3. LITHOLOGY AND CLAY MINERALOGY OF SEDIMENTS FROM SITE 337, DSDP LEG 38

N. V. Renngarten, M.A. Rateev, V.D. Shutov, and V. A. Drits,Geological Institute of the Academy of Sciences, USSR

DESCRIPTIONS OF THE SEDIMENT SERIES

The sediments cored at Site 337 to the depth of 180meters are divided according to their lithologic andmineralogic characteristics into two series (Figure 1).

Series 1 (0-42.2 m, Samples 2061-2081)Pelitomorphous clays with foraminiferal shells, coc-

colith marls, unsorted sand-silt-clays, rare tuff layers,and an absence of siliceous organisms. The series isdivided into two subseries.

Subseries 1 (0-28 m, Samples 2061-2076)

Alternating slightly silty marls and foraminiferalclays with polymictic, unsorted sandy/clayey sedimentswith terrigenous material which includes: fragments ofbasalts, granites, hornblende and biotite schists, andquartzites. These were derived via ice-rafting.

Clay Mineralogy

Sediments of Subseries 1 (Pleistocene) contain in theclay fraction: illite, chlorite, montmorillonite, and asmall amount of kaolinite (Table 1). The principal claycomponent is illite. The illite does not have expandableinterlayers in its structure; the octahedral positions arepredominantly populated by Al cations. This is apolytype 1 Md modification, sometimes with an ad-mixture of 1 M. The illite polytype was determined bythe electron diffraction method of oblique structures,or with the aid of diffraction patterns of unorientedpreparations preheated to 550°C. The illite content inthe subseries is constant and averages about 60%.

A second clay component is chlorite with a max-imum content of 30%or less. It belongs to the trioc-tahedral modification. Intensity ratios of the basalreflections (a low intensity of 001 and 003 reflections)indicate a heightened content of Fe cations in the oc-tahedral structure, i.e., it is an Fe-chlorite. However,the mineral has a very low resistance to thermal treat-ment. After a sample is heated for 1 hr at 55O°C, allreflections characteristic of chlorite disappear, or thereare weak reflections at d = 13.2-13.6Å. This indicates adefective structure and, specifically, an apparently "in-sular" (partly hydrated) structure of one-level brucitelayers. The data obtained suggest that, to a large extent,the chlorite was formed as a result of structuralalterations of biotite. The content of biotite in thesediments is high.

In this subseries, the montmorillonite content is in-significant, averaging 15%-20% with a maximum of30%. Another common clay mineral (Samples 2062,2063, 2067, 2073) is a mixed-layer clay with the follow-ing diffraction characteristics: the diffraction pattern ofthe untreated sample shows a broad continuous reflec-tion, appearing as a "plateau," in the region of d = 11-

14Å; in the glycerine-saturated sample, the diffractionpattern shows a broad diffuse peak from 14 to 19Å witha maximum at d 17-18Å. Also, the reflection at d

4.7Å becomes broader. The data indicate the mixed-layer clay has montmorillonite layers with varyingdegrees of hydration alternating in its structure in anunordered fashion and in varying proportions. Thedegree of hydration, for the most part, is dependentupon the type of exchange cations. The cations seem,for the most part, to be K, Ca, and Mg. After glycerinesaturation, the montmorillonite layers expand to17.7Å. However, the vermiculite interlayers which aresaturated with K cations, expand to only 14Å. Thus, itappears that after glycerine/saturation a mixed-layerphase of irregularly alternating 17.7 and 14Å layers isformed, with a prevalence of the 17.7Å layer. Afterheating, all layers contract to 9.6-9.8Å. It is possiblethat the mineral is also a product of biotite disintegra-tion. The transformation of biotite through vermiculiteto dioctahedral montmorillonites is a well-knownprocess and is a widespread occurrence in sedimentaryrocks and weathering crusts.

Another modification of montmorillonite (Samples2065, 2066, 2070) is a mineral whose interlayers containprimarily K cations in the exchange state. Therefore,the diffraction pattern of an untreated sample has themontmorillonite reflection with d = 11Å. This is oftenseen only as a background of heightened intensity, a"train" spreading out from the illite reflection (001)towards lower angles. However, the mineral retains itscapacity to expand after saturation. The mont-morillonite contains iron and dissolves in IN HC1. Twoalternative explanations for the structuralcharacteristics of this mineral are suggested: the mont-morillonite is authigenic and developed from transfor-mation of an alkaline pyroclastic mineral. Potassiumaccumulated either as a result of adsorption of thesecations from seawater, or the K cations could havebeen supplied from the disintegration of basalt orbasalt glass. If it is so, the process can be considered an"embryonic" form of glauconitization; however, it ismore likely that the montmorillonites were also formedby the alteration of biotite. A portion of the K cationsare removed from interlayers. The remaining ones can-not bond the silicate layers, and thus the layers becomecapable of expanding.

