Deep Sea Drilling Project Initial Reports Volume 39

38. OCCURRENCE OF INOCERAMUS REMAINS IN LATE MESOZOICPELAGIC AND HEMIPELAGIC SEDIMENTS

Jörn Thiede,' School of Oceanography, Oregon State University, Corvallis, Oregonand

Menno G. Dinkelman, Department of Geology, The Florida State University, Tallahassee, Florida

ABSTRACT

Remains of the bivalve genus Inoceramus have long been knownto occur in Cretaceous neritic marine sediments from many regionsof the globe. In recent years, Inoceramus fragments and prisms havealso been found in fine-grained hemipelagic and pelagic Mesozoicsediments sampled by the Deep Sea Drilling Project. A commoncharacteristic of these occurrences is that they have been found mostfrequently in drill sites close to continental margins, thoughoccurrences from open ocean paleoenvironments have also beenreported. Since the Inoceramus fossils have been observed insediments presently under several hundred to several thousandmeters water depth, a re-evaluation of the paleoecology of this fossilgroup seems timely, especially with respect to paleodepth ofdeposition. It can be shown that Inoceramus was confined to theupper bathyal and neritic environments (continental and islandslopes and shelves) where they lived as epibenthos on thesubstratum. In several regions these sediments indicate reducingconditions below the sediment/water interface.

INTRODUCTION

Macrofossils are relatively rare in the sedimentsrecovered by the Deep Sea Drilling Project in the worldocean (see also Kauffman, 1976). Macrofossils occur ina number of drill sites where the nature of the sedi-ments and their contained fossil assemblages indicatewarm shallow-water environments at different times ingeologic history. However, most of the reportedmacrofossil occurrences seem to be restricted to lateMesozoic pelagic and hemipelagic sediments andrepresent molluscs, largely cephalopods and bivalves.This fact is not so intriguing with respect to cephalo-pods because they belong largely to the marine nektonand their shells can drift over wide stretches of openocean after they have died (Schafer, 1962). The occur-rences of remains of large bivalves, however, pose adifferent problem, since most marine bivalves areknown to live on and in the sea bottom either asinfauna, or as attached or free-living benthos in shallowto moderate water depths (Thorson, 1957).

Many of the large bivalve remains which have beenfound in oceanic Late Cretaceous sediments cored andsampled at sites drilled by the Deep Sea Drilling Project(see Table 1) belong to the genus Inoceramus. Thisgenus, now extinct, produced a large number of widelyused guide fossils in the epicontinental Late Cretaceous

'Present address: InstituttBlindern, Oslo 3, Norway.

for geologi, Universitetet i Oslo,

(Albian-Maestrichtian; Kauffman, 1968, 1969; Seitz,1956). The Inoceramus shells are round to egg-shaped,both shells being asymmetric, as is common for manyspecies belonging to genera closely related toInoceramus (Muller, 1963). Most shells are ornamentedwith typcal concentric rings, and specimens of the LateCretaceous Inoceramus frequently possess a very thickostracum which can easily fall apart along the crystalboundaries of its large calcite prisms. The size of shellsvaries from a few centimeters to several decimenters indiameter.

Ecologically, Inoceramus is known to occur in a widevariety of continental and island margin marinepaleoenvironments, in different water depths and onmany different substrates. It is interesting to note thatInoceramus seems to have adapted to live as epibenthoson soft mud bottoms indicative of poorly oxygenatedconditions, either in the sediment or in the overlyingbottom water (Kauffman, 1967; Frey, 1972). It has alsobeen suggested that Inoceramidae have their highestdiversities in middle to outer shelf sediments(Kauffman, 1967), and that large thin and relatively flatshells are typical of species living on soft mud surfaces.Though recent relatives of Inoceramus (e.g., the bivalvegenus Isognomon) live in warm temperate to tropicalshallow waters, the apparently wider range of habitatsoccupied by Inoceramus indicates that this modernanalog cannot be used to evaluate the paleo-environment of the latter genus. However, Inoceramusmight produce mero-planktonic planktotrophic larvaeduring its reproductive cycle, as oysters do for example

899

TABLE 1Listing of Inoceramus Occurrences in DSDP Sites up to Leg 43 (Compiled after DSDP Descriptions,

as Listed in References of this Paper)3Wσw

pÖδ

Vol. Site Core Section Appearance of Inoceramus

WaterLatitude Depth

Longitude (m)

SedimentDepth

(m) Sediment Type Age

21

21

21

21

47.2

48.2

48.2

105

4

6

7

8

13-14

1

2

33-38

4-6

6

1-2

2+6

All

6

4-6

Scatteredthroughout

Fragments and lower in coreabundant prisms

Common fragments

Abundant prisms

Common prisms

Common to abundant shellfragments and prisms

Rare to abundant fragments

Large pieces of shells

Prisms oflnoceramus(l) foutogether with fragments of

12 111A 11

15 146 31

21 204 6-8

22 211 12-14

22 217 23-25

217 36-37

217A 13

217A 15

26 255 9-10

1-6

Thoughout

Notspecified

aptychi, parts of barnacles,rhyncholites, nepionic shells ofbivalves, and holothurian skeletalelements

Fragments and prisms, in somesamples more than 50% of washedresidue

Few prisms

Rare prismatic Inoceramusisp.indet, fragments, up to 12 mmlong; transportation from originalsite of deposition not ruled out

