site 838 hole a core 1h cored 0.0-3.7 mbsf smear slide
TRANSCRIPT
135-838A-1HSMEAR SLIDE SUMMARY (%)
TEXTURE:
SandSillClay
COMPOSITION:
ClayForaminilersNannolossils
2.130D
8
92
30862
SITE 838 HOLE A CORE 1H
GraphicLith. Structure
CORED 0.0-3.7 mbsf
10YR3/3
10YR3/2To
10YR4/2
Description
CLAYEY NANNOFOSSIL OOZE
Major lithology: CLAYEYNANNOFOSSIL OOZE, dark brown(10YR 3/3) to dark grayish brown(10YR 4/2), structureless except forscattered pumice clasts and mottling inSection 2, 80 cm, through Section 3,50 cm.
Minor lithology: None.
135-83BA-2HSMEAR SLIDE SUMMARY (%):
Clay
COMPOSITION:
Accessory miner
ClayFeldsparForaminilorsGlassNannolossils
SITE 838 HOLE A CORE 2H CORED 3.7-13.2 mbsf 838A-2H 1
GraphicLith. Structure
o 8
I P
10YR3/3To
10YR4/2
10YR3/2
10YR4/2
10YR4/3
10YR3/2
10YR4/3
Description
CLAYEY NANNOFOSSIL OOZE
Major lithology: CLAYEYNANNOFOSSIL OOZE, very darkgrayish brown (10YR 3/2) to brown(10YR 4/3), generally structureless.Pumice clasts up to 18 mm in diameteroccur scattered throughout.
Minor lithology: VITRIC CLAYEYNANNOFOSSIL MIXED SEDIMENTpresent within burrow structures inSection 3,146-148 cm.
135838A-3HSMEAR SLIDE SUMMARY (%)
TEXTURE:
SandSillClay
COMPOSITION:
Accessory mineralClayForaminifers
2,130M
85105
s —520
5,8
M
9010
5
10
7,40M
101377
308
SITE 838 HOLE A CORE 3H CORED 13.2-22.7 mbsf 838A-3H
GraphicLith. Structure
55 t F O
O
O
O i
10YR4/3
2.5Y
10YR4/3
10YR3/3
10YR4/3
Description
CLAYEY NANNOFOSSIL OOZE
Major Irthology: CLAYEYNANNOFOSSIL OOZE, brown to darkbrown (10YR 4/3). generallystructureless. Scattered dasts includepumice fragments up to 3.3 cm indiameter and a rounded ash clast 2 cmin diameter (Section 2, 85 cm).
Minor lithologies: VITRIC SAND WITHFORAMS, grayish brown (2.5Y 5/2), innormally graded, planar-laminatedintervals from Section 2,109 cm, toSection 3,10 cm, and in Section 5,from 2 to 8 cm. Pumice clast, 2.5 cm indiameter, occurs at the scoured basalcontact in Section 3. The uppercontacts of these intervals aregradational with the overlying clayeynannofossil ooze. VITRIC CLAYEYNANNOFOSSIL MIXED SEDIMENT,very thin (2 mm) layer in Section 7,40cm. Distinct but irregular boundaries.May represent disrupted fine volcanicash layer.
135-83BA-4HSMEAR SLIDE SUMMARY (%):
TEXTURE:
SandSillClay
COMPOSITION:
Accessory minor;ClayFeldspar
1,100 3 , 8 00 D
eo3010
ils Tr10Tr
100
5
5,61D
100
Tr
6,73D
100
5
SITE 838 HOLE A CORE 4H CORED 22.7-32.2 mbsf 838A-1H jl 1
GraphicLith.
: L J. J. -•I A X J •
Structure
_ Ck. _
I P
2.5Y6\2
2.5Y5\2
10YR3/3To5Y
2.5/1
10YR4/3
Description
CLAYEY NANNOFOSSIL OOZE andVITRC SAND
Major lithologies: CLAYEYNANNOFOSSIL OOZE, dark brown(10YR 3/3 to 10YR 4/3), generallystructureless. Scattered clasts includepumice and mud clasts. VITRIC SAND,light brownish gray (2.5 Y 6/2) tograyish brown (2.5Y 5/2) and black (5Y2.5/1). Very coarse grained andmoderately well sorted, withsubrounded to angular grains. Threethin (4 to 9 cm), fining-upward beds areintβrbeddθd with clayey nannofossilooze in Section 4,27-135 cm. Adiscrete vitric volcanic sand bed occursin Section 5,22-72 cm.
Minor lithology: VITRIC SAND WITHCLAY AND FORAMS. Light brownishgray (2.5 Y 6/2). Structureless.