Subseries 2 (28-42.2 m, Samples 2077-2081)

A predominance of coccolith marls. A thin ash layer.No ice-rafted clastic material.

Clay Mineralogy

The clay fraction of Subseries 1 consists almostentirely of montmorillonite ( 70%), illite ( 20%-25%),and kaolinite (5%-10%) (Table 1). A characteristic

21

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DEPTH SERIESSJBSERIES,

PACKETS

28.0

66.0

104 0

LITHOLOGICCOLUMN

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CORE, SECTION, INTERVAL (cm)AND SAMPLE NO. (GIN)

1-3, 86-88 (2063)

1-4, 87-89 (2064)

1-5, 85-87 (2065)

1-6, 109-111 (2066)

2 - 1 , 90-92 (2067)

2-2, 90-92 (2068)

2-3 , 90-92 (2069)

2-4 , 90-92 (2070)

2-5 , 100-102 (2071)

2-6, 90-92 (2072)

3-7 , 30-32 (2073)

3-6, 8-10 (2075)

4-1 , 90-94 (2076)

4-4 , 91-93 (2078)

5-1 , 68-70 (2079)

5-2, 100-102 (2080)

5-4, 100-102 (2081)

THICKNESS OF SERIESSUBSERIES (m)

6-2 , 67-69 (344)

7 - 1 , 75-77 (345)

7-2, 75-77 (346)

7-3, 75-77 (347)

7-4, 77-79 (348)

7-5, 77-79 (349)

7-6, 77-79 (350)

8 - 1 , 75-77 (351)

8-2, 76-78 (352)

9-2, 77-79 (353)9-3, 75-77 (354)9-4, 75-77 (355)9-5, 75-77 (356)9-6, 75-77 (356A)10-1 , 110-112 (357)10-2, 75-77 (358)10-3, 75-77 (359)10-4, 75-77 (360)10-5, 75-77 (361)10-6, 75-77 (362)1 1 - 1 , 75-77 (363)11-2, 75-77 (364)11-3, 75-77 (365)11-4, 78-80 (366)11-5, 79-84 (367)

12-1 , 78-80 (368)

12-2, 76-80 (369)12-3, 76-78 (370)

12-5, 119-121 (371)

42.2

65(70.8)

28

14.2

18

38

9

LITHOLOGIC DESCRIPTION OF SERIES

Pelitomorphous clays with foraminifera,coccolith marls, unsorted s i l t - c l ay .

Rare thin tu f f layers; complete absenceof siliceous organisms.

Pelagic clays of both zeo l i t i c and sub-stant ia l ly siliceous types with individualthin layers of sandy/silty clays and vo l -canic glasses; a characteristic featureis a complete absence of calcareousorganisms and a widespread distr ibut ion ofsiliceous organisms.

ALTERED BASALTS

Figure 1. Stratigraphic column at Site 337, including lithologic descriptions and descriptions of clayminerals and clay mineral associations.

22

LITHOLOGY AND MINERALOGY OF SEDIMENTS, SITE 337

LITHOLOGIC DESCRIPTION OF SUBSERIES

Alternating low-silt marls and foraminiferaclays with polymictic unsorted sand-clay;terrigenous material consists of fragments ofbasalts, granites, hornblende, and biotiteschists, quartzites. For the most partassociated with ice-rafting.

Predominance of coccolith marls; a thin ashlayer; absence of clastic or ice-rafted debris.

Montmorillonite clays with thin layers ofbasic tuffs and ashes and some fragments ofvolcanic glasses in clay; a phillipsiteassociation is present in tuffs.

Montmorillonite clays with abundant remainsof siliceous organisms (Radiolaria, diatoms,spicules), increasing down section; frag-ments of basic volcanic glasses are immersedin clay; a characteristic feature is thedevelopment of montmorillonite with abnormallyhigh spacings of up to 19.6Å (in saturatedstate) at the expense of SiO,, absorption.

