2. lithology and clay mineralogy of the sediments … · 2. lithology and clay mineralogy of the...

2. LITHOLOGY AND CLAY MINERALOGY OF THE SEDIMENTS FROM SITE 336,DSDP LEG 38

P. P. Timofeev, N. V. Renngarten, and L. J. BogolyubovaGeological Institute of the Academy of Sciences, USSR

INTRODUCTION

Site 336 was drilled through a series of Cenozoicdeposits and penetrated basalt (Figure 1). The totalpenetration was 515 meters. The sedimentary series to adepth of 463 meters was studied. Available were 122samples from sedimentary series and six samples fromthe al-tered basalt zone. Basically the purpose of thestudy did not include the basalt, therefore, the follow-ing section is a very brief characterization of the sam-ples from this zone. However, we would like to notethat redeposited disintegration products of the alteredbasalts are present in the sedimentary series.1

ALTERED EXTRUSIVE ROCKSAltered basalt was recovered from the 472-482 meter

interval (Cores 39, 40). The lower 4 meters (Samples1113, 1112) are composed of a dark, greenish-black,friable rock, in which the relict primary structure isclearly seen. The matrix consists of diversely orientedsmall plagioclase laths with the spaces between thembeing filled with glasses, ore minerals, and pyroxene.Nearly all the plagioclases are entirely replaced bymontmorillonite, and there appears to be segregationsof crystalline zeolite aggregates (clinoptilolite). Twometers above, a rock of a similar character is present(Sample 1111), but with less of a distinctly preservedprimary structure, due to shapeless, diffuse areas ofnew montmorillonite units. Even higher (~2.0 m), therock is mottled (dark green with brown spots) due tothe presence of iron hydroxides and green montmoril-lonite areas (Sample 1110). The primary structure ofthe parent rock is no longer traceable. The upper 2meters of the interval contain rocks (Samples 1109,1108) with an intense red-brown color from ironhydroxides. Petrographic examination indicates that,for the most part, these areas represent mont-morillonites permeated with iron hydroxides.

X-Ray MineralogyThese samples were subjected to investigation by X-

ray. The <O.OOl mm fraction was decanted and ana-lyzed (Table 1). Zeolite was isolated and identified byX-ray.

'For the purposes of this paper, the sediments have beengrouped into "series" (Figure 2). The "series" do not necessarily cor-respond to "units" as defined by shipboard sediraentologists (see SiteReport chapter, this volume). Also, the sediment terminology is thatof the authors, and may not correspond to shipboard designations.Sample numbers are those assigned by the authors for the investiga-tions.

In Samples 113-110, which characterize the lower7.5-8 meters of the basalt section, the predominant(more than 90%) component is montmorillonite, whichhas an increased content of iron in octahedralpositions. The high iron content is emphasized by theabsence of reflection with d = 4.8Å in the diffractionpatterns of preheated preparations, and by a completedissolution of the mineral in muriatic acid. Anotherfeature of the montmorillonite is a good crystallization,recorded in diffraction patterns by an integer series ofdistinct sharp reflection with d(OOi)=17.6-17.8Å in aglycerine-saturated preparation. In samples from theupper part of the basalt section (Samples 1109, 1108),montmorillonite remains ferruginous, but is badlycrystallized, and has an abnormally high d value of 19.2to 18.9Å in the diffraction pattern of the glycerine-saturated preparation.

Analyses of the <O.OOl mm fraction and, particular-ly, the 0.010-0.001 mm fraction, isolated from theabove samples, indicate the presence of zeolite of theclinoptilolite group. The zeolite yields a distinct seriesof reflections with d = 8.9Å, 7.97Å, 3.96Å, and 3.20Å.

It appears that the section under consideration con-sists of an extensively altered alkaline basalt. The over-lying red clay, which does not exhibit features of theprimary structure of the parent rock, may be a sub-aerial weathering crust. For the montmorillonitizedand zeolitized basalt with a relict primary structure, it isuncertain whether it represents a deeper weatheringzone or postvolcanic, hydrothermal transformation ofthe extrusive body.

SEDIMENTARY SERIESThe sedimentary section penetrated by Site 336

ranges in age from middle or late Eocene throughPleistocene. A study of samples from this section in-dicates that a number of features, such as externalappearance, and color (in dry state), permit subdivisionof the section into three main series (units), each ofwhich can be further subdivided into subseries(subunits). In some parts of the section, it is possible tofurther single out characteristic packets and groups oflayers.

Series 3 (Cores 20-37)Series 3 (Samples 1044-1107) represents the lower

part of the Cenozoic (Oligocene-Eocene, 220-454 m). Itis 234 meters thick and differs considerably from thetwo overlying series. It is also possible to distinguishfour lithologic subseries (subunits) with some commonfeatures justifying their interpretation as belonging toone series.

P. P. TIMOFEEV, N. V. RENNGARTEN, L. J. BOGOLUBOVA

AGE

).-PLEISTOCENE

PLI

PLIO. to

CENE

2

EOCE

NE

DEPTH SERIES,SUBSERIES

(<n)

I

VI59

0,216

I I I

-.464

1 1 1 !

III2

. ,

III4

BASALT

LITHOLOGICCOLUMN CORE

1

2

3

4

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

4041

42

43

44

204 ,

2 !

1 ,

2 ,

1 ,

1 ,2 ,5,

1 ,6 ,

1 ,5,

1 ,

2 ,4 ,

1 ,

1 ,

1 ,

6 ,

3 ,

2 ,

1 ,

1 ,3,

1 ,4 ,

1 ,

1 ,4 ,

1 ,

1 ,

1 ,

1 ,

2 ,

1 ,5,

1 ,

1 ,

1 ,4 ,

1 ,4 ,

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

70-72 (100-102

80-82

80-82

46-48

001)"1003)1005)

306); t

(1008);

(1010)

120-123 (1011•103-105 (1015)14-16 (1113-114126-128

79-8147-49

317)3;1017)1020)

( 022):(1026)a

139-141 (102787-89 (1029)

81-83

68-7068-70

87-84

(1030)

(1031);(1033)

( 034);

56-58 (1036)

119-125 (103740 44 ' l t » ; J

70-72

90-82

80-8275-7775-7175-7764-6696-98

79-81

79-8179-8!

