BLAKE-BAHAMA BASIN, DEEP SEA DRILLING PROJECT SITE …

20. PALEOECOLOGY AND STRATIGRAPHY OF JURASSIC ABYSSAL FORAMINIFERA IN THEBLAKE-BAHAMA BASIN, DEEP SEA DRILLING PROJECT SITE 5341

F. M. Gradstein, Geological Survey of Canada, Bedford Institute of Oceanography,Dartmouth, N. S. B2Y 4A2, Canada

ABSTRACT

At Site 534, Blake-Bahama Basin, 66 brownish to olive green to gray black shale samples from Cores 127 to 70, ofthe middle Callovian-Valanginian, contain an assemblage of foraminifers with 36 calcareous taxa in 9 families and 35agglutinated taxa in 8 families. The average number of taxa per sample is about 5, with a spread of 0 to 19 and a modeof about 8. Sample weight (10-50 g) is not correlated to species diversity and to specimen abundance, which means thata better recovery tool is more rather than bigger samples per core.

R-mode cluster analysis using Jaccard and Dice coefficients of variation on 25 taxa occurring in 5 or more samplesshow a low level of association. One cluster includes the Kimmeridgian, carbonate-rich environment assemblage withLenticulina quenstedti, Ophthalmidium carinatum, Neobulimina atlantica n. sp., and Epistomina aff. uhligi. Threeclusters comprise stratigraphically persistent taxa of the genera Reophax, Bigenerina, Bathysiphon, Glomospira, Glo-mospirella, Lenticulina, Rhizammina, Psammosphaera, Dentalina, Lagena, Marginulina, Pseudonodosaria, and Tro-chammina. Strikingly similar Jurassic assemblages at other Atlantic and Indian oceans sites, which also backtrack to~ 3-km water depth, show that the Jurassic abyssal fauna principally consists of small-sized agglutinated taxa in 8 or sofamilies, small-sized nodosariids in a dozen or so genera, and variable numbers of epistominids, ophthalminids, spirri-linids, and turrilinids. There is high (< 100) species and high (<50) generic diversity, patchy specimen representation,and low species communality between stratigraphically successive samples. The fauna is accompanied by radiolarians,calcispherulids, aptychi, Saccocoma, and largely continues in the Early Cretaceous.

Coeval shallow-marine (neritic) Jurassic assemblages have a much more limited representation of agglutinated taxa.Miliammina, Trocholina, Patellina, Paalzowella, Citharina, Tristix, and large Ammobaculites and Ammomarginulinamay be exclusive of this niche, which in general contains larger and more sculptured forms.

At Site 534,18 taxa group in 3 stratigraphically successive assemblages. The co-occurrence of Conorboidesparaspis,Gaudryina heersumensis, Textularia hauesleri, Trocholina nodulosa, and Globuligerina aff. oxfordiana in Core 110, al-though possibly transported in part, has no oceanic correlative at other sites, which agrees with the interpretation thatthis Oxfordian assemblage geomagnetically correlates to M-25, not penetrated at other DSDP sites.

The co-occurrence of Lenticulina quenstedti and Epistomina aff. uhligi at DSDP Sites 534, 391, 105, and 367 maybe a Kimmeridgian event; it correlates to M-22 to M-19. The co-occurrence of Dorothia praehauteriviana and Lenticu-lina nodosa at Sites 534, 391, 101, 105, 370, and 416 can be used to correlate late Valanginian strata.

Multiple biostratigraphic comparison at Site 534, Cores 127 to 91, shows Oxfordian-Kimmeridgian-Tithonian stageassignments to be 1 to 5 cores apart.

INTRODUCTION

Our knowledge of the Jurassic foraminiferal fauna inabyssal environments is limited and as far as I knowconfined to assemblages in the Upper Jurassic at DSDPSites 99, 100, 105, 367, 391, and 416 in the North Atlan-tic (Luterbacher, 1972; Kuznetsova and Seibold, 1978;Site 391 report, Benson, Sheridan et al., 1978; Sliter,1980) and Site 261 in the Indian Ocean (Kuznetsova,1974) (Fig. 1). So-called bathyal assemblages of theMiddle and Late Jurassic have been reported from theFrench Jura and Apennines by Wernli and Septfontaine(1971) and Farinacci (1965). The deep-water fauna con-sists principally of small-sized nodosariids and small ag-glutinated taxa belonging to a dozen or less families andvariable admixtures of epistominids, opthalmiids, andspirrilinids, frequently accompanied by radiolarians, cal-cispherulids, aptychi, and Saccocoma. Larger-sized ag-

BaitimoreTrough

416, 370Essaouira Basin

Aaiun Tarfaya Basin

Senegal Basin

367

Sheridan, R. E., Gradstein, F. M., et al., Init. Repts. DSDP, 76: Washington (U.S.Govt. Printing Office).

Figure 1. Jurassic "sedimentary wedge" basins, adjacent to the cen-tral North Atlantic, and location of Deep Sea Drilling Sites 99,100, 105, 367, 391, 370, 416, and 534, at which we attempted tocore Middle through Late Jurassic sediments laid down on oceaniccrust. Site 370 failed to reach Jurassic strata.

537

F. M. GRADSTEIN

glutinated taxa of Ammobaculites, Lituoliidae, orna-mented ostracodes, and echinoderm platelets and spinesare absent or known only from microfacies studies oflimestones. Questions as to what is exactly the differ-ence between abyssal, bathyal, and neritic Jurassic mi-crofauna and what are the biogeographic and biostrati-graphic distributions relative to the early history of theAtlantic-Tethys Ocean remain unanswered. Lack ofdeep-water sample material suitable for study is an out-standing problem.

During DSDP Leg 76, Middle and Late Jurassic (abys-sal) (Figs. 1, 2) sediments were cored continuously inHole 534A in the Blake-Bahama Basin, about 500 kmeast of Florida.

In this paper I will examine the Jurassic foraminiferalrecord in Cores 127 through 91 from a taxonomic, envi-ronmental, and stratigraphic point of view. For the sakeof continuity, the study has been extended upward toCore 70 in the Early Cretaceous, which also makes pos-sible a better assessment of faunal changes between theJurassic shaley and Early Cretaceous limestone forma-tions. The chapter is divided into four sectons. First, ageneral description of the main lithology and microfos-sil content is presented, with an eye on large-scale varia-tions, turbiditic versus pelagic influences, and so on.Secondly, attention is paid to the taxonomy and compo-sition of the foraminiferal assemblage in relation to otherdeep- and also shallow-marine Jurassic assemblages, andto the so-called flysch-type agglutinated foraminiferalfauna of the Cretaceous/Tertiary. Next is an attempt toderive paleoecologic information using the age versusdepth relationship as a means of estimating Jurassic pa-leowater depth and R-mode cluster analysis (based onthe Dice coefficient of similarity) to demonstrate the de-gree of association of taxa. In the last section, regionalbiostratigraphic and chronostratigraphic value of theassemblages is evaluated in the framework of multiplestratigraphy.

One taxon, Neobulimina atlantica n. sp., is new tothe literature and described in the Taxonomic Notes atthe end of the chapter. Four plates of scanning electronmicroscope pictures illustrate taxa that occur frequentlyand/or are stratigraphically useful. It should be stressedthat the taxonomy warrants refinement, particularlywhen more use can be made of comparative collections.

GEOLOGICAL BACKGROUND

DSDP Site 534 has the geographic coordinates 28°20.6'N and 75°22.9'W (Fig. 3). Water depth is 4974 m,and drilling at the Site reached a total depth of 1666 m;the bottom 30 m in cores 127 to 130 is oceanic-type ba-salt (Logothetis, this volume). Using nannofossil, radio-larian, and dinoflagellate stratigraphy, the basal varie-gated shales are dated as middle Callovian and the Ju-rassic/Cretaceous boundary is placed between Cores 91and 92. This boundary coincides with the top of thegrayish red calcareous claystones of the Cat Gap For-mation, at the level of seismic Horizon C. This meansthat the Callovian through Tithonian sedimentary sec-tion above basalt is 35 cores or 294 m thick, at 1340 to1636 m below the seafloor. Core recovery is 141.1 m oralmost 50%.

Our principal objective at Site 534 was to extend ourknowledge of the Jurassic Atlantic Ocean beyond whatwas known from earlier drilling at several sites duringLegs 1,11, and 44 in the western Atlantic and Legs 41and 50 in the eastern half, off northwest Africa. Prior to1980, at no ocean site had rocks been penetrated muchbelow seismic Horizon C, or older than the Late Juras-sic, in the marine magnetic zone closer to the continen-tal margin than M-25. In a nutshell, this history is de-picted in Figure 2. Sites 99,100, and 105 (Leg 11, Hollis-ter, Ewing, et al., 1972) and Site 367 (Leg 41, Lancelot,Seibold, et al., 1978) are located in the magnetic strip ofM-25 or landward on the edge of the so-called Jurassicmagnetic Quiet Zone (JQZ), which is devoid of high-

Age

100

NW Atlantic

100 105 391 534

NE Atlantic

416 370 367

W Pacific

462

IndianOcean

261

Cretaceous

- 135

Ea, 150-

175-

— Keathley

— Sequence

Jurassic

200

M-25

Quiet Zone

(predicted)

Oceanic crust

Figure 2. Schematic illustration of the DSDP quest for the oldest oceanic sediments. (The lack of geomagneticreversals during much of the Jurassic period of ocean history only allows indirect assumptions to be madeabout the age and timing of opening and early spreading across the oceans' central ridges. Question marksshow the inferred stratigraphic positions of basement, which was shown by the Hole 534A basementsamples to be one to several stages too old [see text].)

538

PALEOECOLOGY AND STRATIGRAPHY OF JURASSIC ABYSSAL FORAMINIFERA

Figure 3. Location of Site 534 on the landward site of the marine Jurassic magnetic Quiet Zone (JQZ).(Present water depth at the Site is 4974 m; total depth cored is 1666.5 m below the seafloor.)

amplitude magnetic anomalies. At these sites, drillingbottomed in reddish calcareous shale to gray, shaleylimestone deposited in the Oxfordian-Kimmeridgian.At both Site 391 (Leg 44, Benson, Sheridan, et al.,1978), which is 15 nautical miles southwest of 534, andSite 416 (Leg 50; Lancelot, Winterer, et al., 1980), drill-ing penetrated to the JQZ region but failed to reachbasement or extend much in Jurassic strata. In the Pa-cific, Site 462 (Leg 61, Larson, Schlanger, et al., 1981)failed to reach JQZ rocks. In the Indian Ocean, in frontof the western Australian passive margin, at Site 261(Leg 27, Veevers, J. J., Heirtzler, J. R., 1974), on aboutM-22, Oxfordian-Kimmeridgian shaley sediments wereencountered on the basement.

