College of
OCEANIC & ATMOSPHERIC SCIENCES
Mapping, geochemical sampling
and submersible observations of
recent activity on the
San Clemente fault zone
27 March to 4 April 2000.
Marta E. Torres
James McManus
and
Chris Goldfinger
OREGON STATE UNIVERSITY
Data Report 180
Reference 00-4
MARILYN POTTS GUIN LIBRARY
H. 11 ELD MARINE SCIENCE CENTER
OR[r,0N STATE UNIVERSITY
t
POR1. OREGON 9736*
i
TABLE OF CONTENTS
INTRODUCTION ................................................................................................... 2
1.1 Scientific objectives .............................................................................................. 2
2. STATION SUMMARY .......................................................................................... 3
3. GEOPHYSICAL SURVEY ........................................................................................ 8
4. WATER COLUMN PROGRAM ................................................................................ 8
4.1 Methane Analyses ............................................................................................... 11
4.1.1.Preliminary Results ....................................................................................... 11
1.
4.2 Methane oxidation ............................................................................................... 12
5. MULTICORE PROGRAM ........................................................................................ 12
5.1 Pore water analyses ............................................................................................. 13
5.2 Methane .............................................................................................................. 14
5.2.1 Preliminary Results ....................................................................................... 14
5.3 Methane oxidation ............................................................................................... 14
5.4 Foraminifera ....................................................................................................... 14
5.5 Sediment provenance studies ............................................................................... 15
6. ALVIN OPERATIONS ............................................................................................. 16
6.1 Introduction ......................................................................................................... 16
6.2 Navigation ........................................................................................................... 17
6.3 Geological surveys .............................................................................................. 17
6.4 Bottom sampling ................................................................................................ 18
6.4.1 Authigenic barites ......................................................................................... 18
6.4.2 Alvin push cores ........................................................................................... 19
6.4.3 Bottom water samples ................................................................................... 22
6.4.4 Benthic Barrel
...................................................................................
(OSU)
22
6.4. 5. Benthic landers ........................................................................................... 24
APPENDIX 1
Multicore logs and pore water data
APPENDIX 2
Alvin dive logs
APPENDIX 3
Alvin push core logs, methane and pore water data
APPENDIX 4
Abstracts submitted to the AGU fall meeting. San Francisco, CA Dec. 2000.
1
1. INTRODUCTION
1.1 Scientific objectives
In the majority of the seeps studied so far venting occurs in open-ocean waters, and
thus, the chemical signature associated with the fluid discharge is strongly masked by
bottom water processes. Hence, it has not been possible to unravel the contribution of
fluid-seepage to elemental distributions within the sediment record away from the
immediate seep area. At the San Clemente Fracture Zone, fluids are being discharged
within one of the basins of the California Borderlands, thus allowing us to evaluate the
effect of cold seepage within a depositional basin. We know that venting at the San
Clemente seeps, constitutes a significant source of methane (as evidenced by
development of chemosynthetic communities) and barium (as evidenced by massive
barite deposits) to the bottom water. We also know that fluxes of Ba, U, and Mn in this
basin are as much as a factor of 10 higher than the benthic fluxes from surrounding areas
(McManus et al, 1998). These high benthic fluxes measured in the San Clemente basin
are probably not related to fluid venting at the basin floor as there is no indication of
advective fluid flow into this region of the basin. However, for Ba, the benthic fluxes
measured there are two to four times higher than typical hemipelagic Ba rain rates (e.g.
Dymond et al., 1992). These combined observations indicate that in the San Clemente
basin some process other than the rain of material from the upper water column is
contributing metals to the basin inventory. In this scenario, fluid discharge along the San
Clemente fault zone, followed by deposition of solid phases at seep sites (e.g. POM,
carbonate, barite), results in a significant flux of seep-derived solid material throughout
the basin. As this material undergoes decomposition at the seafloor, the benthic fluxes
will reflect the input of components associated with seepage on the basin wall.
On these premises we designed a field program to:
1) Map, describe, and quantify the rates and composition of fluids discharging along
the San Clemente fault zone, and
2) Quantify the effect of fluid discharge on the budgets of a variety of
geochemically important elements, including barium.
The investigation described in this project will test the hypothesis that fluxes of
carbon, barium, manganese, iron and uranium associated with fluid seepage at the San
Clemente fracture zone significantly affect the geochemical budgets for these elements,
and ultimately result in anomalously high benthic fluxes throughout the San Clemente
basin.
To quantify the significance of fluid seepage we will deploy benthic incubation
devices at a variety of active seeps and basin sites. It has been shown that these
instruments are useful in obtaining fluid flow rates and element fluxes from cold-seeps
(Linke et al., 1994, Torres et al., 1996) as well as from the basin floor (Berelson et al.,
1987; McManus et al., 1996). This simple experiment will allow us to assess, for the first
time, the effect of fluid discharge on geochemical processes, not only at the sites of active
fluid seepage, but also in a basin-wide scale.
To maximize the use of Alvin dives during lander deploymnets on the San Clemente
basin site. We combined these objectives with those of whale-fall studies on a carcass
2
implanted on the San Clemente basin in 1995. The research associated with this large
organic carbon point-sources is part of ongoing biological studies by Craig Smith (U. of
Hawaii) and future (proposed) geochemical investigations by Torres (OSU) and
McManus (LLO).