Montmorillonite clays impoverished insiliceous organisms and enriched in cry-stallized volcanic glasses; breccia-likefragments of altered basalt.

ALTERED BASALTS

DESCRIPTION OF CLAY AND AUTHIGENIC MINERALS

Dioctahedral hydromica (illite), more oftenwithout expandable layers, modifications lMdand 1M 60%; trioctahedral chlorite with de-fective brucite layer (20-30%); K-montmoril-lonite (15-20%); mixed-layer products oftransformation of biotite of the chlorite-vermiculite series; admixture of kaolinite(5-10%).

Na, Ca, Mg-montmorillonite, Al, Fe, orAl-Fe containing (70%); illite (more oftenwithout expandable layers) (20-25%); de-fective chlorite and kaolinite make up asmall admixture in individual thin layers.

Well-crystallized Ca-montmorillonitescombined with mixed-layer montmorillonite-hydromicas forming a spectrum with ratiosfrom 0 to 100%; presence of phillipsite.

Poorly cyrstallized montmorillonites withabnormally high values of d/ -p., ̂ and a

broad profile of basal peaks linked up withsorption of amorphous phases of SiO; ad-mixtures of hydromica, chlorite,and kaolinite.

Montmorillonite with mixed-layer hydro-mica-montmorillonite series; presence ofclinoptilolite.

CLAY MINERALS

Hydromicaceous with chlor-ite and montmorillonite;abundant products ofstadial transformationof biotite.

Montmorillonite withillite.

Mixed-layer, montmoril-lonitic association withphillipsite.

Silica-montmoril-lonite association.

Mixed-layered mont-morillonite associationwith clinoptilolite.

Figure 1. (Continued).

23

TABLE 1Data From X-Ray Analysis of Clay and Other Minerals, Site 337

Age

Plei

stoc

ene

Depth Core, Section, Interval (cm)(m) and (GIN) Sample No.

1-3, 86-88(2063)

1-4, 87-89(2064)

1-5, 85-87(2065)

1-6, 109-111(2066)

2-1, 90-92(2067)

2-2, 90-92

2-3, 90-92(2069)

2-4, 90-92(2070)

2-5, 100-102(2071)

2-6, 90-92(2072)

3-1, 30-32(2073)

3-6, 8-10(2075)

4-1, 90-94(2076)

4-4, 91-93(2078)

Sizeof

Frac-tion(mk)

< l

< l

< l

< l

< l

<l

<l

<l

<l

< l

<l

< l

<l

< l

Montmorillonite

Montmorillonite(little)

Montmorillonite(little)

Montmorillonite(little); containsmicaceous unlabilepackets

K-montmorillonite

-

K-montmorillonite

K-montmorillonite

Ca, K-montmorillo-nite up to 30%

Montmorillonite(little)

K, Na-montmorillo-nite aluminic, ferru-ginous up to 30%

Na, Ca, Mg-montmoril-lonite ~ 50%

Mixed-LayeredMineralsa

(M-V) product ofchanging biotite,closely related tomontmojillonite

-

(M-V) product oftransformation ofbiotite (soluble inHC1)

(M-V) product oftransformation ofbiotite (soluble inHC1)

(M-V) product oftransformation ofbiotite (soluble inHC1)

-

(M-V) intermediatephase of transforma-tion of biotite

Hydromica

Illite ~ 60%

IUite ~ 60%

Illite withoutlabüe beds ~ 60%

Illite withoutlabile beds ~ 60%

Illite ~ 60%

IUite 1M and 1 Md

Illite ~ 60%

Illite ~ 50% (with-out labile beds)

Ulite ~ 50% withgood crystalUzation

IUite 50-60%

IUite ~ 50%

Illite ~ 40%

Illite 20-30%

Chlorite

Trioctahedral vari-ety 15-20%

Trioctahedral vari-ety 15-20%

Trioctahedral, de-veloped on biotitewith an imperfectbrucite bed

Trioctahedral, de-veloped on biotitewith an imperfectbrucite bed

10-20%

10-20%

10-20%

Trioctahedral vari-ety 30% with an im-perfect brucite bed;does not bear heat-ing up to 550°CTrioctahedral, moreperfect structure,can be preservedafter heating at 550° C