The larger part of Leg 76 was devoted to Site 534. Inorder to recover the earliest possible history of seafloorspreading, sedimentation, and biota development, a sitewas chosen as close as possible to the American conti-nental margin, where basement was estimated to be with-in drill-string limit (~ 7 km). The Site is on a small base-ment high in a strip of weak magnetic anomaly in theJQZ called M-28 (Bryan et al., 1980). M-25 is 400 kmeastward and the Blake Spur Anomaly 100 km to thewest (Fig. 3). The latter is a basement ridge phenome-non interpretated as an Early-Middle Jurassic spreadingcenter, which subsequently jumped to the present Cen-tral Ridge. Site 534 is in the region where the previouslynondated seismic reflector D is developed above oceanbasement; it pinches out midway between M-27 and M-28"isochrons" (see Bryan et al., 1980). The continentalmargin west of the Blake Spur contains the Blake Pla-teau, a Mesozoic carbonate platform that may have

been the source of some of the carbonate-rich turbiditesat Site 534, 150 km oceanward on what must have beena Callovian to Tithonian ridge flank or abyssal plain en-vironment.

HOLE 534A, SHELLY MICROFOSSILASSEMBLAGE

A total of 137 claystone samples were studied forshelly microfossils, ranging from Section 534A-127-4 toSample 534A-70-1, 79-81 cm. The complete listing is inTable 1, which also shows (where available) the dryweight in grams prior to processing. Samples were firstfragmented and then boiled for 30 min. in a 35% H2O2and 20 parts Calgon solution, followed by 1/2 min. ofweak ultrasonic. A stack of 45- and 63 /*m sieves wereused for screening. Residue splits were picked clean forspecimens. Microfossil preservation is adequate for gen-eral taxonomic treatment, although in some samplesfragmentation of shells has taken place or moderate tototal carbonate dissolution.

Table 1 illustrates the stratigraphic distribution ofgroups of shelly microfossils in relation to the lithology.Ten stratigraphically successive lithologies have been dis-tinguished, which are from top to bottom:

Cores 70 (and above)-76: Blake-Bahama Formation(5b); very finely laminated marly radiolarian, nannofos-sil chalk, bioturbated chalk and limestone, with minorclaystone and siltstone.

Cores 76-84: Blake-Bahama Formation (5c); thinlyparallel laminated, marly chalk, bioturbated limestone;thin, graded, calcareous siltstone more heterogenousfrom core to core than in Subunit 5b.

539

F.M.GRADSTEIN

Table 1. Micropaleontological and lithological characteristics of Middle-Upper Jurassic and some Lower Cretaceous Hole 534A samples, Cores127 through 70, Blake-Bahama Basin, western North Atlantic Ocean.

Sample

(intervalin cm)

70-1, 79-8170-3, 88-9070-4, 68-87071-1, 26-28

71-2, 109-11171-4, 63-6572-1, 60-6272-3, 100-102

72-4, 32-3473-1, 133-13473-1, 119-12173-3, 47-48

74-2, 62-6474-3, 77-7974-5, 56-5875-1, 44-45

75-3, 39-4175-4, 46-4876-1, 94-8676-3, 15-17

76-6, 51-5377-4, 2-478-2, 78-8078-3, 64-66

78-4, 72-7479-1, 57-5979-2, 64-6579-3, 53-55

80-3, 68-7080-3, 74-7581-1, 58-5981-4, 40-42

81-4, 46-4782-1, 51-5382-1, 64-6683-1, 19-22

83-1, 23-2483-5, 63-6584-2, 75-7784,CC

85-2, 44-4585-3, 11-1286-1, 147-14886-2, 101-102

86-5, 16-1787-1, 25-2787-1, 50-5187-1, 81-82

87-4, 68-7088-1, 50-5288-2, 9-1088-5, 94-95

88-5, 117-11989-2, 66-6789-3, 52-5489-3, 146-148

90-1, 73-7590-3, 52-5390-4, 32-3391-1,20-21

91-3, 37-3891-4, 109-11092-2, 62-6492-3, 22-23

92-5, 56-5793-2, 45-4693-2, 142-14493-3, 6-7

94-1, 30-3294-1, 140-14294-2, 90-91

Weight

(g)(prewashed)

19

2213

2018

2337

16

27

2615

26

22

3116

1830

25

24

15

1018

22122270

23

811

23

26

20

2520

3918

10

18

17

12

1920

3134

Percentage ofcarbonate in

claystones

Range 5-30;average 18%

(9 samples)

Range 14-44%;average 35%(13 samples)

Foraminifers

Calcareousbenthic

XX/

/

oX

/

X

X

//

/

/

/

oX

/

/

/

X///

X

/X

X/

o

Aggluti-nated

benthic

O

o//

oX

/

X

/

/

/

/

oX

/

/

•

//X

oXX

Radio- Calci- Ostra-larians spherulids codes Aptychi

OX/

oXpy

opy

X

/py/py

Opy

O

OpyOpy

Opy• py /

? py /O

oX

oΦ

X

/ /

X

opy

Φ/

o /XpyX?

oOpy

X /XXX /

/X0

X X

o• /

o /XX/

XX /

oX /X /X /•

• X/

oo /X X

/ /

X

Pelecypodfragments

Fish Sponge (Ilnocera-debris Echinoids spicules mus)

O

/

/• ob

/

/

/

X

oo /

o•

/

X X

540


Table 1. (Continued).

GlauconitePhosphate

> pellets ?Algalcysts

Lithologicsubunit Lithological summary Age

Blake-Bahama Formation5b

Very finely laminatedmarly, radiolariannannofossil chalks,bioturbated chalksand limestoneswith minor clay-stone and siltstones

Blake-Bahama Formation5c

Thinly parallellaminated marlychalk, bioturbatedlimestone, thingraded calcareoussiltstone; moreheterogeneousfrom core to corethan 5b

Blake-Bahama Formation5d

Radiolariannannofossil marl,chalk and lime-stone with minorclaystone

76

84

92-2, 40

Cat Gap Formation6a

Grayish redcalcareousclaystone

Olive green gray carbonaceous claystone, laminated; small white and black specksOlive green gray carbonaceous claystone, laminated; small white and black specksOlive green gray claystone, laminatedOlive green gray claystone, laminated numerous white marl clasts

Olive green gray claystone, laminated; numerous white marl clastsOlive green gray, white mottled claystone, bioturbated and laminatedOlive green gray laminated claystoneOlive green gray laminated claystone

Gray, laminated claystone; numerous lenticular marl inclusions < l m mOlive green gray laminated claystone; slight foresetting, mini clastsOlive green gray laminated claystone; slight foresetting, mini clastsGray light gray laminated claystone

Gray light gray laminated claystoneGray light gray laminated claystoneOlive green gray claystone, laminated with light streaksBlack to gray laminated claystone

Black to gray laminated claystoneBlack to gray laminated claystoneBlack to gray laminated claystone; 2 pyritized radiolarian laminaeBlack to gray laminated claystone; 2 pyritized radiolarian laminae

Black to gray laminated claystone; 2 pyritized radiolarian laminaeOlive green to gray laminated claystoneOlive green to gray laminated claystoneOlive green to gray laminated claystone

Olive green to gray laminated claystoneOlive green to gray laminated claystoneOlive green to gray laminated claystoneOlive green to gray laminated claystone

Olive green to gray laminated claystoneOlive green to gray laminated claystoneOlive green to gray laminated claystoneOlive green to gray laminated claystone

Olive green to gray laminated claystoneOlive green to gray laminated claystone; pyritized radiolarian laminaeOlive green to gray laminated claystone; pyritized radiolarian laminaeOlive green to gray laminated claystone; pyritized radiolarian laminae

Olive green to gray laminated claystone; some clay/silt "nests"Mottled, brown claystoneOlive green gray, finely laminated claystoneGreen claystone

Olive green gray claystone; wavy laminationOlive green gray claystone; wavy laminationGreen gray claystone, lenses of white chalky sedimentGreen gray claystone, lenses of white chalky sediment

Green gray claystone, lenses of white chalky sedimentGreen gray claystone, lenses of white chalky sedimentGreen gray claystone, lenses of white chalky sedimentDark green claystone and whitish limestone laminae

Dark green claystone and whitish limestone laminaeDark green claystone and whitish limestone laminaeGreen white mottled claystoneGreen white mottled claystone

Green white mottled claystoneGreen claystone and whitish limestone laminaeGreen claystone and whitish limestone laminaeGreen claystone and whitish limestone laminae

Green claystone and whitish limestone laminaeGreen claystone and whitish limestone lensesGreen claystone and whitish limestone lensesGreen claystone and whitish limestone lenses

Gray green speckeld claystoneGray green speckled claystoneGray green speckled claystoneBrown red claystone and rose white calcareous intercalations

Brown red claystone, greenish streaksBrown red claystone, greenish streaksBrown red claystone, greenish streaks

i Brown red claystone, greenish streaks

Brown red claystoneBrown red claystoneBrown red claystone

Berriasian-Hauterivian

541

F. M. GRADSTEIN


Foraminifers

Sample(intervalin cm)

Weight(g)

(prewashed)

Percentage ofcarbonate in

claystonesCalcareous

benthic

Aggluti-nated

benthicRadio-larians

Calci-spherulids

Ostra-codes Aptychi

Fishdebris Echinoids

Spongespicules

Pelecypodfragments(llnocera-

mus)

94-4, 47-48

94.CC95-1, 36-3895-1, 43-4595-3, 51-53

96-1, 88-8996-1, 89-9096-3, 6-897-1, 8-9

99-1, 4-699-1, 38-4099-3, 77-78100-1, 5-6

100-1, 19-20100-2, 6-7100-4, 46-47101-2, 140-142

101-3, 17-18101A 93-95101-6, 7-9102-1, 78-79

102-2, 64-66102-5, 75-77103-1, 107-108104-1, 49-50

104-1, 60-62104-3, 38-39104A 33-34105-1, 22-23

105-2, 67-68106-1, 52-53107-2, 100-101108-1, 45-47

108-1, 66-68110,CC, 15111-1, 17-19112-1, 7-8

112-1, 10-12112-1, 62-64113-1, 24-26114-1, 105-107

115-1, 6-8115-1,27-28115-1, 33-35115-1, 103-105

116-1, 54-55117-1, 12-13118-1,0-1119-1, 111-112

120-1, 46-47121-1,0-1123-1,48-51123-2, 56-58

123-3, 12-15124-1, 73-75125-3, 60-62125-5, 40-42

125-6, 13-15126-1, 70-73126-2, 68-70126-3, 120-122

126-4, 56-58127-1, 59-62127-3, 40-42127A 13-15

127, 7-9

2219

17

2026

29

20

20

1829

2921

2728

24

122414

15

1635

1216

22191819

25

2222

21161420

123430

37244039

26362336

28515040

39

Range 7-70%;average 30%

Range 17-50%~ 30% in marls

10-15%

Claystones?0%

11-30%;- 2 0 %

/

/

O

/

oXo

X

oo

oX

X

/

oX

XX

XX

X

X

X

o

o

X

/

•

XX

oo

X

ooXXX

o

/

XX

oX

o7

X

/

X

'

X

X

X

o

'

o

7

X

•

X

o• p y• py

• p y

oX

\

•

•

o

/

/

/

/

/

/

;

O

X

/

X

X

X

7

Note: The lithostratigraphic units and broad ages are as shown in the Site 534 report (this volume). For discussion see text. = > 50 specimens, O = 21-50 specimens,X = 6-20 specimens, and / = 1-5 specimens; ab = abraded, py = pyritized.