Varying abundances of prisms

Scattered Prisms and shell fragmentsthroughout

Scattered Rare fragmentsthroughout

1 Shell fragments

1 Occasional fragments

All Thick prismatic fragments

30°

32°157°

32°158°

34°69°

35.10'S35.85'W

26.9'N42.7'E

24.5'N01.3'E

53.72'N10.40'W

2102

2689

2619

5251

92

113.5-115

115-118

126-130.5

115-125

51-60

64-66

576-612

Nannofossil-chalk/ooze

Nannofossil-chalk-ooze

Nannofossil-chalk-ooze

Red and green(clayey) limestone

Maestrichtian

Campanian

Campanian

Campanian

Maestrichtian

Maestrichtian

Maestrichtian

Kimeridgian toValanginian-Tithonian

50u

46°

15°69°

24°174°

09°102°

08°90°

08°90°

31°93°

25.57'N22.05'W

06.99'N22.67'W

27.27'S06.69'W

46.53'S41.95'E

55.57'N32.33'E

55.57'N32.33'E

07.87'S43.72'E

1797

3949

5354

5528

3030

3030

1144

182-190

656-665

131-138

409-437

478-591

591-614

616-625

635-644

88-99

.5

.5

.5

.5

Moderately mottledchalk ooze

Limestones withargillaceous matrix

Tuffaceous sandstoneand conglomerate

Clay-rich nanno oozeand nanno clay,laminated

Micarb chalk, partlyshelly, chert

Dolarenite chert, somesilicified and shellmicarb chalk

Chert, Micrite,Dolomite

Chert, dolomite

Limestones

Lower to upperMaestrichtian

Late Cretaceous(Santonian-Campanian)

(?Early) Cretaceous

Early Campanian toearly Maestrichtian

Campanian tomid-Maestrichtian

Campanian

Campanian

Campanian

Santonian

27

30

33

36

39

261

263

288A

317A

317A

317A

317A

327A

327A

327A

330

330

330

330

356

356

357

357

31-33

20-29

27-30

8

9

10

1213

12

14

1516

1

2

6

7

8

34-38

40

36-38

39-51

All

NotSpecified

NotSpecified

Scatteredthroughout

1

1

1

3

2-6Particularly

5

1-21-6

1-6

1

1-6

1-6

14

Scatteredthroughout

1-6

ScatteredthroughoutScatteredthroughout

Abundant small prisms

Fragments

Common shell fragments

Common large prisms

Solitary prisms

Some prismatic fragments

Large prismatic shell fragments

Fragments

Fragments and prisms

Fragments

Fragment and prisms

Fragments

Fragments

Prismatic fragments

Fragments

Shells and prismatic pieces ofostracum up to several cm longOccasional fragments

Shells and large pieces of ostracum

Prisms and fragments, up to 5 cmlong

12°56.83'S117°53.56'E

23°19.43'S110°58.81'E

05°58.35'S161°49.53'E

ll°00.09'S162°15.78'W

50°52.28'S46°47.02'W

50°55.19'S46°47.02'W

50°55.19'S46°53.00'W

28°17.72'S41°05.28'W

30°00.25'S35°33.59'W

5667

5048

3000

2598

2410

2636

2636

3175

2086

503.5-532

470-746

932-988.5

601.5-611

611-620.5

620.5-630

639.5-641

113

149-156.5

176

129-138.5

176.5-178

309.5-319

319.5-328.5

347.5-353.5

513-655.6

693.5-673.5

607-673.5

673.5-797

Semilithifiedclay stone

Olive-black semi-lithified silty quartz-bearing to quartz-richsilty clay stone

Limestone andsilicified limestone,interbedded with chertClay stonenannofossil oozeblack chertClayey micriticchalk to micriticnannofossil chalkMicritic nannofossilchalk, chert layersNannofossil micriticlimestoneNanno ooze tonanno foram micarboozeZeolitic clay to siltyclay interbedded withmicarb oozeZeolite-richnanno clayZeolite-rich nannoclayNanno clay stone

Olive-black zeolite-rich clay-clay stoneOlive-black sapropeliczeolite-rich clay stoneOlive-black zeoliterich clay stoneMarly calcareous chalk

Calcareous mudstone

Foram-nanno chalkand limestonesGray marly chalk tosilicified limestones

Upper Jurassic(Oxfordian) toLower Cretaceous(Valanginian)?Aptian-upper Albian

Aptian-Albian

Upper Albian-Cenomanian

Lower-middle Albian

Barremian-Aptian

Upper Aptian

Maestrichtian

Late Albian-Santonian

Albian-Cenom anian

Albian

Albian

Callovian-OxfordianCallovian-OxfordianMiddle-LateJurassicSantonian-late Camp anianLate Turonian-ConiacianEarly to lateCamp anianConiacian toearly Camp anian

r>HWKhrtnwNr>LJ

n3oom>

d

w2

[AIN

J. THIEDE, M.G. DINKELMAN

3O0)

:ac

<uj —

<u

sto

n

T3

1>>CS

•s

Blu

i

t o1—1

ton

e

O, £ )

and

lian

-

-J

sil

SOJO

cc

C<U

c3

Cal

c

oo1"0 0

chti

;

•q

1_>p

V

chal

_o

3α<

<u

a_|

and

<uc5<ú

lim

>>M

s

r̂σs

.2

Alb

^>c3

α>T3•fi

bla

c

_>>3

T3

nat

e

C ^03 >>

—< aT3*"" è"V

ari

bro

\lo

ca

q

nian

ö>>W

and

Co<u

lim

>>

Mar

l

q

;one

>>"o

O<u

calc

;

(Ockelmann, 1965). Studies of the distribution of livingmero-planktonic planktotrophic bivalve larvae(Thiede, 1974) have also shown that this type of larvaldevelopment is much more common in warm waterregions of the ocean than in temperate or cold waterenvironments; these larvae are photopositive, driftingmost of the time close to the sea surface, and they areproduced by species living in the upper few hundredmeters of the water column (Thorson, 1965;Ockelmann, 1965). This mechanism might explain therapid worldwide distribution of this genus during lateMeoszoic times.