135 838A•5HSMEAR SLIDE SUMMARY (%):
TEXTURE:
SandSillClay
COMPOSITION:
Accessory minorsClay
0
100
ils 5
0 5, 50
454510
7
5.100D
801010
Tr10
SITE 838 HOLE
Met
er
;
0.5
I.U_
--
-
-
•
:
-
—
—
-
—
—
-
-
-
_
•
•
—
-
11
11
•
GraphicUth.
S S• l • • •
':''•':'••':'••':'
Sec
tion
—
4
—
5
—
7
X
Age
<D
<5o<P
Q.
%
A CORE
Structure
F
O 1
' F *
_ « _
= •O I F
t
5H
Dis
turb
>j
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j!
>
>>>>>>>>>>>>>>>
j
Sam
ple
S
S
S
Col
or
10YR4/3
2.5/1To5Y3/1
iY 2.5/1
CORED 32.2-41.7 mbsf
Description
VITRIC SAND
Major lithology: VITRIC SAND, black(5Y 2.5/1) to very dark gray (5Y 2.5Y3/1), normally graded intervals inSection 1, from 70 to 150 cm, and
Planar-lamination occurs in 2 cm thickintervals in Section 7 at 11 and 30 cm.Rounded dark brown to brown (10 YR4/3) mud clasts of clayey nannofossilooze (up to 4 cm in diameter), occur inSection 2 from 0 to 105 cm. Isolatedmud clasts occur in Section 4 at 20and 100 cm In an otherwisestructureless interval.
Minor lithology: CLAYEYNANNOFOSSIL OOZE, dark brown tobrown (10YR 4/3), generallystructureless. Mottling occurs at thegradational base of these intervals inSection 1 at 70 cm and Section 5 at 7cm.
838A-5H M 1
135838A-6HSMEAR SLIDE SUMMARY (%):
SITE 838 HOLE A CORE 6H CORED 41.7-51.2 mbsf 838A-6H , 1
1,80 2,95 6, 110 CC.3
COMPOSITION:
Accessory minorClayFeldspar
05] ^ Λ
GraphicLhh.
«
m±>W 7 1
Ag
e
Structure
= o
10YR5/3
10YR6/2
10YR6/1
Description
VOLCANIC GRAVEL and VITRICSAND
Major lithologiβs: VOLCANICGRAVEL, light gray to gray (5YR 6/1),generally structureless (partly due todrilling disturbance), and poorly sorted,containing mud clasts of clayeynannofossil ooze. VITRIC SAND, lightgray (10YR 6/1) to brownish gray (10YR 6/2), with thin- to medium-bedded,normally graded layers. Thin bedoccurs in Section 1,0 to 12 cm.CLAYEY NANNOFOSSIL OOZE,brown (10 YR 5/3). structureless.Occurs in Section 1,0-150 cm, as athin bed in Section 7,14-19 cm, and inSection CC.
Minor lithology: None.
135-838A-7HSMEAR SLIDE SUMMARY (%):
TEXTURE:
SandSillClay
COMPOSITION:
Accessory mineralsClayFeldspar
1,140 2,127D D
100
TrTrTr
100
35
10
SITE 838 HOLE
I M
eter
i j j
•
;
;
**
;
;
1
-:
GraphicLith.
v v*I I I<*:*:*V V**************V VV %• V ********&#V V
V V* * * ********VVV*******V**
v v••**************•••••-M••••4V V V
1 Sec
tion
1
—-2
—
3
4
5
6
T
A CORE 7H
Structure
MM* + F
iu tF
O
i ro
o
o
1 D
istu
rb!
!•
|
ii
iijI1!
!
i
ji|ijj
iijjji
i
jiiijj
iiiji
{j
Sam
ple
s
s
Col
or
10YR7/1
10YR6/1
CORED 51.2-60.7 mbsf
Description
VOLCANIC GRAVEL
Major Iithoiogy: VOLCANIC GRAVEL,light gray (10YR 6/1 to 10YR 7/1),generally poorly sorted, withfining-upward intervals from 2 to 50 cmthick. Pebbles are very angular tosubrounded and up to 4 cm indiameter.
838A-7H ] 1
....
135-83 SASH
SMEAR SLIDE SUMMARY (%)
TEXTURE:
Sand
Sill
Clay
COMPOSITION:
Clay
Dokxi>tβ
Feldspar
2,44
D
100
ils Tr
100
Tr
3,20
D
2
98
Tr
35
Tr
Tr
5,50
D
10
90
30
SITE 838 HOLE A CORE 8H
GraphicLit*.