542



GlauconitePhosphate

> pellets ?Algalcysts

Lithologicsubunit Lithological summary Age

103-1, 107 cm

Cat Gap Formation6b

Limestone turbiditesinterbedded withdark greenish grayclaystone

111-1, 7 cm

7a

Variegated darkreddish brown tograyish greenclaystone

117-1, 26 cm7b

Gray limestone turbidites,_ interbedded with dark

variegated claystones |

120 topDark gray marly limestones,

interbedded with darkgreenish gray radiolarian-rich claystone

125-4, 14 cm7d

Greenish black to blackclaystone with radiolariansilt lenses

126-3, 75 cm

Brown red claystone

Brown red claystoneBrown red claystoneBrown red claystoneOlive green gray claystone

Gray brown laminated and bioturbated claystoneGray brown laminated and bioturbated claystoneGray brown laminated and bioturbated claystoneGray brown laminated and bioturbated claystone

Gray brown laminated and bioturbated claystoneGray brown laminated and bioturbated claystoneGray brown laminated and bioturbated claystoneBlack claystone

Red brown claystoneRed brown claystoneRed brown claystoneRed brown claystone

Red brown claystoneRed brown claystoneRed brown claystoneRed brown claystone

Red brown claystoneRed brown claystoneRed brown claystoneDark gray claystone

Dark gray claystoneDark gray claystoneGray brown claystoneGray brown claystone, wavy lamination

Gray brown claystone, wavy laminationGray brown claystone, wavy laminationBrown gray green claystone (soft)Brown red claystone (hard)

Brown red claystoneGrayish brown, bioturbated, calcareous claystoneGray green claystoneGray green claystone

Gray brown claystoneGray brown claystoneReddish brown green, laminated claystoneReddish brown green, laminated claystone

Dark brown gray black laminated claystoneDark brown gray black laminated claystoneDark gray claystoneDark gray claystone

Dark gray claystoneDark gray claystoneGray green claystoneGray green claystone

Gray green claystoneGray green claystone, radiolarian silt laminaGray green claystone, radiolarian silt laminaGray green claystone, radiolarian silt lamina

Gray green claystoneGray green claystone, radiolarian silt laminaGray green claystone, radiolarian silt laminaGray green claystone, radiolarian silt lamina

Gray green claystone, radiolarian silt laminaGray green claystone, laminatedGray black to olive green claystoneGray black to olive green claystone, laminated

Callovian-Tithonian

7eDusky red calcareous

claystone

Gray black to olive green claystone, laminatedDark brown gray claystoneDark brown red claystone, laminated and "beef" structuresDark brown red claystone, laminated and "beef" structures

Brown claystone

127.CC, 10 cm

543

F. M. GRADSTEIN

Core 84 to Core 92, Section 2: Blake-Bahama Forma-tion (5d); radiolarian-nannofossil marl, chalk, and lime-stone, with minor claystone.

Core 92, Section 2 to Core 103, Section 1: Cat GapFormation (6a); grayish red calcareous claystone.

Core 103, Section 1 to Core 111, Section 1: Cat GapFormation (6b); limestone turbidites, interbedded withdark greenish gray claystone.

Core 111, Section 1 to Core 117, Section 1: Unnamedunit (7a); variegated, dark reddish brown to grayish greenclaystone.

Core 117, Section 1 to Core 120 (top): Unnamed unit(7b); gray limestone turbidites, interbedded with dark,variegated claystones. Ogg et al. (this volume) includeSubunits 7a and b in the Cat Gap Formation.

Core 120 (top) to Core 125, Section 4: Unnamed unit(7c); dark gray, marly limestones, interbedded with dark,greenish gray radiolarian-rich claystone.

Core 125, Section 4 to Core 126, Section 3: Unnamedunit (7d); greenish black to black claystone with radio-larian silt lenses.

Core 126, Section 3 to Sample 127, CC: Unnamedunit (7e); dusky red, calcareous claystone.

Based on the multiple biostratigraphy shown in Fig-ure 9, the unnamed unit is Callovian-Oxfordian, theCat Gap Formation essentially Kimmeridgian-Tithoni-an, and the Blake-Bahama Formation samples Berria-sian-Valanginian. Calcispherulids are essentially con-fined to the upper grayish red calcareous claystone sub-unit (6a) of the upper Cat Gap Formation (Tithonian).Interestingly, this is the interval in which radiolarians,either pyritized or filled by chalcedony or calcite spar,are largely absent. Radiolarians are often abundant inthe unnamed unit and particularly in the Blake-Bahamaclaystones. This pattern of exclusion may have some re-gional significance and may be related to productivity inthe upper water column. Ostracodes are rare and scat-tered (see Oertli, this volume); aptychi are more fre-quent in the Tithonian-Berriasian interval, particularlyin the upper Cat Gap Formation, where the carbonatepercentage is highest (50-70%). The higher aptychi con-centrations in Cores 94, 92, and 87 may indicate the in-terval with the lowest sedimentation rate. The frequencydistribution in the next four columns in Table 1 on fishdebris, echinoderms, sponge spicules, and pelecypods(Unoceramus) prisms should be mostly related to down-to-basin transport activity. There is no relation to theunits where more sediment mass transport beds havebeen noticed during core examination.

Foraminifera, both calcareous and agglutinated, aremost consistently present, with diversified and speci-men-rich assemblages in the reddish claystones of Sub-units 7e (Callovian) and 6a (Cat Gap Formation, Titho-nian). Ogg et al. (this volume), advance the idea that thered color is to some extent related to an increase of Feover organic matter and to a slower sedimentation rate.It is not immediately apparent what the effect of theseagents would be on foraminiferal bottom dwellers, but aslower sedimentation rate will produce less dilution ofbiomass in time and increase the number and type ofshells per unit volume of sediment.

Because we expect that the sedimentation rate fluctu-ates considerably from bed to bed or between lithologicunits, the size and weight of the samples taken wouldpresumable not much influence the number of micro-fossil shells and its diversity. Of course, if sample sizevaries more than the sedimentation rate, the effect willdecline, but in my samples, which vary a factor of 2-4 insize, the reasoning holds. I correlated the four frequen-cy classes of foraminifers (rare, common, frequent, andabundant) and the number of taxa per sample to theweight of the sample (Fig. 4). Where there was an in-sample difference between agglutinated and calcareousfrequencies, the larger of the two classes per sample wasused. Spearmans rank correlation suggests very low like-lihood of correlation (R = -0.04282) and so does theKendall rank correlation test. Of course, either of theagglutinated or calcareous frequencies might be posi-tively correlated to sample size, but such is not the caseeither. Changes in sedimentation rate, probably coupledwith productivity and dissolution rates, produce abun-dance and diversity changes that are not offset by thesize of the sample. Denser sampling frequency per coreor formation is a more effective recovery tool than larg-er sample size at a few discrete levels.

There are no carbonate content values at the exactlevel of the samples, but inspection of the generalizedcarbonate content log in Table 1 suggests that there is anincrease of foraminiferal shells in intervals with morecarbonate. Obviously, fluctuations of the level of thecarbonate compensation depth (CCD) and of the lyso-cline have influenced the living and fossil record. Verydark-colored shales and carbonate-poor or Carbonate-free shales are virtually devoid of taxa, even aggluti-nated ones, as in Sub units 7c and d. Reducing bottomconditions during periods of high organic influx or ashallow CCD will reduce the record.

Using the shelly microfossil and macrofossil debrisrecord together, some evidence for distinctive strati-graphic intervals with increased reworking can bemapped. A number of samples contain a sorted, verysmall-sized (>60 µm), and often abraded assemblage,as in Sections 534A-112-1, 534A-115-1, 534A-123-1,and 534A-126-3 and -4. This may be a distal turbiditecomponent, which in the case of Core 123 is almostwholly calcareous. Composition of the tiny-sized assem-blage is not noticeably different from normal-sized as-semblages in adjacent samples, which suggests transpor-tation of deeper-water meiofauna. In Cores 110 and 94some specimens of unique taxa occur, which more likelyare shallow-marine contaminants like Trocholina, Co-norbina, Conorboides, and even the tiny globigeri-nids. Further evidence for reworking and transportationcomes from an abundance of abraded calcareous debrisor abraded tests in Sections 534A-89-5, 534A-88-2, and534A-82-1.

Summing up the evidence, reworking may thus par-ticularly occur in Cores 127 to 123 (Callovian), 115 to110 (Oxfordian), and 89 to 82 Gate Berriasian). Furtherstudies are necessary to determine if this reworking ispart of a more systematic basin record, which could belinked to periodic changes in sedimentary style.

544


50

40

11

E 3 0 1

E2 20

10

•t• •I

1-5 6-20 21-50 >50 specimens

Frequency classes of foraminifers per sample

50

40

1•σ

re

5

30

20

10

••••• • • •

10 15

Number of taxa per sample

20 25

Figure 4. There is no positive correlation at a reasonable level of sig-nificance (using Kendall or Spearman rank correlation tests) of thefrequency of foraminifer specimens per grams of sediment and ofthe number of taxa per grams of sediment. (The number of sam-ples is 66, Cores 534A-70-127, sample size varying from 10-50grams. This probably means that the sedimentation rate and disso-lution rate exert more influence on the foraminiferal number anddiversity ("biomass") than the five-fold difference in sample size.More closely spaced sampling appears a more effective tool for re-covery than larger-sized samples.)

TAXONOMY

The taxonomy used is conservative, which means thatI have lumped specimens showing evidence of grada-tional morphologic features. The presence in the litera-

ture of different names for only slightly different mor-phologies and the fact that only one-third or so of alltaxa occurs in any number of specimens, which are quitesmall (often > 150 µm) and of moderate preservation,make detailed taxonomy a difficult undertaking. Also,many taxa vary slightly from the well-established mor-phologies (of shallow-marine environments) but notenough to warrant special taxonomic treatment. A fewcomments are added in the Taxonomic Notes on se-lected taxa.