The finding of Inoceramus in sediments which arefound at great depth in the ocean is not in agreementwith the above facts. Several possibilities arise whichwill be evaluated using the occurrences of Inoceramussampled in cores of the Deep Sea Drilling Project:

1) The Inoceramus could have been living in the deepsea during the late Mesozoic.

2) Inoceramus remains could have been displacedfrom shallow water regions into deep water environ-ments.

3) The sediments and the contained Inoceramusremains have undergone vertical tectonic movementssince their deposition.

INOCERAMUS IN LATE MESOZOICDEEP SEA SEDIMENTS

The data reported and discussed here were takenfrom the Initial Reports of the Deep Sea DrillingProject, and for the most recent legs from the publishedreport in Geotimes. It is critical to this project that noquantitative, only qualitative, descriptions of theoccurrence of Inoceramus are available for severalDSDP legs; it was therefore impossible in severalinstances to evaluate the occurrences to their fullextent; this would have required redescription of thecores, impossible within the necessary time frame. Alloccurrences are listed in Table 1 and are described anddiscussed below; for further details the reader isreferred to the source.

DSDP Leg 39 OccurrencesLet 39, Site 356 on the southern part of Sào Paulo

Plateau (Southwest Atlantic Ocean off Brazil), Figure1: Inoceramus shells and pieces of their thick prismaticostracum up to severall centimeters long (Figure 2) arecommon constituents in laminated medium to darkgray calcareous mudstones and olive-gray dolomiticmarly chalks of late Turonian (Micula staurophoraZone), Coniacian, Santonian to Campanian (Tetra-lithus gothicus Zone) age. Several clay pebble con-glomerates in Core 39 indicate that portions of thissediment column have been displaced from nearbytopographic highs. No other megafossils have beenobserved.

Leg 39, Site 357 on the western Rio Grande Rise(Southwest Atlantic Ocean), Figure 1: Inoceramusshells and large pieces of the ostracum have beenobserved in laminated medium to dark gray marlyforaminifer nannofossil limestones of early Santonian{Marthasterites furcatus Zone) to late Campanian/early

902

LATE MESOZOIC INOCERAMUS REMAINS

Figure 1. Positions of drill sites with Cretaceous Ino-cQX iVmx•s>-bearing sediments occupied during Legs 39 and40 of the Deep Sea Drilling Project.

Maestrichtian (Tetralithus trifidus Zone) age (Figure 3).The abundance of Inoceramus has been plotted versusdepth subbottom (Figure 4) illustrating that this fossilgroup is restricted almost entirely to the Santonian.These sediments are believed to have been deposited inan island slope/outer shelf sublittoral to bathyalenvironment a few hundred meters below the formersea surface (Thiede et al., 1975; Thiede, 1977). Thisinterpretation is supported by evidence from benthicforaminiferal faunas (Sliter, this volume).

Observations of Previous DSDP LegsThe distribution of sites with Inoceramus in late

Mesozoic sediments (Table 1) has been plotted inFigure 5. Some observations in the site reports are notclearly enough described to allow the identification ofInoceramus. Thus the discussion has been restricted toundisputable evidence, and all questionableoccurrences are omitted. Exceptions are made for thereported occurrences in sediments recovered fromDSDP Sites 105 and 211 where the authors believe theavailable evidence to be positive.

Leg 3, Site 21 (Maxwell, Von Herzen, et al., 1970) onthe eastern part of Rio Grande Rise (SouthwestAtlantic Ocean) Figure 5: Inoceramus remains havebeen observed in Campanian {Planuglobulina glabrataZone) to Maestrichtian (Rugotruncana subcircum-nodifer Zone) pink foraminiferal nannofossil chalkswhich are underlain by a Campanian/pre-Campanian

coquina of unquestionable shallow water origin (asproven by the presence of remains of red algae). Wholeshells of Inoceramus have been observed in severalplaces in the Maestrichtian sediments, but in mostinstances the shells have disintegrated into large piecesor even into the calcitic prisms which are so typical ofthe Inoceramus ostracum. There is no evidence forredeposition, and it is believed that these Inoceramuslived in an island margin paleoenvironment (Thiede,1977).

Leg 6, Site 47 (Heezen, Fischer, et al., 1971a) on thecrest of the Shatsky Plateau (tropical SouthwesternPacific Ocean), Figure 5: Inoceramus shells are commonin white foraminifer nannofossil oozes of Maestrichtian(Globotruncana gansseri - Lithraphidites quadratusZone and Åbathomphalus mayaroensis = Tetralithusmums Zone) age.

Leg 6, Site 48 (Heezen, Fischer, et al., 1971b) on thecrest of Shatsky Plateau (tropical West Pacific Ocean),Figure 5: Prismatic Inoceramus fragments and wholeshells have been observed in white nannofossil oozes ofMaestrichtian {Åbathomphalus mayaroensis = Tetra-lithus murus and Globotruncana gansseri = Lith-raphidites quadratus Zones) age. No evidence fordisplacement has been reported. Shatsky Rise is amorphological feature which rises to less than 3000 m,while the surrounding sea floor is approximately 6000meters deep (Heezen, Fischer, et al., 1971a).

Leg 11, Site 105 (Hollister, Ewing, et al., 1972) at thenorthern limit of Hatteras Abyssal Plain (WesternNorth Atlantic), Figure 5: Prisms of Inoceramus{l) arefound scattered throughout a red and green clayeylimestone of Kimmeridgian to Tithonian age. Theassociation of Inoceramus^) with remains of pelagiccrinoids and rare radiolarians suggest an upper bathyalenvironment.