Trioctahedral vari-ety 20-30%

Trioctahedral vari-ety after biotite

Trioctahedral vari-ety with an imper-fect brucite bed

Trioctahedral vari-ety with an imper-fect brucite bed

Kaoli-nite Zeolites

10-20%

10-20%

10-20%

10-20%

10-20%

10-20%

10-20%

5-10%

to 5%

to 10%

to 5%

5-10%

5-10%

OtherMinerals

Quartz

Quartz

Quartz

Quartz,feldspars

Quartz,feldspars

Clay MineralAssociations

Hydromicaceouswith chlorite andmontmorillonite;abundance ofproducts of stagetransformationof biotite

Montmorilloniticwith illite

to

Sδ

<u

8o

s

<u<üuo/-\

O<u

ddl

So_>>

w

50.2

58.7

61.8

63.3

68.3

79.3

82.3

87.3

90.3

93.3

95.3

96.8

99.8

5-1,68-70(2079)

5-2, 100-102(2080)

5-4, 100-102(2081)

6-2, 67-69(344)

7-3, 75-77(346)

7-4, 80-82(348)

7-5, 77-79(349)

8-2,76-78(352)

9-3, 75-77(354)

9-5, 75-77(356)

10, 275-77(358)

10-4, 75-77(360)

10-6, 75-77(362)

11-1,75-77(363)

11-2,75-77(364)

114,78-80(366)

< l

< l

< l

Rock

Rock

<IO

<IO

Rock

<IO

<IO

<IO

<IO

<IO

<IO

Rock

<IO

Montmorillonitealuminic up to 70%

Ca, Mg-montmorillo-nite slightly ferrugi-nous - 90%

Mg, Ca-montmorillo-nite ferruginous-90%

Calcic form 50-60%

Calcic form 60-70%

Calcic form 75-80%

Magnesium-calcicform ~ 80%

Sodium-magnesium-calcic form ~ 80%

Calcic form -80%

Calcic form -80%

Calcic, poorly crys-tallized form withadsorbed SK>2- 5 0 %Poorly crystallizedwith adsorbed SKDΛ-60%

Poorly crystallizedwith adsorbed Siθ2-60%

Poorly crystallizedwith adsorbed Siθ2-75%Poorly crystallizedwith adsorbed Siθ2-75%

Poorly crystallizedwith adsorbed Siθ2-60%

_

_

Spectrum from 0 to100%, 15-20%

Spectrum from 0 to100% ~ 15%

20% interbeds ofhydromicaceoustype ~ 10%

Not over 69%

Spectrum from 0 to100%, 15-20%

15-20% interbeds ofmicaceous type~ 10%

Spectrum with 20%interbeds of mica-ceous type - 1 0 %

_

_

_

-

_

—

Illite 20-30%

IUite 20-30%

- Traces

20% labile interbedsof montmorillontictype ~ 15%

20% labile interbedsof montmorillonitictype -10%

Illitic type ~ 10%

Illitic t y p e - 15%

20% labile interbedsof montmorillonitictype - 10%

Illitic type - 1 5 %

Illitic type ~ 10%

Up to 10% of labile 10%interbeds of mont-morillonitic type,30%

Up to 10% labile 5-10%interbeds of mont-morillonitic type,30%

Illitic type -30% 10%

Illitic type-15% 10%

Up to 20% labile 5%interbeds of mont-morillonitic type10-15%

Illitic type 30% 10%

5-10%

_

_

_

_

5%

_

_

Little

Little

10%

5-10%

10%

Little

Little

Little

Abundanceof zeoliteon volcanicglass

Phillipsite10-15%

-

—

—

_

-

_

_

-

-

-

_

_

Quartz,feldspars

Quartz,feldspars,amorph.SiO2

Quartz

Quartz

Quartz,feldspars,amorph.SiO2

Quartz,feldspars

Quartz,feldspars

Quartz,amorph.SiO2

Quartz,feldsparamorph.SiO2

Quartz,feldspars

Quartz,feldspars

Quartz,amorph.SiO2

Quartz,feldspars,amorph •SiO2

Mixed-layermontmorilloniticwith phillipsite

Siliceousmontmorillonitic

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feature of the montmorillonites is a varying iron con-tent in its structure. This mineral characteristic wasqualitatively determined by the distribution of the basalreflections in the diffraction patterns of glycerine-saturated, and 550°C preheated samples. Diffractionpatterns of strongly ferruginous montmorillonites,when saturated with glycerine, have a relatively low in-tensity of reflections ([004], [005] and [006]). Thus, theydiffer from the diffraction patterns of aluminum mont-morillonites. Diffraction patterns of preheated samplesgive particularly clear data on the extent of the mont-morillonite iron content. Strongly ferruginous mont-morillonites have no reflection at i/(002) 4.7-4.8A. Incontrast, dehydrated aluminum varieties have a ratherintense (002) reflection. An intermediate intensity cor-responds to an intermediate iron content for the mont-morillonite. Chemical analyses were available for somesamples, which enabled a more reliable division of themontmorillonites according to their iron content (Table2). They were divided into three groups: predominantlyaluminum, aluminum-iron, and iron-containing.

