Deep Sea Drilling Project Initial Reports Volume 84 · 2007. 5. 1. · 565-30,CC through 565-34,CC. Very rare species reworked from the Oligocene and Pliocene are also in the Pleisto-cene

8. CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY OF THE MIDDLE AMERICA TRENCHAND SLOPE, DEEP SEA DRILLING PROJECT LEG 841

Mark V. Filewicz, Union Oil Company of California, Ventura2

ABSTRACT

DSDP Leg 84 recovered Tertiary and Upper Cretaceous calcareous nannofossils along the landward slope of theMiddle America Trench at five sites offshore of Guatemala and one site offshore of Costa Rica. At four sites, drillingreached tectonized, ophiolitic basement that underlies Pleistocene (Hole 566), upper Miocene (Hole 566C), lower Eo-cene (Sites 569 and 570), and possibly lower Maestrichtian/upper Campanian (Site 567—Upper Cretaceous limestoneabove basement may be displaced) slope sediment. Three significant hiatuses occur within the area of drilling and en-compass most of the middle to lower upper Miocene, lower Oligocene, and middle Eocene intervals. Short, localizedhiatuses occur in Pleistocene and Pliocene sediment. Reworking of calcareous nannofossils caused by downslope dis-placement of older sediment occurs at all the sites, and is especially significant within lower Miocene (Helicosphaeraampliaperta Zone) sediment penetrated at Site 567, 3 km upslope from the trench floor. One new Miocene Discoasterspecies (Discoaster tuberi Filewicz, n. sp.) is described in this chapter.

INTRODUCTION

During Leg 84, ten holes were cored at five sites alongthe landward slope of the Middle America Trench (MAT)offshore of Guatemala, and one hole was cored at an-other site along the same slope margin offshore of Cos-ta Rica (Figs. 1-3). Tertiary sediment containing age-di-agnostic nannofossils was recovered at all six sites (alongwith a 1.5-m-thick Upper Cretaceous limestone in Hole567A). Additional drilling of the trench floor, landwardslope, and shelf was achieved on the first MAT transect,north of the Tehuantepec Ridge off Acapulco (DSDPLeg 66), and on the second MAT transect offshore ofGuatemala (DSDP Leg 67). The primary objective of thethird MAT transect drilled on Leg 84 was to determinethe age, structure, and stratigraphy of the slope sedi-ments present landward of the trench offshore of Guate-mala. A similar objective was met during Legs 66 and67 for their respective geographic positions along theMAT axis, but drilling was terminated without the de-sired slope penetration when gas hydrates (clathrates)with a seismically undefined base were penetrated. Leg84 is the first cruise approved by the JOIDES advisorypanels to specifically drill into gas hydrates above theirseismically defined base, and to study clathrate origin andoccurrence in the marine environment.

A total of 700 samples from 200 cores (1043 m of sec-tion) recovered on Leg 84 was examined for nannofossilsunder the light microscope. Calcareous nannofossils arerelatively continuous in occurrence, and provide detailedbiostratigraphic correlation when present. A list of zon-al and age assignments for these cores is presented inFigure 4. Assemblage preservation varies from moderateto poor, with extensive overgrowth of species morpho-types in lower Eocene (Sites 569 and 570) and lower

von Huene, R., Aubouin, J., et al., Init. Repts. DSDP, 84: Washington (U.S. Govt.Printing Office).

2 Address: Union Oil Company of California, Ventura, CA 93003.

Maestrichtian/upper Campanian (Site 567) limestonespenetrated above basement. Assemblage numbers rangefrom rare to abundant, with occasional dilution of thespecies content because of high sedimentation rates with-in the Holocene to Pleistocene mudstones. Thin intervalsof Pliocene and upper to middle Miocene sediment aredominated by siliceous micro fossils, and are barren ofcalcareous nannofossils.

Tertiary and Late Cretaceous nannofossil species con-sidered in this report are listed alphabetically accordingto generic epithet in the Appendix.

BIOSTRATIGRAPHY

The Pleistocene to Holocene zonation utilized in thisstudy is after Gartner (1977). Zonal boundaries are some-times tentative, especially at the Emiliania huxleyi Zone/Gephyrocapsa oceanica Zone boundary (first occurrenceof E. huxleyi) and Gephyrocapsa oceanica Zone/Pseu-doemiliania lacunosa Zone boundary (last occurrence ofP. lacunosa), owing to (1) high sedimentation rates andclastic input, which have diluted the nannofossil, assem-blage, and (2) a high abundance of siliceous microfos-sils, which may be due to the close proximity of thesetrench-slope sites to shore, where upwelling can inject sur-face waters with high nutrient levels favorable to diatomproductivity.

Intermittent downslope sediment displacement, as doc-umented by sedimentary structures and benthic forami-nifers (Baltuck et al., this volume), has sporadically re-worked specimens of Helicosphaera sellii and Calcidis-cus macintyrei, which are zonal guide species, thus caus-ing further difficulty in zonal assignments for the lowerPleistocene. Stradner and Allram (1982) and Musylov(1982) experienced similar problems in their attempt tozone Pleistocene MAT-slope mudstones.

The Pliocene through Eocene zonation utilized is af-ter Bukry (1973, 1975) and Okada and Bukry (1980). TheCalcidiscus macintyrei Subzone (CN12d) is relabeled Dis-coaster triradiatus to avoid confusion with the Pleisto-

339

M. V. FILEWICZ

10°

110° 105° 100° 95° 90° 85°

Figure 1. Locations of Legs 84, 67, and 66 in relation to regional tectonic structures offshore of Central America.

cene C. macintyrei Subzone of Gartner (1977). The lower/middle Miocene boundary is tentatively placed at theSphenolithus heteromorphus Zone/Helicosphaera amplia-perta Zone boundary (first occurrence of C. macintyreior last occurrence of H. ampliapertá). The Oligocene/Miocene boundary is placed at the Discoaster deßandreiSubzone/Cyclicargolithus abisectus Subzone boundary(last continuous occurrence of C. abisectus) after Okadaand Bukry (1980), and the lower/middle Eocene boundaryis placed at the Discoaster sublodoensis Zone/Discoas-ter lodoensis Zone boundary (first occurrence of D. sub-lodoensis) after Hardenbol and Berggren (1978).

Upper Cretaceous nannofossils within a 1.5-m-thicklimestone penetrated in Hole 567A are assigned to Stan-dard European stage nomenclature after Theirstein (1976).

SITE SUMMARIES

Site 565 (09°43.69'N, 86°05.44'W; water depth 3099 m)

Coring in Hole 565 recovered 328 m (34 cores) of Pleis-tocene and upper Neogene (upper Miocene and lower Pli-ocene undifferentiated) homogeneous trench-slope mud-stone. This site is off the Nicoya Peninsula of Costa Ricaon the landward slope of the MAT (Fig. 3), and was select-ed primarily to identify the age and lithologic characteris-tics of sediments within and below the slope cover; it isthe only Leg 84 site that was not drilled off the Guate-malan MAT landward slope.

Calcareous nannofossils occur consistently through-out this section in rare to frequent abundances; preser-vation ranges from poor to moderate, owing to dissolu-tion. Heavy terrigenous mixing throughout the intervaland close proximity to the nannofossil CCD (especially inSamples 565-7,CC through 565-28,CC, as documentedby benthic foraminifers [McDougall, this volume]) arethe significant factors contributing to the low nannofos-sil abundances and etched preservation. Species which in-dicate cold surface-water temperatures, such as Cocco-lithus pelagicus, are extremely rare, suggesting that paleo-temperatures did not prohibit assemblage abundance ordiversity. The ranges of selected nannofossil taxa, alongwith qualitative information describing assemblage abun-dance and preservation, are presented in Figure 5.

Nannofossil zonal markers, though rare, are presentthroughout the section, and allow delineation of fourHolocene/Pleistocene zones and two zones within the Pli-ocene. Low diversity of the Discoaster assemblage untilterrigenous admixture became less (Sample 565-29,CC at276.5 m) does not allow a precise subdivision of the up-per Pliocene Discoaster brouweri Zone, but both the topand bottom of the D. brouweri zonal interval are welldefined by last-occurrence datums of D. brouweri andSphenolithus neoabies.

Reworking of Cretaceous nannofossils is rare to non-existent from the Pleistocene to upper Pliocene intervalthrough 29,CC. Upper Cretaceous reworking is more prev-

340

14° 0091° 00'

CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY

90° 00'

13° 00

GUATEMALA

Figure 2. Locations of Leg 84 and Leg 67 sites offshore of Guatemala. Esso Petrel no. 1 well is also shown.

alent within the upper Miocene and lower Pliocene from565-30,CC through 565-34,CC. Very rare species reworkedfrom the Oligocene and Pliocene are also in the Pleisto-cene (565-5,CC), but never form a significant assemblageconstituent.

Core 565-1 is tentatively assigned to the Emilianiahuxleyi Zone, and contains frequent Emiliania sp. cf. E.huxleyi.

The interval from Section 565-2-3 through Sample 565-8-2, 109 cm is assigned to the upper Pleistocene Gephy-rocapsa oceanica Zone, and is dominated by Calcidiscusleptoporus and small Gephyrocapsa spp. (sensu Gart-

ner, 1977). Core 565-7, which has a common abundanceof nannofossils with moderate preservation, containsthe first rare but consistent occurrence of reworked Cre-taceous species Watznaueria barnesae. Soft, light grayangular calcareous blebs in Section 565-2-3, which arelithified in Section 565-4-4, contain overgrown Neogenespecies and are therefore not reworked from significantlyolder sediments.

The interval from Sample 565-9-4, 106 cm, through565-9,CC is barren of nannofossils, but Sample 565-10,CC contains the highest occurrence of Helicosphaerasellii, along with Pseudoemiliania lacunosa. The combined

341

M. V. FILEWICZ

1OC

i 1 1 1 1 r

Costa Rica

1 ^ 1 1 1 Vt/>*tk. . I 1 1 1

I I I I I LLL I

3600

-87° -86°

Figure 3. Location of Site 565 offshore of Costa Rica.

- 8 5 C - 8 4 °

presence of these two species is indicative of the lowerPleistocene Helicosphaera sellii Zone. Approximately10 m of a barren interval, from middle Core 565-9 tomiddle Core 565-10, is therefore bracketed for place-ment of the unobserved Pseudoemiliania lacunosa Zone.This would represent a significant decrease in sedimentaccumulation rates (see Introduction and fig. 4 of Site565 report, this volume), from 165 m/m.y. for the top80 m of the section to about 13 m/m.y. between approx-imately 80 and 90 m. If sediment accumulation rates areassumed to have been relatively constant for the entirecored interval, then there is the possibility of a minorunconformity (no greater than 0.9 m.y.) within this in-terval. Sediment accumulation rates below Core 9 wereapproximately 125 m/m.y. down to the total depth ofSite 565.

The interval from Sample 565-1 l.CC through Sam-ple 565-12-4, 74 cm contains the highest rare occurrenceof Calcidiscus macintyrei, which would place this inter-val within the lower Pleistocene C. macintyrei Zone.

Sample 565-12,CC contains the highest consistent oc-currence of Discoaster brouweri, which indicates that the

Pliocene/Pleistocene boundary falls within Core 12. Sam-ples 565-12,CC through 565-30-4, 130 cm are assignedto the upper Pliocene Discoaster brouweri Zone, andcontain a nannofossil assemblage not of sufficient diver-sity to warrant further subdivision. Discoaster brouweriranges throughout this interval, but other important Dis-coaster zonal markers, such as D. pentaradiatus and D.surculus, are absent down to Section 565-29,CC. Disco-aster tamalis and other significant lower Pliocene-upperMiocene Discoaster species were not observed.

Sample 565-30,CC contains the highest occurrence ofSphenolithus neoabies, and is assigned to the lower Pli-ocene Recticulofenestra pseudoumbilica Zone. Reworkedupper Cretaceous species, including the upper Maestrich-tian species Micula murus, consistently occur within thiscore and continue to occur with regularity to 565-34,CC.This suggests erosion of Upper Cretaceous marine sedi-ments from upslope.