Leg 12, Site 111 (Laughton, Berggren, et al., 1972) onOrphan Knoll off eastern Canada (Northwest AtlanticOcean), Figure 5: Inoceramus fragments and prismshave been found in early to late Maestrichtian{Globotruncana gansseri - Reinhardtites anthophorusand Globotruncana stuarti-G. contusa-Globotruncanellamayaroensis = Arkhangelskiella cymbiformis Zones)white nannofossil oozes and chalks (Figure 6), whichhave been deposited in an outer neritic and upperbathyal paleoenvironment (van Hinte, 1972). Thesesediments are underlain by shallow water marinesediments capping the continental fragment of OrphanKnoll. Inoceramus make up more than 50% of thecoarse fractions of several early and late Maestrichtiansamples.

Leg 15, Site 146 (Edgar, Saunders, et al., 1973) in theCaribbean (Figure 5): Few Inoceramus prisms havebeen found in Late Cretaceous foraminiferalradiolarian limestones. No detailed age determinationis available for Core 31 with Inoceramus remains, butthis core is directly under- and overlain by Santonian{Globorotruncana concavata carinata Zone) sediments.

Leg 21, Site 204 (Burns, Andrews, et al., 1973) east ofthe Tonga Trench (Southwest Pacific Ocean) Figure 5:Up to 15 mm long white calcareous prisms have beenfound in tuffaceous pebbly granule conglomerates ofprobable Late Cretaceous age. It is not certain that

903


356 34-2

(B)Figure 2. Typical appearance o/Inoceramus fragments in the sediments of Site

356 on the Sao Paulo Plateau. (A) from Core 34, Section 2; (B)from Core38, Section 3. Scale: The numbers are 3 mm high.

these prisms are Inoceramus remains, as similar shellstructures are known from other thick-shelled bivalvetaxa. Furthermore, sedimentary structures, and round-ing and sorting of the sediment associated with Ino-ceramus, suggest displacement after deposition in ahigh energy environment.

Leg 22, Site 211 (von der Borch, Sclater, et al., 1974a)just south of the Java Trench and west of ChristmasIsland (Eastern Indian Ocean), Figure 5: Varyingabundances of Inoceramus prisms have been found invariegated nannofossil oozes and clays of earlyCampanian to early Maestrichtian age {Eiffellithusaugustus and Tetralithus nitidus trifidus zones).Interpretation of the calcareous microfossil assem-blages allows for a depositional environment either onthe inner shelf or on the upper slope. In the latter case itis conceivable that downslope movement has affectedthe sedimentary assemblages.

Leg 22, Site 217 (von der Borch, Sclater, et al., 1974bon the eastern flank of the northern Ninetyeast Ridge(East Indian Ocean), Figure 5: Inoceramus has beenfound together with other megafossils in shelly micarbchalks of Campanian to middle Maestrichtian age{Globotruncanella mayaroensis Zone; Eiffellithusaugustus-Tetralithus nitidus trifidus zones) (Figure 7).Remains of Inoceramus and oysters make up 20%-30%of the total sediment; they are believed to indicate arelatively shallow paleoenvironment.

Leg 26, Site 255 (Davies, Luyendyk, et al., 1974) onBroken Ridge (Southeast Indian Ocean), Figure 5:Inoceramus remains have been detected in LateCretaceous (= Santonian) {Marthasterites furcatusZone) hard gray limestones with interbedded blackcherts.

Leg 27, Site 261 (Heirtzler, Veevers, et al., 1974a) inArgo Abyssal Plain northwest off Australia (East

904


Figure 3. Typical occurrences of Inoceramus remains in Santonian sediments from Site 357 on the western Rio Grande Rise(Core 47: (A)Section 4, 75-100 cm; (B) Section 4, 125-150 cm; (C) Section 5, 75-100 cm; (D) Section 6, 0-25 cm).

Indian Ocean), Figure 5: Numerous small prisms ofdisintegrated Inoceramus occur in Kimmeridgian darkbrown claystones (see also Speden, 1974). A shallowenvironment of deposition is inferred from faunalevidence.

Leg 27, Site 263 (Heirtzler, Veevers, et al., 1974b) onthe eastern margin of Cuvier Abyssal Plain (SoutheastIndian Ocean), Figure 5: Inoceramus fragments havebeen observed in olive-black semilithified quartz-bearing to quartz-rich laminated silty claystones ofCretaceous (Aptian?) age. The accompanying benthicforaminiferal faunas (Scheibnerová, 1974) indicate ashallow to extremely shallow marine paleoenvironmentof probably <IOO meters water depth.

Leg 30, Site 288, (Andrews, Packham, et al., 1975) onthe eastern salient of the Ontong-Java Plateau (WesternPacific Ocean), Figure 5: Inoceramus shell fragmentsare common to abundant in laminated, partiallysilicified limestones interbedded with chert of Aptian tolate Albian age (Eiffellithus turriseiffeli Zone). Faunalevidence indicates sedimentation well above thecarbonate compensation depth.