Analysis of the data has shown that, in this subseries,montmorillonites of varying iron contents alternate.There is a relative increase in iron content (Samples2079, 2082, 2080, 2078, 2081). The mica-like compo-nent of the subseries belongs either to nonexpanding il-lites, or to hydromicas. The hydromicas usually containapproximately 20% expandable interlayers. Chlorite,present in the subseries, is also trioctahedral with adefective brucite layer.

Series 2 (Cores 5-4 to 12-5,42.4-113.0 m; early or middleOligocene and Pliocene)

The series consists of a yellow, brown, gray,yellowish-orange clay, with rare, indistinct layers ofsandy siltstones, volcaniclastic tuffs, and ashes. Azeolite mineralization is confined to the upper portion.The bulk of the sediments contains remains of siliceousorganisms, which first appear in the upper part of theseries, and are unvaryingly present to the base.

The clay, forming the bulk of sediments, ischaracteristic. It consists of Fe-montmorillonites(typical minerals of pelagic sediments) developed at theexpense of the transformation (halmyrolysis) oftholeiitic basalts (Table 2, Samples 344, 346). Char-acteristics of this mineral group and their origin havebeen studied in detail on materials from DSDP Legs 2,20, 27 (Kossovskaya and Shutov, 1975; Kossovskaya etal., 1963, 1975).

A distinctive montmorillonite was noted in Sample344, containing 18.56% Fβ2θ3. This clay was formed bythe accumulation of decomposed hyaloclastics, and ahydrothermal influx of ferruginous solutions. Anothercharacteristic of this sample is the relatively highmanganese content (to 0.28%). The remaining samplesof the entire series fall within the composition range ofpelagic clay associated with the decay of basalthyaloclastics. However, with increasing depth in theseries, there is a slight increase in AI2O2 (15.63% to16.70%), a drop in FeaOs (10.02% to 6.81%), and an in-crease in K2O (1.92% to 2.66%) and ‰ O (3.73% to4.09%).

26

LITHOLOGY AND MINERALOGY OF SEDIMENTS, SITE 337

TABLE 2Chemical Composition of Samples, Site 337

SiO2

TiO2

A12O3

F e 2 θ 3

FeOCaOMgOMnONa 2 O

K2OH 2 O+

H 2 O -

CO2

C

P2O5s F e 2 S

Σ

Siθ2gwSiθ2am

<lOµm

Subseries 12072

51.750.98

17.309.60

0.790.752.64

0.130.823.246.25

5.26-

0.080.21

99.80

10.201.75

Fraction

Subseries 22077

49.871.20

15.38

10.110.420.822.100.090.450.968.109.190.420.13

0.80

99.86

—

-

344

41.14

1.34

12.1117.63

0.171.583.160.272.591.877.759.790.09

0.18

99.61

2.202.21

Bulk Fractions

Series 2Early or Middle Oligocene and Pliocene

Subseries 2344

38.511.41

12.73

18.560.18

1.663.320.282.621.908.15

10.290.09

0.19

99.99

346

48.001.05

14.399.24

0.14

0.773.260.103.431.77

1.918.69

0.190.056.52

99,51

5.94

1.49

346

44.021.13

15.6310.020.150.843.540.113.731.922.089.45

0.210.057.08

99.97

Subseries 2352

47.58

1.2214.70

8.00

0.712.293.300.113.331.85

4.697.510.24

0.170.203.59

99.52

7.34

1.50

352

42.70

1.35

16.278.830.782.533.64

0.123.682.04

5.188.280.260.190.223.96

100.03

Subseries 3370

47.96

1.1215.15

6.180.240.723.690.143.722.41

7.188.030.34

0.072.71

99.66

7.421.38

370

43.10

1.2316.70

6.810.260.794.05

0.154.092.66

7.80

8.840.37

0.082.98

99.91

Note: Sample 2072 = (2-6, 100-102 cm), silty clay; Pleistocene; Sample 2077 - (4-2, 30-32 cm), tuff;Pliocene. Sample 344 = (6-2, 67-69 cm), volcaniclastic tuff; Sample 346 = (7-2, 75-77 cm), clay,pelagic,ferrimontmorillonitic; Sample 352 = (8-2, 76-78 cm), clay, pelagic diatoms, ferrimontmorillonite; Sam-ple 370 (12-3, 76-78 cm), clay, pelagic with zeolites.