Samples 565-31,CC through 565-34,CC contain thesame low-diversity nannofossil assemblage present in 565-30,CC, along with the rare occurrence of Miocene spe-cies Catinaster sp. aff. C. mexicanus and very rare Dis-

342

Age

Holo.

Ple

isto

cene

Φ

§ -o°-Φ

ΦcΦO .

5E

Φ

Φ~cΦ

?É

Φ

Φ

Zone

Emiliania huxleyi

Gephyrocapsa oceanica

Pseudoβmiliania lacunosa

small Gephyrocapsa

Helicosphaera sellii

Calcidiscus macintyrei

CN12

CN 11

CN10

CN9

CN8

CN7

CN6

CN5

CN4CN3CN2

CN1

CP19

CP18CP17

CP16

CP15

CP14

CP13

CP12

CP11CP10CP9

Discoasterbrouweri

Reticulofenestrapseudoumbilica

Amaurolithustriconiculatus

Discoasterquinqueramus

Subzone

CN12dCN12CCN12bCN12aCN11bCN11aCN10cCN10bCNlOaCN9bCN9a

Discoaster triradiatusDiscoaster pentradiatusDiscoaster surculusDiscoaster tamalisDiscoaster asymmetricusSphenolithus neoabiesCeratolithus rugosusCeratoliihus acutusTriquetrorhabdulus rugosusAmaurolithus primusDiscoaster berggrenii

Discoaster neohamatus

Discoaster hamatus

Catiπaster coalitus

Discoaster exilis

Sphenolithus heteromorphusHelicosphaera ampliapertaSphenolithus belemnos

Triquetrorhabduluscarinatus

Sphenolithusciperoensis

CN1CCN1bCN1aCP 19bCP 19a

Discoaster druggiiDiscoaster deflandreiCyclicargolithus abisectusDictyococcites bisectusCyclicargolithus floridanus

Sphenolithus distentusSphenolithus predistentus

Helicosphaerareticulata

DiscoasterbarbadiensisReticulofenestraumbilica

CP15bCP15aCP14bCP 14a

Isthmolithus recurvusChiasmolithus oamaruensisDiscoaster saipanensisDiscoaster bifa×

Nannotetrina quadrate

Discoaster sublodoensis

Discoaster lodoensisTribrachiatus orthostylusDiscoaster diastypus

Landward MAT slope offshore Guatemala

Lower

567, 567A

5671 ,CC/2,CC

567A1 -4, 50/3-6, 33

3,CC/13,CC|18-1/18.CC

late Campanian—early Maestrichtian 19-1,60/19,CC

566, 566A,566C

566

1-2/5-2,83

566A1,CC

566C1 ,CC/H2,CC

Middle

569

1 -2/4.CC

5,CC/6,CC

7-2, 10/7-7,CC/8-2,2

8,CC/9,

6, 11

3C

10-2, 20/10,CC11-2, 71/12.CC

13-4, 3/26-4, 44

27-1, 19/27.CC

569A

1-1,99

2-1, 147/6-1, 43

7-1, 143

7,CC

8-1, 74/8.CC

9-1, 18/9.CC

10-1,1

568

1-2,80/6-2,43

6-4, 43/11-1, 89

11.CC/13-2,61

13-4, 45/21-C C

23.CC/25-2, 148

25-4,23/28-2,11

28-6, 10/38-2. 14738-4, 138/42-3, 1 26

42-7, 40/44-4, 70

Upper

570

1-2/6-6,37

6,CC/8,CC I

9.CC/23-4, 47

23-6, 36/25-4, 36

25.CC/26.CC

26-4, 23/27-1,50

28-1,43/35-1,30

35-4, 5/35-4, 40

35-5, 45/35.CC

36-2, 10/36.CCI37-1,28

37-1, 42/38-1, 55

LandwarMAT slopoffshore

CostaRica

de

565

1,CC

2-3/8-2, 109

9-4, 106/9,

10.CC

11 ,CC/12-4, 74

12.CC/30-4

30.CC

31-4,129/34 ,cc

>ro>

IZ>zzo3coCΛ

r

o3

Figure 4. Age and zonal assignments for Leg 84 holes based on calcareous nannofossils. Sample numbers representing upper and lower limits of a given zone or age areseparated by a slash; sample intervals in cm. MAT = Middle America Trench.

M. V. FILEWICZ

Ag

e

Holo.

cCU

toe

eis

CL

)cen

e

late

CL

<D

e. P

lioce

neto

1. M

ioce

ne

Nan

no

foss

ilzo

ne

E. huxleyi

Gephyrocapsaoceanica

Indet.

H. selliiCalcidiscusmacintyrei

Discoasterbrouweri

R. pseudoumbilica

ft pseudoumbilicato

Discoasterquinqueramus

Co

re

1

2

3

4

5

6

7

8

9

10

11

1?

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

Su

b-b

ott

om

dep

th(m

, to

bas

e o

f co

re)

10.5

20.0

29.5

39.0

48.5

58.0

67.5

77.0

86.5

96.9

105.5

115.0

124.5

134.0

143.5

153.0

162.5

172.0

181.5

191.0

200.5

210.0

219.5

229.0

238.5

248.0

257.5

267.0

276.5

286.0

299.5

309.1

318.7

328.3

Ab

un

dan

ce

R

R

B

R

F

R

C

R

B

R

oc cc

R

RR

R

R

R

R

R

C

R

R

R

R

B

R

R

F

C

CC CC

F

R

Pre

serv

atio

n

M,E

M,E

P.E

M,E

M,E

P,E,0

M,E

P.O

M,E

P.E

PAF

M,E

M,E

P.E

M,E

P.E

P.E

M,E

M,E

M,E

M,E

P,E

P.E

P.E

P.E

P.E

M,E

M,E

M,E

M,E

M,E

M,E

Em

iliania

hu×

leyi

Ca

lcid

iscu

s le

pto

poru

s

\

I

I

I

II

sma

ll G

ep

hyr

oca

psa

sp

p.

He

lico

sph

ae

ra

cart

eri

Dis

coa

ste

r br

ouw

eri

Helic

osp

haera

selli

i

1

1

Pse

ud

oe

mili

an

ia l

acu

nosa

|

1

11•

1|

11

Calc

idis

cus

ma

cin

tyre

i

Dis

coa

ste

r su

rcu

lus

1

Dis

coa

ste

r p

en

tara

dia

tus

Dis

coa

ste

r a

sym

me

tric

us

1

Sp

he

no

lith

us

ne

oa

bie

s

Retic

ulo

fenest

ra pse

udoum

bili

ca

11

CO

cCO

ü

><

Φ

Eo

d<o

Φ

CO

c

O

11

Re

wo

rke

d C

reta

ce

ou

s s

pe

cie

s

Figure 5. Range of stratigraphically significant calcareous nannofossils at DSDP Site 565. (Seenote to Table 1 for explanation of abbreviations.) Solid line indicates consistent occurrence ofspecies through cored section. Dashed line indicates sporadic species occurrence.

coaster berggrenii. A specific zonal assignment for thisinterval is not possible, and only a general age of late Mio-cene or early Pliocene is applicable.

Site 566

Three shallow holes (no sediment was recovered fromHole 566B, which is not considered here) were drilled atSite 566 along the east flank of an erosional canyon onthe trench slope, 22 km upslope from the axis of the Gua-temalan MAT. Upper Miocene to Pleistocene sediment

was recovered on shallow ultramafic basement in all threeholes. Drilling took place in an actively eroding canyon,however, and older slope sediments may have been previ-ously removed. Nannofossil occurrence, abundance, andpreservation are summarized in Table 1.

Upper Pleistocene nannofossils are abundant and wellpreserved. Slight dissolution of placoliths resulted in thedestruction of the central bar in some specimens of Ge-phyrocapsa. Pliocene nannofossils occur in lesser num-bers with similar, slightly etched preservation; poorly pre-

344


Table 1. Distribution of calcareous nannofossils at Site 566.

Age

Holocene-late

Pleisto-cene

latePlioc.

Miocene

?

Zone

subzone

Emilianiahuxleyi-

Pseudoemilianialacunosa

Discoasterbrouweri

quinqueramus

(interval in cm)

Hole 566

1-2, 29-301,CC2-2, 32-332-4, 32-33

2,CC3,CC4-2, 56-574,CC5-2, 83-84

5.CC6-1, 69-708,CC9,CC

Hole 566A

l.CC

Hole 566C

1,CC2-1, 45-462,CC3,CCH2.CC5.CC

Sub-bottom

(m)

1.804.005.838.82

10.0012.3014.3721.9024.24

31.4032.1052.8055.80

7.00

59.3059.7668.8078.50

109.10117.20

cT3G

a<

CCBFC

cFCR

BBBB

F

RRFRRB

atio

n

S

&

M, EM, E

P.O

M, EM, EP, OEM, EP, O

M, E

P, O, EP, OP, OP.O

p, o

ia h

ux

|

1

C

ocea

nica

CS

hyr

&

cR

FRF

omeg

ahy

roca

psa

Gep

RR

R

RR

tner

, 19

77—

smal

lsp

p. s

ensu

Gai

1

hyr

Gep

CC

F

CCFCR

cint

yrei

3

HU

.

RR

F

R

RR

R

R

'3

11"3

Cre

FF

f•

F

FR

F

R

RR

cart

eri

ohae

raco

sH

el

FF

R

RRF

R

R

R

R

wal

lich

iiph

aera

soo

Hel

R

a st

ylife

r

Ci

bdt

Rha

R

ia l

acun

osa

UD

tjlUJé

α.

R

V

opel

agi

cus

thu

s m

•ol

iC

oc

V

his

tric

a

5a

•s

CO

SSy

ro

V

onu

s s

g

Nan

R

lagi

cus

thu

s pe

coll

Coc

R

rter

ith

us

caC

oc

R

sell

iiph

aer

a

o

We/

R

1o

q

F

R

tara

dia

tus

i

s

V

R

RR

woa

bies

lit h

us

)en

oS

ph

R

RR

F

FR

s

'a p

seu

dou

mb

i

c

2

for

R

'rca

lari

ste

r in

t

S

D/5

R

R

ggre

nnii

ter

ber

5

Dis

<

R

RRR

nqu

era

mu

s

ö

S)

RRRFR

bise

ctus

occi

tes

yoi.

Die

V

anta

rcti

cus

occi

tes

yoc

Die

R

mur

aul

a

V

arne

sae

.α

3

V

CM

/MS

a

σo.

Dis

V

Note: Checklist Abundance: A = abundant (more than 10 specimens per field of view at × 800); C = common (1-10 specimens per field of view at × 800); F = few (1 specimen per 2-10 fields ofview at × 800); R = rare (1 specimen per 11-100 fields of view at × 800), V = very rare (1 specimen per 101-1000 fields of view at x 800). Assemblage Abundance: A = abundant; C = common;F = few; R = rare. Preservation: G = good, M = moderate, P = poor, E = etching, O = overgrown.

served upper Miocene nannofossil assemblages occur invery low numbers, with overgrowth of Discoaster spe-cies, fragmentation of Ceratolith species, and etching ofplacolith species indicating significant diagenesis and pos-sible downslope transport.

Reworking of nannofossils is sparse and restricted pri-marily to Cretaceous species in Holes 566 and 566C. Sphe-nolithus neoabies (middle Miocene to lower Pliocene) oc-curs in Sample 556A-1,CC in an unusually low abun-dance, indicating that its presence is also a result of re-working into an upper Pliocene sample.