Leg 33, Site 317, (Schlanger, Jackson, et al., 1976) onthe Manihiki Plateau (Western Pacific Ocean), Figure5: Unreplaced Inoceramus prisms are contained inblack cherts (Core 8) of late Albian/Cenomanian age.Valves and prismatic fragments also occur in laminatedand mottled light olive-gray nannofossil micritic lime-

905


DISTRIBUTION OF BIG BIVALVE FRAGMENTS

Core

Number

Below Sea

Bottom

Depth (m)

36

43

44 ~45Z4 6 _47

49

5θ"

600

650

700

Age

LATE

CAMPANIAN

EARLY

CAMPANIAN

SANTONIAN

Number of Fragments Visible/Section

[ I

3

1 r 1 \ 1 1 r 1 1 1

7 9 n 13 15

SITE 357

RIO GRANDE RISE

750

800

Figure 4. Distribution of Inoceramus in Cretaceous sediments of Site 357 of the DeepSea Drilling Project on the western Rio Grande Rise.

stones of? Barrëmian-Aptian (Leupoldina cabri, Globi-gerinelloides algerianus, Hedbergella trocoida, andTicinella roberti zones) and early to middle Albian age.They overlie volcanogenic sand and siltstones of EarlyCretaceous age which were probably deposited inrelatively shallow water.

Leg 36, Site 327, (Barker, Dalziel, et al., 1976a) onthe elevated eastern part of the Falkland Plateau (SouthAtlantic Ocean), Figure 5: This part of the FalklandPlateau was subaerial sometime before the MiddleJurassic (Barker, Dalziel, et al., 1974). Inoceramusfragments and numerous remains of thin-walledpelecypods have been found in early Albian toSantonian (Prediscosphaera cretacea/Eiffellithus turris-eiffeli/Lithraphidites alatas zones) and Maestrichtian(Nephrolithus frequens Zone) zeolitic clays interbeddedwith micarb oozes and nannofossil-foraminifer micarboozes. The zeolitic clays grade downward into light toolive-gray nannofossil chalks in which thin-walledpelecypod tests are common. The common occurrenceof pelecypods may imply an upper bathyal environmentof deposition.

Leg 36, Site 330 (Barker, Dalziel, et al., 1976b) on theelevated eastern part of the Falkland Plateau (SouthAtlantic Ocean), Figure 5: This hole bottomed ingneisses and granites which are overlain by Middle andLate Jurassic sand- and siltstones with lignites.Inoceramus remains have been observed enclosed inearly-middle Albian {Prediscosphaera cretacea Zone)nannofossil clays which overlie sapropelic claystones ofNeocomian and Aptian age. Inoceramus has also beenmentioned in sapropelic claystones of Callovian-Oxfordian age {Vekshinella stradneri Zone), where they

are associated with thin-shelled pelecypods andbelemnite rostra. The nature of the sedimentary recordis suggestive of a continental shelf environment.

Observations in Post Leg 39 DSDP Drill Sites

Leg 40, Site 361 (Bolli, Ryan, et al., in press,a) nearthe base of the southwest African continental rise,Figure 5: A fragment was found in grayish brown shaleof Late Cretaceous age. The inferred environment ofdeposition is bathyal.

Leg 40, Site 364 (Bolli, Ryan, et al., in press, b) in theAngola Basin on the southwest African continentalmargin (Figure 5): Inoceramus have been observed inlate Campanian to early Maestrichtian {Tetralithustrißdus Zone) brownish to reddish calcareous marly,nannofossil chalks (Bolli, Ryan, et al., 1975). They havealso been found in late Aptian to early Albian{Globigerinelloides algerianus = Parhabdolithusangustus Zone) chalks and limestones together withammonites. It seems surprising that no Inoceramushave been observed in Site 363 (E Walvis Ridge) (Bolli,Ryan, et al., in press, c) though it samples sedimentscorresponding in age and facies to Inoceramus bearingdeposits at Sites 356 and 357 sediments in the westernSouth Atlantic Ocean (see above).

Leg 43, Site 382 (Tucholke, Vogt et al., 1975) nearNashville Seamount in the western North Atlantic(Figure 5): Inoceramus prisms occur in variegated,laminated brownish clays and claystones of lateCampanian-early Maestrichtian age (Globotruncanaarea Zone). Coarser beds contain silt- and sand-sizedgrains of zeolites and volcanic glass. Inoceramus platesalso occur in marly limestone and calcareous claystone

906


of early Campanian age (Globotruncana elevata Zone).These marly limestones and calcareous claystones areinterbedded with thicker volcaniclastic breccias whichshow occasional cross-bedding and one example ofreversed grading. The highly vesicular nature of thebasalt clasts in the breccias indicate extrusion in lessthan 1000 meters of water. Downslope displacement ofthe volcaniclastic detritus, possibly as massive slumps,is suggested by the admixtures of fresh to highly alteredclasts (Tucholke, personal communication, 1976).

No Inoceramus have been mentioned in the availabledescriptions of sites drilled on Legs 41, 42, and 44.

THE PALEOENVIRONMENT OF THE LATEMESOZOIC INOCERAMUS-BEARING PELAGIC

AND HEMIPELAGIC SEDIMENTS

Distance to Continents and IslandsAs evident from the descriptions, most sites (Table 1,

Figure 5) where Inoceramus has been observed aresituated close to continents, oceanic islands, formerislands, or at least on former shoals. This is welldocumented for the drill sites on Rio Grande Rise(Thiede, 1977), on Ninetyeast Ridge (Pimm et al.,1974), on Orphan Knoll (van Hinte, 1972), on CuvierPlateau (Scheibnerová, 1974), on the Falkland Plateau(Barker, Dalziel, et al., 1976a and b), and in theCaribbean (Edgar, Saunders, et al., 1973). However, itis less well understood in drill sites on anomalousoceanic crust, such as the Ontong-Java Plateau(Andrews, Packham, et al., 1975) the Manihiki Plateau

(Schlanger, Jackson, et al., 1976), and the Shatsky Rise(Heezen, Fischer, et al., 1971a, b), though it can be as-sumed that these rises subside in a fashion similar tonormal oceanic crust (Detrick et al., 1977) and that theywere close to the sea surface during late Mesozoic time.

