6. site 1122: turbidites with a contourite foundation€¦ · shipboard scientific party chapter 6,...
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SHIPBOARD SCIENTIFIC PARTYCHAPTER 6, SITE 1122: TURBIDITES WITH A CONTOURITE FOUNDATION 57
Figure F16. Biostratigraphic summary chart of Site 1122 showing correlation between the four microfossilbiohorizons and age assignments. Numbers are ages (Ma).
Site 1122
0
100
200
300
500
Dep
th (
mbs
f)
Gr. puncticuloides 0.7-0.8
DIATOMS RADIOLARIANSNANNOFOSSILS
PLE
IST
OC
EN
E
AgeFORAMINIFERS
400
600
MID
DL
E M
IOC
EN
E
Gr. hirsuta 0.45
3.8
T. elliptipora 0.65-0.7
N. continuosa 11
Gr. praemenardii 13.2
Gr. zealandica 16.7
H. karstenii (Acme) 0.42
H. karstenii 0.18-0.19
A. ingens 0.64
E. huxleyi 0.24
P. lacunosa 0.42
R. asanoi 0.85
R. asanoi 1.16
G. parallela 0.95
Gephyrocapsa (large) 1.2
1.2
1.44
Gephyrocapsa (medium) 1.72
~ 3.54
>10.4 C. miopelagicus LO
<17.4 C. premacintyrei FO
C. macintyrei 12.34
S. heteromorphus 13.52
S. universus 0.46
E. calvertense 1.92
L. nautiloides 1.93PLIOCENE
S. barboi 12.5
N. denticuloides11.3-12.7
D. dimorpha 12.2
Dissolution facies; only reworked
Paleocene diatoms present
Miocene species present
LATE
EARLY PLIOCENE
?
< 2.6
Gr. miozea 15.9
SHIPBOARD SCIENTIFIC PARTYCHAPTER 6, SITE 1122: TURBIDITES WITH A CONTOURITE FOUNDATION 58
Figure F17. Age-depth curve using multiple microfossil and polarity chron datums for Hole 1122C. Thebest fit line is drawn according to subjective weighting of the chronostratigraphic and geochronologic pre-cision of the events and approximate average rate of sedimentation. Numbers by datums (e.g., F1) denoteevents listed in Table T8, p. 127. Wavy line at 490 mbsf represents a stratigraphic disconformity.
N13
F6
0 1 2 3 11 12 13 14 15 16
0
100
200
300
400
500
600
N1
F1
N2
R1
D3
D4
N6
F3 N9
D6
F4
D7 N12
D1
N5
N4
F2
N7
N8
R2
D2
N3
N10D5
N11
R3
Sed. Rate= ~400 m/m.y.
Sed. Rate= ~100 m/m.y.
Sed. Rate= ~20 m/m.y.
F5
Age (Ma)
Tephra
Tephra
TephraTephra
Tephra
Tephra
4 5 6 7 8 9 10
Dep
th (
mbs
f)
SHIPBOARD SCIENTIFIC PARTYCHAPTER 6, SITE 1122: TURBIDITES WITH A CONTOURITE FOUNDATION 59
Figure F18. Summary of the changing characteristics of the foraminiferal faunas at Site 1122.
Litho-stratigraphic
Unit
PlanktonicFauna
BenthicFauna
ABC
D
Normal,well-preserved,oceanic fauna
Deep-water assemblagewith addition of smallshelf and bathyal forms
Normal,well-preserved,oceanic fauna
Only deep-waterassemblage
ALarge, thick-walled,oceanic fauna, few orno small forms
Only deep-waterassemblage
Barren or rapidlyburied fauna of smallforms (winnowings) - minor reworkedOligocene
Barren or only deep-water assemblageB
Variable oceanic fauna
Only deep-waterassemblageA
Normal oceanicfauna
Dominantly mid-shelffauna (large and small) with minor deep-water assemblage
Tur
bidi
te-
dom
inat
edC
onto
urite
-dom
inat
ed
B
Deb
ris fl
ows
and
coar
se s
edim
ents
UN
IT I
UN
IT II
UN
IT II
I
Dis
solu
tion
Mio
cene
Plio
cene
-Ple
isto
cene
SH
IPB
OA
RD
SC
IEN
TIFIC P
AR
TY
CH
AP
TE
R 6
, SIT
E 11
22
: TU
RB
IDIT
ES W
ITH
A C
ON
TO
UR
ITE F
OU
ND
AT
ION
60
Figure sponsible for major sedimentinput.
