Deep Sea Drilling Project Initial Reports Volume 20

20. VOLCANIC GLASS IN ABYSSAL CLAYS SAMPLED AT DSDP LEG 20 DRILLING SITES,NORTHWEST PACIFIC

E. John W. Jones, Department of Geology, University College London

INTRODUCTION

Volcanic glass is an important component of many partsof the silty clay sequences recovered on Leg 20 of the DeepSea Drilling Project (Figure 1). The proportion of vitricmaterial varies widely, from almost 100% in ash layers totrace amounts (less than 2%) dispersed in some of theabyssal brown clays. Photomicrographs of a selection ofsmear slides containing glass shards and splinters arepresented in Plate 1.

The occurrence of volcanic glass in deep-sea clays in thewestern Pacific has, of course, been known for along time(Murray and Renard, 1891). Piston cores taken within anextensive zone, some 1000-1300 km wide, on the ocean-ward side of the Japan and Kurile arcs generally contain atleast one layer of vitric ash (Ninkovich et al., 1966; Horn etal., 1969; 1970). A few studies of the glass in core sampleshave been made, such as those of Ninkovich et al. (1966),but they have necessarily been restricted to relatively young(Pliocene-Recent) accumulations. The cores recovered onLeg 20 have now provided an opportunity of examiningvolcanic glass deposited at much earlier periods on thewestern edge of the Pacific plate. This report presentsanalyses of glass shards from sediments as old as Cam-panian, based upon refractive index and electron micro-probe studies. The principal objective of this preliminaryinvestigation has been to define, insofar as the limitednumber of cores allows, the major compositional variationsof the vitric fraction of sediments laid down during the lateMesozoic and Tertiary.

PREPARATION OF SAMPLES ANDMETHODS OF ANALYSIS

Twelve core samples were chosen to provide a repre-sentative selection of glass from the clays recovered at thenorthern drill sites (Sites 194 to 198; Figure 1; Table 1). Inaddition, one sample (VIII; Table 1) from Site 199 at theedge of the Caroline Abyssal Plain was examined.

In order to concentrate the glass shards, about 3 cc ofthe sediment was boiled in hydrogen peroxide. The residuewas washed and then filtered through a 62.5µ sieve, theprocess being repeated until the clay-sized fraction waseliminated.

The variation of refractive index of the glass within eachsample was determined by comparing roughly 200 grainswith a series of liquids whose indexes were measured with anAbbe refractometer in sodium light. The spread in values isshown by a series of histograms in Figure 2. Most of thesamples are unimodal, some distributions being sharplypeaked (Samples I and VI). It was on the basis ofcompositional variations revealed by refractive index thatshards were selected for analysis with the microprobe in

order to study differences in composition within a singlesample and between samples of different ages and locations.

The glass shards were separated by hand and mounted inepoxy resin for polishing. Plate 2 shows an example of theresult of the mounting and polishing procedures. Smallquartz, feldspar, and other grains inevitably contaminatedthe sample, but these could generally be identified byexamining the polished mount in transmitted light. About10 glass grains were selected, and three analyses were madeon each for nine major elements. The results for each grainwere averaged and the microprobe correction applied usinga computer program written by Mason et al. (1969).

COMPOSITIONAL VARIATIONS

Based upon the refractive index of the vitric componentthe samples fall into two quite distinct groups: thosecontaining glass, usually colorless, whose values fall below1.56; and those with glass shards, usually yellow or brownin color, the refractive indexes of which are generally higherthan this figure (Figure 2). If we disregard the sample fromSite 199 (Sample VIII), which is well south of the otherdrilling locations and also contains reworked materialaccording to paleontological examinations by H. Hekel andV. Krasheninnikov, it can be seen that the low refractiveindex (R.I.) glass is confined to the Tertiary and Quater-nary clays. Quaternary Sample I from Site 194 and upperMiocene Sample VI have sharply peaked histograms indi-cating a relatively narrow range of compositions. The glasswith high refractive index is found in significant quantitiesonly in the Cretaceous sediments of the northern drillingsites. In these clays the refractive index of over 80% ofshards falls between 1.57 and 1.60.