(1039);

(1041)

(1042);(1045);(1048)a;(1050);(1054);(1057);

(1060);

(1063);(1066) ;

109-111 (1068)

99-101

27-29

86-90

111-1

(1071);

(1074);

(1077);

8 (1080

120-122 (108158-60 (1084);

111-113 (1086)

120-122 (1089)

100-102 (109075-77 (1093);

74-7674-77

1 , 136-13E(1104): 5

1 ,

1 ,4 ,1 ,

83-85

99-10:88-90

(1096);(1099);

2, 140-142 (1001);5, 120-122 (1004)2, 60-62 (1006)4;

, 110-112 (1007)2, 80-82 (1009)

; 2, 55-57 (1012);; 5, 44-46 (1015);1 , 84-88 (1017); 2,; 3, 62-64 (1018);6, 58-60 (1021)

2, 58-62 (1023); 46, 84-86 (1026)

; 3, 89-91 (1028);

3, 68-70 (1032);

2, 58-60 (1035)

; 4, 80-84 (1038);

4 , 100-110 (1040)

2, 75-77 (1043); 35, 75-77 (1046); 6

3, 80-82 (1002);

3, 89-81 (1013);6, 74-76 (1016)85-88 (1017)5;

t , 73-75 (1019);

90-92 (1025);

75-77 (1044);75-77 (1047)

1, 118-120 (1048); 2, 75-77 (1049);,75-77(1051 );5,75-77(1052) ; 6 , 75-77 (1053

2, 94-96 (1055); 35, 96-98 (1058); 6

2, 79-81 (1061); 3

2, 79-81 (1064); 35, 79-81 (1067); 6

96-98 (1056);86-88 (1059)

79-81 (1062)

79-81 (1065);79-81 (1063)

a ; 3, 109-111 (1069); 6, 109-111 (1070)

3, 109-111 (1072)

3, 27-29 (1075); 6

3, 110-114 (1078);

; 2, 110-112 (10826, 109-111 (1085)

; 2, 75-77 (1087);

; 2, 81-83 (1091);5, 75-77 (1094); 6

2, 86-88 (1097); 35, 122-125 (1106)

6, 109-111 (1073)

27-29 (1076)

6, 111-116 (1079)

; 3, 99-101 (1082);

3, 75-77 (1088)

3, 78-80 (1092);75-77 (1095)

62-66 (1098);

(1101); 2, 64-65 (1102); 3, 52-53 (1103); 4,122-12434-36 (1105); 6, 38-40 (1106); 6, 123-125 (1106)a

(1107)

(1108)(n i l ) ;

133-135 C

2, 103-105 (1109)5, 124-126 (1112)

3, 84-86 (1110);

THICK-NESS

OFSERIES

o,58

• -v50

o,56

LITHOLOGIC DESCRIPTION OF SERIES

Mostly dark, bluish-gray unsorted sandy-silty-clayey tuffaceous rocks; in

make up s i l t y clays with spots of brown colloidal organic matter, withdispersed pelitomorphic carbonate; in interbeds and accumulations of foram-ini fera shel ls; many fragments of brown volcanic glass, basalt; in a heavy

are also grains of zircon, pink garnet; especially characteristic is thedetr i ta l material: i t is purely polymictic, terrigenous: fragments ofquartzites, quartzite sandstones, metamorphic shales, limestone; t e r r i g -enous material was supplied into sediments during ice- raf t ing.

clay matter is monomineral-montmorillonite ferruginous, poorly crysta l -l i zed , authigenic.

•

aceous-silty material (mostly fragments of basalt rocks, montmoril-lonit ized t u f f s ) ; coal par t ic les, col loidal humus, pyrite are constant.The heavy fraction contains ore grains, zircon, pyroxene, amphibole,apati te, garnet, ch lo r i to id , epidote; presence of authigenic zeolite is

Figure 1. Lithologic-mineralogic summary, Site 336.

10

LITHOLOGY AND CLAY MINERALOGY, SITE 336

LITHOLOGIC-PETROGRAPHIC DESCRIPTIONOF SUBSERIES

An admixture of sandy particles (basaltfragments, altered tuffs, clay balls)increases upwards; in interbeds insedimentation breccia; clay excretionsare typical.

Pelitomorphic homogeneous clays withauthigenic pyrite and irregular accumu-lation of phillipsite.

mixed-layered phase "hydromica-montmoril-lonite" (20% montmorillonite packets)and pure ferruginous montmorillonite.

of plant organic matter pyrite; there isgypsum in interbeds in accumulations ofsandy material, ferruginous concretions,abundance of phillipsite.

LAYERS

Foraminiferas

Accumulations ofauthigenic. glauconite.

Phillipsite

genie glauconite.

Tuff withphillipsite.

DESCRIPTION OF CLAY ANDAUTHIGENIC MINERALS

Characteristic polymineral composition. The main component in montmorilloniteof various degree of ferruginicity (50-60%); middle part of the membercontains "montmorillonite-hydromica" with 20% micaceous beds; in the lowerpart of the member the montmorillonitic mineral is poorly crystallized;chlorites differ in degree of imperfection; hydromicas (20-35%) yield up to20% of labile montmorillonitic beds; kaolinite content 10-20%.

Composition of a clay fraction is monomineral, represented by a very badlycrystallized montmorillonitic mineral (100%); traces of terrigenous minerals.

Persistent presence of clinoptilolite combined with montmorillonitic mineral(S5-9O%), very poorly crystallized. Presence of hydromica, kaolinite andchlorite from 0-5-10%. Hydromica contains up to 20% of labile montmoril-

The main component (75-80%) in mixed-layered mineral montmorillonite-hydromica containing from 10-30% micaceous beds; considerable amounts ofhydromica (5-15%) from 20-25% of montmorillonitic beds. Phillipsite ispeculiar to some samples; chlorite content (imperfect and perfect) isinsignificant.

The main component in mixed-layered mineral montmorillonite-hydromica(90%); characteristic is constant presence (5-10%) of phillipsite, itsamount increasing in the 0.01 fraction; a hydromica admixture isinsignificant; no chlorite and kaolinite.