The worldwide distribution of the epibenthicInoceramus, which has not only been found incontinental margin drill sites but also in sites onisolated oceanic islands, is in agreement with theassumption that this genus developed mero-planktoniclarvae during its reproductive cycle. These larvaeusually live only a few weeks before they try to find asubstratum suitable to settle on; however, if they arenot successful in doing that, they might be able toremain planktonic for several additional months, as hasbeen observed for larvae of Recent benthic gastropods(Scheltema, 1971), thus allowing them more time tofind a suitable environment to complete their develop-ment to adult molluscs.

Type of SubstratumSediments containing Inoceramus are usually

relatively fine grained biogenic oozes or terrigenousmuds which in many cases are known to overliesediments indisputably deposited in very shallow water.Unlike the case of many outcrops of shallow watermarine sediments of late Mesozoic age (Kauffman,1967; Frey, 1972), the Inoceramus in deep-sea drill coresare usually not accompanied by a wealth of otherbenthic megafossils (however, see also Kauffman,1975). They have been found in ocean sediments

Figure 5. Positions of Deep Sea Drilling Project sites with Late Cretaceous Inoceramus-Z>eßmzg• sediments (see Table 1).

907


obviously deposited under well oxygenated conditions,such as at Sites 364 (Bolli, Ryan, et al., 1975), thoughthe majority of Inoceramus occurrences have beenreported from laminated, dark mudstones and chalkswhich must have been deposited under reducingconditions, resulting in the scarcity of a benthicinfauna. Since Inoceramus is believed to belong to thebenthic epifauna and to be autochthonous, the inter-face between anaerobic and aerobic conditions musthave been at the sediment/water interface.

minimum 100-200 m) at time of deposition of thesesediments. These reconstructions are probably correctbecause aseismic ridges seem to subside in a fashionsimilar to regular oceanic crust (Detrick et al., 1977).They are similarly successful for drill sites located onrelatively small slices of continental crust surroundedby normal oceanic crust, i.e., Sites 327 and 330. At pres-ent the paleodepth of deposition of many continentalmargin sites cannot be reconstructed in the same detail,since their history of subsidence is not fully understood

182-

tto

m

o

_α

sub-

Met

ers

190-

(190-199)

11-1

-11-2

•

11-3

11-4

11-5

11-6

--11,CC

-12.CC

5

j

Frequency of INOCERAMUS (in percent of coarse fraction)

10 15 20 25 30 35 40 45 50 55 60

late Maestrichtian

—

i

^_^——~ " early

____̂ - Maestrichtian

Cenomanian

Figure 6. Distribution of Inoceramus remains in Maestrichtian sediments from OrphanKnoll, Northwest Atlantic Ocean (after van Hinte, 1972). The sediments directly aboveCore 12-111A-11 are of early Eocene age; a major hiatus is suspected between Cores10 and 11 of Hole 111 A (Laughton, Berggren, et al, 1972).

Paleodepth

The water depth of time of deposition of many of theInoceramus-bçanng sediments remains an openquestion because many sites are either on anomalousoceanic crust, on continental crust, or close to thecontinental margin above a crystalline basement ofunknown age and nature (Table 1). Attempts toreconstruct the water depth at time of deposition ofthese sediments have been carried out for the sites onRio Grande Rise (Thiede, 1977), on Ninetyeast Ridge(Pimm et al., 1974), Orphan Knoll (van Hinte, 1972),and Cuvier Plateau (Scheibnerová, 1974); all seem topoint to a relatively shallow depth (maximum 500 m,

(Kinsman, 1974), since crystalline basement belowthem has not been sampled.

The fact that Inoceramus has been observed at severaldrill sites in sediments which have been deposited underreducing conditions is in agreement with the previouslydiscussed paleodepth information (Thiede and vanAndel, 1977). Sediments on the upper continental slopeand on the outer shelf in certain regions are known toresemble those deposited under reducing conditionssince they are deposited under bottom waters ofreduced oxygen contents (oceanic midwater oxygenminimum) and since their contents and accumulationrates of organic matter are high compared to the openpelagic environment (van Andel, 1964). Oxidation of

908


500-

-

-

-

-

550-

_

_

600-

-

-

-

Core

25

26

27

28

29

30

31

32

33

34

35

36

37

13A

14A

15A

Number of Fragments Visible/Section

3 5 7 9 Age

late Campanianto early

Maestrichtian

Campanian

Figure 7. Distribution of Inoceramus remains in Cam-panian to early Maestrichtian sediments from Holes 217and 217A on the eastern flank of the northern Ninety eastRidge (von der Borch, Sclater, et al., 1974b).

the organic matter depletes the available oxygenalready at the sediment/water interface. This creates areducing environment below this interface, but allowsan epibenthic life on top of the sediments, includingInoceramus.

CONCLUSIONS

1. Remains belonging to the extinct genus Ino-ceramus have been found in deep-sea drill cores fromthe Atlantic, Pacific, and Indian oceans.

2. All occurrences can be linked to a paleo-environment close to continental and island margins oron shoal areas in the open ocean. The worldwidedistribution of habitats of Inoceramus and theoccupation of isolated biotopes in the pelagic realmsuggest that Inoceramus developed larvae such as theirrecent relatives do. During the mero-planktonic stageof development, such larvae can drift across wide openocean regions.

3. Inoceramus, which is known to occur togetherwith rich megafossil faunas in many late Mesozoicmarine shallow water paleoenvironments in continentalplatform deposits, invaded the sublittoral-upperbathyal region of the ocean. Since Inoceramus belongedto the epibenthos, it was even able to occupy sedimentsunder reducing conditions below the sediment-waterinterface. Sediments of this type are known to occur inregions where the oceanic midwater oxygen minimumis impinging upon shallow areas.