JL JLTf "L JLJLT••JL •I•T
CORED 60.7 - 70.2 mbsf 838A-8H : 1
Structure
I p
s
5Y5/1To
2.5Y5U
2.5Y5\4
5Y5/1To
2.5Y5U
10YR4/3
Description
VOLCANIC GRAVEL
Major lithologies: VOLCANICGRAVEL, gray (5Y 5/1), poorly sorted.Contains numerous clasts of clayeynannofossil ooze (up to 15 cm Indiameter), mafic rocks, and pumice (upto 7 cm in diameter). CLAYEYNANNOFOSSIL OOZE, brown to darkbrown (10YR 4/3) with mud clasts andoccasional mottling.
Minor Ihhology: CLAY, reddish brown(5YR 5/4), occurs in Section 2 from 40to 47 cm.
135-B3βA•9HSMEAR SLIDE SUMMARY (%)
TEXTURE:
Sand
Sill
Clay
COMPOSITION:
Accessory minerals
Clay
Feldspar
Glass
Nannofossils
Radiolarians
1,56
D
100
Tr
95
Tr
5
TrTr
SMEAR SLIDE SUMMARY (%)
TEXTURE:
Sand
Siil
Clay
COMPOSITION:
Accessory minerals
Clay
Feldspar
6,110M
353530
22820
1,129 2,76D M
100
10
585
45505
331579
2,112D
100
10
585
3,113 5,9M M
100
TrTrTr100Tr
1090
Tr9010
Tr
SITE 838 HOLE
Met
er
;
0.5j
:
l.<>
-
-
-
-
-
—
z—
z---
—
--
-
-
—
-
-
GraphicLith.
[•:•:•."!
> Φ~Φ~Φ"
* » :
W.J• Φ Φ ΦΦ Φ Φ i
Se
ctio
n
•>
I —
3
4
—
6
Ti
Age
A COHb
Structure
O Φ
—
O*
<>
_ *II
0
III
O
F
o
9H
Dis
turb
iI
Sam
ple
S
S
s
s
5
S
S
Co
lor
10YR3/3
5YR2.5/2
2 5Y2/0
5YR3/3
2.5Y2/0
CORED 70.2-79.7 mbsf
Description
VITRIC SAND
Major lithologies: VITRIC SAND, black(2.5 Y 2/0), fine- to coarse-grained.with common bedding and planarlaminae. In Section 2,0-30 cm bedsdip up to 45°. Common mud clasts andvolcanic clasts up to 5 cm in diameter,including indurated clasts in Section 1,140-145 cm, and Section 4,40-45 cm.Also occurs as thin interbed within clayin Section 1, 34-48 cm.MUD-SUPPORTED VOLCANICGRAVEL, black (2.5Y 2/0) gravel indark reddish brown (5YR 3/3) clayeynannofossil ooze matrix. Shows anoverall fining-upward sequence inSection 6, with gravel decreasing insize from 5 to 0.5 cm. CLAY, darkbrown (10YR 3/3), generallystructureless, occurs in Section 1,17-71 cm, Section 4, 75-80 cm. CLAYWITH FELDSPAR, dark reddish brown(5YR 5/6), occurs in Section 4,143 cm,through Section 5,150 cm. Generallystructureless, but containing somepebble-sized clasts.
Minor lithologies: SANDY CLAYMIXED SEDIMENT. Olive brown (2.5Y 4/4). Occurs in Section 4,100-120cm. Clast of CRYSTAL-RICH TUFFWITH FELDSPAR AND ZEOLITESoccurs in Section 4,110 cm.
838A-9H [I 1
135-83 BΛ-IOHSMEAR SLIDE SUMMARY (%):
SandSillClay
COMPOSITION:
Aceossory mineralsCalciloClayFeldsparGlassZoolilo
SITE 838 HOLE
Met
er
1.0;
-
-
-
-
-
-
-
—
-
:
—
;
;
In
;
—
—
-
J
Graphic
Lith.
• . •.• vr-•-•
*******
• m. ^ t\f i ^ ' .
; : : : : : : :
******** * * * * *
•~. ~. •~. •~
*******
K::::*******
Se
ctio
n
1
—
3
5
6
TC(
Φ
Φc
o—
1
A GORb
Structure
Φ
- O- -
Φ
- - -
- - -
Φ
Φ
Φ
Φ
10H
Dis
turb
|
i
Sam
ple
S
Co
lor
5Y4/3
5Y3/1
5Y3/1
2.5Y 7/C
CORED 79.7-89.2 mbsf
Description
VITRIC SAND and VOLCANIC SANDYGRAVEL
Major lithologies: COARSE VITRICSAND, olive (5Y 4/3) to very dark gray(5Y 3/1). Marked by an overall upwardfining throughout Sections 1, 2, and 3.Thin bed occurs in Section 6, 0-13 cm.VOLCANIC SANDY GRAVEL, verydark gray (5Y 3/1). Pumice clastsoccur throughout Section 4 (maximumdiameter 4 cm) and Section 6(maximum diameter 6 cm). Vagueplanar bedding varying in thicknessfrom 1 to 16 cm occurs in Section 4.Sections 4, 5, and 6 are poorly sortedand generally structureless.