The main component in montmorillonite (90%), well crystallized in thelower part, but poorly crystallized in the upper part, clinoptilolite is

ASSOCIATIONS OF CLAY ANDAUTHIGENIC MINERALS

Kaolinite-chlorite-hydromica-montmorillonite.

Si 1i ceous-montmori1loni te

Clinoptilolite-montmori1lonite (ad-mixture of hydromica, chlorite, andkaolinite).

Mixed-layered montmorillonite-hydromicaceous (admixture of hydro-mica, chlorite, kaolinite, sometimesphillipsite).

Phillipsite-mixed-layered-montmori11oni te-hydromi caceous.

Cli nopti1oli te-montmori11oni te.

Figure 1. (Continued).

11


TABLE 1Data of the X-Ray Analysis of Clay Minerals (Fraction: <l and <IO mk), Site 336

Depth(m)

290-292

7.20-7.22

10.10-10.12

11.30-11.32

17.30-17.32

27.96-27.98

36.70-36.73

41.03-41.05

52.26-52.28

64.79-64.81

74.89-74.91

93.31-93.33

113.68-113.70

132.08-132.10169.06-169.08

183.30-183.34

185.90-185.94

208.40-208.42

216.8-216.82

221.25-221.27

224.25-224.27

233.27-233.25

237.44-237.46

243.36-243.38

244.79-244.81

247.79-247.82

252.29-259.31

260.79-260.81

267.09-267.11

273.99-274.01

Sample(Interval in cm)

1-2, 140-142

1-5, 120-122

2-1,110-112

2-2, 80-82

3-1, 80-82

4-2, 46-48

5-1, 120-123

5-4, 103-105

6-5, 126-128

8-1, 79-81

9-1, 139-141

10-1, 81-83

11-2,68-70

12-2, 58-6015-1, 56-58

16-4, 80-84

16-6,40-44

19-2, 90-92

20-1, 80-82

20-4, 75-77

20-6, 75-77

21-6, 77-75

22-2, 94-96

22-6, 86-88

231,79-81

23-3, 79-82

24-4, 79-81

24-5, 79-81

25-3, 106

26-1,99-10

No. ofSample"Gin"

1001

1004

1005

1006

1008

1010

1011

1014

1020

1022

1027

1030

1031

10351036

1038

1038a

1040b

1041

1042

1045

1047

1053

1055

1059

1060

1062

1066

1067

1069

1071

Size ofFraction

(mm)

<O.OOl

0.01

<O.OOl

<O.OOl

<O.OOl

<O.Ol

<O.OOl

<O.Ol

<O.OOl

<O.Ol

<O.OOl

0.01

<O.OOl

<O.Ol

<O.OOl

Zeolites

Absent

Absent

Absent

Clinoptü-olite

Not found

Clinoptil-olite

Not found

Not found

~ Clinoptil-olite

Phillipsite

MontmprilloniticMinerals

Ferruginous andaluminic

Aluminic, mixed-layer, with 10-15%micaceous beds

Ferruginous, mixedlayer with 10-15%micaceous beds

Aluminic-ferrugi-nous

Almunic-ferruginous mixedlayer with 20-25%micaceous beds

Ferruginous, poorlycrystallized with ab-normally high valueof c?-reflec on dif-fractogram of a spec-imen saturated with

~\glycerine fFerruginous

Ferruginous, poorlycrystallized with ab-normally high valueof <i-reflec on dif-fractogram of a spec-imen saturated withglycerine

Aluminic-ferruginous

Aluminic-ferruginous, poorlycrystallized, withabnormally high<i-reflec on diffrac-togram of a speci-men saturatedwith glycerin


Ferruginous, mixedlayer, with 30%micaceous beds

Micaceous Mineral

Al-hydromica 1 Mdwith 20% mont-morillonite beds

Illite without mont-morillonitic beds

Al-hydromica 1 Mdwith 20% montmo-rillonite layers

The same

Al-hydromica 1 Mdwith 20% montmo-rillonite beds

Illite

Illite (traces)

Not found


Not found

Illite


Al-hydromica with20% montmorillon-ite beds


Chlorite

Perfect

Imperfect

Perfect

Imperfect

Perfect

Perfect

Imperfect

Perfect

Perfect(traces)

Not found

Not found

Perfect(traces)

Not found

Imperfect

Imperfect

Kaolinite

Containedas an ad-mixture(10-20%)

Contained asan admixture(10%)

Not found

Traces

Associationof Clay andAuthegenic

Minerals

1vpó

"a

rjao

c0A.oó

'εo

•5

<N

òa

_O

1?©<NC

α>

[c"o

'5

o

§ °

o<u

^ ^ " §

f J J i

Age

Iöo

çP-T3Cocau0a

OH

co_galca

-3u

10

b

caö0

W

12


TABLE 1 - Continued

Depth(m)

282.27-282.29

285.27-285.29

292.86-292.90

298.61-298.66

331.20-331.22

336.58-336.60

350.11-350.13

352.75-352.77

369.20-369.22

388-388.02

393.77-393.75

425.74^25.76

435.86^35.88

440.22^40.24

443.23^43.25

453.83-453.85

472.99-473.03

474.53-174.55

475.84-475.86

477.38-477.40

479.24-479.26

483.33^83.35

Sample(Interval in cm)

27-1, 27-29

27-3, 27-29

28-1, 86-90

28-6,111-116

30-1, 120-122

30-5,58-60

31-1,111-113

31-3, 75-77

32-1, 120-122

33-1,100-102

33-5, 77-75

35-1, 74-76

36-1, 136-138

364-122-124

36-6, 123-125

37-1, 83-85

39-1, 99-103

39-2, 103-105

39-3, 84-86

39-4, 88-90

39-5, 124-126

40-1, 133-135

No. ofSample"Gin"

1074

1075

1077

1079

1081

1084

1086

1088

1089

1090

1094

1096

1101

1104

1106a

1107

1108

1109

1110

1111

1112

1113

Size ofFraction

(mm)