Some of the compositional variations have been investi-gated with the electron microprobe. Tables 2 to 7 sum-marize the analyses of each of the shards so far examined.As expected from earlier work on the relationship betweenrefractive index and silica content (Tilley, 1922; Williams etal., 1954; Ross and Smith, 1955), the high refractive indexshards of Sample VIII are mainly of basic composition(Figure 3, Table 7). Microprobe analyses have not yet beencarried out on the Cretaceous samples (IX-XIII), but therange of refractive indexes is similar to that of Sample VIII(Figure 2), indicating a preponderance of glass of basiccomposition. The presence of basic glass in Cretaceoussediments is unexpected because shards of this compositionare usually assumed to be particularly susceptible todiagenetic alteration. Some alteration is seen (Plate 1 [6]),but it is usually quite minor. According to measuredhydration rates of glassy margins of submarine basalts(480-2OOµ2/1000 years; Moore, 1970) silt-sized basic glassshards should not occur in late Mesozoic sediments, yetthey are present in significant amounts in the Campanian

389

E. J.W.JONES

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196 198

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CAROLINEABYSSAL

PLAIN

LEGEND

VOLCANOGENIC SEDIMENTS

ABYSSAL CLAY

ABYSSAL CLAY (interpreted)130° 1 0"

Figure 1. Stratigraphy at the DSDP Leg 20 drilling sites discussed in text. Locations of clay samples from which glasswas extracted for analysis are indicated by Roman numerals (see Table 1 also). The cored intervals are indicated inblack.

I . I .

kkkkk

CHALK

CHERT

TURBIDITES

v v v vv v v v

•

390

VOLCANIC GLASS IN ABYSSAL CLAYS

TABLE 1Sample Data

SampleLocation

North EastWater Depth Subbottom

(m) Depth (m) Age

(I)(II)(III)(IV)(V)(VI)(VII)(VIII)(IX)(X)(XI)(XII)(XIII)

194-1-1,194-1-3,196-1-1,195-1-3,195-1-5,194-2-1,195-2-2,199-3-1,198A-3-1196-2-2,196-2-2,196-2-4,196-2-4,

114-11557-59

132-13364-6650-52

145-147141-143146-148,64-6651-5362-6357-59

119-120

33C

33C

30c

32C

32C

33C

32C

13C

25C

30c

30c

30c

30c

58.68''58.68''06.97''46.40''46.40''58.68''46.40''30.78''49.54''06.97'06.97'

'06.97'.06.97'

146°146°148°146°146°146°146°156°154°148°148°148°148°

48.64'48.64'34.49'58.73'58.73'48.64'58.73'10.34'35.05'34.49'34.49'34.49'34.49'

5754575461945968596857545968610059586194619461946194

38.641.138.866.769.5

143.4122.9

78.0110.2106.0106.1109.1109.7

QuaternaryQuaternaryQuaternaryPlio/PleistocenePlio/PleistoceneUpper MioceneMiddle MioceneMiddle Miocenea

Late CretaceousCampanianCampanianCampanianCampanian

aWith reworked Early Tertiary components.

(75 m.y.) clays of Hole 196. It is interesting to note thatbasaltic glass showing only minor alteration has been foundin even older sediments. Brew and Muffler (1965) andMuffler et al. (1969), for example, have described studiesmade on relatively fresh basaltic glass extracted from tuffsof Upper Triassic age in southeast Alaska. It is not yet clearwhich of many possible factors, such as the low tempera-ture within the abyssal clays of the pH of the interstitialwaters, is responsible for their survival. However, as itappears that the basic component of the vitric fraction isnot preferentially removed during diagenesis, the glass inthe clays may be used to infer the volcanic history of thesource areas.