The series is divided into three subseries based on themineralogic composition of the sediments.

Subseries 2i (Cores 5-4 to 7-6, 42.2-66.0 m)

The upper boundary of the subseries is definite withoverlying calcareous silts with foraminifera. The lowerboundary is less distinct, overlying clays with an abun-dant siliceous microfossil content. The clays ofSubseries 2 are yellow and often orange and brown.The upper part of the subseries contains volcaniclasticlayers. The layers consist of aggregates, sometimesferruginous glassy fragments, some altered to claymatter, and intergrown druses of phillipsitemicrocrystals. The phillipsite shows weak reflections7.1, 5.3, 3.18 on the X-ray pattern (Sample 344). In theother samples, the clay contains sand-size fragments ofbasic plagioclase, aggregate quartz grains, fragments ofbrown and light volcanic glasses, and small prismaticapatite crystals (Samples 346, 348). In the lower part ofthe subseries, there is a layer of volcanic glass (Sample350), consisting of a slightly crystallized mass with apeculiar curvilinear "pale-like" structure. Fragments ofhornblende crystals are present within the slightlycrystallized glass.

Clay Mineralogy

The characteristics of the ferrimontmorillonites ofthis subseries are specific. They are marked by veryhigh values of basal reflections at t/(ooi) = 15.5-15.6Å in

untreated samples, and high peaks with d = 18Å insaturated samples. This is a sign of a good mineralcrystallization. The minerals belong to the Ca form.The heightened values of the basal reflection (d = 18Å)in glycerine-saturated samples may be attributed eitherto the overall finely dispersed nature of the mineral, orto the presence of mixed-layer clays. Apart from reflec-tions with d(oo2) = 8.9Å-9Å belonging to the second-order basal reflection of true montmorillonite, diffrac-tion patterns of saturated samples show series of peaksin the 9.1-10.0Å interval. These reflections often mergeto form a characteristic horizontal plateau (Sample346). This suggests a continuous series of mixed-layermontmorillonite-hydromica units with a micaceous-to-expandable layer ratio varying from 0 to 10%. The con-tent of the mixed-layer phase does not exceed 10%-15%.The usual weak resistance to acid treatment observed isalso characteristic of the ferrimontmorillonite (Sample348).

Along with montmorillonite and the series of mixed-layer clays genetically associated with it, there is also atrue micaceous mineral present (Samples 347, 348).They are present in a limited quantity, not greater than10%-15%. There is also a small admixture of defectivechlorite with reflection d = 13.6-13.8Å. These aresometimes combined with 7.1Å on diffraction patternsof preheated samples, and a 7Å mineral preserved afterboiling the samples in 10% HC1 (kaolinite) (Sample348).

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N. V. RENNGARTEN, M. A. RATEEV, V. D. SHUTOV, V. A. DRITS

Subseries li (Cores 8-1 to 11-5,66.0-104.0 m)

The subseries consists of light-yellow, gray andbrown-gray carbonate-free clays, with abundantremains of siliceous microfossils (Radiolaria, diatoms,and sponge spicules). These are present in the clay andincrease with depth to the base of the subseries. Theclay is a fine-aggregate and often nearly isotropic.Along with siliceous skeletons, the sediment containsnumerous fragments of various volcanic glasses.Brown, diverse volcanic glass fragments (N = 1.605-1.610) prevail. They are characterized by angular con-tours, with a vesicular surface and rugged edges. Insamples where they are especially abundant, there arealso large fragments of fresh basic plagioclase crystals(Sample 354).