Beside the Catalogue of Foraminifera (Ellis, Messi-na, et al., 1940-1982) and my own collections, use wasmade of the following references: Bartenstein and Brand(1951), Lutze (1960), Wall (1960), Oesterle (1968), Ohm(1967), Wernli (1971), Luterbacher (1972), Bartenstein(1974), Kuznetsova (1974), Bielecka and Geroch (1977),Kuznetsova and Seibold (1978), Sliter (1980), Gradsteinand Berggren (1981) and Barnard and Shipp (1981).Specimens of Neobulimina atlantica n. sp. (Plate 3,Figs. 1-12) were studied by S. Geroch (Krakow), H. P.Luterbacher (Tubingen), I. Premoli Silva (Milano), W.V. Sliter (Washington), and P. Ascoli (Dartmouth, N.S.) (personal communications, 1980-81). None of thesecolleagues were aware of a comparative record of such astubby Neobulimina taxa.

Special attention was given to Jurassic planktonics,but only 12 specimens were isolated—in two samplesfrom 534A-110,CC. The test size of 60 µm makes syste-matic identification tentative, compounded by encrus-tation of coccoliths, which, according to S. Honjo(Woods Hole) (personal communication, 1981), mayhave happened as a result of ingestion by larger animalsin the food chain. Deposition of these tiny specimensthus may have occurred as part of faecal pellets sedi-mentation, at a time when planktonic foraminifers werealso present in the Jurassic Tethys ocean (Oxfordian),rather than scattered in the marginal Tethys waters orbordering epicontinental seas (Bajocian through Oxfor-dian-Kimmeridgian). Alternatively, the planktonics, assuggested in the previous section, may be a shallow-ma-rine contaminant. Jurassic planktonic taxonomy leavesmuch to be desired, but rather than running ahead ofstudies in progress, I have preferred to match more orless coeval records. Two types are present in the relevantliterature, a more globose, trochospiral form with anarched aperture, "Globigerina" helvetojurassica Haeus-ler and an often low-spired (tiny) form with a virgulineor arched aperture, Globuligerina oxfordiana (Grigelis).The Sample 110,CC specimens match the latter betterthan the former (Plate 2, Figs. 1-10).

The total foraminiferal assemblage in Cores 127through 70 of Hole 534A consists of at least 36 calcare-ous taxa in nine(?) families and at least 35 agglutinatedtaxa in eight families. The 36 calcareous forms belong in19 genera, whereas there are at least 23 genera of agglu-tinated foraminifers. The complete taxonomic listingfollows. The number of specimens in the samples is indi-cated in frequency classes: ra (rare) = 1 to 5 specimens,co (common) = 6 to 20 specimens, and fr (frequent) >21 specimens; the number indicates the amount of sam-ples in which the taxon was found (maximally 66).

545

F. M. GRADSTEIN

AGGLUTINATED BENTHIC FORAMINIFERA

AstrorhizidaeRhizammina sp.Rhabdammina sp.Bathysiphon discreta (Brady)Bathysiphon sp.Hyperammina sp. 2 Bartenstein

(1974)Hippocrepina sp.

SaccamminidaePsammosphaera sp.

AmmodiscidaeAmmodiscus sp.Glomospirella gaultina (Berthelin)Glomospira charoides (Jones and

Parker)Glomospira gordialis (Jones and

Parker)Glomospira irregularis (Grzybowski)Lituotuba sp.

HormosinidaeHormosina sp.Reophax aff. horridus (Schwager)Reophax helveticus (Haeusler)Reophax sp.

LituolidaeHalophragmium aequale (Roemer)Haplophragmium inconstans

Bartenstein and BrandHaplophragmoides sp.Haplophragmium sp.

TextulariidaeSpiroplectammina helvetojurassica

Kubler and ZwingliTextularia haeusleri Kaptarenko and

ChernoussovaTextularia sp.Bigenerina jurassica (Haeusler)Bigenerina arcuata Haeusler

TrochamminidaeTrochammina globigeriniformis

(Parker and Jones)Trochamminoides pygmaeus

(Haeusler)Trochamminoides hyalinus

(Haeusler)Trochammina quinqueloba GerochTrochamminaf?) deformis Grzy-

bowskiTrochammina sp.

AtaxophragmiidaeDorothia praehauteriviana Dieni

and Massari?Dorothia sp.Gaudryina heersumensis LutzeKarreriella sp.Verneuilina sp.

CALCAREOUS BENTHIC F<

NodosariidaeLenticulina quenstedti (Guembel)Lenticulina (Darbyella) muensteri

(Roemer)Lenticulina nodosa (Reuss)Lenticulina aff. reticulata

(Schwager)Lenticulina spp.Dentalina communis (d'Orbigny)Dentalina incerta TerquemDentalina spp.Pseudonodosaria humilis (Roemer)Pseudonodosaria spp.Nodosaria jurassica Guembel

ra-frra-cora-corara

ra-fr

ra-fr

ra

ra-frra-fr

ra-fr

rara

rarara-cora-co

ra

ra-co

rara

ra

ra

rara-cora-co

ra

ra

ra-co

ra

ra-co

ra-co

ra-co

rararara

>RAMI>

rara

rara-co

ra-frra-frrara-cora-corara

242511

3

9

53610

5

12

1199

12

11

1

3

153

3

5

4

45

3

2

1151

fIFE

76

22

1314

11732

rarararararararararararara-cora

ra

ra-fr

ra

ra

ra-cora

ra

ra

ra-co

ra-co

ra-co

ra-co

3513312

123641

111

1

7

1

1

101

1

1

10

2

2

11

Nodosaria aff. prima d'OrbignyNodosaria spp.Frondicularia nikitini UhligFrondicularia franconica GuembelFrondicularia sp.Oolina sp.Palmula subparallel (Wisniowski)Lingulina sp.Marginulina aff. /nβyor(Bornemann)Marginulina spp.Ramulina spandeli PaalzowSaracenaria sp.Lagena laevis (Montagu)Lagena sp.

PolymorphinidaeGuttulina aff. pygmaea (Schwager)

TurriliαidaeNeobulimina atlantica n. sp.

Anomalinidae?Gavelinella sp.

DiscorbidaeConorbina sp.

CeratobuliminidaeEpistomina aff. uhligi MjatliukConorboides paraspis (Schwager)

InvolutinidaeTrocholina nodulosa Seibold &

SeiboldTrocholina transversarii Paalzow

NubeculariidaeOphthalmidium carinatum Kubler

and ZwingliOphthalmidium milioliniformis

(Paalzow)Ophthalmidium sp.

SpirrilinidaeSpirrilina sp.

PLANKTONIC FORAMINIFERA

Globuligerina aff. oxfordiana ra 2(Grigelis)

It can be seen from this list that the assemblage is composed of afew more common species and many more rare ones. The more com-mon ones include several simple agglutinated taxa, one or two nodo-sariids, Neobulimina, and Ophthalmidium.

PALEOECOLOGY

The fact that Hole 534A penetrated "basement" ofan oceanic-type basalt allows the use of backtracking(Sclater et al., 1977) as a means to estimate the paleo-bathymetric trends through time. The excercise is per-formed by Sheridan (this volume) and establishes thatSite 534 probably started in the Callovian at an averagemid-ridge depth of 2.7 km and had slowly sank to about3.3 km in the Berriasian. This depth estimate situatesthe Site 534 seafloor well in the abyssal realm, and weshall consider this factor in further discussion.

An appraisal of the Jurassic assemblage in Cores 127to 70, relative to other ones of similar or dissimilar ageand environmental setting, has to take into account theeffects of redeposition and stratigraphic bias. It then be-comes more meaningful to consider the observed assem-blage to reflect an in situ fauna.

Evidence for reworking was discussed earlier and in-cludes the specimens in Core 110 of Trocholina spp.,Conorbina, Conorboides, and possibly Globuligerina.The specimens may be contaminants from neritic(?) en-vironments on the Blake or Bahama Plateaus, west-ward.

546


There is also evidence for reworking in Cores 127 to123, 115 to 110, and 89 to 82 (see the section on shellymicrofossil assemblage), but with the exception of thefew specimens in Core 110, there appears to be no ap-preciable difference in composition between samples in-side and outside these cored intervals. Most of the re-working probably amounted to local transportation intothe deepest part of the sedimentary basin.

A stratigraphically unique, but probably in situ as-semblage occurs in Cores 105 through 95, Kimmeridgi-an-Tithonian, with persistent and common specimensof Neobulimina atlantica n. sp., Epistomina aff. uhligi,Lenticulina quenstedti, and Ophthalmidium carinatum(see the Fig. 5 dendrogram). I consider this assemblage aresponse to the carbonate-richer episode when the red-dish calcareous claystone of the upper Cat Gap Forma-tion (Subunit 6a) was deposited. At this time the CCDhad dropped considerably, and the seafloor was prob-ably close to the aragonite compensation depth (ACD).

Other stratigraphic trends do not involve (groups of)taxa that occur in appreciable number, except for the ar-rival of Dorothia praehauteriviana, at the top of the in-terval studied. This is an in situ form, common to Neo-comian oceanic sites.

Prior listing of all taxa shows that the calcareous as-semblage is made up of Nodosariidae, 25 species in 12genera, and the odd taxon in the Polymorphinidae, Tur-rilinidae (Neobulimina), Ceratobulimindae (Epistomi-na), and Nubeculariidae and Spirrilinidae. Few taxa oc-cur with any number of specimens and only about one-third of all taxa occur in more than six (10%) of thesamples, including Lingulina, Lenticulina, Lagena, Spi-rillina, Epistomina, Ophthalmidium, and Neobulimina.

There are 16 taxa that occur in at least seven or moresamples and that are not exclusively rare, including (inorder of descending stratigraphic persistency):

Glomospirella gaultina in 36 samplesRhizammina sp. 24Dentalina communis 14Len ticulina spp. 13Lingulina sp. 12Lagena laevis 11Spirillina sp. 11Glomospira charoides 10Epistomina aff. uhligi 10Ophthalmidium carinatum 10Reophax helveticus 9Reophax sp. 9Psammosphaera sp. 9Neobulimina atlantica n. sp. 7Pseudonodosaria humilis 7Lenticulina quenstedti 1The average number of taxa per sample is about five,

with a spread of 0 to 19, and a mode of about eight.In order to aid with the delineation of specific groups

of taxa that can be of paleoecological (or stratigraphi-cal) significance in the stratigraphically successive 66samples, the data were subjected to R-mode clusteranalysis. The method used is based on a computer pro-gram developed by G. Bonham-Carter (1967). The coef-ficients of variation used include the Jaccard C/Nx +

N2-C and Dice 2C/NX + N2 coefficients, in which C =the number of samples in which taxon A and B co-oc-cur; Nj = the number of samples with taxon A, andN2 = the number of samples with taxon B. The Dicecoefficient emphasizes communality, which in the patchyHole 534A data leads to slightly better clustering thanthe Jaccard coefficient. The occurrences of A and Bwere entered in three frequency classes: rare = 1 to 5specimens; common = 6 to 20 specimens, and frequent> 21 specimens. The final clustering is affected both bythe degree of association and by the relative frequencyof taxa. In order to arrive at meaningful answers onlytaxa were entered that occur in five or more samples.This culling of the data reduces the assemblage fromabout 70 to 25(!) species. The R-mode dendrogram, us-ing the Dice coefficient weighted-pair group method, isshown in Figure 5.