<O.Ol

<O.OOl

<O.Ol

<O.OOl

<O.OOl

<O.Ol

<O.OOl

<O.Ol

<O.OOl0.01

<O.OOl0.01

<O.OOl

<O.OOl

<O.OOl

<O.OOl

0.01

Zeolites

Not found

Phillipsite

Not found

Phillipsite

Not found

Phillipsite

Not found

Phillipsite

Clinoptilolite

Clinoptilolite

MontmorilloniticMinerals

Ferruginous, mixedlayer with 10-15%micaceous bedsFerruginous, mixedlayer with 30%micaceous beds

The same as sample1074

Ferruginous, poorlycrystallized, withabnormally highvalue of <i-reflec ondiffractogram of aspecimen saturatedwith glycerine


Ferruginous, mixedlayer, with 20%micaceous beds

Ferruginous, mixedlayer with 10-15%

Mixture of ferrugi-nous and alumnic-

Ferruginous, withan admixture ofmixed layer, with10-15% micaceousbeds


Ferruginous, mixedlayer with 30%micaceous bedsFerruginous, poorlycrystallized, with ab-normally high valueof cf-reflec on a dif-fractogram of a spec-imen saturated withglycerinThe same as Sample

Ferruginous, poorlycrystallized, with ab-normally high valueof c?-reflec on a dif-fractogram of a spec-imen saturated withglycerin

Ferruginous

Micaceous Minerals

Al-hydromica 1 Mdwith 20% mont-morillonite bedsAl-hydromica 1 Mdwith 25% mont-morillonite beds

The same as sample1074



Illite

Not found


Not found

Not found

Al-hydromica 1 Mdwith 20% montmo-rillonite beds (traces)

Chlorite

Perfect

Not found

Not found

Not found

Not found

Not found

Kaolinite

Traces

(5-10%)

Not found

Not found

Present10%

Present(5-10%)

Not found

Associationof Clay andAuthegenic

Minerals

Mix

ed-l

ayer

ed m

ontm

oril

loni

te-

hydr

omic

aceo

us (

adm

ixtu

re o

fhy

drom

ica

5-20

%, c

hlor

ite,

kao

lini

te5-

10%

, so

met

imes

phi

llip

site

)

Phy

llip

site

mix

ed-l

ayer

mon

tmor

illo

nite

-hyd

rom

icac

eous

(90

%)

Cli

nopt

ilol

ite-

mon

t-m

oril

loni

te (

90%

)

Age

te E

ocen

eat

e E

ocen

e

0cu

Mid

dr

late

Eoc

ene

Mid

dle

oB

asa

Deposits of this series consist of sandy silty clays.They are dark gray with a greenish-brown tinge. Thebrownish color is a particular characteristic for thelowest part of the series (Subseries 34). The dark color islargely attributable to scattered organic (vegetable)

matter. For the most part, it consists of a fine car-bonaceous detritus and colloidal humus. Shreds ofhigher plant tissues with a preserved cellular structureare present. Pyrite is regularly present in the form ofspherical grains and irregular aggregates, and pyritiza-

13


tion of vegetable remains is often noticeable. Siliceousskeletal remains and fragments of sponge spicules arenearly absent, and calcareous shells are very rare.

A very uniform composition is present for the heavymineral fraction. The 0.10-0.05 mm fraction has amarked predominance of ore components (up to 100%)consisting of pyrite, or (in a variable quantity) pyritewith magnetite, leucoxenized ilmenite, and ironhydroxides. There are also single grains (rarely morethan 5%-10%) of zircon, monoclinic pyroxene,hornblende, apatite, chloritoid, garnet, and minerals ofthe epidote group. Generally, the rocks are free of anyconstant admixture of a considerable amount ofpyroclastic material, however rare single fragments oftransparent acid volcanic glass are present. However,the series has three distinct thin ash tuff layers (mont-morillonitized and zeolitized), containing authigeniczeolite (phillipsite and clinoptilolite).

Subseries 34 (Cores 32-27)It has a thickness of about 75.7 meters (368.0-453.5

m) (Samples 1107-1089). Grain size analyses indicatethey are sandy silty clays, however petrographicanalysis shows that the clay matrix is composed ofclastic material. It appears to be a mixture of claydetritus, coal microparticles, and iron hydroxides.Fragments of the clay aggregates differ in microstruc-ture, color shades, and iron content. Among the clayaggregates, one can distinguish fragments of brownishmontmorillonite and ochreous basic basalt, light greennodular pieces (usually smooth-contoured) of mont-morillonitized tuffaceous rocks (Figure 2), and frag-ments of sedimentary claystones (with scattered carbondust). Also present are clay pellets aggregated in situ byorganic activity.

Immersed in this nonuniform, microbreccia claymass are sand and silt-sized particles of feldspars,quartz, altered basalt fragments, and rounded, acid ex-trusive fragments. Often the fragments enrich in-dividual clay layers (e.g., Samples 1106, 1105, 1100), orappear as randomly scattered rare inclusions.

Rocks of this subseries contain a great deal of pyrite,crystalline gypsum, and carbonaceous detritus in-cluding colloidal humus matter and shreds of tissuesfrom dry land vegetation. The deposits, especially in thelower horizons (Cores 36, 37), are typically character-ized by a presence of oval and isometric ferruginousconcretions (0.5 and 0.15 mm). These are brown andmassive, with polished glossy or fissured opaque sur-faces. Usually these ferruginous units are accompaniedby sand size quartz grains and rock fragments coveredby a glossy iron-bearing crust (Figure 3). Some biogenicclay pellets and rounded clay pieces are covered withthin iron films, as well as by a network of fissures.

Finally, a characteristic feature of the subseries is anabundance of authigenic zeolite segregations. Aggre-gates of very small (0.2-0.01 mm) well-formed mono-clinic zeolite crystals permeate the clay matrix fillingthe pores and developing around clastic grains. Themineral has a low birefringence and, therefore, appearsisotropic in very small crystals. X-ray data indicate thezeolite belongs to the phillipsite group, and at the baseof the subseries (Sample 1107), to clinoptilolite.

•

: • | l | !

Figure 2. Light green nodular pieces of montmorillonitizedtuffaceous rock. ×46.

Figure 3. Rock fragments covered by a glossy iron-bearingcrust. ×45.