0
200
400
600
Dep
th (
mbs
f)
turb
idite
s
Lithology
lithi
f.
sed.
cont
ourit
esco
ntou
rites
F19. Provenance of diatoms in the Neogene of Hole 1122C and implications for a major change in processes re
Ple
isto
cen
e
Bru
nhes
AgeSedimentation
rates
Jar.
Old.Mat
uyam
a
high
38 cm/k.y.
Plio
c.
Gauss
Mio
cen
e
10 cm/k.y.
Provenance of diatoms
Bounty Trough
+
autochthonous
reworked
Pliocene, Miocene,
diatoms
coastal areas
pelagic plankton
mostly
Antarctic/Subantarctic
diatoms
Paleogene diatoms
B R F C D
Zeoliteabundance
xxx
xxxx
5-10 cm/k.y.~
1122C
lithifiedsediment
Antarctic/Subantarctic
AA
BW
-flo
w
Processesresponsible
do
wn
slo
pe
tran
spo
rt f
rom
Bo
un
ty T
rou
gh
are
a
?
allochthonous and
Paleogene
reworked
? in
crea
sed
uplif
t of S
outh
Isla
nd N
Z
Chrons
SHIPBOARD SCIENTIFIC PARTYCHAPTER 6, SITE 1122: TURBIDITES WITH A CONTOURITE FOUNDATION 61
Figure F20. Whole-core magnetic susceptibility from Hole 1122C from the Bartington loop of the ship-board automated multisensor track, archive-half continuous measurements of NRM intensity, and intensi-ty of remanence after 20 mT of demagnetization from the pass-though cryogenic magnetometer. Verticaland subvertical lines in the lower 500 mbsf of the hole indicate intervals of nonrecovery of core.
0 0.2 0.4
Intensity (A/m) - NRM
0 0.1 0.2Intensity (A/m) - 20 mT
0 0.001 0.002
0
100
200
300
400
500
600
Susceptibility (SI)
Dep
th (
mbs
f)
SHIPBOARD SCIENTIFIC PARTYCHAPTER 6, SITE 1122: TURBIDITES WITH A CONTOURITE FOUNDATION 62
Figure F21. Whole-core inclination of Hole 1122C after alternating-field demagnetization to 20 mT on thepass-though cryogenic magnetometer. Polarity interpretation is given on the right. Black (white) shadedintervals indicate normal (reversed) polarity and hatched shading indicates intervals where polarity couldnot be determined because of poor recovery. Chrons are identified from correlation with the GPTS (Candeand Kent, 1995; Berggren et al., 1995) constrained by biostratigraphy (see discussion in “Biostratigraphy,”p. 13, and Fig. F25, p. 66).
309
325 326327331339
342
400412
439 442445 451
454458
494496
519522
C5Br
C5r.2rC5r.2n
C5r.1n
C2n
C1r.1r
C2r.1r
Bru
nh
es
Matu
yam
a
Gauss
C5
C5B
PL
EIS
TO
CE
NE
PLIO
.M
IOC
EN
E
JaramilloCobb Mtn.
Olduvai
0.780.78
0.991.071.19
1.771.95
2.15~ 3
9.93
11.08
~ 15-16
Age
(M
a)
Epo
ch
Chr
ons
Pol
arity
Dep
th(m
bsf)
?
?
?