The low refractive index glasses are products of extremedifferentiation, with silica contents often exceeding 75%(Tables 2-6). The expression

R.I. = 1.693 - (0.00226 × % SiO2)

can be used as a rough guide to compositional variation(Figure 3). It is not an exact relationship, since othercomponents besides SiO2 (such as water) are known tohave a pronounced influence on refractive index (Ross andSmith, 1955), and they have not been estimated at thisstage of the investigation. It is significant that samples lyingfarthest from the least-squares line in Figure 3 have thehighest residuals in the microprobe analyses (100% which isthe total of elements investigated); this may express a highvolatile content.

The results of the analyses of the glass shards aredisplayed on AFM diagrams in Figures 4 and 5 and onvariation diagrams in Figures 6 to 9. It can be seen that arange of compositions is represented, the greatest variationbeing found in Sample VIII from Site 199. CaO and FeOfall rapidly with increasing silica content, while the decreaseof MnO and MgO is more gradual. These compositionaldifferences reflect stages in the differentiation of parentalmagmas in the source areas. The Neogene samples from thenorthern drilling sites clearly fall towards the acidic end ofa differentiation trend (Figure 5), and the overlapping ofthe Miocene-Recent fields suggests that the volcanoes fromwhich the glass originated may be closely associated in their

development. On the AFM and major element variationdiagrams, the glass from Site 199 is quite distinct from theNeogene glass recovered at the northern sites, implying twoquite separate source areas.

A preliminary examination of Quaternary acidic andCretaceous basic glass has been made using a scanningelectron microscope (Samples I, XI, and XIII; Plates 3-9) inorder to compare their morphology. Some importantdifferences in the internal structures and surface texturesare revealed.

The most obvious point of contrast lies in the strikingvesicularity of the Quaternary acidic material and thealmost complete absence of vesicles in the Campanian glass.In many of the acid shards the vesicles are pipe-shaped(Plate 4), the diameters of the pipes usually lying between 1and 20µ. The overall shape of the shard is controlled by thedirection of the pipe vesicles (Plates 3, 4, and 5), a featurewhich has been observed in vitric ash from Katmai byHeiken (1972). In some shards the vesicles are pod-shaped(Plate 2 [3]). Scalloped surfaces are also quite common.Plate 6 shows an arrowhead-shaped shard which appears tohave been part of the wall of three pod-shaped vesicles. Thepipe- and pod-shaped vesicles were evidently formed at arelatively late stage by the elongation of roughly sphericalcavities through the flow of extremely viscous acidicmagma at a high level in the parental volcano.

The glass extracted from the Campanian clays, on theother hand, is very rarely vesicular. Droplet-shaped shardsindicative of quenching of a relatively fluid magma arecommon (Plates 8 and 9). Other shards are markedlyangular with smooth surfaces and show striking examples ofconchoidal fracturing (Plate 7). Some percussion structuresformed during comminution mimic those seen at a verymuch larger scale when basaltic glass is shattered with ahammer. Concentric and radial percussion marks are welldisplayed on Plate 7.

SOURCE AREAS

The analyses have shown that the glass in the Neogene-Recent sediments recovered at the northern drilling sites isof quite different composition from that found in the

391

E. J.W.JONES

III

IV

194-1-1N = 438Quat.

114-115

194-1-3 : 57-59N = 151Quat.

196-1-1N = 207Quat.

132-133

195-1-3 : 64-66N=166Plio./Pleist

195-1-5 : 50-52N = 229Plio./Pleist.

194-2-1 : 145-147N = 238Upper Mio

195-2-2 = 141-143N=369M. Mioc.

199-3-1 : 146-148N = 209M. Mioc. + early Tert.

reworked

198A-3-1 64-66N = 272Late Cret.

196-2-2 •• 51-53N = 186Campanian

196-2-2N=247Camp.

196-2-4N=215Camp.

196-2-4N = 231Camp

61-63

57-59

119-120

M50TT52 I 1.5i I 1.561 1.58 I 1.60 I 1.62 I149 1.51 153 1.55 157 159 1.6! 163Refractive Index

Figure 2. Refractive index of glass particles in clays from Positions I to XIII in Figure 1. N is the number of glass grainsexamined in each sample. Each histogram is plotted on the same scale. The samples are annotated according to the usualDSDP convention (i.e., 196-2-4, 119-120 was taken from between 119 and 120 cm below the top of the fourth section ofCore 2 at Site 196).