The degree of association is relatively low. Morecommon co-occurrences include these "clusters":

1) Reophax helveticusBigenerina jurassicaReophax sp.

2) Glomospirella gaultinaLenticulina spp.Rhizammina sp.

3) Dentalina communisLagena laevis

4) Lenticulina quenstedtiOphthalmidium carinatumNeobulimina altantica n. sp.Epistomina aff. uhligi

The analysis confirms the so-called "Kimmeridgiancarbonate richer environment" assemblage with Neo-bulimina atlantica n. sp., and so on, in "cluster" no. 4.The other three "clusters" are rather arbitrarily limitedto the tightest-linking elements of what appear to be twolarger "clusters" of stratigraphically persistent taxa. Themost striking elements include those in cluster no. 2,which consists of the three stratigraphically most com-mon taxa. It is not obvious what the reason for correlat-ing might be, but further research may shed light onthese communality relationships. One is probably justi-fied in arguing that species of the genera Reophax, Big-erina, Bathysiphon, Glomospira, Glomospirella, Len-ticulina, Rhizammina, Psammosphaera, Dentalina, La-gena, Marginulina, Pseudonodosaria, and Trochammi-na are significant and unspecialized elements of Jurassicabyssal fauna.

It is instructive to make a comparison to other knownabyssal Jurassicc assemblages. Table 2 lists all oceanic(Upper) Jurassic micropaleontological sites. Paleo-wa-ter depth estimates using backtracking do not indicateshallower than average depth for the basal sediments onocean crust, and the water depth ranges from 2.7 km forthe oldest to 3.3 km for the younger deposits.

Excellent reports on these sites by the shipboard bio-stratigraphers allow insight into the compositional vari-ation, which is expressed in Table 3. In the absence ofcomparative collections only a minor effort was made tostandardize taxonomic nomenclature. There is a strikingsimilarity in overall composition to the Indian Ocean

547

F. M. GRADSTEIN

-0.00 0.10 0.20 0.30 0.40Similarity coefficient

0.50 0.60 0.70 0.80 0.90 1.00

Reophax helveticusBigenerina jurassicaReophax sp.Bathysiphon discretaGlomospira charoidesGlomospirella gaultinaLenticulina spp.Rhizammina sp.Psammosphaera sp.Dentalina communisLagena laevisMarginulina sp.Pseudonodosaria humilisGlomospira gordialisTrochammina deformisTrochamminoides pygmaeusSpirrilina sp.Karreriella sp.Lenticulina muensteriLenticulina quenstedtiOphthalmidium carinatumNeobulimina atlantica n. sp.Epistomina aff. uhligiAmmodiscus sp.Nodosaria spp.

Figure 5. Dendrogram expressing the degree of association (mutual occurrences in samples) of those 25taxa that occur in at least 5 samples. (Pattern shows "best" clusters. The method used is an R-modeclustering based on the Dice coefficient of association, with weight to the relative abundance duringlinkage of pairs.)

Table 2. Jurassic micropaleontological (foraminiferal) literature referred to in this study based on continental and oceanic sites, with estimates ofpaleo-water depth using backtracking (Sclater et al., 1977).

Area

N. AtlanticN. AtlanticN. AtlanticN. AtlanticN. AtlanticN. AtlanticN. AtlanticIndian Ocean

Basin

Bahama EscarpmentBlake-BahamaBlake-BahamaBlake-BahamaBlake-BahamaMoroccan BasinMoroccan BasinArgo Abyssal Plain

DSDPhole

99100105391C534A367416216

Basement

Not coredM-25M-25"M-28", JQZ"M-28", JQZJQZ edgeJQZM-23

Sedimenton

basement

Not coredOxf.-Kimm.Oxf.-Kimm.Not coredm. CallovianOxf.-Kimm.Not coredOxf.-Kimm.

TotalJurassic

foraminiferalassemblage

Oxf.-Kimm.Oxf.-Kimm.-Tith.Oxf.-Kimm.-Tith.Tithonianm. Call.-Tith.Oxf.-Tith.-Tith.TithonianOxf.-Kimm.-Tith.

Presentwaterdepth(m)

491453255251496349744758

5125

Sedimentthickness

(m)

63014121636

542

Jurassicwaterdepth(km)

<333

3-3.53-3.5

33-3.5

3

Reference

Luterbacher, 1972Luterbacher, 1972Luterbacher, 1972Gradstein, 1978this chapterKuznetsova and Seibold, 1978Sliter, 1980Kuznetsova, 1974 Bartenstein, 1974

Note: JQZ = Jurassic magnetic Quiet Zone.

assemblage (DSDP Site 261), as evidenced by 18 Ox-fordian-Kimmeridgian through Berriasian-Valanginiansamples from Cores 29 to 35, discussed by Kuznetsova(1974) and Bartenstein (1974). The overall similarity, asshown further on, supports the interpretation of a "com-parable" abyssal environment. These authors reported90 taxa (there are 70+ in Hole 534A) in (?)44 genera(compared to 42 in 534A), belonging in 12 families (18in 534A).

Both the agglutinated and calcareous benthic familyand generic record for the early Indian Ocean closelymatch those in Hole 534A. Among the calcareous taxa,the ones missing in Suite 261 are the shallow-marine con-taminants (in four families) and Neobulimina n. sp.,Ophthalmidium, and Globuligerina. The authors reportthe same high species diversity and patchy stratigraphicdistribution. Relative abundance of taxa is more difficultto compare, but it appears that more common taxa inSite 261 also include Glomospirella gaultina, Glomospi-ra charoides, G. gordialis, Dentalina communis, Spiril-lina, and Lenticulina. There are also common occurrenc-

es of Textularia, Dorothia, Trochammina, and some dif-ferent nodosariids, which is at odds with Hole 534A, butthis characteristic is most likely to fluctuate from siteto site, due to patchiness and sampling, and geographicand water-mass variations.

The Oxfordian-Kimmeridgian through early Neoco-mian assemblage studied by Luterbacher (1972) in thesame general region as Site 534 also allows instructivecomparison. The total number of samples more or lessequals that recovered at Site 534. DSDP Site 105 has afairly rich, quite well preserved assemblage, mainly ofsimple agglutinated taxa and nodosariids; a few inter-vals are rich in radiolarians, ostracodes, aptychi, andSaccocoma. A few samples contain almost all epistomi-nids or are dominated by Ophthalmidium. DSDP Site100 has a less diverse assemblage, almost all simple ag-glutinants and nodosariids and Spirillina.

Stratigraphically more persistent and/or locally morecommon taxa at Site 105 are Bathysiphon, Tolypammi-na, Hyperammina, Reophax, Haplophragmoides, Spiril-lina, Spirophthalmidium, Ophthalmidium, Epistomi-

548


Table 3. Composition at the family and genus levels of Middle to Late Jurassic oceanic-abyssal and shallow-marine (?deep neritic)-epicontinental as-semblages of foraminifers.

Astrorhizidae

Saccamminidae

Ammodiscidae

Hormosinidae

Lituolidae

Trochamminidae

Ataxophragmiidae

Textulariidae

Nodosariidae

Polymorphinidae

Turrilinidae

Ceratobuliminidae

Nubeculariidae

Spirrilinidae

Globigerinidae

RhizamminaRhabdamminaBathysiphonHyperamminaHippocrepinaSaccorhizaKalamopsis

PsammosphaeraPelosinaSorosphaeraLagenammina

AmmodiscusGlomospirellaGlomospiraLituotubaAmmovertellaAmmolagena

HormosinaReophax

HaplophragmiumHaplophragmoidesAmmobaculitesPlacopsilinaCribrostomoides

TrochamminaTrochamminoides

DorothiaGaudryinaKarreriellaVerneuillina

SpiroplectamminaTextulariaBigenerina

Lenticulina (incl. Darbyella)DentalinaPseudonodosariaNodosariaFrondiculariaPalmulaLingulinaMarginulinaRamulinaSaracenariaLagenaVaginulinaPlanulariaBojarkaellaAstacolusOolina

GuttulinaEoguttulinaGlobulinaRectoglandulina

Neobulimina

Epistomina

OphthalmidiumNubeculinella

Spirrilina

Globuligerina

DSDP534(this

chapter)

XXXXX

X

XXX

X

XX

XX

XXXX

XXX

X

<s>XXXXXXX

X

X

X

X

X

X

X

Abyssal-oceanic

DSDP 261Kuznetsova, 1974Bartenstein, 1974

X

XXXX

XX

XXXXXX

XX

XXXX

®

X

X

XX

®X

®XXXXXXXXXX

?x

X

X

DSDP 100/105Luterbacher, 1972

X

XX

X

X

XX

X

XXX?x

X

X?x?x

XXX

(g)(X)®09®XXXX

X

®X

®

XX

X

XX

X

X

SaskatchewanWall, 1960

®X

X

X

®+Ammomarginulina

X

X

+ TriplasiaAmmobaculoides

ßö®

®

XX

<8>+ Citharina

TristixX

XXX

Conorboides

XX

X

Shallow marine-epicontinental

W. GermanyLutze, 1960

X

X

X

X

+ TriplasiaX

<S>X

X

®XX

+ CitharinaTristix

X

X

XConorboides

XX

X

W. GermanyMunk, 1980

X+ Tolypammina

?X

X

X

®XXXXXXXXX

+ Citharina

X

X

XX

®

Grand BanksGradstein, 1977

?X

X

X

X

X

XX

®X

X

X

X

(S>Reinholdella

X

X

X

Note: Genera with five or more species are circled. + Quinqueloculina + Paalzowella + Paalzowella + PaalzowellaMassilina Trocholina Patellina PatellinaMiliammina Bullopora

na, Dentalina, Lenticulina, Astacolus, Pseudonodosaria,and Marsonella. At Site 100 this list is shorter. The list-ing includes many of the persistent Site 534 genera. Theoverall micropaleontological characterization of Sites105 and 100, taxonomic affinity at the genus level of70%, and family representation well compare to Site

534. The sporadic occurrence of glomospirid-type formsand the absence of Neobulimina are notable differences.

In summary, the Atlantic and Indian oceans abyssalMiddle-Late Jurassic foraminiferal "fauna" has a highspecies (100) and high generic (50) diversity, patchyspecimen representation, and low communality at the

549

F. M. GRADSTEIN

species level. The assemblage consists principally ofsmall-sized agglutinated taxa in eight or so families,small-sized nodosariids in a dozen or so genera, andvariable additions of epistominids, ophthalmidids, spi-rillinids, and turrilinids. The assemblage is accompaniedby radiolarians, calcispherulids, aptychi, and Saccoco-ma, and, except for calcispherulids, Saccocoma, and afew index foraminifers, continues into the Early Creta-ceous.