HOLE 1122C
Ash
ho
rizon
s
(12 mbsf)
(137 mbsf)
(317 mbsf)(328 mbsf)
(390 mbsf)
(454 mbsf)(457 mbsf)
Vrica ?C1r.2r
Reunion
-80 -40 0 40 80
0
100
200
300
400
500
600
Inclination (° at 20 mT)
Dep
th (
mbs
f)
SHIPBOARD SCIENTIFIC PARTYCHAPTER 6, SITE 1122: TURBIDITES WITH A CONTOURITE FOUNDATION 63
Figure F22. A–I. Vector component diagrams of AF demagnetization behavior of representative discretesamples from Hole 1122C. A, B, G, I show a reversed field drilling-induced overprint on normal polaritysamples. B, C show radial remagnetization from attempts to demagnetize samples with AF fields above 50mT.
37.16 mbsf (Jmax = 1.23x10-2 A/m)
Inclination
0 AF field (mT) 60
1
J/J
max
N,Up
E,H
49.60 mbsf (Jmax = 3.17x10-2 A/m)
J/J
max
0 AF field (mT) 80
1
N,Up
E,H
Inclination
J/J max
0 AF field (mT) 80
1
J/J
max
N,Up
E,H
Inclination
J/J max
0 AF field (mT) 70
1
J/J
max
N,Up
E,H
Inclination
0 AF field (mT) 80
1
J/J
max
N,Up
E,H
Inclination
0 AF field (mT) 80
1
J/J
max
N,Up
E,H
Inclination
0 AF field (mT) 60
1
J/J
max
N,Up
E,H
Inclination
0 AF field (mT) 60
1
J/J
max
N,Up
E,H
Inclination
0 AF field (mT) 80
1
J/J
max
N,Up
E,H
Inclination
129.00 mbsf (NRM = 3.17x10-2 A/m)
235.24 mbsf (Jmax = 3.17x10-2 A/m) 272.49 mbsf (Jmax = 1.14 x10-2 A/m) 321.75 mbsf (NRM = 2.55x10-3 A/m)
369.38 mbsf (Jmax = 2.83x10-3 A/m) 419.94 mbsf (NRM = 6.54x10-3 A/m) 561.89 mbsf (Jmax = 8.69x10-3 A/m)
A B C
D E F
G H I
SHIPBOARD SCIENTIFIC PARTYCHAPTER 6, SITE 1122: TURBIDITES WITH A CONTOURITE FOUNDATION 64
Figure F23. Isothermal remanent magnetization (IRM) and backfield acquisition curves for representativediscrete samples from Hole 1122C. A. Samples from above 250 mbsf, remanence saturates by 300 mT, andBcr is between 50 and 75 mT. B. Samples from 300–400 mbsf, remanence saturates by 300 mT, and Bcr is <50mT. C. Samples from beneath 400 mbsf, remanence does not saturate until nearly 1000 mT for samplesfrom 483 and 457 mbsf, Bcr values vary between 25 and 75 mT. Remanence does not become saturated until200–500 mT and Bcr is <50 mT for all samples.
-1000 -500 0 500 1000
-1
-0.5
0
0.5
1
J/Jm
ax
129.00138.82159.71185.61217.24
A
Depth (mbsf)
-1000 -500 0 500 1000
-1
-0.5
0
0.5
1
J/Jm
ax
330.62330.66339.54339.59398.38
B
Depth (mbsf)
-1000 -500 0 500 1000
-1
-0.5
0
0.5
1
Applied Field (mT)
J/Jm
ax
446.81457.67483.98513.62562.39598.61
C
Depth (mbsf)
SHIPBOARD SCIENTIFIC PARTYCHAPTER 6, SITE 1122: TURBIDITES WITH A CONTOURITE FOUNDATION 65
Figure F24. A-F. Plots of normalized intensity of magnetization with progressive AF and thermal demagne-tization of saturation isothermal remanent magnetization (SIRM) for selected samples from Hole 1122C.