Hole 566 (12°48.34'N, 90°41.79'W; water depth3745 m)

A total of 56 m (9 cores) of Holocene through Pleis-tocene mudstone, resting upon serpentinite basement, wasdrilled. The interval from Section 566-1-2 through Sam-ple 566-5-2, 83 cm is assigned to the upper Pleistocene/Holocene Emiliania huxleyi Zone and Pseudoemilianialacunosa Zone. Abundant, minute placoliths with affin-ities to E. huxleyi were observed in Sample 566-1-2, 29-30 cm, together with small Gephyrocapsa spp., Crena-lithus spp., Helicosphaera carteri, and Gephyrocapsaoceanica. Cores 566-2 through 566-4 are also dominatedby this assemblage without the presence of E. sp. cf. E.

huxleyi. Specimens of Pseudoemiliania lacunosa occursporadically in Cores 566-1 and 566-4, which makes ex-act assignment of the P. lacunosa/G. oceanica Zoneboundary tenuous. Sample 566-3,CC contains very rareNannoconus sp. reworked from the Cretaceous.

Samples 566-5,CC through 566-9,CC contain serpen-tinite, and are, of course, barren of nannofossils. Mud-stone fragments mixed with serpentinites in 566-9,CC con-tain the same Pleistocene nannofossil assemblage as seenin the section above, and are derived from downholecaving.

Hole 566A (12°47.91'N, 90°41.99'W; water depth3826 m)

Hole 566A was drilled 1000 m downslope from Hole566, along the axis of the same submarine canyon. Onlyone core (7 m) was recovered; it contained mudstonemixed with serpentinite in Sample 566A-1,CC. The ma-rine mudstone in this sample is probably upper Pliocene;it contains a flora dominated by Crenalithus spp., H.carteri, Discoaster brouweri, Calcidiscus macintyrei, andvery rare Discoaster pentaradiatus. The co-occurrenceof these species indicates the Discoaster brouweri Zone.Very rare specimens of Sphenolithus neoabies, which isubiquitous throughout lower Pliocene and upper Mio-

345

M. V. FILEWICZ

cene sediment, are thought to be reworked, since theymake up less than 0.1 % of the assemblage and no otherlower Pliocene species are present.

Hole 566C (12°48.84'N, 90°41.53'W; water depth3661 m)

Hole 566C is approximately 1000 m upslope from Hole566, again near the axis of the submarine canyon. Hole566C is the deepest hole (136.6 m) drilled at this site,and contains 66 m (7 cores) of upper Miocene mudstoneson serpentinite basement. Core 566C-H1, a wash core re-covered from a depth of approximately 50 m, contains amixed Pliocene/Pleistocene assemblage composed ofsmall Gephyrocapsa spp., H. carteri, and very rare Dis-coaster pentaradiatus.

Samples 566C-1,CC through 566C-3,CC contain Dis-coaster berggrenii, Discoaster quinqueramus, and Sphe-nolithus neoabies, and are assigned to the upper MioceneDiscoaster quinqueramus Zone. Very rare reworked Cre-taceous species are present in 566C-2,CC; 566C-3,CCcontains very rare reworked Micula mums, a species re-stricted to the late Maestrichtian.

No sediment was recovered from Core 566C-4, and awash core (566C-H2) taken at approximately 109 m con-tains the same upper Miocene nannofossils as previouslyencountered uphole. Cores 566C-5 through 566C-7 onceagain contained serpentinite.

Site 567

Holes 567 and 567A were drilled on the landward toeof the Guatemalan MAT, approximately 110 m fromDSDP Site 494 and 3 km from the trench floor. Drillingobjectives were (1) to penetrate basement lithology andpossibly drill through to the subducted oceanic slab, and(2) to elucidate the stratigraphic sequence of Tertiarythrough Upper Cretaceous trench-slope deposits recordedby marginal recovery in cores from Site 494. Biostrati-graphic results from Site 494 cores (Aubouin, von Huene,et al., 1982) were consistently compared with sedimentsrecovered throughout the drilling of Site 567, as a refer-ence for lithology and age control.

Approximately 176 m of Pleistocene sediments werewashed until continuous coring (31 cores, 283 m) beganclose to the Pleistocene/Pliocene boundary. A short se-quence of lower Pleistocene through Pliocene mudstonewas recovered to 220 m above lower Miocene sediment.Disturbed sediment containing lower Miocene, Oligocene,middle Eocene, and Cretaceous angular lithic clasts in amud matrix (usually lower Miocene) was also cored be-tween 260 and 368 m. I shall discuss further the evidencethat this sequence represents a sedimentary breccia rath-er than a drilling breccia. Igneous basement was drilledfrom 385 to 501 m (total depth).

Poorly preserved calcareous nannofossils occur in rareabundance within the Pleistocene/Pliocene sediments ofboth Hole 567 and Hole 567A (Table 2). Assemblagepreservation and diversity is better, and abundance isgreater, in the lower Miocene sediment. Nannofossil pre-servation and abundance fluctuate from overgrown oretched rare specimens to moderately preserved common

specimens within the Oligocene, middle Eocene, and Up-per Cretaceous angular lithic fragments.


Core 567-H1 (wash core) is Pleistocene, as indicatedby the occurrence of small Gephyrocapsa spp. and G.oceanica in Sample 567-Hl,CC. A mixture of middle toupper Miocene species such as Catinaster coalitus andSphenolithus heteromorphus also occurs, indicating thatreworking of Miocene sediments occurred in Pleistocenetime.

Sample 567-1,CC contains rare Discoaster brouweriand Calcidiscus rnacintyrei; 567-2,CC contains only smallGephyrocapsa spp. Both cores are assigned to the lowerPleistocene (probably Calcidiscus macintyrei Zone), andthey are probably very close to the Pleistocene/Plioceneboundary.


Samples 567A-1-4, 50 cm through 567A-3-6, 29 cmcontain sparse lower Pliocene nannofossil assemblageswhich include Reticulofenestra pseudoumbilica, Spheno-lithus neoabies, Calcidiscus macintyrei, Discoaster pen-taradiatus, and Discoaster asymmetricus, mixed with rarereworked middle and upper Miocene species such asDiscoaster sp. cf. D. bollii and Catinaster coalitus. Thisinterval is assigned to the lower Pliocene, and Sample567A-3-6, 32-33 cm contains long-ranging species whichcould be Miocene to lower Pliocene.

The interval from Section 567A-3,CC through Core567A-10 (65 m) is assigned to the lower Miocene Helico-sphaera ampliaperta Zone, and contains such age-diag-nostic species as H. ampliaperta, H. mediterranea, H.scissura, and Sphenolithus heteromorphus and Discoas-ter deflandrei. The unconformity between lower Plioceneand lower Miocene sediment therefore occurs betweenSamples 567A-3-4, 28-29 cm and 567A-3,CC, at ap-proximately 220 m, this is in general agreement with agecorrelations with Site 494 (basal Pliocene unconformityat 225 m). Below this horizon, Site 567 lithologic and bio-stratigraphic sequences and interpretations differ signif-icantly from those for Site 494 (see Introduction and ta-ble 6 of Site 567 report, this volume).

Lower Miocene sediment (H. ampliaperta Zone) wasalso encountered in Hole 498A (3 km west along strikeof the lower trench slope), and 40 to 50 km north in themiddle slope are penetrated at DSDP Sites 496, 568, and569, and approximately 80 km north on the shelf edge,as documented at the Esso Petrel well (Seely, 1979). Butonly 110 m to the north, at Site 494, lower Miocene nan-nofossil species are absent.

Cores 567A-11 to 567A-13 consist of a mixture of an-gular clasts of variable lithology, which contains moder-ately preserved Oligocene, middle Eocene and Upper Cre-taceous nannofossil assemblages in association with lowerMiocene mud matrix. This can be explained by distur-bance and brecciation of multiple aged sediments by eitherrotary drilling or downslope mass transport. The Leg 67

346


staffs preliminary interpretation of the broken, angularlithic fragments recovered from Site 494 (245-285 m) isthat they constitute a drilling breccia, and that the old-est lithology recovered thus represents the in situ forma-tion. Accordingly, a stratigraphic sequence of lower Mi-ocene, middle Eocene, and Upper Cretaceous sedimentsoverlying possible basement was reported. Sedimentscored at Site 567 yielded better recovery, and in manycases interformational conglomerates of angular lithicclasts in a coherent matrix can be observed. This wouldsuggest that the angular clasts were emplaced by slump-ing or other types of downslope movement and are ge-netically part of a sedimentary breccia. The youngest ageobtained from the clasts or matrix would, of course, thenrepresent the true age of deposition.

Discrete angular lithic clasts and matrix (often ob-scured) were selectively sampled to determine the upperand lower limits of age spread. Results are tabulated inTable 3, and indicate that reworking of a middle Eoceneto Oligocene clast occurred as high as Section 567A-7-2,whereas the first reworked Upper Cretaceous occurs inSection 567A-8-4. Both matrix and clasts are lower Mio-cene from lower Section 567A-8-4, to 567A-10,CC. Clastsfrom Cores 567A-11 and 567A-12 are Oligocene and Up-per Cretaceous (probably Campanian), and clasts fromCore 567A-13 are primarily middle Eocene or UpperCretaceous. Matrix mudstone from Sample 567A-13-2,20-21 cm contained Cretaceous to Oligocene nannofos-sils, whereas soft mud (possible matrix) from 567A-11,CC, 567A-12,CC, and 567A-13,CC consistently yield-ed a youngest nannofossil age of early Miocene (Helico-sphaera ampliaperta Zone). Deposition would then havetaken place in the early Miocene, with erosion, masstransport, and redeposition of subaerially exposed Oli-gocene through Upper Cretaceous sediments as coher-ent lithic clasts.

Core 567A-14 through Section 567A-17,CC recoveredweathered blue serpentinite mud, which may or may notbe age equivalent to that of the blue mud sequence re-covered at Site 494 (225-245 m). Both blue mud se-quences are barren of nannofossils.

Sample 567A-18-1, 49 cm contains H. ampliaperta,H. carteri, and Triquetrorhabdulus milowii, along withscattered Cretaceous and Eocene species, and is assignedto the lower Miocene Sphenolithus belemnos Zone or He-licosphaera ampliaperta Zone.

Sample 567A-18,CC contains the base of a blue ser-pentinite mud overlying 6 cm of soft gray mudstone whichcontains traceable bedded layers truncated by an appar-ent erosional contact. Lithic clasts within the serpentin-ite mud were selectively examined for nannofossils, whichindicate either middle Eocene or upper Cretaceous sedi-ment. The soft gray mudstone below the serpentinite mudcontains a middle Eocene flora, along with very rare lowerMiocene specimens of H. ampliaperta, which is againindicative of lower Miocene sediment dominated by re-worked material.

Core 567A-19 recovered 1.5 m of marly limestone con-taining moderately recrystallized species of upper Creta-ceous nannofossils. The presence of Broinsoniaparca, Mi-cula staurophora, Ceratolithoides aculeus, and Uniplana-

rius gothicus indicates that this sediment, as sampledthroughout Sections 567A-19-1 and 567A-19,CC, is up-per Campanian/lower Maestrichtian. This limestone isthe lowermost recovered marine sediment overlying ig-neous basement, but the possibility of downslope dis-placement cannot be ignored, since it represents an ageand lithology which has consistently been found reworkedthroughout Tertiary sediments from Core 567A-8 andbelow.

Cores 567A-20 through 567A-29 recovered gabbro con-glomerates, serpentinites, and metabasalts, which are,of course, barren of in situ nannofossils. Blue serpen-tinite mud was examined throughout this interval to de-termine the extent and stratigraphic level of downholecontamination. Very rare Tertiary species were observedin Sections 567A-20-1 and 567A-24,CC, indicating thatdownhole sluff is minimal and does not originate fromany particular horizon.

Age Comparison of Pre-Pliocene Sediments from Sites494 and 567

Post-cruise sampling of lithologies from the Site 494Pre-Pliocene section (Sample 494-20-4, 56-57 cm throughSample 494-30-1, 100-101 cm) revealed nannofossil as-semblages similar in age to those reported by Musylov(1982). Middle Miocene nannofossils were observed inSample 494-21-1, 55 cm, and middle Eocene nannofos-sils indicative of the Reticulofenestra umbilica Zone (onezone younger than Musylov's age determination) rangefrom Sample 494-22-4, 15 cm through Sample 494-27-3,55 cm. Lower Miocene nannofossils are not present with-in angular mudstone chips or matrix sampled from thisinterval; this indicates that approximately 50 m of mid-dle Eocene mudstone is present at Site 494, just 110 mnorth of Site 567.