392


TABLE 2Compositions of 10 Glass Grains from Sample I

(194-1-1, 114-115; Quaternary)

SiO2

CaOA12O3

TiO2

MgO

1

78.20.5

10.7—

0.3

2

80.40.7

10.50.1_

3

80.10.5

10.00.3_

4

64.47.7

19.70.05_

Grain

5

80.50.59.70.20.1

6

82.40.6

10.40.10.1

7

80.10.7

10.40.20.3

8

75.10.79.30.1_

9

81.00.59.20.03—

10

81.60.49.80.2—

Average

79.90.6

10.00.10.1

FeO 0.7 0.04 0.8 1.1 0.7 0.6 0.6 0.7 0.7 0.7 0.7MnO 0.03 0.04 0.04 - 0.1 0.1 0.1 0.04 0.1 0.1 0.07K2O 2.7 2.4 2.1 0.1 2.0 2.4 2.2 1.9 2.5 2.5 2.3

Total 93.1 94.3 93.8 93.1 93.9 96.8 94.6 87.8 94.0 95.3 93.8

TABLE 3Compositions of 14 Glass Grains from Sample IV

(195-1-3, 64-66; Plio/Pleistocene)

SiO2

CaOA12O3

TiO2

MgOFeOMnOK2ONa2O

Total

1

79.22.3

11.20.30.22.70.11.00.7

97.8

2

66.27.8

12.80.62.08.20.30.30.8

99.0

3

63.36.4

12.41.01.88.80.30.20.3

94.4

4

65.47.4

13.40.63.29.50.20.41.1

101.1

5

65.08.7

16.30.81.59.30.30.22.8

104.9

6

73.85.7

11.90.71.56.90.20.50.8

101.9

Grain

7

76.54.1

11.90.81.24.60.10.3-

99.3

8

68.76.1

12.00.51.37.40.20.30.5

96.9

9

72.45.3

13.40.60.86.50.20.40.3

99.8

10

82.33.0

10.60.40.32.80.10.4-

99.8

11

64.07.9

12.80.92.18.70.20.30.4

97.2

12

68.46.3

14.30.70.97.20.20.31.0

99.3

13

71.65.5

12.30.91.38.00.20.40.4

100.6

14

69.35.4

13.30.61.48.10.20.21.5

100.1

Average

70.45.9

12.80.71.47.10.20.40.8

99.7

TABLE 4Compositions of 9 Glass Grains from Sample V

(195-1-5; 50-52; Plio/Pleistocene)

SiO2

CaOA12O3

TiO2

MgOFeOMnOK2ONa2O

Total

1

78.61.4

11.20.3-

1.30.10.90.08

93.9

2

83.61.5

12.60.20.11.10.040.92.3

102.2

3

82.91.7

11.30.20.11.30.10.90.08

98.6

Grain

4

81.91.6

11.10.10.11.30.11.10.4

97.8

5

85.21.6

10.50.20.21.40.051.00.08

100.2

6

80.61.5

11.20.10.11.10.040.80.4

96.0

7

82.51.1

12.30.30.21.30.081.21.5

100.3

8

78.21.7

10.70.20.21.20.071.10.09

93.4

9

79.51.8

10.40.10.41.20.11.01.1

95.6

Average

81.41.5

11.30.20.21.20.081.00.7

97.6

393

E. J.W.JONES

TABLE 5Compositions of 14 Glass Grains from Sample VI

(194-2-1, 145-147; Upper Miocene)