Minor lithology: VITRIC CLAYEY SILT,dark grayish brown (2.5Y 4/2) occurs inSection 1, 0-22 cm. Containsabundant rounded clasts of induratedclaystone up to 8 cm in diameter.
838A-10H 1
135-838A-11H
SMEAR SLIDE SUMMARY (%):
Sand
Sill
Clay
Accessory i
Clay
Feldspar
SITE 838 HOLE
I M
eter
1
:
1.0
_;:-
:
:
j—
—:
--
-I
-
II11
1II |
-
-
—
z
GraphicLith.
m.>*****•*v v1*1*1*1*•t i i<> vm ,J KW I;i; : :;
nV VbV Vv vΦ Φ Φ 4
• 4h Φ Φ Φ
rΦ%V» Φ Φ Φ>x xΦ"Φ"Φ*4
V Λ*Φ* *Φ*4
1 S
θct
ion
l
•j
2
3
4
-
_
6
X
1 A
ge
1
1o51
S§:
A CORE
Structure
_ _ _
_ _ _
11H
| D
istu
rb |
jj|!j
jji
i!
jjii!j
jjijij
i
j
iiiiii
jjiit
Sam
ple
S
Co
lor
5Y3/1
5Y5/1To5Y
4/1
5Y5/1
CORED 89.2-98.7 mbsf
Description
VOLCANIC GRAVEL
Major lithologiθs: VOLCANIC
GRAVEL, generally structureless.
composed of a mixture of poorly sortedpumice and angular mafic hyaloclastiteclasts that range in size from 0.5 to 3cm. Indurated mudclasts occur inSection 2, 100 cm, and Section 6, 20
cm. COARSE VITRIC SAND, generallycoarse and poorly sorted; similar incomposition to the vitric volcanic
gravel.
Minor lithology: None.
838A-11H 1
838A 12X NO RECOVERY
838A 13X NO RECOVERY
13&838A-14XSMEAR SLIDE SUMMARY (%):
Clay
COMPOSITION:
SITE 838 HOLE A CORE 14X CORED 113.9-118.5 mbsf 838A-14X ; 1
Accessory minerals TiClay 3<FeldsparGlass 55
Met
er GraphicLith.
~ ~ ~ ~
Sec
tion
1
Ag
e
Structure
Dis
turb
Sam
ple
s
Co
lor
2.5Y5/4
Description
VITRIC CLAYEY SILTSTONE WITHFELDSPAR
Major lithology: VITRIC CLAYEYSILTSTONE WITH FELDSPAR, lightolive brown (2.5Y 5/4), planar- andcross-laminatθd in the upper 16 cm ofthe core.
Minor lithology: None.
45—j
SO—|
55—:
SO—
β 5 —
7 0 —
7 5 —
8 0 —
8 5 —
9 0 —
100
105
110
SIS
120
!25
130
\ 135
140
145
150
135-838A-15XSMEAR SLIDE SUMMARY (%):
SandSillClay
COMPOSITION:
SITE 838 HOLE A CORE 15X CORED 1 1 8 . 5 - 1 2 3 . 1 mt>sf 838A-16X ! 1 838A-17X I CC
Accessory minerals 5Clay 4!Feldspar 11Glass 2!Rock fragment 1!
135-83BA-16XSMEAR SLIDE SUMMARY (%)
TEXTURE:
SandSillClay
COMPOSITION:
CarbonalβGoothileMagnelileNalrdilePlagioclasePyroxeneSmeclite
1.3
D
98
2
-
2
Tr
115εTr76
135-83BA-17XSMEAR SLIDE SUMMARY (%):
COMPOSITION:
CarbonateForaminilorsGoolhilβNalrolilePlagioclasePyroxeneSmβctilo
T
G
11717
Met
er |
:
GraphicLith.
Sec
tion
X
Ag
e
Structure
= -u-
Dis
turb
$
s
Co
lor
2.5Y4/4
Description
VITRIC SANDSTONE and VITRICCLAYEY SILTSTONE
Major lithologtes: VITRICSANDSTONE, olive brown (2.5Y 4/4),with faint planar laminae, from 0 to 9cm. VITRIC CLAYEY SILTSTONE,very dark grayish brown (10YR 3/2),structureless, from 9 to 16 cm.GRANULAR VITRIC SANDSTONE,olive brown (2.5Y 4/4), with faint planarlaminae, from 16 to 32 cm. Mean grainsize is 2 to 3 mm
Minor lithology: None.
