredeposited, carried down from higher levels, and buriedagain below the lysocline on the clays, together with theautochthonous arenaceous forms.

Once their ages and ranges are better known, thesedeep-water assemblages of arenaceous foraminifera mayeventually become useful for dating and correlatingclays deposited below the lysocline and void of otherindex fossils.

Planktonic foraminifera are fairly frequent and of usefor dating Lower Cretaceous sediments only in twoshort intervals, Cores 11-17 at Site 259 and Cores 9-11 atSite 260. They are described and figured byKrasheninnikov (this volume, Chapter 33), who datesthose at Site 259 as Albian and those at Site 260 as?upper Albian. Benthonic calcareous and arenaceousforaminifera are also frequent in these intervals. Exceptfor Cores 30-32 at Site 259, where arenaceousforaminifera are frequent, and Cores 30-33 at Site 261and Cores 17-29 at Site 263, where calcareous andarenaceous forms are frequent to common, the otherLower Cretaceous sediments drilled only contain poor,mainly primitive arenaceous foraminifera.

The benthonic foraminiferal assemblages, inparticular the calcareous assemblages, were found usefulfor dating the sediments and interpreting the paleo-environment. The Albian-Aptian benthonicforaminifera at Sites 259, 260, and 263 described and

995

H. M. BOLLI


• abundant; O common; * frequent; X rare; — absent;


Depth(m)

0.0- 9.5

9.5- 19.0

47.5- 57.0

95.0-104.5

161.5-171.0

171.0-180.5

180.5-190.0

190.0-199.5

199.5-209.0

209.0-218.5

218.5-228.0

228.0-237.5

237.5-247.0

247.0-256.5

256.5-266.0

266.0-275.5

275.5-285.0

285.0-294.5

304.0-313.5

313.5-323.0

332.5-342.0

342.0-351.5

361.0-370.5

180.0-389.5

399.0-408.5

418.0-427.5

437.0-446.5

446.5-456.0

465.5-475.0

484.5-494.0

503.5-513.0

522.5-532.0

532.0-532.2

Core

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

Foraminifera

Benthonic

Aren.

-

-

-

-

•k

•k

•k

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

•k

•k

ooo

Calc.

X

X

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

X

ooo

Plankt.

-

•

•

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

—

-

-

-

-

-

-

-

L. Plio. or y

U. Mio. or y.

U. Cret.probablycomacianor younger

Valangi-nian

L. Cret./

U. Jurassic

Nannoplankton

X

-

•

•

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

X

-

-

-

-

X

-

X

•

O

•

•

•

•

Holocene

Pliocene

L. Mio. or y

Hauter./Val.

Valangi-nian

Berias.Val. or

Tith./Kim.

U. Oxford.

Radiolaria

•

•

-

-

-

-

-

•

•

oX

•

O

•k

•

•

O

O

o•k

•

•

X

X

X

O*X

O

OX

-

-

Quaternary

Conia-ciantoAlbian

o01

2s_o

Dinoflagellates

-

-

-

•

•

•

4

4

4

4

4

»

»

»

»

»

L. AlbianorU. Aptian

Aptian

?Kim./Tith.

Pollen/Spores

X

X

X

X

L. Cret.

L. Cret.

-

Calcisphae-rulidae

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

O

•

•

Ostracods

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

X ? Jur.

Molluscs

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

O

•

•

FishDebris

-

X

X

-

•

•

oO

O

-

-

-

X

-

-

-

-

-

-

-

X

-

X

-

-

-

-

-

O

O

*

-

-


figured by Scheibnerova (this volume) allow for closecomparison with known Australian faunas, in particularfrom the Great Artesian Basin and the Canning Basin.Conclusions on age and ecology were drawn largelyfrom such correlations.

The benthonic calcareous multichambered are-naceous foraminifera of the Lower Cretaceous/UpperJurassic at Site 261, Cores 28-33, are described, andfigured by Kutznetsova (this volume). Her conclusionsare that no real index forms are present which wouldallow for reliable stratigraphic dating, though somespecies from the deeper cores are indicative for UpperJurassic, and some from the higher cores are knownfrom the Lower Cretaceous Valanginian.