Upper Cretaceous, probably upper Campanian orlower Maestrichtian, marly limestone is present from Sam-ple 494-28-1, 10-12 cm through Sample 494-28-1, 50-52cm. It is underlain by more middle Eocene mudstonefrom Sample 494-29-1, 86 cm to Sample 494-29-2, 37 cm,above another occurrence of Upper Cretaceous lime-stone sampled at 494-30-1, 100-101 cm. The Cretaceouslimestone in Core 494-29 can therefore be interpreted asa displaced lithology within the middle Eocene. TheUpper Cretaceous limestone within Core 494-30 is thelowermost marine sediment encountered at Site 494above the igneous pebbles at total depth, and may ormay not be displaced. Since the sediments are structur-ally complex and highly irregular below the unconform-able surface of the Neogene slope cover (Site 567 report,this volume), the 100 m of lower Miocene sedimentarymelange encountered at Site 567, 110 m closer to thetrench axis on the down side of a normal fault, may be aresult of the tectonic activity typical near an active sub-duction zone.


Hole 568 was drilled on the upper middle slope of theGuatemalan MAT, approximately 1 km north of DSDPSite 496 and 48 km landward from the trench axis. A to-tal of 417.7 m (44 cores) of Holocene/Pleistocene through

347

M. V. FILEWICZ


Age

earlyPleist.

earlyPliocene

earlyMiocene

early

Zoneor

subzone

Calcidiscusmacintyrei

Reticulofenestrapseudoumbilica-

Amaurolithustricorniculatus

Helicosphaeraampliaperta

Helicosphaeraampliaperta orSphenolithus

belemnos

early Maestrichtian-late Campanian

Sample(interval in cm)

Hole 567

1,CC2,CC

Hole S67A

1-4, 50-521-6, 70-72l.CC2-1, 36-372-4, 54-552-6, 57-582,CC3-2, 49-503-2, 115-1163-4, 28-293-4, 115-1163-6, 32-33

3-6, 115-1163,CC4-2, 60-614,CC5-2, 148-1495-4, 136-1375,CC6-2, 37-386-4, 100-1016-5, 39-406.CC7-1, 107-1087-2, 8-97-2, 11-128-2, 99-1008-4, 46-478-4, 53-548-4, 78-798,CC9-2, 108-1099-4, 108-1109,CC10-2, 18-1910-4, 43-4410.CC11-1, 72-7311-2, 14-1511,CC12-2, 78-7912-4,9-1112-4, 78-7912-5, 44-4512.CC13-1, 70-7113-1, 109-11013-1, 147-14813-2, 20-2113,CC

14-2, 2-314-2, 38-3914-2, 54-5514.CC16.CC17-1, 80-8117,CC18-1, 15-16

18-1, 48-4918.CC18.CC18.CC18.CC

19-1, 60-6119-1, 74-7519.CC

Sub-bottomdepth

(m)

185.80195.50

200.51203.71205.20205.57210.25213.28214.90216.90217.56219.69220.56222.73

223.56224.60226.71234.10237.09239.97243.60245.47249.10249.99253.10254.18254.68254.71265.20267.67267.7'4267.99271.90274.49277.49280.70282.39285.64289.50290.22291.14298.40300.69303.00303.69304.85307.30308.01308.39308.77309.01316.20

317.73318.09318.25325.10342.80343.61351.70351.86

352.19352.82352.82352.82352.82

359.31359.45360.20

1-α

<

R

R

R

R

R

RBB

RR

B

RBR

FFB

FBR

FFFBRBR

RFRRFFFR

F

F

RR

FFC

cF

RFFC

cRRF

BBBBB

BBR

I•

CFCF

RcF

c

£

P,EP,EO

M,EP,OP,EP.O

P.EM,E

M.E

M.E

P.OM,E

M,E

P.OM,OM.EM

P,OE

P.OM,0R,OMP,EMM,EP,OEP,OM,EP,0P,OM.EM.EM.OM,OM,OM,EOP.OM.EOM,EOM,OM,EP,OP.EM.E

P.O

M.EM.OP,OMM

P.OP,0P.O

.5

RR

R

R

R

R

R

R

RRR

R

RF

R

CC

ccRC

F

cC

ccF

R

FCC

cF

5:

R

97

7-s

ma

llu

Gar

tner

, 1

;pp.

sen

s

O

R

|

.,

RR

R

p

R

R

R

R

'wen

Ja

δ

R

V

V

R

R

Tint

yrei

5

R

R

R

1j

R

R

R

R

R

FR

R

R

R

R

F

F

FR

FR

F

R

R

R

R

R

R

•

mi,

•

&

R

RR

R

arad

iatu

:pe

nt

t

ö

V

R

R

imb

ilic

ai p

seu

do,

g

-̂311,

V

R

R

R

R

R

R

F

R

R

ican

us

is p

elth

i

ter

~o ^ö • i

(J (J

R

RR

R

R

R

R

R

R

RRR

RF

F

R

R

C

R

RFF

RR

R

RF

FF

ibil

is

mta

rcti

c,

1 |& a

δ δ

R

R

R

R

R

R

FR

F

F

ter

|

δ

R

R

R

R

FFR

R

RRRR

RFFRFRRR

FF

VR

F

R

•ca

lari

s

|

a

Sδ

R

a J

"δ. 2

* "a.

sec

?lic

δ S

R R

R

R

R

•de

rsi

ji

Q

R

R

RR

R

J

us

h.lil

f

RR

RR

RRRRRR

RR

R

R

R

i ga

rtn

er

%

^ 3

FR

F

R

F

FF

R

R

FF

RR

F

FRR

RR

F

F

sflo

rida

,

J

>cli

o

FF

F

RFFF

R

FRRFFFR

FF

F

R

R

C

C

impl

iape

~al

ijorn

k

ε g

8 8

RF R

R

R

R

F1FRF

RF

R

R

VR

R

R

R

V

inte

rmed

.

1g,a;

R

R

R

d

|

0

R

RR

R

ulus

milt

|

ror

X,

R

R

R

R

R

ilti

pora

'•';::

s

R

R

R

R

R

R

R

R

3 2

1 E"i g

1 I

R R

RRR

R

R

IaQ

R

R

R

R

natu

su

lus

cari

ha

bd

• S"

R

R

R

R

R

isot

rem

a

1 i& •s

elk

isc<

* 1

R

R

R

V

R

cE

RR

R

R

rhom

ba

Ip

R

R

Note: See note to Table 1 for explanation of abbreviations

lower Miocene mudstone was recovered. The primary ob-jective at this site was to monitor and study the occur-rence of gas hydrate, which had been previously encoun-tered at Site 496, causing termination of drilling.

Abundant nannofossil assemblages are well preservedthroughout the Pleistocene (Core 568-1 through Section

568-21,CC), but lack consistent occurrences of the indexspecies Pseudoemiliania lacunosa and Helicosphaera sel-lii (Table 4). Specimens of Calcidiscus macintyrei are re-worked in Cores 568-1 through 568-11.

Middle Miocene to lower Pliocene nannofossils are rareto absent, but moderately preserved when present in Cores

348


Table 2. (Continued).

liI 38 S,

8 a

§ δ I

HII i

If I

s s..3 | g

I 1 *£ * ò

fiS 3.3 g

1 3

S 5 SO o δ

5 8 3 gP 2 € Il l

δ δ

I i5

I f II J I " JI i 11 ii 11 i

C a; Q <g•

I 3

1 1 1•§ § |a | ae ?»

£ J! 3 3 E

I? ö Q Q ü

s I3 a

H

3 I

R R RR

RR R R

F FR

R RF R

R FF R C

R F

R R

V V

R R R

RR

R R R RR

R RR R R R R V R

R R

R R

RF

F C

R R R R R

R R R

C RF R R R R F R

F F

C R

R R

R F

FR F

F

568-23 through 568-25 (Table 5). Middle and lower Mio-cene nannofossils encountered in Cores 568-27 through568-41 contain rare to common and only moderately pre-served nannofossils. Upper Oligocene or lower Miocenenannofossils in Cores 568-42 and 568-43 are rare andare poorly to moderately preserved. Sample 568-44,CC(417.7 m total depth) is barren of age-diagnostic nanno-fossils.

Reworking of nannofossils other than C. macintyreiis minimal; several lower Pleistocene to middle Miocenespecies are present in Cores 568-1 through 568-5. Sam-ples 568-1-2, 80 cm through 568-6-2, 43 cm are assignedto the Holocene or upper Pleistocene Emiliania huxleyiZone or Gephyrocapsa oceanica Zone on the basis of oc-currence of Gephyrocapsa oceanica, Helicosphaera car-teri, small Gephyrocapsa spp., and possibly E. huxleyi.

349

M. V. FILEWICZ

Table 3. Nannofossil age determinations of selected, apparently in situ lithologiesfrom Hole 567A, cores 6-18. Age spread suggests reworking of Oligocene, mid-dle Eocene, and Late Cretaceous clasts into an early Miocene sedimentary brec-cia. See Table 2 for distribution of taxa.


6-4, 100-1016-4, 100-1017-2, 11-12

8-4, 46-47

8-4, 78-798-4, 81-82

10-2, 18-19

11-1, 72-73

12-4, 9-1112-5, 44-45

13-1, 70-71

13-1, 104-110

13-1, 147-14813-2, 20-2113.CC

18.CC

18.CC

18,CC

Lithology

Gray mudstoneGray mudstoneHard blue-green

mudstoneGray mudstone

Gray mudstoneGray mudstone

Light gray mud-stone

Gray mudstone,mottled

Soft blue mudstoneSoft white lime-

stoneFirm, dark brown

mudstoneGray-brown

mudstoneGray limestoneSoft gray mudSoft gray mud

Soft green mud-stone

Soft white mud-stone

Soft gray mudstone

Description

Angular clast (1 cm)MatrixAngular clast (1 cm)

Small clast (5 mm)with matrix

MatrixBrecciated bedded layer

(~ 1 cm thick)Brecciated bedded layer

(1-2 cm thick)Matrix with small

(1 mm) clastsClastClast

Angular clast (1 cm)

Angular clast (1 cm)

Angular clast (~ 5 cm)MatrixMatrix

Clast

Clast

Possible matrix under-lying serpentinitemud

Age

MioceneMiocene (prob. early)Oligocene-mid. Eocene

Mixed: clast—Late Cret.matrix—earlyMiocene

early Mioceneearly Miocene

early Miocene

Oligocene

Late Campanian-Maest.Late Campanian-Maest.

middle Eocene

middle Eocene

CretaceousMixed: Oligocene-Cret.Mixed: early Miocene-

Late Cretaceousmiddle Eocene

Late Cretaceous

Mixed: middle Eocenewith rare earlyMiocene

Samples 568-6-4, 43 cm through 568-11-1, 89 cm, areassigned to the upper Pleistocene Pseudoemiliania lacu-nosa Zone on the basis of the same assemblage as thatjust mentioned, with the addition of P. lacunosa and theabsence of E. huxleyi. Cores 1 through 11 (Section 1) ofHole 568 are approximately age-equivalent to Cores 1through 11 of Hole 496.

The interval from Sample 568-11,CC through Sam-ple 568-13-2, 61 cm is tentatively assigned to the smallGephyrocapsa Zone on the basis of the dominant abun-dance of small Gephyrocapsa spp. and the lack of G.oceanica. This interval is approximately equivalent to theinterval from Sample 496-11-3, 60 cm through Sample496-12-2, 62 cm, where Musylov (1982) also lists abun-dant small Gephyrocapsa spp.

The interval from Sample 568-13-4, 45 cm throughSample 568-21,CC is assigned to the lower Pleistocene,and is equivalent to Sections 14-1 through 24-5 of Hole496. There is little change from the assemblage encoun-tered upsection, and the sporadic, rare occurrences of P.lacunosa and Helicosphaera sellii make zonal assignmentdifficult. Lack of Calcidiscus macintyrei in this section(though apparently reworked above Core 568-12) sug-gests that the lowermost Pleistocene may be absent.