4. Inoceramus can therefore be used as a sensiblepaleodepth indicator in pelagic and hemipelagic sedi-ments where this genus represents the sole megafossil.

ACKNOWLEDGMENTSBoth authors thank the Deep Sea Drilling Project (US-

NSF) for the invitation to join Leg 39 in the South AtlanticOcean. We are also grateful to our fellow shipboard scientistsfor the joyful collaboration on board the ship and during thepostcruise meeting. J. Thiede's part in this study has beensupported by the Office of Naval Research under ContractN00014-76-C-0067.

REFERENCESAndrews, J.E., Packham, G., et al., 1975. Site 288. In

Andrews, J.E., Packham, G., et al., Initial Reports of theDeep Sea Drilling Project, Volume 30: Washington (U.S.Government Printing Office), p. 175-229.

Barker, P.F., Dalziel, I.D.W., et al., 1974. Leg 36: Geotimes,v. 10, no. 11, p. 16-18.

, 1976a. Site 327. In Barker, P.F., Dalziel, I.D.W., etal., Initial Reports of the Deep Sea Drilling Project,Volume 36: Washington (U.S. Government PrintingOffice), p.

, 1976b. Site 330. In Barker, P.F., Dalziel, I.D.W., etal., Initial Reports of the Deep Sea Drilling Project,Volume 36: Washington (U.S. Government PrintingOffice), p.

Bolli, H.M., Ryan, B.F., et al., 1975. Basins and margins ofthe eastern South Atlantic: Geotimes, v.20, no. 6, p. 22-24.

, in press (a). Site 361. In Bolli, H.M., Ryan,W.B.F., et al., Initial Reports of the Drilling Project,Volume 40: Washington (U.S. Government PrintingOffice).

, in press (b). Site 364. In Bolli, H.M., Ryan,W.B.F., et al., Initial Reports of the Deep Sea DrillingProject, Volume 40: Washington (U.S. GovernmentPrinting Office).

., , in press (c). Site 363. In Bolli, H.M., Ryan,W.B.F., et al., Initial Reports of the Deep Sea DrillingProject, Volume 40: Washington (U.S. GovernmentPrinting Office).

Burns, A.E., Andrews, J.E., et al., 1973. Site 204. In Burns,A.E., Andrews, J.E., et al., Initial Reports of the Deep SeaDrilling Project, Volume 21: Washington (U.S.Government Printing Office), p. 33-56.

Davies, T.A., Luyendyk, B.P., et al., 1974. Site 255: InDavies, T.A., Luyendyk, B.P., et al., Initial Reports of theDeep Sea Drilling Project, Volume 26: Washington (U.S.Government Printing Office), p. 281-294.

Detrick, R.S., Sclater, J.G., and Thiede, J., in press.Subsidence of aseismic ridges: Earth Planet. Sci. Lett.

Edgar, N.T., Saunders, J.B., et al., 1973. Site 146/149. InEdgar, N.T., Saunders, J.B., et al., Initial Reports of theDeep Sea Drilling Project, Volume 15: Washington (U.S.Government Printing Office), p. 17-168.

Frey, R.W., 1972. Paleoecology and depositional environ-ment of Fort Hays limestone member, Niobrara chalk(upper Cretaceous), west-central Kansas: Univ. KansasPaleont. Contrib. Art. 58 (Cretaceous 3).

Heezen, B.C., Fischer, A.G., et al., 1971a. Site 47. In Fischer,A.G., Heezen, B.C., et al., Initial Reports of the Deep SeaDrilling Project, Volume 6: Washington (U.S. Govern-ment Printing Office), p. 67-143.

, 1971b. Site. 48. In Fischer, A.G., Heezen, B.C., etal., Initial Reports of the Deep Sea DrillingVolume 6: Washington (U.S. GovernmentOffice), p. 145-169.

Project,Printing

909


Heirtzler, J.R., Veevers, J.J., et al., 1974a. Site 261. InHeirtzler, J.R., Veevers, J. J., et al., Initial Reports of theDeep Sea Drilling Project, Volume 27: Washington (U.S.Government Printing Office), p. 129-192.

, 1974b. Site 263. In Heirtzler, J.R., Veevers, J.J., etal., Initial Reports of the Deep Sea Drilling Project,Volume 27: Washington (U.S. Government PrintingOffice), p. 279-335.

Hollister, CD., Ewing, J.I., et al., 1972. Site 105. In Hollister,CD., Ewing, J.I., et al., Initial Reports of the Deep SeaDrilling Project, Volume 11: Washington (U.S. Govern-ment Printing Office), p. 219-312.

Kauffman, E.G., 1967. Coloradoan macroinvertebrateassemblages, central Western Interior, United States. InKauffman, E.G. and Kent, H.C. (Eds.), Paleoenviron-ments of the Cretaceous Seaway—A Symposium: GoldenColorado (Colorado School of Mines), p. 67-143.

, 1968. The Upper Cretaceous Inoceramus of PuertoRico: Transact. 4. Caribbean Geol. Conf. (Port-of-Spain,Trinidad, 1965): Trinidad and Tobago (CaribbeanPrinters), p. 203-218.

., 1969. Population systematics, radiometrics andzonation: the new biostratigraphy: Chicago J. Paleontol.,v. 43, p. 890.

_, 1976. Deep-sea Cretaceous macrofossils: Hole317A, Manihiki Plateau. In Jackson, E.D., Schlanger,S.O., et al., Initial Reports of the Deep Sea DrillingProject, Volume 33: Washington (U.S. Government Print-ing Office), p. 503-535.