SiO2

CaOA12O3

TiO2

MgOFeOMnOK2ONa2O

Total

1

72.60.6

10.40.1—

0.60.063.60.1

88.2

2

72.91.0

11.00.4-1.0—

2.6-

88.8

3

78.30.6

12.50.2—

0.50.033.31.6

96.9

4

78.30.8

10.3_—

0.60.063.00.7

93.7

5

73.50.6

10.8_

0.10.50.033.11.6

90.3

6

78.00.6

11.00.04—

0.80.052.21.2

93.8

Grain

7

69.20.9

11.1_—

0.80.13.90.7

86.7

8

78.31.0

10.40.10.30.9_

2.90.1

94.1

9

82.60.5

11.90.1—

0.60.023.11.6

100.4

10

74.10.7

10.9—-

0.70.023.60.4

90.3

11

74.40.6

12.60.1—

0.80.042.11.4

92.1

12

71.81.0

11.60.08-

1.00.041.50.3

87.2

13

70.00.9

11.8——

0.60.083.51.3

88.0

14

75.90.7

12.4—-

0.70.022.30.9

92.9

Average

75.00.8

11.30.10.030.70.042.90.9

91.7

TABLE 6Compositions of 11 Glass Grains from Sample VII

(195-2-2, 141-143; Middle Miocene)

SiO2

CaOA12O3

TiO2

MgOFeOMnOK2ONa2O

Total

1

78.11.79.40.20.31.6-

0.80.6

92.8

2

76.91.7

13.70.10.11.40.051.1-

95.2

3

74.31.9

11.60.10.041.90.060.60.8

91.3

4

83.91.1

11.5_

0.11.4-

1.0-

99.9

5

80.40.79.90.2—

1.40.081.2-

94.0

Grain

6

85.11.4

13.70.20.41.90.030.30.2

103.2

7

77.42.1

10.20.40.42.00.081.1-

93.4

8

78.61.39.70.2_1.70.10.70.8

93.1

9

91.31.8

10.10.10.32.10.050.7-

106.6

10

72.32.18.90.20.21.50.061.50.9

87.6

11

73.80.9

10.7(?0.10.091.50.090.8-

87.9

Average

79.31.5

) 10.90.20.21.70.050.90.3

95.1

TABLE 7Compositions of 11 Glass Grains from Sample VIII

(199-3-1; 146-148; Middle Miocene with Reworked Early Tertiary)

SiO2

CaOA12O3

TiO2

MgOFeOMnOK2ONa2O

Total

1

61.76.7

24.80.10.070.5—

0.94.9

99.7

2

56.911.528.4

0.30.020.7_

0.34.1

102.3

3

53.67.7

24.80.20.070.5_

0.77.1

94.7

4

48.920.1

2.61.3

10.59.10.20.03-

92.7

5

50.610.922.3

0.20.10.80.050.24.9

90.1

Grain

6

47.018.95.32.94.78.20.090.55.1

92.7

7

45.920.7

5.43.0

14.68.00.2_-

97.8

8

50.911.927.6

0.11.23.50.030.64.6

100.4

9

54.011.929.2

0.20.63.60.080.053.8

103.5

10

57.18.6

25.60.20.090.8—

0.24.8

97.3

11

57.011.229.1

0.20.30.80.050.45.1

104.1

Average

49.412.928.0

0.10.79a1.30.100.14.3

96.0

aExcludes Grains 4 and 7.

394


1 6O

,199-3-1

1-56-

×

1

2

i1.50.

195-1-3

195-2-2

194-2-10

1-4840 50 60 70

SiO2(%)

Figure 3. Relationship between refractive index and Si02 content for six glass samples.

80 90

Upper Cretaceous clays, a difference which is also reflectedin their morphology. A contrast in composition because ofdiagenetic changes is precluded by the earlier considera-tions. Thus, the fine-grained vitric ejecta reaching this partof the Pacific plate evidently changed from a basic to amore acidic character during some period between the LateCretaceous and early Miocene (Figure 2). The core samplesare too few to provide more exact dating (Figure 1). Thissignificant shift in composition could mirror a change in thecharacter of volcanism in the source areas, a change ofsource area, or both. The abundance of glass of acidic andintermediate types and the lack of a large basic componentare strong reasons for believing that the glass in theNeogene-Recent clays originated in the island arc region tothe west. Furthermore, the glass generally has a low TiO2