The question should be asked how different the(deep) neritic Late Jurassic fauna was from the deep seaones, particularly because niches probably were broaderthan today. The Late Cretaceous through Recent recordis of much higher diversity in families, genera, andspecies in a physically more differentiated marine en-vironment. Although the following taxonomic-paleo-ecologic comparison far from answers that question, itprovides some insight into Jurassic paleoecological rela-tionships, as a practical aid to further interpretation.

Table 3 lists the genera found in shallow-marine-epi-continental deposits of Saskatchewan (Wall, 1960), WestGermany (Lutze, 1960; Munk, 1980—Feuerstein Bankonly) and the Grand Banks (Gradstein, 1977, and un-published data). This record was limited to a deep nerit-ic environment, using mainly broad geological criteriaand biofacies trends. I exclude the shallow-marine, pho-tic zone record, which in lower latitudes includes largerforaminifers. As is the case with the comparative recordfor the oceanic sites, there is some taxonomic bias, but itis minor in view of the extent of the record.

Major differences in the neritic record (Table 3) arethe lack of many simple agglutinated genera, a muchless complete representation of agglutinated families,the presence of large Ammobaculites and Ammomargi-nulina, and the presence among the calcareous forms ofMiliammina, Trocholina, Patellina and Paalzowella, and

Citharina and Tristix. Specimens are on average largerthan in the oceanic realm, and many more sculpturedtaxa occur. There seems to be no striking difference incomparing the score of genera with the highest speciesdiversity (5); but the diversity in the shallow-marine,neritic record of epistominids, Ammobaculites, and spi-rillinids (which, according to Munk's [1980] detailedand quantitative study, flourish in reefal environment)is not found in the oceanic sites.

The extensive, although relatively specimen-poor, ag-glutinated record in the Jurassic abyssal sites provides alink to more modern deep-marine assemblages ("fau-na"). Many of the more simple agglutinated generaprobably evolved little or not at all through time andmay be of Paleozoic origin. In contrast, the Jurassic cal-careous record, which goes back into the Triassic, is pre-actualistic. Nodosariid- or, for example, epistominid-dominated assemblages disappeared after the Early Cre-taceous.

Figures 6 and 7 provide some insight into the compo-sition of deep-water agglutinated assemblages throughtime. Compositional data are based on my comparativeresearch using actual collection of Brady's (1884) Re-cent ocean benthos fauna, the Recent Newfoundlandslope fauna (Schafer and Carter, 1981), the Maestrichti-an through Paleogene of the Labrador and Newfound-land shelves, and the Paleogene of the Central NorthSea (Gradstein and Berggren, 1981), the Maestrichtianand Paleocene Guayaguare and Lizard Spring Forma-tions of Trinidad, and the early Eocene Discovery andScoresby dredges on Burdwood Bank, southwestern At-lantic Ocean (Gradstein, unpublished data). In some ofthe listed geological sites, agglutinated taxa predominat-ed among the foraminifers but such is not necessarilythe case in the Recent. There is a strong resemblance inoverall composition of the Maestrichtian through Pa-

100

B

Figure 6. A. Number of genera of agglutinated foraminifers recognized in Cores 534A-70 to 127, Callo-vian-Neocomian, western North Atlantic Ocean. (For legend see Fig. 7.) (Communality of the Hole534A assemblage with the other deep-water [bathyal-abyssal] assemblages is over 95% [at the genuslevel]. This figure varies little from older site to younger site through time, although the number ofgenera evolved, preserved, and/or recovered increased through time.) B. Number of taxa of ag-glutinated foraminifers recognized at the sites of Figure 6A. (Communality of the Site 534 assemblagewith the other [younger] assemblages at the species level is less than 15% [see text].)

550


20

10

AstrorhizidaeSaccamminidae

Hormosinidae

19 28

Rzehakinidae

1 9 2 1 3 5 2 1 8 5 6 6 5 4 2 2 2 2 8 6 7 4 1 1 2 1

Ataxophragmiidae

Trochamminidae

27 16 16 18 9 6 6 34 11 10 7 10 5Number of agglutinated genera of Foraminifera organized per family in:

The Recent oceans (Brady, 1884)The Recent Newfoundland Slope (Schafer and Carter, 1981)The Maestrichtian-Paleogene of the Labrador and Newfoundland Shelves and North Sea (Gradstein and Berggren, 1981)The Maestrichtian—Paleogene of Trinidad (Gradstein, unpublished data)The Eocene of Burdwood Bank, southwestern Atlantic (Gradstein, unpublished data)Cores 127—70 of DSDP 534A, Callovian—Neocomian, western North Atlantic Ocean

Figure 7. Number of genera of agglutinated foraminifers organized per family in Cores 534A-70 to 127, Callovian-Neocomian, western NorthAtlantic Ocean. (At the bottom of each bar is the number of taxa recognized. Family representation is essentially equal through time forall of these deep-marine assemblages, but the relative proportion of genera varies. In general the Recent bathyal-abyssal fauna has thehighest number of genera evolved and recovered. Note the low number of Lituolidae and Ataxophragmiidae in the Jurassic assemblage ofHole 534A. Among the Astrorhizidae and Saccamminidae there are many delicate tests that do not preserve in the fossil record.)

leogene assemblages and the Recent slope or ocean fau-nas, both at the genus and family levels. Also, the samegenera, for example, dominate the Newfoundland Pa-leogene and Recent slope, but communality at the spe-cies level is only 12 to 15%, the result of evolutionaryturnover. A more detailed discussion is presented byScott et al. (in press).

Similarity of the Hole 534A Jurassic agglutinated as-semblage with geologically younger ones is over 95% atthe genus level. Virtually all of the 23 Jurassic genera al-so form part of the geologically younger assemblages,but Specimens are relatively small and not particularlycoarse grained. In the Cretaceous and Tertiary new gen-era appear like Uvigerinammina, Rzehakina, Cystam-mina, Recurvoides??), Plectina, Cyclammina. And theRecent record has many delicate forms that do not fos-silize; it also has been much more split.

The number of agglutinated taxa recognized in Hole534A is also lower by a factor of 1.5 to 4, and speciessimilarity with younger sites is only about 15% or less,with Bathysiphon discreta, Glomospira charoides, G.gordialis, G. irregularis, Reophax aff. horridus, Tro-chammina globigeriniformis, and T. aff. deformis. Themajority of species in Hole 534A probably disappearedin the Early Cretaceous.

At the family level the assemblages from the strati-graphically different sites are essentially equal, but therelative proportion of genera per family varies. Again,

the Recent bathyal-abyssal fauna has the highest num-ber of genera recovered and recorded (Scott et al., inpress), and the Jurassic assemblage in Hole 534A has arelatively low number of Lituolidae and Ataxophragmi-idae.

The comparative taxonomic study of the agglutinatedcomponent of the Jurassic oceanic assemblage indicatesrelative taxonomic stability above the species level intime. This conclusion can be used to delineate fossil as-semblages in the major oceanic or clastic wedge-slopeenvironments. Comparison suffers in the sense that theproportion of each taxonomic unit may vary from geo-logic site to site and in each site from sample to sample.As far as Hole 534A is concerned, specimens are smallerand much less numerous than in the other geologicalsites, which may reflect abyssal-plain versus clastic-wedgeslope conditions. The fact remains that diversity is high,as opposed to more monotypic, shallow-marine, neriticfaunas. The Jurassic agglutinated assemblage in Hole534A has a remarkable communality above the specieslevel to geologically younger deep-marine assemblages.

BIOSTRATIGRAPHY

An evaluation of the distribution in time of the Juras-sic foraminifers in Hole 534A follows three avenues.First, there is a distribution chart of selected taxa withdistinct stratigraphic range (Fig. 8); secondly, the localrelative ranges are compared to the literature; thirdly,

551

F. M. GRADSTEIN

Species

Sample(core-section,

interval in cm)

70-1,79-8072-1,60-6288-5,117-11991-1,20-2193-3, 6-794-1,30-3295-1,43-4596-3, 6-899-1,4-699-3, 77-78

100-4,46-47101-2, 140-142101-4, 46-47101-4,93-95101-6,7-9102-5,75-77104-3,38-39105-1, 22-23108-1,45-47110,CC110,CC (15)112-1,10-12113-1,24-26116-1,54-55126-3, 120-122126-4,56-58127-1,59-62

<- c <s .α sg "5C « « « .E ». c

- 2 ^ 2 o ? •p α.o>

8E • D

<ilISHI

•3 8O-T3

M

* - Cj ' "* S m * ^ C 5 S

g ö • <O CD

I II I I 51 . ö g j • δ1 |δ S

10 .£ S •c •c

? i 5 ! .«

ill!| 3

* ."δ. J s s> -ùj < u. OQ c5 cj cb

üil

Figure 8. Distribution of stratigraphically useful (or potentially so)foraminiferal species in Cores 534A-70 to -127.

the chronostratigraphic interpretation is compared tothe multiple chronostratigraphy in Hole 534A (Fig. 9),on the basis of reports on nannofossils (Roth, Medd,and Watkins), dinoflagellates (D. Habib and W. Drugg),radiolarians (P. Baumgartner), calpionellids (J. Remane),ammonites and aptychi (O. Renz), and ostracodes (H.Oertli) (this volume).

A range chart (Fig. 8) of 18 taxa that have a distinctrelative stratigraphic distribution or are reportedly of"zonal" use shows at least three shoulders. There is abasal assemblage, concentrated in Core 110 with Palmu-la subparallel^ Trocholina nodulosa, Textularia haeus-leri, Gaudryina heersumensis, Conorboides paraspis, andGlobuligerina aff. oxfordiana. The next assemblage,which appears and disappears in Cores 102 to 95, includesNeobulimina atlantica n. sp., Epistomina aff. uhligi,

Lenticulina quenstedti, and an occurrence of Frondicu-laria nikitini. At the top of the section studied there areLenticulina nodosa and Dorothia praehauteriviana inCores 72 to 70, together with Trochammina quinquelo-ba. The latter first appears in Core 105.

A chronostratigraphic evaluation of the "shoulders"suggests the Oxfordian for the basal one in Core 110,the Kimmeridgian-Tithonian for Cores 102 through 95,and the late Valanginian for Core 72 and up. Thebiostratigraphic correlation potential of the assemblagesin the Atlantic realm (Luterbacher, 1972; Kuznetsova,1974; Gradstein, 1977, 1978; Jansa et al. 1979, 1980;Sliter, 1980) is as follows.