Samples 568-22-2, 146 cm through 568-23-2, 90 cmare dominated by siliceous microfossils and are barren ofcalcareous nannofossils. Samples 568-23,CC through 568-25-2, 148 cm are middle Miocene to lower Pliocene, judg-

ing by the occurrence of H. carteri, C. leptopora, Disco-aster brouweri, Sphenolithus abies, and Reticulofenestrapseudoumbilica. Sample 568-24,CC is barren of calcare-ous nannofossils. This section is probably equivalent to acondensed upper Miocene through lower Pliocene sec-tion (496-26-3, 67 cm through 496-28-5, 28 cm) at Site496.

The presence of a short upper Pliocene section, whichwas established for Site 496 (Sections 496-25-2 through496-26-3), was not observed for Site 568 on the basis ofthe micro fossil disciplines; this suggests the developmentof an unconformity between sites. The absence at bothsites, of sediments definitely belonging to the Catinastercoalitus through Discoaster neohamatus zones suggests thepresence of a second, more extensive upper middle tolower upper Miocene unconformity or condensed sectionin this region.

Samples 568-25-4, 23 cm through 568-28-2, 11 cm aremiddle Miocene and assigned to the Discoaster exilisZone. Rare Discoaster exilis, D. challengeri, and Disco-aster sp. cf. D. bollii are present in Sample 568-25-4, 23cm, and Sample 568-27,CC contains Coccolithus mio-pelagicus and Discoaster adamanteus with D. exilis.

Samples 568-28-6, 10 cm through 568-38-2, 147 cm areassigned to the middle Miocene Sphenolithus heteromor-phus Zone. They contain a well-developed assemblagewith S. heteromorphus, D. exilis s. ampl., Discoastersignus, C. miopelagicus, H. carteri, and Discoaster varia-

350


Table 4. Distribution of Holocene and Pleistocene calcareous nannofossils at Site 568.

Age

Holocene-late

Pleisto-cene

late

Pleisto-cene

early

Zoneor

subzone

Emilianiahuxleyi-

Gephyrocapsaoceanica

Pseudoem ilian ia

smallGephyrocapsa

Gephyrocapsa~Calcidiscus

macintyrei


1-2, 80-811,CC2-2, 144-1452-4, 138-1392-6, 146-1472,CC3-2, 135-1363-4, 135-1363-6, 135-1363,CC4-2, 118-1194-4, 118-1194,CC5-2, 144-1455-4, 144-1455-6, 144-1455,CC6-2, 43-44

6-4, 43-446.CC7-2, 48-497-4, 48-497,CC8-4, 36-378-6, 36-378,CC9-2, 149-1509-4, 149-1509,CC10-2, 149-15010-4, 146-14710,CC11-1, 88-89

11, CC12-2, 144-14512.CC13-2, 60-61

13-4, 45-4613.CC14-4, 105-10614-6, 61-6214.CC15-2, 97-9815-6, 60-6115.CC16-2, 15-1616-6, 15-1616.CC17-4, 85-8617-6, 85-8617.CC18-2, 24-2518-4, 24-2518,CC19-2, 89-9019-4, 45-4619.CC20-2, 94-9520-4, 94-9520,CC21-1, 137-13821.CC

Sub-bottomdepth(m)

2.313.406.359.29

12.3713.0015.8618.8621.8622.7025.3928.3932.3035.2538.2441.2542.0043.94

46.9451.4053.3956.3961.1065.9768.9770.4073.4076.4080.1083.1086.0689.4090.29

98.80101.75108.30110.41

113.26117.80123.36125.92127.40129.88135.51137.20138.86144.86146.90152.26155.26156.50158.25161.25166.20168.60171.16176.00178.45181.45185.70187.08187.30

idan

ce

3

<

FCFFFCRRFCFFFCCFCC

FCFFFFCCCC

cccccA

cAA

AAAAACFFFFFFFFCCCCCCBCCFF

:rvat

ion

15

PM, EP, E

PP, EM, EP, E

M, EM, EM, EP, EOP, EM, EM, EM, EM, EM, EP, EO

M, EM, EM, EM, EM , EP, EP, OM, EM, E

p, oM, EP.OP, OM, EP.O

M, EP, OM, EM, O

M, OM, EM, EM, OM, EP.O

P, OEP, EM, EP .OP, EP.OP, EP, EM. EP, EM, EP, EM, EM, E

P .OM, EM, EM, E

lyro

caps

a om

ega

a,0

RR

R

RF

RRRRFR

R

R

R

F

FFR

lyro

caps

a oc

eani

ca

a,öFCRFFF

FCFFFRFFFF

FFF

RRRFFFC

FFF

R

R

RFRFF

RFCFFRFR

R

alit

hus

doro

nico

ides

δccFFCCFFCCC

ccccccccccccccFcccccccccccccccccF

ccccccccccccc

ccF

c

tner

, 19

77—

smal

lly

roca

psa

spp

. se

nsu

Gai

O

ccccccFFC

cccccccccccccccFA

cccccccAAAA

AAAAACC

cccccccccA

ccA

cRFF

idis

cus

lept

opor

us

j ;

aRF

F

RFF

PFRRFF

RFRFR

FR

RFRRFF

F

FF

FFFRC

FF

FFFFFFRRRFC

RCFR

idis

cus

mac

inty

rei

aFR

RR

R

RF

R

R

R

R

R

?osp

haer

a ca

rter

i

FF

FFFRRFFFRFFFRFF

RFRRRRFFRF

cFRFR

FFFF

C

ccccFF

FRRFFRRFRFRFC

cFF

-

δ

F

R

R

R

R

A

R

RR

R

^osp

haer

a w

alli

chii

R

R

R

R

R

R

'ilic

osph

aera

si

bog

ae

R

R

RRR

R

R

R

doe

mil

ian

ia l

acu

nos

a

3

V

V

RRRR

R

R

FR

R

F

R

R

toli

thu

s cr

ista

tus

aü

V

R

•aco

spha

era

saxa

e

•nol

ithu

s ne

oabi

es

M %

R

R

R

R

voco

ccit

es a

ntar

ctic

us

z

3

RR

FRF

F

R

R

R

?osp

haer

a pu

lchr

a

5to

R

R

R

R

ica

•ulo

fene

stra

ps

eudo

umbi

i

R

no

lith

us

hete

rom

orph

us

R

oast

er b

rouw

eri

R

R

-osp

haer

a se

llii

as

R

R

R

R

R

R

R

orha

bdus

ser

ratu

s

"50

R

V

R

olit

hina

jap

onic

a

s

V

R

R

oast

er b

ergr

enni

i

.nau

eria

bar

nesa

e

Rol

ithi

na p

lana

3

R

R

oast

er b

arba

dien

sis

Q

R

Note: See note to Table 1 for explanation of abbreviations.

351

Table 5. Distribution of Pre-Pleistocene calcareous nannofossils at Site 568.

i IZone Sub-bottom •α £

or Sample depth _g <ßAge subzone (interval in cm) (m) < £

22-2, 146-147 198.37 B, 22-4, 98-99 200.89 B

22-6, 146-147 204.37 B23-2, 149-150 208.10 B

23.CC 214.80 R M, E24-2, 84-85 217.14 B

cene D.brouweri- 24-3, 100-101 218.81 R P, E. . D. exilis 24-4, 84-85 220.14 BM l O c e n e 24-6,84-85 223.14 B

25-2, 148-149 227.49 B

25-4, 23-24 229.24 F M, O25.CC 234.20 R M, E

Discoaster 27-2, 67-68 246.08 F P, Oexilis 27-4, 67-68 249.08 B

27.CC 253.40 F P, OE28-2,10-11 255.01 F P, O

28-6, 10-11 261.01 F P, O28.CC 263.10 C M, E29-4,51-52 268.11 F P, O29-6,51-52 271.11 F P, O29.CC 272.60 C M, E30-2, 28-29 274.39 F P, O

middle 30-4, 33-34 277.43 BMiocene 30,CC 282.30 F M, E

31-1, 110-111 283.41 F M, ESphenolithus 31.CC 292.00 C M, EO

heteromorphus 32-2, 58-59 294.09 F M, EO32-6, 59-60 300.10 F P, O33-2, 30-31 303.40 F P, O33-4, 30-31 306.40 C M, O35-4, 130-131 327.01 C M36-6, 130-131 339.81 C M, O37-2, 46-47 342.67 C M, OE37-4, 45-46 345.66 B37.CC 350.20 B38-2, 146-147 353.17 F P, O

38-4, 138-139 356.09 R P, O

amphaperta 4 M > 4 2 _ 4 3 3 8 4 . 2 3 F P.O

e a r l y 42-3, 125-126 393.26 R M

M i o c e n e 42-7,40-42 398.42 F M„ , , 43.CC 408.40 R M, En^l7"Z• 44"2> 69-70 410.60 R P.OD.deflandre, ^ 6 9 _ 7 0 4 1 3 m R p> o

44.CC 417.70 B



bilis. Only 3 m of section (Core 496-30, Sections 7 and 8)are assigned to the S. heteromorphus Zone at Site 496.The 78-m thickness of this same zone penetrated at Site568 may be a result of greater sedimentation rates in thisupslope area during part of the middle Miocene.

Samples 568-38-4, 138 cm through 568-42-3, 126 cmare assigned to the lower and middle Miocene Helico-sphaera ampliaperta Zone. They contain H. ampliaper-ta, S. heteromorphus, H. intermedia, H. euphratis, andDiscoaster deflandrei, and are equivalent to Cores 31through 40 of Hole 496 (drilling there ceased with Core40). Deposition of sediment breccia at Site 567 also oc-curred during the time corresponding to this lower Mio-cene zone.

Samples 568-42-7, 40 cm through 568-44-4, 70 cm (firmmudstone lithologies) are considered lower Miocene, andcontain consistent occurrences of Helicosphaera euphra-tis, D. deflandrei, Triquetrorhabdulus carinatus, andSphenolithus moriformis. No specimens of Cyclicargo-lithus abisectus or Dictyococcites bisectus are present,indicating that Oligocene sediments were not penetrat-ed. High bedding-angle dips, a poorly preserved mix-ture of upper Eocene to Miocene diatoms, and the oc-currence of pyritized radiolarians suggest that the Eo-cene to lower Miocene unconformable surface encoun-tered upslope in the Esso Petrel well (Seely, 1979) mayhave affected sedimentation in Cores 42-44 of Hole568. If so, one of several hypotheses (see Site 568 report,this volume) is that the subcropping Eocene lithologiesmay have afforded a rough surface topography, whichwould allow local reworking, together with high-angledraping of the overlying lower Miocene to upper Oligo-cene sediments along a highly irregular erosional sur-face.

Sample 568-44,CC is barren of any age-diagnosticnannofossils.

Site 569

Two holes were drilled at Site 569 above a seismicallydefined basement high on the mid-slope of the Guate-malan MAT, 32 km upslope from the trench axis. Sam-pling of slope sediments (charged with gas hydrates, asdocumented at Site 497) and basement complex were theprimary objectives at this site.

Recovery in Hole 569 included 250.7 m of Pleistoceneto upper Oligocene mudstone. Hole 569A, offset about900 m west and directly over the high, was washed to246 m to recover upper Oligocene and probably lower Eo-cene sediment above several meters of metabasalt base-ment at 361 m (total depth).

Calcareous nannofossils are frequent to common andmoderately preserved within most of the Pleistocenethrough upper Eocene intervals (Table 6), except for thelower Miocene interval from 125 to 231 m in Hole 569,where assemblage diversity and abundances drop. LowerEocene nannofossils are also rare and heavily recrystal-lized within Sample 569A-10-1, 1-2 cm.

Reworking is minimal and largely restricted to thePleistocene, where several rare Cretaceous species wereobserved.