content (less than 1%), which, according to Chayes'criterion (Chayes, 1964), is indicative of a circumoceanic,rather than an oceanic, source region. The Japanese arc hasprobably contributed substantial amounts of vitric materialto these clays as Neogene-Quaternary acid, and inter-mediate volcanic activity was widespread there (Murakami,1960; Takai et al., 1962; Oide, 1968). Furthermore, thevolcanogenic clays thicken to the west according to thedrilling results (Heezen et al., 1973) and seismic reflectionprofiles (Heezen and Jones, this volume). Site 199 is too farsouth to be included within the influence of the Japanesearc; this accounts for the contrasting composition of thevitric component of Sample VIII.

During the Late Cretaceous there was extensive acidicand intermediate volcanism in the Japanese arc which, inplaces, continued into the early Tertiary. Ichikawa et al.(1968) have documented four main stages of activity insouthwest Japan during this period. Vast quantities of

acidic pyroclastics were produced, particularly during aGyliakian-early Urakawan episode. These covered a widearea of Japan and would also have been carried far out tosea to contribute to abyssal deposits in the same way as inmore recent periods. Basic activity at this time was quitesubordinate. However, in the Upper Cretaceous clays at thenorthern drilling sites, acidic shards are rare and basic glassis abundant. This is an observation which is interpreted hereas indicative of a large northward or northwestwardmovement of the Pacific plate since the Cretaceous.Accepting rates of motion based on the age of theequatorial carbonates in the Leg 20 cores (Heezen et al.,1973), the northern drilling sites would have been some2000 km further to the southeast during the Late Creta-ceous and thus are well outside the influence of island arcvolcanism. The source of the basic glass in these UpperCretaceous clays is problematic. The small content of acidicglass (Figure 2) suggests a quite local derivation from nearbyoceanic volcanoes.

ACKNOWLEDGMENTS

I thank J.F. W. Bowles, who carried out the microprobeanalyses reported here, and M. 0'Halloran for preparing thepolished mounts. I am grateful to Susan James who wasresponsible for taking the SEM photographs. Linda Knapphelped to prepare the glass for analysis. I also thankProfessor T. Barnard and Neil Fortey for their helpfulcomments.

REFERENCES

Brew, D. A. and Muffler, L. J. P., 1965. Upper Triassic glassfrom Hound Island, Keku Strait, S. E. Alaska: U. S.Geol. Survey Prof. Paper 525C, p. C38.

395

E. J.W.JONES

(Plio./Pleist.)

IV

(Plio./Pleist,

VI

(Upper Mio.

VII

(Middle Mio.)

VIII

(Middle Mio. +

reworked early Tert.)

M

Figure 4. AFM diagrams to illustrate the variation in composition of the glass shards (A=Na2θ+K2θ; F=FeO + MnO;M=MgO). (Roman numerals refer to samples in Table 1 and Figure 2.)

396


VI I I (Middle Mio. +reworked early Tert,

VI (upper Mio.)

VII (Middle Mio.)

IV (P l io . /P le is t . )

'o°0'\ V (P l io . /P le is t . )

M

Figure 5. Summary of compositional variation plotted on AFM diagrams. (Roman numerals refer tosamples in Table 1 and Figure 1.)

397

o00

3 -I

2 -

K20: Plio./Pleistocene

3 -

2 -

1 -

IV

) rπ 1 1

50 60 70

% SiO2

Na2O: Plio./Pleistocene

IV

α

50

r80

Δ vQD _ ΔΔ

1 I I I I

60 70 80

% SiO2

3 -

2 -

1 -

OO

8K

20: Miocene VI

VIII

VII

6 -

4 -

2 -

A 4 vii +

π *i i 1 1 1 r

50 60 70 80

% SiO2

VIII

4 \ 1 Na

2O: Miocene

VI

oo <> o

T

50 60 70

% SiO2

80

Figure 6. Variation diagrams~Na2θ andK20. (Roman numerals refer to samples in Table 1 and Figure 1.)