Bartenstein (this volume) investigated the primitivearenaceous foraminifera only, that is the one- and two-chambered forms, at Site 261, Cores 29-33 and also atSite 259, Core 32. These taxa allow for no age

determination, but are useful as ecological indicators.Calcareous nannoplankton is also abundant in Cores

11-17 at Site 259 and in Cores 9-11 at Site 260, where italso continues to be frequent until the bottom of Core18. Nannoplankton is virtually absent at Site 261, Cores5-27, dated by other fossil evidence as Albian-Aptian,but becomes abundant in the basal part of this site, inCores 28-33, where it indicates a sequence ranging fromupper Oxfordian to Hauterivian/Valanginian.

The distribution pattern of nannoplankton is variablein the Lower Cretaceous at Site 263. It is common inCores 5-7 and 22-29, scarce in the interval in betweenCores 8-21. The interval Cores 5-27 is dated upperAlbian, based on Eiffellithus turriseiffeli, a generallyaccepted index form common to rare in Cores 22-27.The calcareous nannoplankton is described and figuredand the ages and ranges discussed by Proto Decima (thisvolume).

996


997


©abundant; Ocommon; ^frequent; x rare; —absent;


„ ForaminiferaDepth

(m) 1 1 B e n t n

Core Benth. Plankt. Nannoplankton Radiolaria Diatoms Pteropods Ostracods Molluscs

0.0-5.0 _ J * _ _ • O O O * X

5-0-14.5 2 X Φ V ~Φ_ ~Φ ~* x

14.5-24.0 3 X Φ 1J, ~Φ

24.0-33.5 4 X Φ_ | ~j~ J L S ~ ~× ~×"

33.5-43.0 5 X Φ - # β * O | X X

43.0-52.5 6 * I _•_ I £ O "5 ~× ×"~

52.5-62.0 7 X Φ | | O ^ X

62.0-71.5 8 X rò « * I

71-5-81 .0 9 X » O X X

81.0-90.5 10 * Φ O O X

90.5-100.0 11 X O X

100.0-109.5 12 X « « V r ~X X

109.5-128.5 13 X » S j * • . " J . " " Z ! ü ×

128.5-138.0 14 X ^ 0 O ^ " θ " >( X

138.0-147.5 15 X » | » ^ X X X~ ~

147.5-157.0 16 X S ^ = O

157.0-166.5 17 X " ! « _ • _ < , S _ • T 1 "x" "x"

166.5-176.0 18 X " S ^ ^ S O "•" «

176.0-185.5 19 X " | j ü . β « i O_ £ X

185.5-195.0 20 X ^ ^ ^ ^ ^ | V ~O ^

195.0-204.5 21 X » „ | #^ ° | « ~ l T" ~ ~ ~X

204.5-214.0 22 X » "] ^ _ _ T 1 1 " 0 "ET ~ ~ ~

214.0-223.5 2 3 X ^ # ^ O * ×

223.5-233.0 24 X | ' ^ # u 9 it

233.0-242.5 25 X # ^ ^ Φ ^ -k

242.5-252.0 26 X S - O x ?M. Plei-

252.0-261.5 27 X " # _ •* x

s t o c e n e

261.5-271.0 28 X ° °" X -

271.0-280.5 29 * - - X X

280.5-290.0 30 * - - X X

290.0-299.5 31 * ^ - - X X

299.5-309.0 32 * Φ > - - X X X

309.0-318.5 33 * <g - - X X

318.5-328.0 34 * ü Φ o — — X X X

328.0-337.5 35 * * \ — - X X X

337.5-347.0 36 * « - - X X *

347.0-356.5 37 * „, I - - X X *

356.5-366.0 3 8 * j g ^ ) | - - X X X

366.0-375.5 39 * | o O ~% ~ ~ ±_ *

375.5-385.0 40 0 * ^ ^ 0 °~ - - X X X. , tI3 (_)

385.0-394.5 41 O c O - - * X

394.5-404.0 42 0 o , 0 - - * X

404.0-413.5 43 O ." I S O - * X

413.5-423.0 44 O O " è S O - - X *

°- U. Plio.