Fractions (<O.OOl mm) separated from rocks of sub-series 34 were subjected to X-ray investigation. Despitethe fact that the clay component is obviously clastic andincludes variously shaped clay fragments, the mineralcomposition is not particularly varied. There is apredominance of an iron-bearing mixed-layer mineral(montmorillonite-hydromica) which contains from10%-15% to 30% of randomly distributed mica layers.The mixed-layer character of the mineral is recorded indiffraction patterns of glycerine-saturated prepara-tions. The patterns merge into a wide diffuse reflectionof a continuous spectrum from d = 8.8Å to 9.8Å.

In the clay fraction (<O.OOl mm) of the upper part ofSubseries 34 (Samples 1089, 1090, 1096), traces ofhydromica containing up to 20% montmorillonitelayers are present. In the 0.010-0.001 mm fraction(Sample 1094), illite was present without expandablelayers and, therefore, retaining in the diffractionpatterns of glycerine-saturated preparations an integerseries of reflections with dmi) = 10Å.

Another characteristic feature of the <O.OOl mmfraction is a presence of phillipsite, a zeolite with strongsharp reflections of d = 7.0Å and d= 3.17Å on the dif-fraction patterns of the untreated sample. In Core 37,Sample 1107 contains, in the <O.OOl mm fraction, azeolite of the clinoptilolite group, which is typical ofrocks of the underlying basalt series.

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Thus, the rocks of Subseries 34 are characterized bythe association: mixed-layer phase of montmorillonite-hydromica with phillipsite. The variation of featureslower in the section suggests a basis for subdividing thesubseries into two packets.

Lower Packet

The lower packet (Samples 1107-1102) has a thick-ness of 19 meters (434.5-453.5 m). Sandy clays dom-inate (with a sand content up to 40%) and contain ironooids. The content of the iron ooids in the 0.5-0.25 mmfraction attains 50%. In several, extremely clayey layers(Samples 1104, 1102), there is a great deal of scatteredorganic matter (Corg is within the limits 1.26%) andsome humusified clay aggregates, which give thedeposits a micronodular texture. Near the upperboundary of the packet there is a layer of montmoril-lonitized and zeolitized ash tuff almost without anypreservation of its primary ash structure (Sample 1101,435.9 m).

Upper Packet

The upper packet (Samples 1100-1089), with athickness of 56.5 meters (368.0-434.5 m), is character-ized by a gradual decrease down section in the amountof vegetable detritus, iron concretions, and an increasein clastic clays and pieces of light green montmoril-lonitized tuffaceous rocks (with relics of ash structure).

Subseries 33 (Cores 29 to 31)The subseries is 47 meters thick and is present in the

interval from 311.0 to 358.5 meters (Samples 1088-1081). It is composed of deposits largely similar tothose of the underlying subseries (34). The sedimentsare dark gray greenish-brown-tinged clays with a non-uniform admixture of sandy particles of feldspars,quartz, basalt fragments, and acid vitroclasts. Therocks have abundant authigenic zeolite, the clay matrixhas a clastic texture. Iron concretions, characteristic ofthe lower subseries, are absent, and among the clasticclay fragments of light green montmorillonitized tuffsare present. Rare basalt fragments are present, and thecontent of scattered carbonaceous detritus is lower. Aprincipal and characteristic feature of subseries 33, areconcretions of dense green glauconite-like matter(Samples 1086, 1084). The concretions (0.50-0.20 mm)have an isometric and irregular shape, but with round-ed surfaces. Many concretions are coated with iron ox-ides on their surfaces and, as a rule, covered by anetwork of fine shrinkage fissures (Figure 4). This mayindicate a colloidal nature for the primary matrix ofthese concretions.

Petrographically, the concretions resemble glau-conite. The concretions (in thin sections) have smoothand bay-like outlines because of syneresis fissures.Under crossed nicols, an aggregate polarization is seen,and the interference color is the tinged green mineralcolor. According to X-ray data, however, the con-cretions consist of mixed-layer montmorillonite-hydro-micaceous phase (20% mont.), and iron montmoril-lonite.

The composition of the clay fraction of the subseriesis identical to that of the lower subseries (34). The maincomponent (80%) is an iron mixed-layer mineral

Figure 4. Grains of glauconite covered by a network offine drying (shrinkage) fissures. ×25.

Figure 5. Phillipsite crystals. X2850.

(montmorillonite-hydromica). It contains 10% or 15%,and frequently as much as 30%, micaceous nonexpand-able layers. Phillipsite is present in the clay fraction ofmany samples (Figure 5).

Subseries 3i (Cores 24 to 28)The subseries is 44 meters thick (254.8-298.7 m) and

consists of deposits (Samples 1079-1063) substantiallydiffering from those of the lower two subseries. Thesubseries consists of dark gray greenish-tinged clays,which are no longer characterized by a clastic texture ofclay matrix. The sediments are composed of a pelito-morphous clay material, generally rather uniform, withuniformly scattered fine carbonaceous detritus. In mostcases, the clay shows a secondary micronodular texture(Figure 6) associated with bioturbation. However, insome places relics of a primary texture are preservedthin, horizontal lamination, emphasized by an optically

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Figure 6. Secondary micronodular texture of the claymass. y×23.

oriented arrangement of clay and coal particles. Thismay be an indication of rather quiet sedimentation con-ditions for the pelitomorphous material. Silt and sandgrains are present in the clays. They form sparse in-clusions, but more often accumulate in separate thinlayers. Amid the clastic material is a large amount ofpieces of light greenish montmorillonitic tuffs, basaltfragments, acid vitroclasts, grains of plagioclases andquartz, and rounded clay pellets. At times, the clays areso enriched by these clay clots that they acquire amicrobreccia-like texture (Sample 1074). At a depth of267.1 meters, the layer is especially saturated withsandy material and includes scattered, small pebbles.

In the heavy mineral fraction of the subseries oregrains still prevail, among which are pyrite, magnetite,and leucoxenized ilmenite. Also present are: monoclinicpyroxene, hornblende (from single grains to 5%),zircon, apatite, garnet, and chloritoid grains.