io -

8 -

6 -

4 -

2 -

CaO: PIio./Pleistocene

σ

aIV

D

α

α

V

• •^ri

12 -

10 -

I T T

50 60 70 80

% SiO2

6 -

4 -

2 -

A •

CaO: Miocene

V I I I

50

VI

60 70 80

SiO

10 -1

8 "

6 -

4 -

2 -

sIV

FeO: PIio./Pleistocene

6 -

4 •i

2 -

• •

V I I I

FeO: Miocene

VII

VI

50i

60 70 80 50 8060 70

% SiO 2 % SiO 2

Figure 7. Variation diagram-CaO and FeO. (Roman numerals refer to samples in Table 1 and Figure 1.)

399

oo 30 i

20-

10-

A12O

3: Plio./Pleistocene

~T~50

D

D

60 70

% S i O 2

Δ V

Δ

η 1-80

30 -

20 -

10-

±A

A

AA

A

A A

A

VIII

A12O

3:

VI

Miocene

?O 0 Q

* ^ + +

50 60T I

70

SiOo

80

VII

3 -

2 -

1 -

MgO

i

: Plio./Pleistocene

D

DD

D

D

1 1 1

IV

D

I

DD D

D

I—A

T r50 60 70 80

%

4 -

3 -

2 -

1 -

A

A

A1

MgO:

VIII

* A

A A1

Miocene

VII

A VI +g. ."* .

50 60 % sio

2

70 80

Figure 8. Variation diagram-A^Oj and MgO. (Roman numerals refer to samples in Table 1 and Figure 1.)

1.0 -

0.8 -

0.6 -

0 . 4 -

0.2-1

α

D O

D D

D G

CD D D

D

IV

TiO2: Plio/Pleistocene

T~50 60

T70

% S i O 2

•i

π

SM Δ

•fc

mm

~r80

3 -

2 -

1 -

TiO2: Miocene

VIIIA

AA"~~l—

50

VI

~r60

70

+ VII

a- +

80

% SiOc

0.

0.

0.

3 -

2 -

1 -

MnO

Plio/Pleistocene

i i i50 60

DLXJ

D D

TV1 V

170

mo

ami

•Δ A

i80

v

•••

I

0.

0.

0.

3 "

2 -

1 _

A

A

A

VIIIA

I 150

A

MnO

Miocene

i i60

VI °o _HS

1

70

+ + + +

1 1

80

V I I

o

°/o SiO 2 % s i θ 2

Figure 9. Variation diagram~Tiθ2 and MnO. (Roman numerals refer to samples in Table 1 and Figure 1.

i>2no

E. J.W.JONES

Chayes, F., 1964. A petrographic distinction betweenCenozoic volcanics in and around the open oceans: J.Geophys. Res., v. 69, p. 1573.

Heezen, B. C, MacGregor, I. D., Foreman, H. P., Forristall,G., Hekel, H., Hesse, R., Hoskins, R. H., Jones, E. J. W.,Kaneps, A., Krasheninnikov, V. A., Okada, H., and Ruef,M. H., 1973. Diachronous deposits: a kinematic inter-pretation of the post-Jurassic sedimentary sequence onthe Pacific plate: Nature, v. 241, p. 25.

Heiken, G., 1972. Morphology and petrography of volcanicashes: Geol. Soc. Am. Bull., v. 83, p. 1961.

Horn, D. R., Delach, M. N., and Horn, B. M., 1969.Distribution of volcanic ash layers and turbidites in theNorth Pacific: Geol. Soc. Am. Bull., v. 80, p. 1715.

Horn, D. R., Horn, B. M., and Delach, M. N., 1970.Sedimentary provinces of the North Pacific: Geol. Soc.Am. Mem., v. 126, p. 1.

Ichikawa, K., Murakami, N., Hase, A., and Wadatsumi, K.,1968. Late Mesozoic igneous activity in the inner side ofsouthwest Japan: Pacific Geol., v. 1, p. 97.

Mason, P. K., Frost, M. T., and Reed, S. J. B., 1969.Program for calculating corrections in quantitative X-raymicroanalysis: IMS Rept. No. 2.