Kinsman, D.J.J., 1974. Rift valley basins and sedimentaryhistory of trailing continental margins. In Fischer, A.G.,Judson, S. (Eds.), Petroleum and global tectonics: Prince-ton (Princeton University Press), p. 83-126.

Lancelot, Y., Seibold, E., et al., 1975. The eastern NorthAtlantic: Geotimes, v. 20, no. 7, p. 18-21.

Laughton, A.S., Berggren, W.A., et al., 1972. Site 111. InLaughton, A.S., Berggren, W.A., et al., Initial Reports ofthe Deep Sea Drilling Project, Volume 12: Washington(U.S. Government Printing Office), p. 33-159.

Maxwell, A.E., von Herzen, R.P., et al., 1970. Site 21. InMaxwell, A.E., von Herzen, R.P., et al., Initial Reports ofthe Deep Sea Drilling Project, Volume 3: Washington(U.S. Government Printing Office), p. 367-411.

Muller, A.H., 1963. Lehrbuch der Palaozoologie. Vol. II.Invertebraten. Pt. 1. Protozoa-Mollusca I: Jena (VEBGustav Fischer Verlag).

Ockelmann, K.W., 1965. Developmental types in marinebivalves and their distribution along the Atlantic coast ofEurope: Proc. I. Europ. Malac. Congr. (1962), p. 25-35.

Pimm, A.C., McGowran, B., and Gartner, S., 1974. Earlysinking history of Ninetyeast Ridge, northeastern IndianOcean: Geol. Soc. Am. Bull., v. 85, p. 1219-1224.

Schaffer, W., 1962. Aktuo-Palaontologie nach Studien in derNordsee: Frankfurt/M (Verlag Waldemar Kramer).

Scheibnerovà, V., 1974. Aptian-Albian benthonicforaminifera from DSDP Leg 27, Sites 259, 260, and 263,eastern Indian Ocean. In Heirtzler, J.R., Veevers, J.J., et

al., Initial Reports of the Deep Sea Drilling Project,Volume 27: Washington (U.S. Government PrintingOffice), p. 697-741.

Scheltema, R., 1971. The dispersal of the larvae of shoal-water benthic invertebrate species over long distances byocean currents. Proc. 4. In Crisp, D.J. (Ed.), Europ. Mar.Biol. Symp.: Cambridge (Cambridge University Press),p. 7-28.

Schlanger, S.O., Jackson, E.D., et al., 1976. Site 317. InJackson, E.D., Schlanger, S.O., et al., Initial Reports ofthe Deep Sea Drilling Project, Volume 33: Washington(U.S. Government Printing Office), p. 161-300.

Seitz, O., 1956. über Ontogenie, Variabilitat und Bio-stratigraphie einiger Inoceramen: Palaont. Z., v. 20, p. 3-6.

Speden, I.G., 1974. Cretaceous Bivalvia from cores, Leg 27.In HeirtzlerQ J.R., Veevers, J.J., et al., Initial Reports ofthe Deep Sea Drilling Project, Volume 27: Washington(U.S. Government Printing Office), p. 977-981.

Thiede, J., 1974. Marine bivalves; Distribution of mero-planktonic shell-bearing larvae in eastern North Atlanticsurface waters: Palaeogeogr., Palaeoclimat., Palaeoecol.,v. 15, p. 267-290.

, in press. The subsidence of aseismic ridges:Evidence from sediments on Rio Grande Rise (S.W.Atlantic Ocean): Am. Assoc. Petrol. Geol. Bull.

Thiede, J., et al., 1975. Sediments on Rio Grande Rise (SWAtlantic Ocean): Subsidence of an aseismic ridge: Nice,France, 9. Congr. Internat. Sediment., v. 8, p. 67-70.

Thiede, J. and van Andel, T.H., 1977. The paleoenviron-ment of anaerobic sediments in the late Mesozoic SouthAtlantic Ocean: Earth Planet. Sci. Lett., v.33, p.301-309.

Thorson, G., 1957. Bottom communities (sublittoral orshallow shelf): Geol. Soc. Am. Mem., v. 67, p. 461-534.

, 1965. The distribution of benthic marine molluscaalong the NE Atlantic shelf from Gibraltar to Murmansk:Proc. 1. Europ. Malac. Congr. (1962), p. 5-23.

Tucholke, B., Vogt, P.R., et al., 1975. Glomar Challengerdrills in the North Atlantic, Geotimes, v. 20, no. 12,p. 18-21.

van Andel, T.H., 1964. Recent marine sediments of the Gulfof California; Am. Assoc. Petrol. Geol. Mem., v. 3,p. 216-310.

van Hinte, J.E., 1972. List of selected Mesozoic planktonicand benthonic foraminifera and ostracoda, and conclu-sions on age and environment. In Laughton, A.S.,Berggren, W.A., et al., Initial Reports of the Deep SeaDrilling Project, Volume 12: Washington (U.S. Govern-ment Printing Office), p. 115-119.

von der Borch, C.C., Sclater, J.G., et al., 1974a. Site 211. Invon der Borch, C.C., Sclater, J.G. et al., Initial Reports ofthe Deep Sea Drilling Project, Volume 22: Washington(U.S. Government Printing Office), p. 13-36.

von der Borch, C.C., Sclater, J.G., et al., 1974b. Site 217. Invon der Borch, C.C., Sclater, J.G., et al., Initial Reports ofthe Deep Sea Drilling Project, Volume 22: Washington(U.S. Government Printing Office), p. 267-324.

910

Deep Sea Drilling Project Initial Reports Volume 39

Documents