Clay Mineralogy

The clay retains a montmorillonitic composition, butits character is substantially altered. In the upper partof the subseries, where siliceous organisms are abun-dant, montmorillonite is represented by a well-crystallized Ca-form with a mixed-layer unit (Samples352, 354, 356). However, lower in the section it isreplaced by a poorly crystallized form. The latter hasabnormally high values of d(oo\), and wide basal peakprofiles equal (in the saturated state) to 18.8-19.2Å.There also is a typical broad halo in the 3.0-4.5Åregion, associated with an abundance of amorphousmaterial (uncrystallized glass or opal, Samples 160, 162,164). Abnormally high values of basal reflections andtheir diffuse shape are very probably due to the sorp-tion, by montmorillonite, of amorphous Siθ2. Samplesboiled in soda indicate a distinctly decreased spacing ofd(ooi), and an improved overall configuration.However, even in this "regenerated" form, the mont-morillonite of this subseries differs noticeably from itscounterpart in the upper part of the subseries. It retainsits poor crystallization and is devoid of any mixed-layerunits. There is a further tendency for it to lose its ironcontent and to gain in S1O2 (Table 2, Sample 252).Accessory clay minerals include: illite-type hydromica,defective chlorite, and kaolinite. This association isfound with pelagic, essentially siliceous sedimentation,where, with authigenic forms of disorderly mont-morillonite, terrigenous admixtures of other clayminerals are also deposited.

Subseries 33 (Cores 12-1 to 12-5,104-113.0 m)The subseries is thin and consists of light, grayish-

brown clays, frequently deformed, and often trans-formed into a breccia together with small fragments ofthe altered basement basalt. The basic sediment natureis often nonuniform. Remnants of siliceous organismsdecrease noticeably. Only large Radiolaria chambersare sporadically present. The sediment includes abun-dant fragments of crystallized glasses, quartz andfeldspar grains, shreds of montmorillonite-chloriteaggregates, sometimes with very fine zeolite (?)microcrystals derived from altered underlying basalts.In the diffraction patterns of the clay and clay fractions,reflections with d = 2.97-2.98Å are constantly record-ed. These belong to a Ca-Mg carbonate, also derivedfrom the altered basalt basement (Samples 369, 371).

The chemical analysis of clay from the least alteredparts of the core indicates a decrease in iron contentand an increased silica content (Table 2, Sample 270).However, the clay as a whole is characterized by asharp predominance of well-crystallized mont-morillonite of the Ca-form in combination with a seriesof mixed-layer units genetically related to it. In themixed-layer clays, interlayering units dominate inwhich a micaceous phase is present in amounts of 10%-20% to 90%. This is expressed in the diffraction patternsof saturated samples by characteristic sharp peaks withd = 9.1-9.3Å and d = 9.8-9.9Å (Samples 368, 369, 370).Sometimes weak reflections with d = 8.9, 7.6, 3.19Å arepresent, suggesting zeolites of the clinoptilolite series.

On the whole, the mineral association of the sub-series shows noticeable traces of interaction of thesediments with the underlying basement of hydrother-mally altered basalt.

PRINCIPAL RESULTS AND CONCLUSIONS1. Two sediment series corresponding to DSDP unit

subdivisions have been identified and investigated. Amore detailed subdivision of the series into subseriesbased on mineralogic data has been discussed.

2. Although Site 337 is located on the top of riftmountains at the eastern edge of "extinct axis" in theNorwegian Basin, the location did not have a signifi-cant effect on the sedimentation of the Pleistocenedeposits. The sediments were derived via ice-rafting anderosion of the floor of the Norwegian Basin.

An intensive supply of "exotic" sedimentary materialby ice-rafting is apparent by the abundance inPleistocene deposits of unsorted sand-silt and clays,with pebbles of granites, siltstones, limestones, biotite,and amphibolite schists. A higher sedimentation rate isindicated in the "Glacial" as compared with the Ter-tiary.

This sedimentation, associated with "glaciation" hasaffected the formation of the clay minerals in thePleistocene section. A major role was played by thesediment components supplied by ice-rafting,specifically the abundance of micas which made up to70% of the clay fraction. They are represented by dioc-tahedral illite-type hydromica (predominantly withoutexpandable layers or rarely with more than 10%-20%expandable layers). The polytype modification ofhydromicas is mostly 1 Md, and partly 1 M.