Authigenic phillipsite is constantly present in form-ing small isolated aggregates. The main component ofthe thin clay fraction of this subseries is an iron mixed-layer montmorillonite-hydromica, containing from10%-15% to 30% nonexpandable mica layers. In somesamples, a very poorly crystallized Fe-montmorilloniteis found. In the diffraction patterns of glycerine-saturated preparations (Sample 1079), it is identified byan abnormally high value of the first small-angle basalreflection of 19.4Å. Hydromica, in whose structure upto 20%-25% montmorillonite layers are present, isregularly present (5%-15%). In some samples, thehydromica content is 20%-25%. Minor admixtures ofkaolinite and chlorite (traces, 5%-10%) were noted.Chlorite, in most samples, has crystallochemicalfeatures indicating that it is recent and well crystal-lized. It is resistant to thermal treatment, and in thediffraction patterns of preparation preheated to 55O°C,it retains the chlorite peak {d = 14Å-14.3A). In theupper part of the subseries, a defective chlorite ispresent. In the diffraction patterns of preheatedpreparations, it is indicated by a reflection in the rangeof </= 13.5Å.

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Subseries 3i (Cores 20 to 23)The thickness of the subseries is 38 meters (216-254

m). Its main component is clay, which is dark gray andslightly greenish. Fine carbonaceous detritus is scat-tered uniformly through it, and shapeless pyritesegregations as well as single fragments of spongespicules and small nests of zeolite are present.

The subseries contains two distinct ash layers. One ispresent at a depth of 248.3 meters. The second, between235.6 and 237.4 meters, is a montmorillonitized andzeolitized tuff with a clear vitroclastic structure. Onlythe outer outlines of some glass fragments have beenpreserved, with crystalline aggregates of zeolitesegregated inside them as microdruses.

Spaces between the glass fragments are filled withcryptocrystalline montmorillonite. X-ray data indicatethat the montmorillonite is iron containing and wellcrystallized, with a reflection of 17.6A (in glycerine-saturated preparation) (Figure 7).

In the lower part of the subseries up to the tuff, theclays are very homogeneous with a small content ofsilty particles and sparsely scattered sand grains. Theclay matter is pelitomorphous and fine scaled; in someplaces, a similar optical orientation of clay particles isobserved, which together with the corresponding posi-tion of coal particles, underscores a fine horizontallamination of the initial sediment. This primary textureis usually bioturbated. The deposits contain aggregateinclusions of zeolite and pyrite segregations with anirregular shape. X-ray data indicate that the <O.OOlmm fraction largely consists (up to 90%) of aferruginous, poorly crystallized montmorillonitemineral, whose crystal features are evident indiffraction patterns of glycerine-saturatedpreparations. These are characterized by a low-contrastbroad reflection in the low-angle region withabnormally high spacings of the order of 18.2-19.0Å.The reflection is often recorded in the diffractionpattern as a "plateau" with a constant intensity. Afterprocessing the fraction with soda, repeated X-raystudies indicated a normal montmorillonitic reflection

Figure 7. Iron montmorillonite, X5700.


in the low angle region. It is presumed that the abnor-mally high spacing values (d = 19.0Å) are due to thepresence of absorbed amorphous silica. Besides mont-morillonite, the clay fractions contained hydromica in20%-25% of the montmorillonite layers; its quantity nor-mally was not greater than 5%, reaching 10% only at thebase of the subseries. Diffraction patterns also showtraces of kaolinite and chlorite (perfect and defective).

The second ash layer gives way to overlying clays ofthe same nature—pelitomorphous, fine scaled, withscattered coal powder, zeolite nodes, and noticeable(Samples 1045, 1046, 1049, 1050, 1052) admixtures ofsandy and coarse-grained material. Pieces of basalt, palegreen montmorillonitized tuffaceous rocks, acid ex-trusives, quartzites, grains of quartz and feldspars withclay rounded pellets (of a local origin) are so abundantin some clay layers that they give rise to a microbreccia-like rock texture. In some samples there are single, butvery large, fissured, light green glauconite grains.

Typical of all rocks of the subseries is a low content ofthe heavy fraction and a uniform mineral composition.Ore minerals present include pyrite, magnetite, andleucoxenized ilmenite. Other minerals, as single grains,are: pyroxene, hornblende, zircon, garnet, chloritoid,apatite, and epidote with censite. Among the accessoryadmixtures of vitroclastic tuff, grains of leucoxenized il-menite prevail (85%), as well as pyrite (5%-10%) and, insingle grains, magnetite, zircon, monoclinic pyroxene,and sphene.

Series 2 (Cores 14 to 19)

Series 2, in the interval from 159 to 216 meters, has athickness of 57 meters. The upper boundary of thisseries has been somewhat nominally determined as nosamples are available from the interval with its contactwith Series 1 (Cores 13 and 14). However, the depositsof Core 14 are classified with Series 2, as they contain upto 30% glauconite. This is a very characteristic mineralof the deposits of Series 2. The sediments of this serieshave a light color: in the lower part of the section, theyare predominantly yellowish-gray and in the upper part,gray with olive-green shades. By size designation, thedeposits are clay siltstones and fine-grained silty clayeysands. All sediments are tuffaceous.

The main characteristics of the series are as follows:there is a characteristic content of pyroclastics (frag-ments of acid, less frequently, basic glasses, horn-blende, pieces of basalt, fragments of prismatic pyrox-ene crystals, and plates of fresh brown biotite); an in-creased siliceous content due primarily to the presenceof remains of siliceous organisms (sponges, diatoms,and Radiolaria) and to a partial decomposition of vitro-clastic material; and authigenic glauconite, either in situor slightly redeposited. The characteristics of the claycomponent are very specific. The clay matter is mono-mineralic, represented by iron montmorillonite andlargely authigenic. The lower 19.8 meters of the sectionare composed of sediments (Samples 1040-1043), whichcan be described as tuffaceous spongolites, because oftheir content of vitroclastic material and spongespicules.

Beginning at a depth of 195.7 meters and above,glauconite is a very dominant component. The grains

are bright green and have a rounded irregular (butsmoothly contoured) shape; open syneresis fissures arenoticeable. Under crossed nicols, the glauconite has anaggregate polarization. The glauconite grains are usual-ly larger than the average sizes of the quartz, feldspar,and other grains. The glauconite mass fills the channelsin some sponge spicules.