There is a first-order correlation of the co-occurrenceof Dorothia praehauteriviana and Lenticulina nodosa,which correlates Cores 72 and up in Hole 534A to Hole391C, Cores 24 to 26, to Hole 101A, Core 10, and toHole 105, Cores 19 to 21, all in the northwestern At-lantic abyssal plain. The most likely age is late Valangin-ian. The same co-occurrence is reported in the easternNorth Atlantic in Holes 370, Cores 38 to 46, and 416,Cores 10 to 22, also dated late Valanginian.

The co-occurrence of Lenticulina quenstedti and Epi-stomina aff. uhligi in Cores 102 to 96 in Hole 534A cor-relates directly to Cores 50 to 52 in Hole 391C, to Cores36 to 37 in Hole 105, and to Cores 35 to 37 in Hole 367.The most likely age for this event is Kimmeridgian,although both taxa on the Grand Banks are known tooccur together in strata as old as the Garantella Zone,Bajocian-Bathonian, extending upward to the level ofAlveosepta jaccardi, late Oxfordian-Kimmeridgian. On-ly the uppermost co-occurrence may be as young as theKimmeridgian.

The co-occurrence in Core 110 of Conorboides paras-pis, Gaudryina heersumensis, Textularia haeusleri, Tro-cholina nodulosa, and Globuligerina aff. oxfordianahas no correlative equivalent to any other DSDP sites;this lack of correlation agrees with the fact that at noneof the other sites were strata underlying the Cat GapFormation penetrated and recovered. The age of the as-semblage is likely Oxfordian (see Oesterle, 1968; Lutze,1960), which agrees with the lack of a record of Jurassicplanktonic foraminifers in circum-Atlantic basins abovethe Oxfordian. This Late Jurassic planktonic record isbased on rich occurrences in the Hauffianum Zone inPortugal (Gradstein, unpublished data; Plate 2, Figs.18, 19), the Mariae Zone in France (Bignot and Guya-der, 1966), the Transversarium Zone off Morocco (Renzet al., 1975), and the lower Epistomina mosquensisZone on the Grand Banks (Gradstein, 1977). The factthat taxa in Core 110 probably were introduced from ashallower environment might lead to too old an age esti-mate for the actual sediments of Core 110, but micro-fossil transportation may well have happened during thestratigraphic life span of the taxa. There certainly is nostratigraphic discrepancy in the foraminiferal record ofthe cores.

It may be feasible to make miscellaneous correlationsbetween Atlantic Site 534 and Site 261 in the IndianOcean (Kuznetsova, 1974) using Trochammina quinque-loba (Oxfordian-Kimmeridgian into Valanginian) and

552

Biostratigraphy and age

Ostracodes

-? Kimm.-Tithon.-

IParanotacy there

Oxford— Kimm.

Ammonites,aptychi

- ~>Paquiericeras -late Valanginian

L. beyrichiTithonian

Foraminifers

Valanginian 72

Calpionellids

e. Valanginian

Berriasian 87-2

Berriasian 90-1

Zone B—, I. Tith.-e. Berr. r=

31 92-2 fir96 III I.Tithonian

Tithnnian 9 2 - 6

Kimmeridgian Zone A

L. quenstedtiE. aff. uhligi

102

- Oxfordian

C. paraspisG. aff. oxfordiana

93-4

Radiolarians

Kimm.—e. Tith.

e. Oxfordian

I. Cal.-e. Oxf.

m. Callovian

Dinoflagellates

D. deflandreiI. Val.-Haut. 76-3D. apicopaucicum

Valanginian81

82-1B. johewingiiI. Berriasian

86-1

87-6

e. Berriasian

91-3

Tithonian

104-2

105-1

Kimmeridgian

111-1

112-1

Oxfordian

121-1122-2

_L_

M

127-2

Nannofossils

85, 3 to 4

early Berriasian

91 CC

C. mexicana

Kimm.-Tithonian

101

V. stradneri

Kimmeridgian

Oxfordian

113

C. margareli

I. Call.-β.Oxf.

121

S. hexum

m. Callovian

127-4

Sub-bottomdepth

(m)

1202

1242 5

1286

1331

1371.5

1410

1455

1495.5

1540.5

1581

1621.5

1666.5TD

=

— -

—

—

—

—

Co

res

75

80

85

90

95

100

105

110

115

120

12b

130

Physical stratigraphy

Lithologic units

5b

Blake-Bahama Fm.

5cWhite-gray laminatedchalk, bioturbatedchalk and limestone,calcareous siltstone,claystone

5d

Cat Gap Fm.

Grayish-red g g

calcareousclaystone

Limestone turbidites _.and greenish claystone

Variegated reddish togreenish claystone ^a

Limestone turbidites y^dark claystone —Marly limestone.greenish red 7cclaystoneBlackish claystone -jgReddish claystone •je

Basalt

Geomagneticreversals

M-16

M-17

10B

M-19

M-20

?M-21M-22

M-23 or M-24

M 94 nr M 9R —

~M-25orM-26-

(Cande)

Seismicevents

= =

= C =

= D' =

I D I

= Basement =

Figure 9. Biostratigraphy, age assignments, lithological units, geomagnetic reversals, and seismostratigraphic events in the Jurassic to Earliest Cretaceous deposits of Hole 534A, Blake-Bahama Basin. (Data follow H. Oertli—ostracodes, ammonites—O. Renz; foraminifers—this chapter; calpionellids—J. Remane; radiolarians—P. Baumgartner; dinoflagellates—D.Habib and W. Drugg; nannofossils—P. Roth, A. Medd, D. Watkins; geomagnetic reversals —J. Ogg; seismostratigraphic events—R. Sheridan, T. Shipley, et al. [all references to this vol-ume].)

öH

Iδ>X

o

c

F. M. GRADSTEIN

Haplophragmoides inconstans (Tithonian-Berriasianinto Valanginian). Future studies will verify and extendmore detailed correlations using some of the taxa listedin Figure 8.

The chronostratigraphic interpretations using differ-ent microfossil disciplines are summarized in Figure 9.The figure clearly shows the agreement using radiola-rians (Unitary Associations 0 and 1 of Baumgartner,this volume), nannofossils {Stephanolithion hexum as-semblage), and middle Callovian dinoflagellates of thebasal claystone beds of lithologic Subunits 7d and e.These beds lack a diagnostic foraminiferal assemblage,as, for example, occurs on the Grand Banks, with Rein-holdella crebra Pazdro var. and Epistomina regularisTerquem (Gradstein, 1977).

There is also good agreement on the upper limit ofthe Cat Gap Formation (Core 92), the top of the Titho-nian nannofossil Conusphaera mexicana Zone, the topof the palynological Tithonian, and the position of cal-pionellid Zone B, which straddles the Jurassic/Creta-ceous boundary in Cores 91 to 90. There is no usefulrecord based on abyssal foraminifers at this boundary.

The foraminiferal assemblage with Conorboides par-aspis in Core 110, dated Oxfordian, could be consideredto be slightly reworked using the Oxfordian/Kimmeridg-ian boundary based on dinoflagellates in Cores 112 to111, but one core difference is limited inaccuracy, giventhe meager record. The nannofossil assemblage of Va-galapilla stradneri at these depths is listed as Oxfor-dian-Kimmeridgian. Geomagnetically, the Conorboidesassemblage correlates to M-24 or M-25 (J. Ogg, thisvolume), which is supposed to be the signature of base-ment in DSDP Site 105. The basal sediment in Site 105hence could be geologically slightly younger and oflithologic Subunit 6b character, which it is. This reason-ing agrees with the absence of the Conorboides assem-blage in Site 105.

The assemblage with Lenticulina quenstedti in Cores102 through 95, dated Kimmeridgian, may well extendinto Tithonian beds if we consider the local floral stra-tigraphies, although such would be unique to the deepsea. The upper assemblage in Cores 72 to 70 with Do-rothia praehauteriviana of the late Valanginian conno-tation correlates well with chronostratigraphic assign-ments, using the late Valanginian Paquiericeras ammo-nite in Core 75 (O. Renz, this volume) and the lowerpart of the Druggidium deflandrei dinoflagellate zonefrom Core 76 and up (D. Habib, this volume).

TAXONOMIC NOTES

Neobulimina atlantica n. sp.(Plate 3, Figs. 1-12)

Diagnosis. A neobuliminid with a short, flaring test, almost aswide as high; the triserial stage is confined to the apex and is poorlyvisible; the biserial stage can be slightly twisted and is broadly ellipti-cal in cross section.

Description. Early stage triserial, almost hidden in the initial, api-cal portion of the test. The biserial stage makes up 95% of the totaltest and consists of 2, 3, or 4 pairs of chambers, which rapidly increasein size such that the test width approaches or equals the length; cham-bers inflated, sutures slightly incised; test cross section elliptical withbroadly rounded ends; wall calcareous (tested with 10% HC1), distinct-ly perforate, and with a slightly pitted (punctate) appearance; apertur-

al face depressed with a large, loop-shaped aperture visible in the lastchamber. The smallest specimen found measured 60 µm (width) by 75µm (length), and the largest one 225 µm (width) by 250 µm Gength).

The Catalogue of Foraminifera (Ellis, Messina, et al., 1940-1982)lists 12 species of Neobulimina in the Upper Jurassic (1 ×), Cretaceous(6×), and Tertiary (5×) strata. All of the known taxa are muchlonger, with a more slender build and a more exposed and pronouncedtriserial stage than the specimens of Hole 534A. For example, in N.varsoviensis Bielecka and Pozaryski from the Upper Jurassic of Cen-tral Poland, the triserial stage takes 20 to 50% of the test and thebiserial stage has up to nine pairs of chambers. In the new taxon N.atlantica, the triserial part is generally 5% or less of the test length andthe biserial part has less than half of the biserial chambers of N. varso-viensis.

Specimens and photographs of N. atlantica were studied by S. Ge-roch (Krakow), I. Premoli Silva (Milano), M. Moullade (Nice), W. V.Sliter (Washington), P. Ascoli (Dartmouth, N.S.), and H. P. Luter-bacher (Tubingen). None of these colleagues is aware of a comparablerecord of N. atlantica n. sp. in the existing literature.