SITE 838 HOLE A C O R E 16X CORED 1 2 3 . 1 - 1 3 2 . 8 mbsf
GraphicLith. Structure
2.5Y4/4
Description
VOLCANIC CONGLOMERATE
Major lithology: VOLCANICCONGLOMERATE, olive brown (2.5Y4/4), grain-supported and induratedgravel, with faint planar stratification.Maximum gravel size is 1 c m Basalcontact with underlying siltstone issharply defined. VITRIC CLAYEYSILTSTONE, dark olive (5Y 4/3) withthin planar lamination. Black dβndritβs,probably of manganese oxide, occur at67 cm. Cross lamination occurs from49 to 51 cm.
Minor lithology: None.
SITE 838 HOLE A CORE 17X CORED 1 3 2 . 8 - 1 4 2 . 4 mbsf
GraphicLith. Structure Description
VOLCANIC CONGLOMERATE
Major lithology: VOLCANICCONGLOMERATE, olive brown (2.5Y4/4), thinly bedded, planar stratified,grain-supported with granule-sizedgrains up to 0.5 cm in diameter. Basalcontact is sharply defined with loadcasts. Occurs with alternating layers ofmedium- to coarse-grained vitricsandstone.
Minor lithology: None.
838A 18X NO RECOVERY
838A 19X NO RECOVERY
s
I0-
I5-
20-
25-
30-
35-
4 0 —
4 5 —
5 0 — !
tat*
6 0 —
β 5 —
7 0 —
75
βo—
8 5 —
9 0 —
9 5 —
I00—
105—
HO—
115—
! 2 0 —
185—
130—
135—
140—
1*45 '•"""
ISO—
εα-
25
30
35
40
45
50
55
SO
65
70
75
80
8 5 —
30
9 5 —
100
105—
110—
115
120—
125
130
135—
140 —
145—I
: (50—I
2 5 — —
3 0 — '. —
35--™" "•"™
4 0 — . —
SO— —
SS— —
g f j — - •
S D • "" "™™™
7 0 — —
7 5 — —
8 0 — —•
85"™— -™T
5HJ—— ^ ^
I—I ^95—IL_ SOS
—i 115
— ; J20
—! 125
; 130
!!35
! ;I4O
ii45
im•
135-838A20H
SMEAR SLIDE SUMMARY (%):
Clay
COMPOSITION:
Accessory I
Feldspar
SITE 838 HOLE A CORE 20H CORED 152.1 -153.8 mbsf 838A-20H 1 CC 838B-9R I CC 838B-10R CC
Met
er
0.5;
GraphicLith.
I
Se
ctio
n
1
<
iStructure i
if
r
Sar
πp
le
s
Co
lor
2.5Y2/0
5Y4/1
2.5Y 2,'Q
Description
VOLCANIC GRAVEL
Major lithology: VOLCANIC GRAVEL,black (2.5Y 2/0), moderate to wellsorted with angular clasts, showing anupward-fining trend. Contains up to95% basaltic fragments, with minorquantities of pumice and greensiltstone. Some black glass withconchoidal fractures (hyaloclastite)occurs. Clasts are up to 4 cm indiameter in Section CC.
Minor lithology: VITRIC SAND WITHACCESSORY MINERALS, dark gray(5Y 4/1), structureless.
838B1W WASH CORE
838B 2R Entire core was given to paleontologists.
838B 3R NO RECOVERY
838B 4R HARD ROCK
838B 5R THROUGH 8R NO RECOVERY
SITE 838 HOLE B CORE 9R CORED 210.9-220.6 mbsf
Met
er
-
GraphicLith.
Sec
tion
JC
Ag
e
StructureD
istu
rb
>S
amp
le
Co
lor
5Y6/2
Description
VITRIC CLAYEY SILTSTONE
Major lithology: VITRIC CLAYEYSILTSTONE, light olive gray (5Y 6/2),structureless.
Minor lithology: None.
SITE 838 HOLE B CORE 10R CORED 220.6 - 230.2 mbsf
Met
er GraphicLith.
mm mm mm -
Sec
tion
Ag
e
Structure
^ =
Dis
turb
Sam
ple
Co
lor
Description
VITRIC CLAYEY SILTSTONE
Major lithology: VITRIC CLAYEYSILTSTONE, olive (5Y 4/4), thinlylaminated with alternating dark- andlight-colored banding.
Minor lithology: None.
SITE 838 HOLE B CORE 11R CORED 230.2-239.9 mbsf
Met
er |
;
GraphicLith.