Samples 569-1-1, 108 cm through 569-4,CC are as-signed to the Holocene/upper Pleistocene Emiliania hux-leyi Zone or Gephyrocapsa oceanica Zone, and containcommon abundances of G. oceanica, Helicosphaera car-teri, small Gephyrocapsa spp., and minute placoliths withaffinities to Emiliania huxleyi. Samples 569-5,CC and569-6,CC (40.0-49.7 m) are also Pleistocene, but speciesdiversity and abundances are unfavorably low for de-tailed zonation. P. lacunosa is present, indicating an ageolder than the G. oceanica Zone. Very rare specimens ofthe Cretaceous species W. barnesae are present in Sam-ple 569-6,CC. Samples 569-7-2, 10 cm through 569-7-6,10 cm are barren of nannofossils.

Sample 569-7,CC (58.9 m) is assigned to the upperPliocene Discoaster pentaradiatus Subzone. It containsfrequent Discoaster pentaradiatus and rare D. brouweriand D. decorus. A change in lithologic color, which mayrepresent the Pliocene/Pleistocene boundary, is presentnear 569-7-6, 49 cm, but samples bracketing the contactare barren of nannofossils. Sample 569-8-2, 2 cm alsocontains rare D. brouweri and D. pentaradiatus, but thelow assemblage diversity and abundance preclude defi-nite zonal assignment. Samples 569-8,CC through 569-9,CC are barren of nannofossils. Lower Pliocene throughupper middle Miocene sediments are absent or representedstratigraphically by the barren/nondiagnostic (all micro-fossil disciplines) section present from 569-8-2, 2 cmthrough 569-9,CC.

Samples 569-10-2, 20 cm through 569-10,CC are mid-dle Miocene and assigned to the Sphenolithus heteromor-phus Zone. Diagnostic species include S. heteromorphus,Discoaster exilis s. ampl., Coccolithus miopelagicus, andDiscoaster signus. The 8-m core interval is age-equiva-lent to the 92-m-thick section penetrated in Sections 28-6through 38-2 from Hole 568.

Samples 569-11-2, 71 cm through 569-12,CC are as-signed to the lower and middle Miocene Helicosphaeraampliaperta Zone, and contain H. ampliaperta, S. het-eromorphus, and Discoaster deflandrei. This 17-m sec-tion is age-equivalent to Sections 38-4 through 42-3 (37 mthick) of Hole 568.

Samples 569-13-4, 3 cm through 569-22,CC (111.2-202.6 m) are lower Miocene on the basis of rare to fre-quent occurrences of moderately to poorly preservedspecimens of D. deflandrei, Cyclicargolithus floridanus,Sphenolithus moriformis, S. conicus, Sphenolithus sp.cf. S. belemnos, and Discoaster saundersi. Sample 569-17,CC also contains rare Triquetrorhabdulus milowii,which is restricted to lower Miocene or younger sediment.The absence of Discoaster druggii indicates that this en-tire interval may be within the Sphenolithus belemnosZone, but low assemblage abundances and diversityprohibit definite zonal assignment. Core 569-23 is domi-nated by siliceous microfossils and barren of nannofos-sils.

Samples 569-26-3, 62 cm and 569-26-4, 44 cm wereselected from a light gray calcareous mudstone within

353

M. V. FILEWICZ


Age

Holocene-late Pleistocene

Pleist.

1. Plioc.

middleMioc.

early Miocene

lateOlig.

early Miocene-late Olig.

lateOlig.

e. Olig.

lateEocene

mid.Eocene

earlyEocene

Zoneor

subzone

Emilianiahuxleyi-

Gephyrocapsaocean ica

P. lacunosa-

C. macintyrei

D. pentaradiatus

Sphenolithusheteromorphus

Helicosphaeraampliaperta

Sphenolithusbelemnos-Discoasterdeßandrei

D. bisectus

D. deßandrei-C. abisectus

D. bisectus

/ C. ßoridanus- \S. distentus

S. predistentus

D. barbadiensis

D. saipanensis

D. lodensis (?)


Hole 569

1-1, 107-1081,CC2-2, 148-1492,CC3-2, 17-183,CC4-2, 70-714.CC

5-2, 16-176-4, 29-306,CC

7-2, 10-117-6, 10-11

7,CC

8-2, 2-49-2, 20-22

10-2, 20-2110,CC

11-2, 71-7212-2, 69-7012.CC

13-4, 3-414-2, 149-15015-2, 103-10416-1, 66-6717-6, 148-14918-2, 138-13919-1, 30-3120-1, 149-15021-3, 34-3522,CC23-4, 43-4424-2, 77-7825,CC26-4, 44-45

27-1, 19-2027,CC

Hole 569A

1-1, 99-100

2-1, 147-1484,CC6-1,42-43

7-1, 42-43

7,CC

8-1, 74-758,CC

9-1, 18-199,CC

10-1, 1-2

Sub-bottomdepth(m)

1.081.204.19

11.1012.7820.6022.8030.30

31.9744.8049.70

5 1 . 3 1

57.31

58.90

60.4370.21

79.6187.40

89.6299.30

106.70

111.24119.00128.14135.77153.79157.27164.41175.30186.75202.60207.53214.38231.40236.35

241.20250.70

247.00

256.98284.30294.33

303.93

313.10

313.85314.88

332.49334.18

351.42

nee

•σ

<

FA

FFRFCC

FRF

BB

C

RB

RR

FBC

RFFBRBFRRRBFRR

C

C

F

FRF

F

C

CC

FF

F

UO

IU

>

a.

P,EM,EP,OEM,EP,OEMP,OEM

P,OE

M

M,E

M,E

P,OEP.OE

M

M

MMP,OE

P.O

P,OEP,OEP.OP.E

P.OP,EP,O

M

M , E

M

MMP.O

P.O

M

MM

P.OP.O

P.O

u G

artn

er,

1977

—sm

all

ΦP

se

ns

|

O

FA

C1-

R

F

F

cF

P

hus

do

ü

FCFlR

cccF

F

C

1

ohae

raso

RCRKRRFF

R

R

F

R

F

F

F

FRR

R

R

RR

R

R

ia h

uxl

a

Uj

7

s

1o

F

R

RRF

R

snjodoi

g.

p

d

FRR

RFFF

R

R

iwer

ite

r br

oi

Q

V

R

R

F

1P

osph

ae

R

R

R

a

a la

cuno

c

a:

R

F

R

irne

sae

ueri

a b(

a

*

R

cint

yrei

cus

ma

"5•ji

ü

R

F

R

a

3

I 'J•c •S

s 3

R R

rcal

aris

ter

inte

R

\

a

Q

F

tara

diat

ute

r pe

n

i.IS

F

R

phus

lith

us h

no

RF

F

C

abil

is

OSI

C5

RF

R

F

R

lagi

cus

thus

pe

o

RF

F

F

FRF

R

RRR

R

FF

R

RR

R

F

F

FF

2

Js

a

Pa•

R

•1 1k. W

1 1

R F

R

tus

ulus

aur

i1g•

R

R

R

opel

agic

thus

m

'•j

R

T)

T|

i ite

scen

sno

cycl

us

?<j

R

R

bies

lith

us

a

to

R

R

R

R

R

R

nus

s ß

ori

da

rgol

ithi

<J

F

F

F

RFF

FRR

R

FRF

FC

F

FFF

F

C

C


354



355

M. V. FILEWICZ

the burrows of a highly bioturbated sediment. They con-tain Discoaster deßandrei, Dictyococcites scrippsae, Heli-cosphaera recta, and H. bramlettei, lack Cyclicargolith-us abisectus and Dictyococcites bisectus, and are mostindicative of the lower Miocene Discoaster deßandrei Sub-zone.

Samples 569-27-1, 19 cm through 569-27,CC (250.7 m)are upper Oligocene, and are assigned to the Dictyococ-cites bisectus Subzone. Age-diagnostic species includeC. ßoridanus, D. deßandrei, T. carinatus, D. bisectus,H. recta, C. abisectus, Sphenolithus ciperoensis, and H.bramlettei.


Sample 569A-1-1, 99 cm, is probably lower Miocene(Discoaster deßandrei Subzone), and contains D. deßan-drei, H. bramlettei, and Dictyococcites scrippsae.

Samples 569A-2-1, 147 cm through 569A-6-1, 43 cmare upper Oligocene, and are assigned to the D. bisectusSubzone. They contain the species C. ßoridanus, D. de-ßandrei, Helicosphaera intermedia, C. abisectus, and H.recta. Sample 569A-7,CC contains frequent, well-devel-oped S. predistentus, and is assigned to the upper lowerOligocene Sphenolithus predistentus Zone. This zone over-lies upper Eocene sediments (Core 569A-8), which sug-gests the presence of a hiatus encompassing the lowerlower Oligocene {Helicosphaera reticulata Zone).

Samples 569A-8-1, 74 cm through 569A-8,CC areupper Eocene, and are assigned to the Discoaster barba-diensis Zone. Discoaster barbadiensis, Recticulofenestraumbilica, and D. scrippsae are present, along with rareCoccolithus formosus and common Cribrocentrum reti-culatum. Sample 569A-9-1, 18-19 cm contains the con-tact of a heavily burrowed and possibly disturbed baseof a light gray calcareous mudstone, which overlies thedark gray mudstone samples from 569A-9,CC. Rare speci-mens of Chiasmolithus grandis are present, which if notreworked, would suggest a slightly older age (upper mid-dle Eocene Discoaster saipanensis Subzone) for all ofCore 569A-9.

Core 569A-10 (360.9 m) penetrated metadiabase base-ment and contains only several centimeters of disturbed,muddy light gray limestone fragments at the top of Sec-tion 569A-10-1. This limestone contains highly recrys-tallized specimens of Discoaster lodoensis, Coccolithuscrassus, C. gammation, Chiasmolithus solitus, D. bar-badiensis, and Sphenolithus radians. This assemblage ismost indicative of the upper lower Eocene Discoasterlodoensis Zone, but extremely poor preservation mayhave destroyed key species which could make it as youngas the lower middle Eocene Discoaster sublodoensis Zone.A second Paleogene hiatus is therefore suggested, encom-passing most of the middle Eocene {Discoaster bifax Sub-zone to possibly Discoaster sublodoensis Zone), betweenCores 569A-9 and 569A-10.

Core 569A-11 recovered metabasalt mixed with apiece of upper middle Eocene limestone displaced fromupsection.


Site 570 was drilled near a relatively shallow, high-intensity magnetic anomaly on the upper slope of theGuatemalan MAT, 40 km upslope from the trench axisand approximately 40 km southwest of the Esso Petrel#1 well (Seely, 1979). Pleistocene through lower Eocenesediments were recovered to a depth of approximately360 m, and contain age-diagnostic nannofossils whichoverlie 10 m of age-indeterminate conglomerate above32 m of penetrated serpentinite basement.

Calcareous nannofossils are well preserved but non-diverse throughout the Pleistocene mudstone, well pre-served and abundant throughout the Pliocene and upperMiocene sediment, and marginally preserved in rare tocommon abundance within the lower Eocene sandy mud-stone and limestone (Table 7).

Reworking of Pliocene nannofossils occurs sporadi-cally throughout the Pleistocene, and becomes especial-ly prevalent in Sample 570-18,CC. Several Paleocene spe-cies were also observed in the lower Eocene sediments sam-pled at 570-36,CC and 570-37-1, 28 cm.

Samples 570-1-2 through 570-23-4, 47 cm are Pleisto-cene. Species diversity is low throughout this interval,and zonal markers such as Pseudoemiliania lacunosa,Helicosphaera sellii, and Calcidiscus macintyrei occur in-consistently. Small Gephyrocapsa spp. are abundant andGephyrocapsa oceanica is absent in Samples 570-6,CCthrough 570-8,CC, which suggests assignment to thesmall Gephyrocapsa Zone. Significant reworking of D.brouweri occurs in 570-18,CC.

Samples 570-23-6, 36 cm through 570-25-4, 36 cm areassigned to the upper Pliocene Discoaster brouweri Zone.They contain D. brouweri, D. pentaradiatus, and Heli-cosphaera sellii. Lack of the consistent presence of Dis-coaster tamalis and Discoaster surculus restricts subzona-tion.