423.0-432.5 45 O * —; X - - X *

432.5-442.0 46 t S? SS

432.5-442.0 4 7 θ X ^ ε U 3 " - - - -


H. M. BOLLI


O abundant; # common; * frequent; X rare; —absent;blank: not investigated.

Depth

(n)

0.0- 5.0

52.5- 65.0

90.5-100.0

109.5-119.0

128.5-138.0

147.5-157.0

176.0-185.5

204.5-214.0

223.5-233.0

242.5-252.0

261.5-271.0

280.5-290.0

299.5-309.0

318.5-328.0

337.5-347.0

356.5-366.0

385.0-394.5

413.5-423.0

451.5-461.0

480.0-489.5

518.0-527.5

556.0-565.5

594.0-603.5

632.0-641.5

670.0-679.5

698.5-708.0

708.0-717.5

727.0-736.5

736.5-746.0

Core

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

Foramini fera

Benthonic

Aren.

X

-

X

•k

X

X

X

k

X

X

X

X

X

X

X

*

X

X

*

*

o**

**

Calc.

X

X

-

X

X

-

—

-

-

-

X

-

—

-

-

-

*

•k

X

*

*

o*k

k

k

it

Plankt.

O

•

O

o-

-_---

-——--------

------

-

Quaternary

U. PIio. or ,y.

L. Paleoceneor younger

?Lower

Albian

?Upper

Aptian

Aptianorolder

Nannoplankton

i

<

O

O

X

X

X

X

X

-

-

X

X

X

X

X

X

ooO

O

•

O

O

o

Quaternary

L. Paleoceneor younger

Upper

Albian

M. Albian .or younger-*L. Cret.s. 1.

Radiolaria

X

X

X'

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

-

-

-

-

-

-

-

-

-

-

-

Quaternary

o

+->

o

Dinoflagellates

O

-

-

>

>

-

o****

o-•o•k

k

prob.LowerAlbian/UpperAptiantoAptian

cI0

εs-<o

Pollen/

Spores

T3

co

4->

O)

Q .

Eo

o_α>

0)O-O-

coα

<S-

<u

=>

Neoc.

Calcisphae-

rulidae

X

-

X

-

-

-

-

-

-

-

-

-

-

-

X

-

-

-

-

-

-

-

-

-

-

Ostracods

-

-

-

-

-

-

-

-

-

-

-

-

-

X

-

-

-

-

-

-

-

-

X

-

×

Molluscs

-

-

-

-

-

-

-

-

-

-

-

-

-

X

X

-

-

-

-

-

-

-

X

-

-

-

U. Alb.

U. Alb.

FishDebris

-

-

-

•k

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

-

-

X

-

-

-

X

-

X


Mesozoic sediments at Sites 259, 261, and 263 werestudied for dinoflagellates, pollen, and spores. Most ofthe investigated samples yielded varied and well-preserved associations of predominantly marinepalynomorphs. Their occurrence and distribution ofpalynomorphs at these sites is discussed by Wisemanand Williams (this volume), who compare their ages andranges with a world-wide range chart compiled by them.Palynomorphs at Sites 259 and 261 are largelycomplementary in their occurrence relative tocalcareous foraminifera and nannoplankton. This aidsin a more complete biostratigraphic interpretation of theintervals concerned and should also be of paleo-ecological significance.

Lower Cretaceous ostracods are described andfigured by Oertli (this volume). They are largelyconfined to Cores 12-17 at Site 259 and to Cores 9-11 atSite 260, where they are associated with richforaminiferal and nannoplankton faunas. They are rareand their occurrence is restricted to a very few samplesat Sites 261 and 263. Most of the specimens wereidentifiable on the generic level, but could not be

assigned to existing species. Ages are very tentative, butthe associations at Sites 259, 260, and 263 suggest asediment deeper than shelf.