~ ~~ *" ~~
Sec
tion |
1
Ag
e
|
Structure
Dis
turb
|
Φ
I<T>
Co
lor
5Y5/3
Description
VITRIC CLAYEY SILTSTONE
Major lithology: VITRIC CLAYEYSILTSTONE, olive gray (5Y 4/2), withsubanguiar igneous Irthic fragmentsand rounded intraclasts. The sedimentis strongly mottled throughout due tobioturbation. Light-colored (calcareous)and dark-colored (clay-silt-rich)mottling occurs.
SITE 838 HOLE B CORE 12R CORED 239.9-249.5 mbsf
Met
er
-
GraphicLith.
Se
ctio
n
1
Ag
e
Structure
\
Dis
turb
>
Sam
ple
Co
lor
5GY 6/1
Description
VITRIC CLAYEY SILTSTONE
Major lithology: VITRIC CLAYEYSILTSTONE, greenish gray (5GY 6/1),locally calcareous and extensivelybioturbated. Calcareous materialoccurs within burrows.
Minor lithology: None.
SITE 838 HOLE B CORE 13R CORED 249.5-259.2 mbsf
Met
er GraphicLith.
--TZJZJZ.
Sec
tion
1A
ge
Structure
i= """ 5
Dis
turb
Sam
ple
Co
lor
5GY6/1
Description
VITRIC CLAYEY SILTSTONE
Major lithology: VITRIC CLAYEYSILTSTONE, greenish gray (5GY 6/1),highly bioturbated and locallyforam-bearing, with local planarlamination and load dasts.
Minor lithology: None.
838B-11R;j 1 : 838B-12R;] 1
s-H^^•— 5-
ISO
SITE 838
cm0
§.25 8" δ
σCO•σ
£g.
CO
50 -
100 -
150 - I
135-838B-4R-1
APHYRIC BASALT
Piece 1
CONTACTS: None.PHENOCRYSTS:
Plagioclase: Trace-1%; 0.5 to 1 mm; euhedral, single crystals.GROUNDMASS: Aphanitic to glassy.VESICLES: 10%-25%; <0.4-1 mm; rounded to irregular; distributed throughout; rarely
cavities to 2.5 mm; density and shape varies from piece to piece; one has about 25%rounded 1 mm vesicles, one has 10% elongate 0.5-1 mm vesicles; other two haveabout 15% very small to 1 mm vesicles giving them a very high groundmass porosityMiaroles: Vesicle fillings and surface coatings of calcite, zeolites, and principallyanhydrite (?-granular, striated, and cleaved crystals); also thin white spots on surfacemay be cryptocrystalline silica.
COLOR: 2.5YR 5/0 to 3/0 gray to very dark gray.STRUCTURE: None.ALTERATION: None to slight.VEINS/FRACTURES: None.ADDITIONAL COMMENTS: Only four pebbles in core; could be clasts or flow rubble. Most
interesting features are small, angular lithic clasts in the largest piece. These are 1-10mm in size, about 1%-2% total of the piece and the largest has a very fine graineddiabasic texture. Two of the pieces in the working half have similar lithic clasts. Traceamounts of olivine phenocrysts tentatively identified. Samples are pebbles withinsedimentary Unit III.
950
SITE 838
135-838A-6H-04 (13-15 cm) OBSERVER: SHE
ROCK NAME: Sparsely phyric plagioclase pumice
GRAIN SIZE: Glassy to microcrystalline
TEXTURE: Pumiceous
WHERE SAMPLED: Sedimentary Unit IIC
PRIMARY
MINERALOGY
PHENOCRYSTSPlagioclase
Quartz?
GROUNDMASSOpaques
Mesostasis
PERCENT PERCENT SIZEPRESENT ORIGINAL (mm)
COMPO-SITION
1 1 0.2-0.8 AnlO-20
tr tr <O.l
tr tr <O.l
15-25 15-25 n/a
MORPHOLOGY
anhedral to euhedral oscillatory zoning, sodic rims on some,glass inclusions rare
anhedral small fragments
anhedral most of these may be contamination asthey appear to be most common in whatwas original void space, some do appearto occur in the glass
n/a typical pumiceous glass network, fewcrystallites; there has been a lot ofobscuring infilling and it is hard toidentify the glassy framework
VESICLES/ SIZECAVITIES PERCENT LOCATION (mm)Vesicles 70-80 everywhere <0.1-1.7
FILLING
none
SHAPE COMMENTSrounded, no alteration fillingirregular, but a lot of dust andor debris in vesicles andelongate cavities, probably from
sediments andmanufacture
COMMENTS: Slide is of a pumice clast from the sedimentary section. There is a lot of dust, dirt and debris in the voidsand vesicles probably from the sediment host and the thin section manufacture; hard to describe much detailbecause of the crushing and breakage. Sample is fresh.