Samples 570-25,CC and 570-26,CC are lower Plio-cene, and contain Reticulofenestra pseudoumbilica, Sphe-nolithus neoabies, D. brouweri, and D. pentaradiatus,indicative of the Reticulofenestra pseudoumbilica Zone.Section 570-27-1 contains silty mud interbedded with gashydrate. The silty mud matrix is assigned to the lowerPliocene Ceratolithus acutus Zone, and contains well-preserved specimens of C. acutus, Discoaster surculus,Sphenolithus neoabies, R. pseudoumbilica, and D. pen-taradiatus. Fractured siliceous dolomite interbedded withgas hydrate in 570-27,CC (258.8 m) is barren of nanno-fossils.

Samples 570-28-1, 43 cm through 570-35-1, 30 cm areupper Miocene, contain Discoaster quinqueramus, D.berggrenii, D. surculus (large morphotype), and rare D.loeblichii, and are assigned to the Discoaster quinquera-mus Zone.

Silty mud matrix sampled from decomposed hydratesof Samples 570-35-4, 5 cm through 570-35-4, 40 cm,just above a thin conglomerate, contains rare Discoasterexilis, S. neoabies, and Discoaster variabilis, which areindicative of the middle Miocene. Sample 570-35,CC

356


(335.6 m) is lower Miocene, contains Helicosphaera am-pliaperta, H. intermedia, Discoaster deflandrei, and Re-ticulofenestra gartneri, and is assigned to the S. belem-nos Zone or upper T. carinatus Zone. Two successive hia-tuses (within Core 570-35) representing 3 m.y. or moreduration probably separate the upper and middle Mio-cene, and middle and lower Miocene sediment.

A sandy mudstone sampled in 570-36-1, 125 cm and570-36-2, 44 cm also provided the matrix support for agas hydrate. This interval is lower Eocene and containsDiscoaster barbadiensis, D. lodoensis, Tribrachiatus or-thostylus, and Coccolithus sp. cf. C. crassus, which areindicative of the Discoaster lodoensis Zone. A hiatus,which spans the Oligocene through middle Eocene (atleast 27 m.y.), is therefore present between Cores 570-35and 570-36. Hard greenish limestone recovered fromSample 570-36,CC (345.2 m) is also lower Eocene (D.lodoensis Zone), and contains abundant recrystallizedspecimens of those species present in the softer lithologyabove, along with Chiasmolithus solitus, Neococcolithusdistentus, Lophodolithus mochloporus, and others.

Limestone sampled in 570-37-1, 42 cm and 570-38-1,55 cm is lower Eocene, contains Discoaster diastypusalong with T. orthostylus and Discoaster binodosus, andis assigned to the Discoaster diastypus Zone. Rare re-working of several Paleocene species occurs within boththe sandy mud and the limestone lithologies from Sam-ples 570-36,CC to 570-37-1, 28 cm.

Samples 570-38,CC through 570-39,CC are essential-ly barren of nannofossils. A soft brown mudstone lithol-ogy in 570-38,CC contains very rare nannofossil speci-mens of the Cretaceous species Watznaueria barnesae andMicula staurophora (species which are commonly re-worked) mixed with sporadic, long-ranging Tertiary nan-nofossil species and Miocene foraminifers. Downholecontamination of this sediment is a distinct possibility.Cores 570-40 through 570-42 (383.3-401.9 m) recoveredserpentinite and are barren of nannofossils.

TAXONOMIC NOTES

One new species of Discoaster was observed on DSDP Leg 84. Allother calcareous nannofossil species considered in this study are listedin the Appendix; these are adequately described and discussed in theliterature.

Discoaster tuberi n. sp.(Plate 1, Figs. 1-9)

Description. Asterolith with six slightly tapered and bent rays,which terminate in short, blunt bifurcations. A large, flaring stellateknob is present on one side and dominates the central area, which is 25to 30% of the asterolith diameter. Knob rays are usually aligned withthe rays of the asterolith. A second small knob on the opposite side ofthe central area is formed by the termination of low ridges, which ex-tend radially along the periphery of each asterolith ray.

Remarks. Discoaster tuberi is most similar in outline and structureto D. exilis. It differs from D. exilis, however, by its more prominent,flaring stellate knob. D. tuberi also possesses two knobs on oppositesides, whereas only a single knob was originally described by Martiniand Bramlette (1963) in the original species description of D. exilis. Il-lustrations of D. exilis in side view by Martini and Bramlette (1963)and in this chapter (Plate 1, Figs. 10-12) do show a definite thickeningof the central area which may be the remnant (or predecessor) of twocentral knobs, suggesting the close, but morphologically distinct, rela-tionship between this species and D. tuberi. D. tuberi differs from D.signus by its short bifurcations, (present even in well-preserved sam-ples containing delicate D. signus morphotypes with intact bifurca-

tions), rays which are consistently thicker, tapered and bent, and devel-opment of a wider central area with a flaring, through-going knob. D.tuberi differs from both D. bollii and D. sanmiguelensis by its longerrays and smaller central area. D. sanmiguelensis also differs by its pos-session of one central-area knob. D. tuberi differs from Eocene Disco-aster species which possess two knobs, such as D. bifax and D. diasty-pus, by its maximum number of free rays (six).

Occurrence. D. tuberi is frequent to common in the middle Mio-cene Sphenolithus heteromorphus (CN4) Zone sediment penetrated onLeg 84 at Site 568. A thin interval of S. heteromorphus Zone sedimentcontaining frequent D. tuberi was also recovered at Site 569. Rare spe-cimens of D. tuberi were also noted in the upper Helicosphaera ampli-aperta (CN3) sediment at this site; they may represent its first evolu-tionary appearance. Specimens of D. tuberi were not observed in sedi-ments younger than the S. heteromorphus Zone at any of the Leg 84sites.

D. tuberi may be restricted in its occurrence to low-latitude, lowermiddle Miocene (upper CN3-CN4) hemipelagic sediments. It is absentin numerous wells and surface sections containing lower to middle Mi-ocene sediments examined by the author throughout California andthe Southern California borderland (north of 32° latitude). D. tuberimay have been taxonomically combined with D. exilis s. ampl. and D.signus s. ampl. in previous studies on low-latitude lower to middle Mi-ocene sediment, especially if it was a rare assemblage constituent andwas not observed in diagnostic side view.

Size. 8-14 µmHolotype. USNM 371078 (Plate 1, Fig. 1-4)Isotype. USNM 371079 (Plate 1, Fig. 5-6)Type locality. Landward slope of the Middle America Trench off-

shore Guatemala, eastern equatorial Pacific, DSDP Sample 569-10.CC(87.40 m)

ACKNOWLEDGMENTS

I thank G. C. Brown and Union Oil Company of California forgraciously permitting shipboard participation on DSDP Leg 84. DavidBukry (U. S. Geological Survey) and Hans R. Thierstein (Scripps In-stitution of Oceanography) kindly reviewed the manuscript and of-fered constructive advice. I am indebted to Cathy Hiebert for typingof the preliminary manuscript, Hal L. Heitman for preliminary edit-ing, and Robert S. Wilton and Larry Willis (all from Union Oil Com-pany of California) for assistance in photo and sample preparation.

REFERENCES

Aubouin, J., von Huene, R., et al., 1982. Site 494: Middle AmericaTrench lower slope. In Aubouin, J., von Huene, R., et al., Init.Repts. DSDP, 67: Washington (U.S. Govt. Printing Office), 27-78.

Bukry, D., 1973. Low-latitude coccolith biostratigraphic zonation. InEdgar, N. T., Saunders, J. B., et al., Init. Repts. DSDP, 15: Wash-ington (U.S. Govt. Printing Office), 685-703.

, 1975. Coccolith and silicoflagellate stratigraphy northwest-ern Pacific Ocean. In Larson, R. L., Moberly, R., et al., Init. Repts.DSDP, 32: Washington (U.S. Govt. Printing Office), 677-701.

Gartner, S., Jr., 1977. Calcareous nannofossil biostratigraphy and re-vised zonation of the Pleistocene. Mar. Micropaleontol., 2:1-25.

Hardenbol, J., and Berggren, W. A., 1978. A new Paleogene numericaltime scale. Am. Assoc. Pet. Geol., Studies in Geology, 6:213-234.

Martini, E., and Bramlette, M. N., 1963. Calcareous nannoplanktonfrom the experimental Mohole drilling. J. Paleontol. 37 (4):845-856.

Musylov, N., 1982. Nannoplankton stratigraphy of Leg 67 drill sites. InAubouin, J., von Huene, R., et al., Init. Repts/DSDP, 67: Wash-ington (U.S. Govt. Printing Office), 383-399.

Okada, H., and Bukry, D., 1980. Supplementary modification and in-troduction of code numbers to the low-latitude coccolith biostrati-graphic zonation (Bukry, 1973-1975). Mar. Micropaleontol., 5:321-325.

Seely, D., 1979. Geophysical investigation of continental slopes andrises. In Watkins, J. S., Montadert, L., and Dickerson, P. W., (Eds.),Geological and Geophysical Investigations of Continental Mar-gins. Am. Assoc. Pet. Geol. Mem., 29:245-260.

Stradner, H., and Allram, F., 1982. The nannofossil assemblage ofDeep Sea Drilling Project Leg 66, Middle America Trench. In Wat-kins, J. S., Moore, J. C , et al., Init. Repts. DSDP, 66: Washing-ton (U.S. Govt. Printing Office), 589-639.

Thierstein, H. R., 1976. Mesozoic calcareous nannoplankton biostra-tigraphy of marine sediments. Mar. Micropaleontol., 1:325-362.

357

M. V. FILEWICZ


Age

Holocene-late Pleistocene

earlyPleistocene

1.

Pliocene

e.

1.

Miocene

m.

e.

earlyEocene

Zoneor

subzone

Emilianiahuxleyi-

Pseudoemilianialacunosa

smallGephyrocapsa

smallGephyrocapsa-

Calcidiscusmacintyrei

Discoasterbrouweri

R. pseudoumbilica

C. acutus

Discoaster

quinqueramus

Discoasterexilis

S. belemnos-D. deflandrei

D. lodoensis

D. diastypus


1-2, 36-37l.CC2-4, 36-373-2, 75-763,CC4-2, 25-264.CC5-4, 51-525,CC6-6, 36-37

6,CC7-4, 46-478-2, 36-378,CC

9-1, 18-1910-2, 36-3711-2, 17-1812.CC14-2, 129-13015-2, 127-12816-2, 55-5617-2, 94-9518.CC19-4, 68-6920-2, 38-3921,CC22-2, 9-1023-4, 47-48

23-6, 36-3724-4, 33-3425-4, 35-36

26-1, 23-24

26-4, 23-2427-1, 49-50

27,CC

28-1, 43-4429-2, 56-5730-1, 8-931-1, 143-14432-1, 54-5533.CC35-1, 29-30

35-4, 5-635-4, 39-40

35-5, 45-4635.CC

36-2, 10-11

36,CC

37-1, 42-4338-1, 54-55

Sub-bottomdepth

(m)

1.874.809.67

19.7627.2028.9536.8041.8246.4054.27

56.0060.9767.5775.40

75.5986.9696.38

113.90126.39136.08145.06155.15172.10177.28183.69201.20202.80215.68

218.57225.04234.56

239.64

244.14249.60

258.80

259.23270.47278.09289.03297.75316.40326.60

330.56330.90

332.46335.60

337.21

345.80

346.23355.34

idan

ce

<

FCFCFFFFCC

ACAA

CFRACFFFFCFFFC

CFF

F

FC

B

CCCFCCF

RR

RR

R

F

CR

o13>

<£

P.OMPM,0MPMPM,EP

MMMM,E

PMP.OM,EPP.OP.OMM.EM.EMM.EP.EM

M.EP.EM.E

M.E

M.EM.E

MM.EM,EM,EMM,EM

MM

MR,E

P.O

P.O

M.OP.O

ao

1Q

lyro

caps

a

&

O

RFRF

R

anic

a

o

!