0
Temperature (oC)
500
J/J
max
100 200 300 400
Field strength (mT)
8070605040302010
159.71 mbsf, SIRM = 3.3 A/m
0
Temperature (oC)
500100 200 300 400 600
J/J
max
Field strength (mT)
8070605040302010
185.61 mbsf, SIRM = 5.8 A/m
0 500100 200 300 400 600
Temperature (oC)
Field strength (mT)
8070605040302010
J/J
max
217.24 mbsf, SIRM = 4.5x10-1 A/m
0
Temperature (oC)
500100 200 300 400
Field strength (mT)
8070605040302010
J/J
max
457.67 mbsf, SIRM = 1.6x10-1 A/m
0 500100 200 300 400 600
Temperature (oC)
Field strength (mT)
8070605040302010
J/J
max
513.62 mbsf, SIRM = 3.3 A/m
0 500100 200 300 400 600
Temperature (oC)
Field strength (mT)
8070605040302010
J/J
max
598.61 mbsf, SIRM = 2.6 A/m
A B C
D E F
SHIPBOARD SCIENTIFIC PARTYCHAPTER 6, SITE 1122: TURBIDITES WITH A CONTOURITE FOUNDATION 66
Figure F25. Age model and correlation of Hole 1122C magnetic polarity zonation with the GeomagneticPolarity Time Scale of Berggren et al. (1995) and Cande and Kent (1995). Where correlation is unambigu-ous, it is shown by a solid black line. Black (white) shaded intervals indicate normal (reversed) polarity andhatched shading indicates intervals where polarity could not be determined because of nonrecovery. Stip-pled lines show constraining biostratigraphic datums and shaded lines show magnetic polarity correla-tions. Undulating lines indicate stratigraphic disconformities and shaded areas indicate levels of uncertain-ty in datums. Correlation is constrained by the following foraminifer, nannofossil, diatom, and radiolariandatums (see discussion in “Biostratigraphy,” p. 13; see also “Biostratigraphy,” p. 10, in the “ExplanatoryNotes” chapter). Foraminifers: F1 (FO of Gr. hirsuta, 0.45 Ma), F2 (LO of Gr. puncticuloides, 0.7–0.8 Ma), F3(several forms younger than ~3.4 Ma, see “Biostratigraphy,” p. 13), F4 (occurrence of N. continuosa and N.pachyderma, ~11.3 Ma), F5 (LO of Gr. praemenardii, ~13.0 Ma), F6 (co-occurrence of Gr. zealandica and Gr.miozea, 16.3–16.7 Ma). Nannofossils: N1 (FO of Emiliania huxleyi, 0.24 Ma), N2 (LO of Pseudoemiliania la-cunosa, 0.42 Ma), N3 (LO of R. asanoi, 0.83 Ma), N4 (FO of G. parallela, 0.9 Ma), N5 (FO of R. asanoi, 1.06Ma), N6 and N7 (range of Gephyrocapsa [large], 1.1–1.36 m.y.), N8 (FO of Gephyrocapsa [medium], 1.66 Ma),N9 (several forms co-occurring, ~3.45 Ma, see “Biostratigraphy,” p. 13), N10 (LO of C. miopelagicus, > 10.4Ma), N11 (FO of C. macintyrei, 12.34 Ma), N12 (LO of S. heteromorphus, 13.52 Ma), N13 (absence of C. prem-acintyrei FO, <17.4 Ma). Diatoms: D1 (LO of Hemidiscus karstenii, 0.18–0.19 Ma), D2 (H. karstenii, acme, 0.92Ma), D3 (LO of A ingens, 0.64 Ma), D4 (LO of T. elliptipora, 0.65–0.7 Ma), D5 (LO of Nitzschia denticuloides,11.3–22.7 Ma), D6 (LO of D. dimorpha, 12.2 Ma), D7 (FO of S. barboi, 12.5 Ma). Radiolarians: R1 (LO of Sty-latractus universus, 0.46 Ma), R2 (LO of L. nautiloides, 1.93 Ma), R3 (FO of E. calvertense, 1.92 Ma). (Figureshown on next page.)