135-838A-8H-01 (137-140 cm) OBSERVER: SHE
ROCK NAME: Sparsely plagioclase phyric pumice
GRAIN SIZE: Glassy to microcrystalline
TEXTURE: Pumiceous
WHERE SAMPLED: Sedimentary Unit IIC
PRIMARYMINERALOGY
PHENOCRYSTSPlagioclase
Quartz
Amphibole
Magnetite
PERCENTPRESENT
1-2
tr
tr
tr
PERCENTORIGINAL
1-2
tr
tr
tr
SIZE(mm)
0.15-1
0.05-0
0.3
0.05-0
.2
. 6
.1
COMPO-SITION
An30?
GROUNDMASSMesostasis 15-20 15-20 n/a
Magnetite
Sulfides
tr tr to 0.010 mm
tr tr 0.002 mm
MORPHOLOGY
subhedral toeuhedralanhedral tosubhedraleuhedral tosubhedraleuhedral tosubhedral
n/a
anhedral
andehdral
oscillatory zoned with sodic rims; 10-20micron glass and fluid inclusionsmany with rounded and irregular edges
pleochroic in pale greens
prominent ilmenite lamellae in some.
mostly glassy, some birefringent spots
may be crystallites; hard to tell withamount of fine grained debris scattered
throughout slidebright fragments in groundmass; many maybe contaminants in fillyellow bright spots in glass
VESICLES/CAVITIESVesicles
SIZEPERCENT LOCATION (mm)80? everywhere 0.02-1.5
FILLINGnone
SHAPE
round,elongate,orirregular
may be primary sedimentary debrisCOMMENTS: No visible alteration but a lot of dust and debris in vesicles and cavities;and shattering produced in thin section preparation. Sample is fresh.
951
SITE 838
135-838A-9H-02 (95-117 cm) OBSERVER: SHE
ROCK NAME: Moderately phyric olivine-plagioclase basalt
GRAIN SIZE: Glassy to microcrystalline
TEXTURE: Vesicular, porphyritic
WHERE SAMPLED: Sedimentary Unit IID
PRIMARYMINERALOGY
PERCENT PERCENT SIZEPRESENT ORIGINAL (mm)
COMPO-SITION
PHENOCRYSTSPlagioclase 2-3
Olivine
Clinopyroxene
GROUNDMASSMesostasis
1 1 0.15-0.3
tr tr 0.1
75-85 75-85 n/a
MORPHOLOGY
anhedral to euhedral small fragments tend to be angular andanhedral; one large glomerocryst (3 mm)of 8 grains; minor glass inclusions insome grainssmall fragments tend to be anhedral.Quench textures are common,sector zoned
euhedral, subhedraland skeletaleuhedral
n/a various amounts (1-5% rarely to 20%)microlites and crystallites ofplagioclase and pyroxene; most piecesvery glassy, some with devitrified andvariolitic groundmass
VESICLES/CAVITIESVesicles
SIZEPERCENT LOCATION (mm)10-20 throughout 0.01-0.2
FILLINGnone
SHAPE COMMENTSround to rarely flattened andovoid elongate, one piece
is graded from flatand elongate to roundvesicles across its1.5 mm width
Slide is a grain mount of very coarse sand (0.5-3 mm) from a volcanic breccia unit. Some of the smallestplagioclase microlites have short swallowtail terminations that bend outwards; these look like the abundantcrystallites found in the nannofossil slides from the core; all of the pieces are very fresh; the pieces arebasically the same rock type though they vary in groundmass crystallinity, phenocryst %, degree ofdevitrification. Many of the vesicles are filled with opaque fragments (probably polishing grit), nogroundmass opaques are evident. Sample is fresh.
952
SITE 838
135-838A-20H-CC (0-10 cm) OBSERVER: SHE
ROCK NAME: Aphyric to sparsely phyric plagioclase basalt
GRAIN SIZE: Glassy to microcrystalline
TEXTURE: Felty to pilotaxitic
WHERE SAMPLED: Sedimentary Unit III
PRIMARYMINERALOGY
PHENOCRYSTSPlagioclase
Clinopyroxene
PERCENT PERCENT SIZEPRESENT ORIGINAL (mm)
COMPO-SITION
tr-3 tr-3 0.3-1.4 An501
tr-1 tr-1 0.1-0.4
Magnetite tr-1 tr-1 0.05-0.15
tr tr 0.2
GROUNDMASSMesostasis
Magnetite
75-80 n/a
MORPHOLOGY
euhedral, rarelysubhedral
subhedral, euhedralto skeletal
broken euhedralgrain
n/a
small, anhedral
zoned to sodic rims, rare glassinclusions; most common in one piece;single crystals in associated withopaquescommonly twinned; glass inclusions insome; one basal section has 1/3 of itscore filled with a clear glass inclusionwith 4 spinel or magnetites growing fromthe pyroxene into the glassisolated and associated with plagioclasein clumps of up to 6 grains; it isgray-white and isotropic with includedgrains of a white, anisotropic mineral(in reflected light)a single grain in one of the pieces
plagioclase, pyroxene crystallinte(<O.Ol m ) abundant, though density andsize varies from piece to piece; apronounced alignment of microlites;often wrapped around phenocrystsscattered thorughout; many appear to bein voids and ar likely contamination;some seem to occur in the glass
VESICLES/ SIZECAVITIES PERCENT LOCATION (mm)Vesicles 3-20 throughout 0.02-1
FILLINGnone
SHAPE COMMENTSsmall ones the most phyric piece isround, the least vesicular; thelarger are other two pieces areelongate less phyric and
similarly vesicular
COMMENTS: Slide is three pebbles mounted together, all angular, glassy, 0.8-1.0 cm long, very fresh; pieces differsomewhat: the phenocryst description refers to the least vesicular piece; one of the more vesicular pieces isaphyric, the other sparsely phyric with the single olivine phenocryst. Sample is fresh.