1&OFCFCFRRRRR

R

R

RRF

R

. se

nsu

Gar

tner

, 19

77—

smal

lsp

ply

roca

psa

IOFCFCFFFFCF

AAAA

CFRACFFC

CF

FC

sell

:ops

hae

ra

R

R

F

R

RR

F

R

oru

sto

pid

iscu

s le

p

"αO

RRRFFRRRRR

FRRR

RFRRFRFR

RFFFF

FRF

F

R

F

R

icoi

des

UO

J

ali

thu

s do

1üFC

FFFFFCC

C

ccccF

CFFRFF

C

RFF

F

R

RRF

1

car

zosp

haer

a

%FFFCFFRRFF

FFRF

FFFFFRRRFRRFFF

FA

t

R

RR

RR

RR

1

:osp

haer

a

3j

R

RR

R

RR

1I5

1

FRR

F

RR

R

F

R

tyre

i

&

idis

cus

mo

ale

U

RR

R

R

R

F

R

R

R

tus

ista

toli

thus

er

g0

R

nira

bili

s

5

'ilic

osph

ae

|

R

R

R

RRRYR

R

tric

a

-5

cosp

haer

a

2

R

R

idia

tus

I

oast

er p

en

SjQ

RR

R

FRF

F

FC

'bie

s

o

•nol

ithu

s n

ti

CO

R

C

C

c

FFCF

CF

R

ε11

11Q

RR

RR

CFR

F

FF

R

FRR


358



359

M. V. FILEWICZ

APPENDIXCalcareous Nannofossils Considered in this Chapter

Broinsonia enormis (Shumenko, 1968) Manivit, 1971Broinsonia parca (Stradner, 1963) Bukry, 1969Calcidiscus gammation (Bramlette and Sullivan, 1961) Loeblich and

Tappan, 1978Calcidiscus leptoporus (Murray and Blackman, 1898) Loeblich and

Tappan, 1978Calcidicus macintyrei (Bukry and Bramlette, 1969) Loeblich and Tap-

pan, 1978Catinaster mexicanus Bukry, 1971Ceratolithoides aculeus (Stradner, 1961) Prins and Sissingh, 1977Ceratolithus acutus Gartner and Bukry, 1974Ceratolithus cristatus Kamptner, 1950Ceratolithus rugosus Bukry and Bramlette, 1968Chiasmolithus consuetus (Bramlette and Sullivan, 1961) Hay and

Mohler, 1967Chiasmolithus grandis (Bramlette and Riedel, 1954) Radomski, 1968Chiasmolithus solitus (Bramlette and Sullivan, 1961) Locker, 1968Chiasmolithus titus Gartner, 1970Chiphragmalithus acanthodes Bramlette and Sullivan, 1961Coccolithus crassipons Bouché, 1962Coccolithus crassus Bramlette and Sullivan, 1961Coccolithus eopelagicus (Bramlette and Riedel, 1954) Bramlette and

Sullivan, 1961Coccolithus formosus (Kamptner, 1963) Wise, 1973Coccolithus miopelagicus Bukry, 1971Coccolithus pelagicus (Wallich, 1877) Schiller, 1930Coronocyclus nitescens (Kamptner, 1963) Bramlette and Wilcoxon,

1967Crenalithus doronicoides (Black and Barnes, 1961) Roth, 1973Cretarhabdus crenulatus Bramlette and Martini, 1964Cribrocentrum reticulatum (Gartner and Smith, 1967) Perch-Nielsen,

1971Cribrosphaerella ehrenbergii (Arkhangelsky, 1912) Deflandre, 1952Cricolithus jonesii Cohen, 1965Cruciplacolithus staurion (Bramlette and Sullivan, 1961) Gartner,

1971Cyclicargolithus abisectus (Muller, 1970) Bukry, 1973Cyclicargolithus floridanus (Roth and Hay, 1967) Bukry, 1971Dictyococcites antarcticus Haq, 1976Dictyococcites bisectus (Hay, Mohler and Wade, 1966) Bukry and Per-

cival, 1971Dictyococcites scrippsae Bukry and Percival, 1971Discoaster adamanteus Bramlette and Wilcoxon, 1967Discoaster asymmetricus Gartner, 1969Discoaster barbadiensis Tan, 1927Discoaster berggrenii Bukry, 1971Discoaster bifax Bukry, 1971Discoaster binodosus Martini, 1958Discoaster bollii Martini and Bramlette, 1963Discoaster brouweri Tan, 1927Discoaster calcaris Gartner, 1967Discoaster calculosus Bukry, 1971Discoaster challenged Bramlette and Riedel, 1954Discoaster decorus (Bukry, 1971) Bukry, 1973Discoaster deflandrei Bramlette and Riedel, 1954Discoaster diastypus Bramlette and Sullivan, 1961Discoaster distinctus Martini, 1958Discoaster druggii Bramlette and Wilcoxon, 1967Discoaster elegans Bramlette and Sullivan, 1961Discoaster exilis Martini and Bramlette, 1963Discoaster germanicus Martini, 1958Discoaster icarus Stradner, 1972Discoaster intercalaris Bukry, 1971Discoaster lodoensis Bramlette and Riedel, 1954Discoaster mohleri Bukry and Percival, 1971Discoaster multiradiatus Bramlette and Riedel, 1954Discoaster pentaradiatus Tan, 1927Discoaster quinqueramus Gartner, 1969Discoaster saipanensis Bramlette and Riedel, 1954Discoaster sanmiguelensis Bukry, 1981Discoaster saundersi Hay, 1967Discoaster signus Bukry, 1971

Discoaster surculus Martini and Bramlette, 1963Discoaster tanii nodifer Bramlette and Riedel, 1954Discoaster tanii ornatus Bramlette and Wilcoxon, 1967Discoaster tanii tanii Bramlette and Riedel, 1954Discoaster tuberi Filewicz, n. sp.Discoaster variabilis Martini and Bramlette, 1963Discoasteroides kuepperi (Stradner, 1959) Bramlette and Sullivan,

1961Discolithina anisotrema (Kamptner, 1953) Bramlette and Wilcoxon,

1967Discolithina japonica Takayama, 1967Discolithina multipora (Kamptner, 1948) Martini 1965Discolithina plana (Bramlette and Sullivan, 1961) Levin, 1965Discolithina vigintiforata (Kamptner, 1948) Loeblich and Tappan,

1966Eiffellithus eximius (Stover, 1966) Perch-Nielsen, 1968Eiffellithus turriseiffeli (Deflandre, 1954) Reinhardt, 1965Ellipsolithus macellus (Bramlette and Sullivan, 1961) Sullivan, 1964Ellipsolithus subdistichus Roth and Hay, 1967Emiliania huxleyi (Lohman, 1902) Hay and Mohler, 1967Fasciculithus tympaniformis Hay and Mohler, 1967Gephyrocapsa oceanica Kamptner, 1943Gephyrocapsa omega Bukry, 1973small Gephyrocapsa spp. sensu Gartner, 1977Helicosphaera ampliaperta Bramlette and Wilcoxon, 1967Helicosphaera bramlettei (Muller, 1970) Jafar and Martini, 1975Helicosphaera californica Bukry, 1981Helicosphaera carteri (Wallich, 1877) Kamptner, 1954Helicosphaera compacta Bramlette and Wilcoxon, 1967Helicosphaera euphratis Haq, 1966Helicosphaera intermedia Martini, 1965Helicosphaera lophota (Bramlette and Sullivan, 1961) Jafar and Mar-

tini, 1975Helicosphaera minuta Muller, 1981Helicosphaera neogranulata (Gartner, 1977) Haq and Berggren, 1978Helicosphaera obliqua Bramlette and Wilcoxon, 1967Helicosphaera recta (Haq, 1966) Jafar and Martini, 1975Helicosphaera rhomba (Bukry, 1971) Jafar and Martini, 1975Helicosphaera scissura Miller, 1981Helicosphaera sellii Bukry and Bramlette, 1969) Jafar and Martini,

1975Helicosphaera seminulum (Bramlette and Sullivan, 1961) Jafar and

Martini, 1975Helicosphaera wallichii (Lohman, 1902) Okada and Mclntyre, 1976Lophodolithus mochlophorus Deflandre in Deflandre and Fert, 1954Lucianorhabdus cayeuxi Deflandre, 1959Manivitella pemmatoidea (Deflandre ex Manivit, 1965) Thierstein,

1971Microrhabdulus decoratus Deflandre, 1959Micula murus (Martini, 1961) Bukry, 1973Micula staurophora (Gardet, 1955) Stradner, 1963Nannoconus sp.Neochiastozygus concinnus (Martini, 1961) Perch-Nielsen, 1971Neochiastozygus distentus (Bramlette and Sullivan, 1961) Perch-Niel-

sen, 1971Neococcolithites dubius (Deflandre, 1954) Black, 1967Orthorhabdus serratus Bramlette and Wilcoxon, 1967Orthorhabdus sp.Prediscosphaera cretacea (Arkhangelsky, 1912) Gartner, 1968Pseudoemiliania lacunosa (Kamptner, 1963) Gartner, 1969Reticulofenestra gartneri Roth and Hay, 1967Reticulofenestra pseudoumbilica (Gartner, 1967) Gartner, 1969Reticulofenestra samodurovii (Hay, Mohler and Wade, 1966) Roth,

1970Reticulofenestra umbilica (Levin, 1966) Martini and Ritzkowski, 1968Rhabdosphaera sty lifer Lohman, 1902Rhabdosphaera tenuis Bramlette and Sullivan, 1961Sphenolithus abies Deflandre, 1954Sphenolithus belemnos Bramlette and Wilcoxon, 1967Sphenolithus ciperoensis Bramlette and Wilcoxon, 1967Sphenolithus conicus Bukry, 1971Sphenolithus heteromorphus Deflandre, 1953Sphenolithus moriformis (Brönniman and Stradner, 1960) Bramlette

and Wilcoxon, 1967Sphenolithus neoabies Bukry and Bramlette, 1969

360


Sphenolithus predistentus Bramlette and Wilcoxon, 1967Sphenolithus radians Deflandre, 1952Sphenolithus spiniger Bukry, 1971Syracosphaera histrica Kamptner, 1941Syracosphaera pulchra Lohman, 1902Thoracosphaera saxae Stradner, 1961Thoracosphaera sp.Toweius sp.Tranolithus orionatus Stover, 1966Transversopontis pulcher (Deflandre, 1954) Perch-Nielsen, 1967

Tribrachiatus orthostylus Shamrai, 1963Triquetrorhabdulus auritus Stradner and Allram, 1982Triquetrorhabdulus carinatus Martini, 1965Triquetrorhabdulus milowii Bukry, 1971Umbilicosphaera sibogae (Weber-von Bosse, 1901) Gaarder, 1970Uniplanarius gothicus (Deflandre, 1959) Hattner and Wise, 1980Uniplanarius trifidus (Stradner, 1961) Hattner and Wise, 1980Watznaueria barnesae (Black, 1959) Perch-Nielsen, 1968Zygodiscus elegans Gartner, 1968Zygrhablithus bijugatus (Deflandre, 1954) Deflandre, 1959

Plate 1. Miocene Discoaster species from the landward slope of the Middle America Trench offshore Guatemala. (All figures are magnified X2000in transmitted light, except Figures 8, 9, and 12, which are illustrated in polarized light at 45°.) 1-9. Discoaster tuberi n. sp., (1-4) holotypeUSNM 371078, Sample 569-10.CC, high to low focus sequence, (5-6) isotype USNM 371079, Sample 568-31-1, 110 cm, high and low focus, (7-8) side view of knob detached from rays, Sample 569-10.CC, (9) side view showing the flaring, through-going knob and slightly bent rays, Sam-ple 568-31-1, 110 cm. 10-12. Discoaster exilis Martini and Bramlette, (10) Sample 568-31-1, 110 cm, (11-12) side view showing thickening ofthe central area, Sample 568-30,CC.

361

Documents

Deep Sea Drilling Project Initial Reports Volume 84 · 2007. 5. 1. · 565-30,CC through 565-34,CC. Very rare species reworked from the Oligocene and Pliocene are also in the Pleisto-cene