In the vitroclastics, acid glasses predominate. Thereare also achromatic smooth and opaque-white, fibrousfragments and smaller amounts of fragments ofvesicular brown basic glasses (n = 1.608-1.610).However, in the heavy fraction, which doubtlesslyreflects the character of the pyroclastic material, thepredominant mineral is monoclinic pyroxene (70%-85%); also present is magnetite, pyrite, single grains ofzircon, rutile, chloritoid. It is possible that, initially, thequantity of basic glasses in primary sediments mighthave been larger, but during diagenesis part becamealtered thus relatively increasing the content of acidglasses.

The clay material of this series appears homogene-ous, finely dispersed and point-polarizing. According toX-ray data, the <O.OOl mm fraction consists almost en-tirely (more than 90%) of iron-containing, poorlycrystallized montmorillonite with low-contrast, wide,often "plateau"-shaped reflections in the low-angleregion with abnormally large spacings (d of the order18.7Å and more than 19.2Å). This diffraction pattern ofthe mineral may be attributed to the presence of ab-sorbed amorphous silica in the interlayers of the struc-ture. After elimination of silica by soda treatment, spac-ing of low-angle montmorillonite reflection becomesnormal.

The clay fraction in the middle part of the series(Samples 1038, 1038a) is represented by pure mont-morillonite. In its upper part, this fraction contains aslight admixture of illite and perfect chlorite. In thelower part of the series, traces of mixed-layerhydromica-montmorillonite phase are present. The0.010-0.001 mm fraction has the same composition asthe <O.OOl mm fraction.

Series 1 (Cores 1 to 13)Series 1, about 159 meters thick (0-159 m), consists of

a variety of lithologies (Samples 1000-1033). For themost part, these are bluish-gray, unsorted, sand-silt-claytuffaceous rocks, replaced in thin interbeds by crystal-vitroclastic tuffs (Samples 1022, 1023, 1025). A subor-dinate role is played here by silt-clay sediments with asmall sandy admixture, permeated by organic substance(Samples 1007, 1009). This series has three major dis-tinctive features as compared with the two lower series.First, it contains sometimes rather abundant (Samples1001, 1006a) well-preserved foraminifera shells (usuallyplanktonic forms). In some thin layers, the clay matter ispermeated with pelitomorphous carbonate (sometimeswith coccolith relics). Second, the sediments are rich inbasic (alkaline) pyroclastics, and contain basaltfragments, pieces of an opaque basic mass ofhyalobasalts, angular fragments of brown basic glasses,feldspars, quartz, monoclinic pyroxene, fragments ofacid extrusive, and achromatic glasses. Finally, thesediments contain a clastic material, which is present invarying proportions with pyroclastic material.

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The elastics are polymictic, transported to the basinby ice-rafting. This terrigenous material includesfragments of quartzite, quartzitoid sandstones withregenerated quartz grains, microcline grains, and grainsof acid plagioclases, cataclastic quartz, fragments ofhornblende metamorphic schists, and limestones. In theheavy mineral fraction are garnet, amphibole, pyroxene,and epidote. Locally derived clastic material includesfragments of basalts (rounded), green mont-morillonitized tuffaceous rocks (with glauconite grainsand sponge spicules), and clay pellets.

The characteristics of Series 1 are very pronounced inthe nature of their clay component. The clay is extreme-ly polymictic, and represented by a kaolinite-chlorite-hydromica-montmorillonite association. The predomi-nant mineral of the association is montmorillonite(~50%-60%) whose structural diversity is determined byvariation in iron content of octahedral positions of 2:1layers, the appearance (in some cases) of mixed-layermontmorillonite-hydromica phases (10%-15% ofhydromica layers), and the degree of crystallization. Analternation of layers is observed in the series, with layerswhose clay fraction contains more ferruginous mont-morillonite alternating with those containing aluminum-rich ones. In the upper part of the series (Samples 1001-1004), two crystallochemical modifications of mont-morillonite are present in the clay fraction: one rich iniron, the other, in aluminum. In the middle part of theseries (Samples 1008-1014), generally mixed-layerphases of montmorillonite-hydromica are present. Inthe clay fraction of the lower part of the series (Samples1022-1031), an iron montmorillonite mineral is presentwith an abnormally high reflection (18.2-18.9Å) in thediffraction pattern of the saturated sample.

Thus, a major feature of the clay composition ofSeries 1 is the constant, considerable (20%-35%)presence of mixed-layer hydromica-montmorillonitemineral of the modification 1 Md with 20% mont-morillonite layers, and a relatively increased quantity ofchlorite (10%-20%) and kaolinite (10%-20%). Chlorite iseither perfect with d = 14.0-14.2Å, or defective, con-tracting during heating to 550°C to 13.6, 13.4, 13.2Å.Perfect chlorite generally dominates. Kaolinite is in-dicated by reflection with d = 7.14 and 3.56Å in the dif-fraction patterns of HCl-treated samples. Chlorite-kaolinite is present as a terrigenous component.

CONCLUSIONSIn summing up the lithologic-mineralogic studies of

the sediments from Site 336, some generalizations canbe given and some specific conclusions made.

1) The Eocene-Pleistocene deposits (greater than 460m), deposited on a basaltic series are easily subdividedinto three sharply differing series. Differences in thesequence reflect the corresponding changes in the tim-ing of tectonic events, the characteristics of volcanicphenomena, and climatic conditions prevalent on theland masses. Within each series, separate subseries andgroups of layers are defined, which emphasize details ofthe series.

Series 3 (lower) is represented by clay deposits withvariable admixture of silt and sand. The clay matrix ispelitomorphic and contains a thin mixture of car-

bonaceous particles and brown colloidal humus. In thesandy silts are basalt fragments altered to varyingdegrees, grains of quartz, feldspars, fragments of mont-morillonitized tuffaceous rocks, acid effusives, andclaystones. Occasional pieces of limestone are noted. Inthe lower part of the series (Subseries 34), in individuallayers, clay is particularly enriched by humus matterand displays a microclotted texture.