Aucellina sp., a bivalve determined as Albian wasrecovered from one sample each at Sites 259, 260, and263 and described and figured by Speden (this volume).The material consists mostly of fragments and somejuvenile forms. At Sites 259 and 260 the specimens occurin Cores 14 and 9/10, respectively, together with richforaminiferal and nannoplankton assemblages. OneBelemnite, Parahibolithes sp. indet. was found in Core26 at Site 263 and an Ammonite fragment, determinedas ?cf. Prohysteroceras (Goodhallites) richardsi, wasrecovered from Site 263, Core 18. Both cephalopodsindicative for upper Albians, are described and figuredby Stevens (this volume).

While searching for isolated specimens ofCalpionellids thought to be possibly present in theLower C r e t a c e o u s / U p p e r Jurass ic shales ,Calcisphaerulidae, fossils of still uncertain systematicposition and thus far almost exclusively figured anddescribed from thin sections of limestones, were rather

998


unexpectedly found. The small, spherical to elongate,single-chambered calcareous tests, most of themmeasuring 40-70µ, are very restricted in their dis-tribution. They are present in the Albian at Site 259,Cores 11 -17; at Site 260 in the Upper Cretaceous of Core6; and in the Albian of Cores 9-15. At Site 261 they arerestricted to Cores 31-33, Upper Jurassic-LowerCre taceous , where they occur in floods.Calcisphaerulidae of probably Albian age are rare atSite 263 where they were noted only in three samples.

Twenty-three different species (19 new, 4 in opennomenclature) could be recognized based on SEM in-vestigation. They are distinguished by general test shape(spherical to elongate), number of layers (1-3) formingthe test wall, size and arrangement of the crystalsforming these walls, and size of the aperture. All areincluded in the genus Pithonella. Tentatively, it isassumed that the Calcisphaerulidae may represent a cyststage of calcareous algae.

The stratigraphic ranges of the individual Pithonellaspecies are restricted within the examined samples. Asno known ages of these new taxa are available, thefossils' ages had to be tied in with the ages of other fossilspresent, in particular nannoplankton and foraminifera.A general introduction to the Calcisphaerulidae, a list ofpublished taxa, and a description and illustration of thespecies isolated in Leg 27 are given by Bolli (this volume,Chapter 39).

Despite a lack of knowledge of the full ranges and alack of correlations with stratotype sections of thefaunas and floras used in these studies, littledisagreement exists in the Leg 27 Cretaceous/UpperJurassic age assignments based on the various fossilgroups. Mostly discrepancies lie within a stage, e.g., atSite 259 where for Cores 11-17 benthonic foraminiferaindicate upper Albian; planktonic foraminifera, Albian;and nannoplankton, middle Albian.

The only real exception to this is in the Cretaceous atSite 263 which is over 600 meters thick in Cores 5-29.Nannoplankton indicates upper Albian for most of thisinterval (Cores 5-27), based on frequent occurrence inCores 22-27 of Eiffellithus turriseiffeli, an index formgenerally acknowledged to first appear in the upperAlbian. This age assignment finds some support by anAmmonite fragment from Core 18 and a Belemnite fromCore 26.

Judging from the considerable thickness, one isinclined, however, to assume that the interval mayrepresent more time than only upper Albian. One couldargue therefore that, based on nannoplankton, only thelower part, that is, Cores 22-27 with frequent E.turriseiffeli, is upper Albian and the upper part Cores 5-21, though not documented by fossil evidence, isslightly younger, possibly Cenomanian.

A longer interval, ranging from lower Albian toBarremian/Neocomian, is postulated by benthonicforaminifera and palynomorphs. However, evidence forthis, in particular with regard to the foraminifera, isapparently not based on outstanding index forms.

Further information on the full ranges of all taxaconcerned will be needed before these discrepancies inage assignment within the Lower Cretaceous at Site 263can be resolved satisfactorily.

REFERENCEBolli, H. M. and Premoli Silva, I., 1973. Oligocene to Recent

planktonic foraminifera and stratigraphy of the Leg 15 sitesin the Caribbean Sea. In Edgar, N. T. and Saunders, J. B. etal., Initial Reports of the Deep Sea Drilling Project,Volume 15: Washington (U.S. Government Printing Of-fice), p. 475-547.

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Documents

47. SYNTHESIS OF THE LEG 27 BIOSTRATIGRAPHY AND PALEONTOLOGY