Type locality and type material. The assemblage of N. atlantica n.sp. consists of a hundred or more specimens in Cores 99 through 102of DSDP Hole 534A, northwestern Atlantic Ocean. The cored intervalis in the Cat Gap Formation of the Late Jurassic. Lenticulina quen-stedti (Gumbel) and Epistomina af f. uhligi Mjatliuk occur in the samecored interval, which also contains some specimens of Trochamminaquinqueloba Mjatliuk and Frondicularia nikitini Uhlig. Nannofossils(Roth et al., this volume) indicate the presence of the Vagalapilla strad-neri and Conusphaera mexicana Zones (Kimmeridgian-Tithonian),whereas D. Habib and W. Drugg (this volume) suggest the Tithonianusing dinoflagellates. Foraminifers rather suggest the Kimmeridgi-an-Tithonian, because L. quenstedti appears to have only been re-corded so far from pre-Tithonian strata. The holotype (Plate 3, Figs. 1,2) and paratypes (Plate 3, Figs. 3-12) have been deposited with theDeep Sea Drilling Collection of the Smithsonian Institute, Washing-ton, D.C., U.S.A,

Epistomina aff. uhligi Mjatliuk(Plate 4, Figs. 1-5)

Specimens vary in degree of convexity of the spiral and umbilicalsides, in degree of thickening of the sutures (limbate to smooth), andin the degree of development of the umbo. Both spiroconvex, plano-convex, and biconvex types occur.

Specimens in Cores 534A-110 to 96 belong to the Late Jurassicbranch of smooth epistominids, for which Epistomina uhligi Mjatliukis the usual name. DSDP Hole 534A specimens show a larger variationin the thickness of spiral suture (which varies from thin to much pro-nounced and limbate) than do those described by Ohm (1967).

Some of the DSDP Hole 534A specimens of E. aff. uhligi compareto Brotzenia sp. ex. gr. B. parastelligera (Hofker), as recognized byLuterbacher (1972) at DSDP Site 105.

The abyssal western North Atlantic Late Jurassic deposits shownone of the abundance in small, reticulate epistominids, as seen inNorth American Atlantic margin deposits of a shallow neritic facies.

ACKNOWLEDGMENTS

I gratefully acknowledge the advice and technical support of I.Premoli Silva, D. Habib, M. Moullade, H. Oertli, H. P. Luterbacher,C. Schafer, G. Bonham-Carter, L. Johnston, Carol Mitchell, F.Thomas, and G. Cook.

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Barnard, T., and Shipp, D. J., 1981. Kimmeridgian Foraminifera fromthe Boulonnais. Rev. Micropaleontol., 24(l):3-26.

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Bartenstein, H., and Brand, E., 1951. Micropalaontologische Unter-suchungen zur Stratigraphic des nordwestdeutschen Valendis. Anh.Senckenb. Naturforsch. Ges., 485:1-336.

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Gradstein, F. M., 1977. Biostratigraphy and biogeography of JurassicGrand Banks Foraminifera. 1st Int. Symp. Benthonic Foraminif-era (B); Mar. Sedimentol. Spec. Publ., 1:557-583.

, 1978. Biostratigraphy of Lower Cretaceous Blake Nose andBlake-Bahama Basin Foraminifers, DSDP Leg 44, western NorthAtlantic Ocean. In Benson, W. E., Sheridan, R. E., et al., Init.Repts. DSDP, 44: Washington (U.S. Govt. Printing Office),663-701.

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Jansa, L. F., Remane, J., and Ascoli, P., 1980. Calpionellid and fo-raminiferal-ostracod biostratigraphy at the Jurassic-Cretaceousboundary, offshore eastern Canada. Riv. Itai. Paleontol., 86(1):67-126.

Kuznetsova, K. I., 1974. Distribution of benthonic Foraminifera inUpper Jurassic and Lower Cretaceous deposits at Site 261, DSDPLeg 27, in the eastern Indian Ocean. In Veevers, J. J., Heirtzler, J.R., et al., Init. Repts. DSDP, 27: Washington (U.S. Govt. PrintingOffice), 673-682.

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Leg 41, Sites 367 and 370). In Lancelot, Y., and Seibold, E., et al.,Init. Repts. DSDP, 41: Washington (U.S. Govt. Printing Office),515-537.

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Luterbacher, H., 1972. Foraminifera from the Lower Cretaceous andUpper Jurassic of the Northwestern Atlantic Ocean. In Hollister,C. D., Ewing, J. I., et al., Init. Repts. DSDP, 11: Washington(U.S. Govt. Printing Office), 561-591.

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Date of Initial Receipt: September 20, 1982

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F. M. GRADSTEIN

Plate 1. Middle-Late Jurassic, DSDP Hole 534A. 1. Bigenerina jurassica (Hauesler). Sample 534A-91-1, 20-21 cm. (Magnification ×90.) 2.Bigenerina jurassica (Hauesler). Sample 534A-127-1, 59-62 cm. (×95.) 3. Bigenerina jurassica (Hauesler). Sample 534A-91-1, 20-21 cm.(× 100.) 4. Bigenerina arcuata Haeusler. Sample 534A-105-2, 67-68 cm. (× 100.) 5. Bigenerina arcuata Haeusler. Sample 534A-105-2, 67-68cm. (× 100.) 6. Bigenerina arcuata Haeusler. Sample 534A-105-2, 67-68 cm. (×95.) 7. Glomospirella gaultina (Berthelin). Sample 534A-113-1, 24-26 cm. (×120.) 8. Glomospirella gaultina (Berthelin). Sample 534A-79-3, 77-78 cm. (×120.) 9. Glomospirella gaultina(Berthelin). Sample 534A-94.CC. (× 120.) 10-11. Trochammina quinqueloba Geroch. Sample 534A-94-1, 30-32 cm. (× 190.) 12. Textulariahauesleri Kaptarenko Chernoussova. Sample 534A-126-4, 56-58 cm. (×250.) 13. Textularia hauesleri Kaptarenko Chernoussova. Sample534A-126-4, 56-58 cm. (×225.) 14. Spiroplectammina helvetojurassica Kubler and Zwingli. Sample 534A-93-3, 6-7 cm. (×105.)15. Gaudryina heersumensis Lutze. Sample 534A-110.CC (15 cm). (× 185.)

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Plate 2. Jurassic planktonic foraminifers, DSDP Hole 534A. 1-2. Globuligerina aff. oxfordiana (Grigelis). Sample 534A-110.CC. (1) ×460.(2) ×420. 3-4. Globuligerina aff. oxfordiana (Grigelis). Sample 534A-110,CC. (1) ×420. (2) ×55O. (Note conspicuous coating with nanno-fossil tests.) 5. Globuligerina aff. oxfordiana Grigelis. Sample 534A-110.CC. (×420.) 6. Globuligerina aff. oxfordiana (Grigelis). Sample534A-110.CC. (× 440.) 7. Globuligerina aff. oxfordiana (Grigelis). Sample 534A-110.CC. (× 500.) 8. Globuligerina aff. oxfordiana (Grige-lis). Sample 534A-110.CC. (×520.) 9-10. Globuligerina aff. oxfordiana (Grigelis). Sample 534A-110.CC. (9) × 1600, (10) ×470. (The enlargedumbilical region in Fig. 9 shows several generations of pustules and fine wall perforation.) 11-13. Globuligerina oxfordiana (Grigelis) 1958.(Holotype, Oxfordian, Lituanian SSR, ×40.) 14-15. Globuligerina oxfordiana (Grigelis), Reinholdella crebara var. Zone-Epistomina mos-quensis Zone, Callovian-Oxfordian (Bittern M-62 well, swc 5380', Grand Banks; × 140; note reticulate ridges pattern, as in Caucasella hoter-ivica (Subbotina), and "Kummerform" wall protrusion over the aperture.) 16-17. Globuligerina oxfordiana (Grigelis), specimen illustrated byBignot and Guyader, 1966, Mariae Zone, early Oxfordian, northwestern France, × 105. 18-19. Globuligerina oxfordiana Grigelis, Hauffi-anum Zone, late Oxfordian, Montejunto, Portugal, × 180. (Note loop-shaped aperture, as in Fig. 17.)

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Plate 3. Middle-Late Jurassic, DSDP Hole 534A. 1-2. Neobulimina atlantica n. sp. holotype. Sample 534A-101-4, 93-95 cm. (× 170.) 3. Neo-bulimina atlantica n. sp. paratype. Sample 534A-101-4, 93-95 cm. (×180.) 3. Neobulimina atlantica n. sp. Paratype. Sample 534A-101-4,93-95 cm. 4-5. Neobulimina atlantica n. sp. paratype. Sample 534A-101-4, 93-95 cm. (×270 or ×260.) 6. Neobulimina atlantica n. sp.Paratype. Sample 534A-99-3, 77-78 cm. (× 190.) 7. Neobulimina atlantica n. sp. paratype. Sample 534A-99-3, 77-79 cm. (× 215.) 8. Neobul-imina atlantica n. sp. paratype. Sample 534A-99-3, 77-78 cm. (× 190.) 9. Neobulimina atlantica n. sp. paratype. Sample 534A-99-3, 77-78 cm.(×190.) 10-12. Neobulimina atlantica n. sp. paratype. Sample 534A-99-3, 77-78 cm. (Fig. 11 is an enlargement of the apertural features;×140, ×38O, and × 190.)

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Plate 4. Middle-Late Jurassic, DSDP Hole 534A. 1. Epistomina aff. uhligi Mjatliuk. Sample 534A-99-3, 77-78 cm. (×90.) 2. Epistominaaff. uhligi Mjatliuk. Sample 534A-102-5, 75-77 cm. (× 45.) 3. Epistomina aff. uhligi Mjatliuk. Sample 534A-99-3, 77-78 cm. (× 90.) 4. Epi-stomina aff. uhligi Mjatliuk. Sample 534A-102-5, 75-77 cm. (×80.) 5. Epistomina aff. uhligi Mjatliuk. Sample 534A-99-3, 77-78 cm.(× 90.) 6. Lenticulina quenstedti (Guembel). Sample 102-2, 64-66 cm. (x 80.) 7. Lenticulina quenstedti (Guembel). Sample 534A-99-3, 77-78cm. (× 80.) 8. Conorboidesparaspis (Schwager). Sample 534A-110.CC (15 cm). (× 165.) 9-10. Conorbina sp. Sample 534A-110.CC (15 cm).(× 175 and × 135.) 11. Ophthalmidium milioliniformis (Paalzow), Sample 534A-104-3, 38-39 cm. (× 120.) 12. Ophthalmidium miliolinifor-mis (Paalzow). Sample 534A-104-3, 38-39 cm. (×120.) 13. Ophthalmidium milioliniformis (Paalzow). Sample 534A-104-3, 38-39 cm.(× 120.) 14. Palmula subparallel (Wisniowski). Sample 534A-113-1, 24-26 cm (× 100.) 15. Palmula subparallel (Wisniowski). Sample534A-113-1, 24-26 cm. (× 100.) 16. Palmula subparallel (Wisniowski). Sample 534A-113-1, 24-26 cm. (× 100.) 17. Frondicularia nikitiniUhlig. Sample 534A-99-3, 77-78 cm. (×IOO.) 18. Frondicularia franconica Guembel. Sample 534A-126-4, 56-58 cm. (×190.)

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