For the series as a whole authigenic zeolites (clinop-tilolite and phillipsite) are very characteristic. In the in-terval from 311.0 to 358.5 meters the clay often con-tains aggregate grains of glauconite, either formed insitu or having undergone only a small amount ofredeposition.

Series 2 (middle) has a thickness of 57 meters. It is es-sentially different compared with Series 3. The series iscomposed of light colored tuffaceous clay siltsand sandy silts. The grain size characteristics are not aresult of mechanical differentiation of the disintegratedmaterial, but a result of the abundance of pyroclasticfragments of basalt and volcanic glass (silt-size),skeletal remains of siliceous sponges, and authigenicgrains (sand-size) of glauconite.

These characteristics, plus the nature of the claymaterial define Series 2. The clay material is mono-mineral, ferruginous, badly crystallized, mont-morillonite. Rocks of Series 2 are noncarbonaceousand do not contain an admixture of vegetable detritus.Deposits of this series are considered pelagic sediments.

Series 1 (upper) is about 159 meters thick. It is com-posed of blue-gray unsorted sandy silt-clay tuffaceousrocks, and contains crystal and vitroclastic tuff. Subor-dinate strata are composed of clay with spots of browncolloidal matter, with scattered pelitomorphic car-bonate, and in places accumulations of foraminiferashells. Fragments of brown volcanic glass and of basaltare ubiquitous. In the heavy fraction are pyroxene,magnetite, leucoxenized ilmenite grains, as well asgrains of zircon and pink garnet. The detrital materialis particularly characteristic. It is very polymictic, ter-rigenous, with fragments of quartz, quartzite, meta-morphic slate, and limestone. The terrigenous materialwas derived by ice-rafting. A second, no less importantpeculiarity of the upper series, is the presence of layersof primarily claystones with pelitomorphic carbonate,and coccolith tests. The latter are present throughout.

2) We suggest that the accumulation of the Cenozoicsediments was associated with tectonic activity sincemiddle Eocene.

The impression seems to be that the lower series wasformed in conditions of gradual deepening and thatdeposition began in shallow water. In this first periodof sedimentation (the lower two subseries), periodicswampy conditions may have been present, which ledto the accumulation of silt, rich in humus, pyrite, andgypsum. The damp and relatively warm climate favoredthe development on dry land of a thick vegetable cover-ing, which insured the gradual influx of vegetablematerial into the depositional environment during thetime of deposition.

The next series, as noted earlier, accumulated in adeep-water zone, where very little vegetable detritusand pelitomorphic, clastic clay material was deposited.

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However, at this time there was the accumulation ofpyroclastic, and in particular vitroclastic, material, aswell as the remains of siliceous organisms.

As a result the tempo of sedimentation was in-creased, deposits accumulated which on the basis ofgrain size did not correspond to those which were usualfor the facies. The abundance of fresh, siliceousvolcanogenic material led to the active development ofdiagenetic processes. Fragments of nonstable basic(perhaps alkaline?) volcanic glass were dissolved, fer-ruginous montmorillonite formed (badly crystallized),and glauconite formed.

Towards the beginning of the formation of Series 1,drastic changes took place in the general climatic condi-tion of the environs of the Norwegian Sea with theappearance of continental glaciers.

Therefore for the upper series of the section de-scribed there are two sharply distinguished lithologicrock types: unsorted sand-silt-clay and primarily clay,which are to a varying degree calcareous. An alterna-tion of even more contrasting rock types analogous inage, is observed in the section from Site 337. There, un-sorted sandy silty claystones alternate not only withclaystones, but also with coccolith marls. Therefore, itseems that the calcareous containing deposits couldhave formed in an interglacial period when normal con-ditions for the accumulation of deposits were renewedfor each facies. On this basis it is important to note thatthe calcareous rocks are found only in the upper seriesof Cenozoic age. They are observed in all sectionsstudied from Sites 336, 337, 346, and 350).

In the case of Site 336 some rocks contain carbonateoriginally deposited. It is biogenous and consists of coc-colith skeletons. In other rocks authigenic carbonate ispresent, which results from the diagenetic transforma-tions of the coccoliths.

We share the opinion of the previous researchers thattowards the beginning of the Pleistocene period thebarrier between the Atlantic and Norwegian Sea watersceased to exist. The warm current of the Gulf Stream

began to exert a favorable influence on the develop-ment of nannoplankton and foraminifera.

3) Several authigenic components were noted par-ticularly zeolites and glauconite. Zeolites are char-acteristic of the lower series (3). It is important to notethat they are not only coincidental with layers of ashytuff, but also widely developed in claystones without avisible admixture of pyroclastic material. Clay material(a mixed-layer phase of montmorillonite-hydromica) ispelitomorphic, is found associated with colloidalhumus, and does not display postsedimentationchanges. Therefore there is no basis for assuming thatthe appearance of zeolites was associated with thetransformation of the clay. It is asserted that in suchcases the formation of zeolites requires the presence ofslightly dissolved alumosilicate pyroclastics.

The presence in the heavy fraction of the clays ofsemidissolved (with teeth-like edges) fragments ofprismatic crystals of fresh monoclinic pyroxene alsotestifies to a former admixture of pyroclastic material.

In the claystone series studied phillipsite and clinop-tilolite are present. Phillipsite is distributed throughalmost the entire series of Eocene clay, and only the up-per part of the series (3i) contains clinoptilolite. It is in-teresting to note that up to now it has been consideredthat the Miocene is the lower age boundary of distribu-tion of phillipsite in oceanic rocks (Atlantic, Pacific,and Indian oceans). Thus, at least for the NorwegianSea, this boundary goes down to the Eocene.

Authigenic glauconite exists in two stratigraphichorizons: in the Eocene (Subseries 33) and in theMiocene (Series 2). X-ray characterizations of theseglauconites are diverse. Eocene glauconite consists, forthe most part, of a mixed-layer phase of hydromicamontmorillonite (about 20% montmorillonite layers)and has only an admixture of pure, ferruginous mont-morillonite. In the Miocene glauconite ferruginousmontmorillonite is prevalent, and the mixed-layerphase of hydromica montmorillonite has a subordinaterole.

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2. lithology and clay mineralogy of the sediments … · 2. lithology and clay mineralogy of the...

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