953
SITE 838
135-838B-4R-01 (0-6 cm) OBSERVER: KRI
ROCK NAME: Sparsely phyric plagioclase basalt
GRAIN SIZE: Fine grained
TEXTURE: Vesicular, porphyritic
WHERE SAMPLED: Sedimentary Unit III
PRIMARY PERCENT PERCENT SIZEMINERALOGY PRESENT ORIGINAL (mm)
PHENOCRYSTSPlagioclase 1-2 1-2 0.2-1.0
Clinopyroxene tr-1 tr-1 <0.5
COMPO-SITION
GROUNDMASSMesostasis
Magnetite
Sulfides
40
1-2
tr
40
1-2
tr
n/a
<O.l
<0.03
SECONDARY REPLACING/MINERALOGY PERCENT FILLINGFine grained 1-2 replacing mesostasisclays
MORPHOLOGY
euhedral
euhedral
groundmass
equant to skeletal
globules
tabular, mostly isolated grains, somewith distinct sodic rimsone grain has a 0.1 mm melt inclusion incenter
extremely fresh; dominantly glassy withplagioclase and ?clinopyroxenecrystallites discernibleilmenite lamellae in many of the larger,equant grainsmost are either at vesicle margins orassociated with plagioclase phenocrysts
COMMENTSthere are a few small patches of the groundmass which show asmall degree of breakdown to fine grained green-brown clays.
VESICLES/CAVITIESVesicles
SIZEPERCENT LOCATION (mm)55-60 throughout <4mm
FILLINGempty
SHAPE COMMENTSround to most large vesicleselongate are highly elongate
one is 4x0.5mm);small ones arerounded
Comments: A pebble within Sedimentary Unit III.
954
SITE 838
135-838B-4R-01 (0-2 cm) OBSERVER: KRI
ROCK NAME: Sparsely phyric plagioclase basalt
GRAIN SIZE: Fine grained
TEXTURE: Porphyritic, vesicular
WHERE SAMPLED: Sedimentary Unit III
PRIMARYMINERALOGY
PERCENT PERCENT SIZEPRESENT ORIGINAL (mm)
COMPO-SITION
PHENOCRYSTSPlagioclase 1-2 1-2 <O.8Clinopyroxene tr tr <0.4
GROUNDMASSPlagioclase 10-12 10-12 <0.2
Mesostasis 20 n / a
SECONDARY REPLACING/MINERALOGY PERCENT FILLINGFine grained 20 replacing mesostasisclays
MORPHOLOGY
euhedral-subhedralsubhedral
euhedral
interstitial
some have abundant melt inclusionsoccur in glomeroporphyritic clusterswith plagioclase
skeletal microlites, randomly orientedexcept around lithic fragmentlargely broken down to fine grainedclays; some clinopyroxene crystallitesand small euhedral magnetites can bediscerned
COMMENTSgroundmass in the lithic fragment is more broken down thanthat in the host
VESICLES/CAVITIESVesicles
PERCENT LOCATION40-45 throughout
SIZE(mm)<0.8mm
FILLINGempty
SHAPE COMMENTSirregular high porosity due
to abundance ofsmall vesiclesthroughout section
COMMENTS: This section contains a lithic fragment about one cm across which is aphyric basalt with slightly largerplagioclase microlites than the host, relatively sharp boundaries with the host, and some alignment of the plagioclasemicrolites in the host surrounding the fragment. The fragment is aphyric, less vesicular, and contains moreinterstitial magnetite than the host, but overall the texture and mineralogy are similar in the two rocktypes. There are several other 1-3 mm fragments in this sample which are probably highly altered lithicfragments, but one may be a pseudomorph of a phenocryst.
955