SHIPBOARD SCIENTIFIC PARTYCHAPTER 6, SITE 1122: TURBIDITES WITH A CONTOURITE FOUNDATION 67
Figure F25 (continued).
N13
F6
0 1 2 3 11 12 13 14 15 16
0
100
200
300
400
500
600
N1
F1
N2
R1
D3
D4
N6
F3 N9
D6
F4
D7 N12
D1
N5
N4
F2
N7
N8
R2
D2
N3
N10D5
N11
R3
Sed. Rate= ~ 400 m/m.y.
Sed. Rate= ~ 100 m/m.y.
Brunhes Matuyama GaussPleistocene Pliocene middle Miocene
C5BrC5rC5n
C5A
n
C5A
r
C5
AB
n
C5A
Cn
C5A
Dn
C5B
n
C5r
.1n
C5r.
2n
Jara
mill
o
Old
uv.
Reu
nion
Sed. Rate= ~ 20 m/m.y.
F5
G P T S
Po
lari
ty
Dep
th (
mbs
f)Age (Ma)
Hole1122C
Ash
Ash
AshAsh
Ash
Ashes
SHIPBOARD SCIENTIFIC PARTYCHAPTER 6, SITE 1122: TURBIDITES WITH A CONTOURITE FOUNDATION 68
Figure F26. Composite sections for MS, GRAPE, and reflectance percentage at 550 nm. For convenience, MSvalues from Holes 1122B, 1122C, and Core 181-1122C-3H are offset by 70 × 10–5, 140 × 10–5, and 240 × 10–5,respectively; GRAPE values are offset by 0.4, 0.8, and 1.2 g/cm3, respectively; and reflectance values are offsetby 8%, 16%, and 22%, respectively. Gaps in the composite section are indicated with triangles. Cores are in-dicated by small numbers. KK indicates the approximate depth of the Kawakawa Tephra (12.62 mcd in Core181-1122A-1H, 13.14 mcd in Core 2H, and 12.74 mcd in Core 3H). (Continued on next page.)
0 200 400
40
30
20
10
0
Dep
th (
mcd
)
Magnetic Susceptibility
(x10-5 SI)
A
B C
1
2
3
4
1
1
2
3
4
5
6
KK
1.5 2 2.5 3
40
30
20
10
0
SITE 1122
GRAPE density
(g/cm3)
1
2
3
4
1
1
2
3
4
5
6
0 20 40
40
30
20
10
0
Reflectance Percentage
(550 nm, smoothed)
1
2
3
4
1
1
2
3
4
5
6
SHIPBOARD SCIENTIFIC PARTYCHAPTER 6, SITE 1122: TURBIDITES WITH A CONTOURITE FOUNDATION 69
Figure F26 (continued).
0 200 400
80
70
60
50
Dep
th (
mcd
)
Magnetic Susceptibility
(x10-5 SI)
A C
4
5
6
7
8
6
7
8
9
10
gap
1.5 2 2.5
80
70
60
50
SITE 1122
GRAPE density
(g/cm3)
4
5
6
7
8
6
7
8
9
10
gap
0 20 40
80
70
60
50
Reflectance Percentage
(550 nm, smoothed)
4
5
6
7
8
6
7
8
9
10
gap
SHIPBOARD SCIENTIFIC PARTYCHAPTER 6, SITE 1122: TURBIDITES WITH A CONTOURITE FOUNDATION 70
Figure F27. Downhole depth offsets between the mbsf and mcd scales for Site 1122. Solid line indicates thetrend for a typical 10% stretch model between mbsf and mcd depths. Composite depth offsets are unusu-ally constant downhole and do not follow a stretch model.
0 5 10 15
Offset (m)
Dep
th (
mbs
f)
Hole 1122A
Hole 1122B
Hole 1122C100
80
60
40
20
0