Moore, J. G., 1970. Water content of basalt erupted on theocean floor: Contrib. Mineral. Petrol., v. 38, p. 272.

Muffler, L. J. P., Short, J. M.3 Keith, T. E. C, and Smith,V. C, 1969. Chemistry of fresh and altered basaltic glass

from the Upper Triassic Hound Island volcanics, south-eastern Alaska: Am. J. Sci., v. 267, p. 196.

Murakami, N., 1960. Cretaceous and Tertiary igneousactivity in western Chugoku: Sci. Rept. YumaguchiUniv. II, v. 21 [In Japanese with English abstract].

Murray, J. and Renard, A. F., 1891. Report on deep-seadeposits based on the specimens collected during thevoyage of H.M.S. Challenger in the years 1872-1876:London (H.M.S.O.).

Ninkovich, D., Opdyke, N. D., Heezen, B. C. and Foster,J.H., 1966. Paleomagnetic stratigraphy, rates of deposi-tion and tephra chronology in the North Pacific deep-seasediments: Earth Planet. Sci. Lett., v. 1, p. 476.

Oide, K., 1968. Geotectonic conditions for the formationof the Krakatau-type calderas in Japan: Pacific Geol., v.l ,p . 119.

Ross, C. S. and Smith, R. L., 1955. Water and othervolatiles in volcanic glass: Am. Mineral., v. 40, p. 1071.

Takai, F., Matsumoto, T., and Toriyama, R. (Eds.) (1962):Geology of Japan. Berkeley (University of CaliforniaPress).

Tilley, C. E., 1922. Density, refractivity and compositionrelations of some natural glasses: Mineral. Mag., v. 19, p.275.

Williams, H., Turner, F. J., and Gilbert, C. M., 1954.Petrography: San Francisco (W. H. Freeman and Co.).

402

E. J.W.JONES

PLATE 1

Selection of smear slides showing glass fragments

Figure 1 Acidic glass in Quaternary Sample I (194-1-1,114-115).

Figure 2 Acidic glass in Plio/Pleistocene Sample V (195-1-5,50-52).

Figure 3 Acidic glass with well-developed pipe vesicles in upperMiocene Sample VII (194-2-1, 145-147).

Figure 4 Acidic glass in middle Miocene Sample VII (195-2-2,141-143).

Figure 5 Basic glass (center) with inclusions. The matrix is azeolitic clay. Sample X (196-2-2, 51-53; Campanian).

Figure 6 Basic glass grain (center) with slight alteration onparts of the margin and in small internal cracks(Sample 196-2-2, 61-63; Campanian)

404


PLATE 1

50

405

E. J.W.JONES

PLATE 2

Glass shards from Sample I (194-1-1,114-115; Quaternary) on polished mount.

406


PLATE 2

407

E. J.W.JONES

PLATE 3

SEM photographs of glass from Sample 1(194-1-1, 114-115; Quaternary).

408


PLATE 3

409

E. J.W.JONES

PLATE 4

SEM photographs of glass from Sample 1(194-1-1; 114-115; Quaternary)exhibiting well-developed pipe vesicles.

410


PLATE 5

SEM photograph of a shard elongated in the direction of the pipe vesicles.Sample I (194-1-1,114-115; Quaternary)

411

E. J.W.JONES

PLATE 6

SEM photograph of a glass shard from Sample I (194-1-1, 114-115; Quaternary)

412


PLATE 7

5 _ ^ . 6

SEM photograph of glass shards from Sample XI (196-2-2; 61-63; Campanian)

Note their marked angularity and the lack of vesicles. The shards showconcoidal fracturing and well-developed radian and transverse percus-sion marks.

413

E. J.W.JONES

PLATE 8

SEM photograph of glass fragments from Sample XI (196-2-2; 61-63; Campanian)

414


PLATE 8

415

E. J.W.JONES

PLATE 9

SEM photographs of glass from Sample XI (196-24, 119-120; Campanian)

416

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Deep Sea Drilling Project Initial Reports Volume 20