Biotite schists with unstable trioctahedral micas werean especially important component. These micas weretransformed to a series of alteration products: mixed-layer vermiculite-montmorillonite minerals, defectivechlorites, and K-montmorillonites. Petrographic obser-vation also shows all stages of corrosion and alterationof the biotite plates in situ, and fully corroborates X-ray data. The presence of this clay minerals assemblagewith hydromica, chlorite, an admixture of mont-morillonite, kaolinite, and mixed-layer units (with thesame ratio of components) was previously noted in theredeposited glacial sediments in the Barents and Whiteseas (Rateev, 1949; Kalinenko and Rateev, 1974). Thisis the basis for the conclusions that in the Pleistoceneclay minerals were ice-transported to the Norwegian-Greenland Sea, either from the north (Spitsbergen) or

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LITHOLOGY AND MINERALOGY OF SEDIMENTS, SITE 337

from the east (Scandinavia). A study of the clayminerals distribution by sediment types indicated thatthe pelagic sediments of the Oligocene/PHocene have amontmorillonite composition for the clay fraction,frequently with zeolite. However, in the Pleistocenesediments the clay fraction has hydromicas (60%), andchlor i te , with admixture of vermicul i te-montmorillonite mixed-layer units (30%).

Therefore, the ice transport of clastic and clayminerals and the abundance of biotite are the maincharacteristics of the Pleistocene sediments. Clastic claymaterial was supplied extensively during the in-terglacial periods. During these periods, the hydromicacomposition of the clay fraction of the Pleistocenesediments was drastically increased. However, duringthe periods of glaciation volcanogenic montmorilloniteincreased. This is not a universal, world-widephenomenon. For example, in the Black Sea, Stoffersand Müller (1972) established an inverse relationship.In the Black Sea sediments of the "glacial" epoch, anincrease of montmorillonite was noted.

3. Series 2 consists of typical pelagic clays, con-taining abundant remains of siliceous microfossils inthe middle subseries. The clay minerals formed byalteration of hyaloclastics and pyroclastics of tholeiiticbasalts, and represented by characteristic ferrimont-morillonite. It is characterized by a high iron content(Fe2θ3 to 10.5%), an approximately equal proportionof K2O and Na2θ, and a very low resistance to acidtreatment. With increasing depth in the series section, aslight drop in iron content and an increase in silica andin the sum total of alkalis was observed (see Table 2).Despite a similar chemical composition and that allferrimontmorillonites belong to the Ca-form markedby high values of basal reflection with d(oo\) = 15-16Å,two mineral types are clearly discernible.

The first is characterized by a high degree ofcrystallization and a presence of genetically relatedpeculiar series of mixed-layer hydromica-mont-

morillonite units with a "complete set" of mica-to-expandable layer ratios varying from 0 to 100%. Theother mineral which is present only in the middle,siliceous subseries is free of any mixed-layer units and ispoorly crystallized. Characteristics of the basal reflec-tion (up to 19.8Å in saturated samples) indicates a"littering" of the montmorillonite interlayers withamorphous silica.

4. Volcaniclastic tuffs and clays with phillipsite arepresent at the boundary between the subseries. Fe-montmorillonite has a high Fe2θ3 content (18.55%)(Table 2). It was formed as a result of inflow of iron-containing solution enriched in manganese. Themanganese is present in the clay, and as isolatedmanganese concretions at the interface between series.

REFERENCESKalinenko, V.V. and Rateev, M.A., 1974. Clay minerals in

sediments of the White Sea: Litologiya i Poleznyeiskopaemye, v. 4, p. 10-23.

Kossovskaya, A.G. and Shutov, V.D., 1975. Minerals-indicators of geotectonic types of the regional epigenesisand its conjugation with metamorphism on continents andin oceans. Crystallochemistry of minerals and geologicalproblems: Moscow (Nauka), p. 19-35.

Kossovskaya, A.G., Drits, V.A., and Alexandrova, V.A.,1963. On trioctahedral micas in sedimentary rocks: Intern.Clay Conf. Proc, Stockholm (Pergamon Press), p. 147-169.

Kossovskaya, A.G., Gushchina, E.B., Drits, V.A., Dmitrik,A.L., Lomova, O.S., and Serebryannikova, N.A., 1975.Mineralogy of Mesocenozoic deposits of the AtlanticOcean (according to the materials of Leg 2 of GlomarChallenger): Litologiya i poleznye iskopaemye, no. 6, p.12-35.

Rateev, M.A., 1949. Mineralogical composition of the clayfraction of recent sea sediments: State Oceanogr. Inst.Proc, v. 5, p. 89-115.

Stoffers, P. and Müller, G., 1972. Clay mineralogy of BlackSea sediments: Sediment. Holland, v. 18, p. 113-121.

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