1.2 CRUISE PARTICIPANTS
Name
Phone
Fax
email
1. Marta E. Tones (F)
OSU
541-737-2415
541-737-2064
mtorres@oce.orst.edu
2. Jim McManus (M)
LLO
218-726-7384
218-726-6979
jmcmanus@d.umn.edu
3. Chris Goldfinger (M)
OSU
541-737-5214
541-737-2064
gold@oce.orst.edu
4. Mark Legg (M)
USD
714-842-0404
714-842-5777
mrlegg@cerf.net
5. Marie de Angelis (F)
HSU
707-826-5621
707-826-4145
mad 1 @axe.hurnboldt.edu
6. Heather Carnocki (F)
HSU
7. Chi Meredith (F)
OSU
541-737-5224
541-737-2064
cmeredith@oce.orst.edu
8. Sarah Kohlbry (F)
LLO
9. Dale Hubbard (M)
OSU
10. Andrea Voorhees
OSU
11. Chris Moser (M)
OSU
skohlbry@d.umn.edu
541-737-4365
541-737-2064
dhubbard@oce.orst.edu
541-737-2064
541-737-5217
541-737-2064
cmoser@oce.orst.edu
12. Bronwen Comberland (F) LLO
13. Tina Willie (F)
LLO
14. Eric Hinen (M)
LLO
218-726-7290
218-726-6979
heinOll2@d.umn.edu
15. Jason Agnich (M)
LLO
218-726-7206
218-726-6979
jagnichl@d.umn.edu
16. Jesse Muratli
OSU
17. Brian Haley
OSU
541-737-2649
542-737-2064
bhaley@oce.orst.edu
18. Robert Miller
U. Mass
617-287-6638
bmiller@soest.hawaii.edu
19. Elena Centeno Garcia
UNAM
56-22-42-85
centeno@servidor.unam.mx
20. Rosa Prol-Ledesma (F)
UNAM
56-22-41-31
prol@servidor.unam.mx
21. Mario Rebolledo Vieyra
UNAM
56-22-41-13
2. STATION SUMMARY
The Stations occupied during the Atlantis Voyage 3, leg 49; which we have
designated as AT0003- are listed in Table 1. Figure 1 illustrates the location of these
stations on a bathymetric map (Figure 2) generated during this cruise (see Section 3)
3
118' 15'W
117' 30'W
117' 45'W
118' 001W
32' 45'N
32' 45'N
re`
32' 30'N
32' 30'N
32' 15'N
32' 15'N
32 00'N
31' 45'N
31'45-N
118' 15'W
300
600
900
1200
117' 30'W
117' 45'W
118' 00'W
1500
1800
2100
Depth (m)
Figure 1. Location of stations on bathymetric map (100 m grid).
2400
2700
3000
Figure 2A. Perspective shaded relief bathymetric image (100 m grid) of the southern California
borderland region, offshore San Diego. View is looking N, lighting is from the SW, and vertical
exageration is 4
Figure 2B. Southern segment of the San Clemente fault. View
is looking NW, lighting from the SW, and vertical exageration is 4.
5
Table 1. Station Summary
Date
27-Mar
Time Station
8:10
I SS
3:00
Long
West
Depth
meters
Observers
Depart San Diego
10:00 AT0003-
28-Mar
Lat
North
AT00032MC
Goldfinger/
Seabeam survey and deploy
transponder nets at both dive
sites. Only calibrated the net at
the scarp site
Multicore deployed at base of
the scarpment, 5 Km from
seeps. Only recovered 5 of the
Legg
32°
13.455'
Moser/
Bronwen
1170
46.607'
8 cores
AT00033AD3532
Dive to scarp. Aborted at 500
meters because of ground
problem
32 °
1170
13.197'
43.029'
12:00 AT0003-
Redeployed Alvin on seep site
32 °
8:00
3AD3533
19:00 AT0003-
Across from the seep site
1170
13.197'
43.029'
32 ° 12.8'
117 ° 43.2'
1800
Torres/
Goldfinger
1800
Torres/
Goldfinger
1820
Hubbard
4CTD
22:45 AT0003-
San Clemente Fault
Goldfinger/
5SS
29-Mar
3:00
AT00036MC
Over the scarp
32 ° 13.4'
8:00
AT00037AD3534
Dive on scarp, deploy barrel,
push cores and retrieve lander
17:00 AT00038SS
30-Mar
Legg
1766
Moser/
Bronwen
32 °
1170
1800
13.197'
43.029'
de Angelis/
Legg
Goldfinger/
Seabeam images of the
southern fracture zone
3:00
AT00039CTD
8:00
AT0003- Scarp and cove
10AD3535
18:00 AT0003-
117 ° 42.5'
Legg
In front of seeps
117 ° 43.2'
1824
Hubbard
32 °
117 °
1805
12.729'
42.231'
Goldfinger/
Cumberland
32 ° 12.8'
San Clemente fault
Goldfinger/
11SS
31-Mar
3:00
AT000312MC
6:00
Legg
Multicore 10 km from seep,
not on turbidite fan
AT0003Scarp- Deploy 1 barrel and 2
13AD3536 landers
32 °
117 °
10.725'
48.734'
320
12.744'
6
1170
42.334'
1897
Moser
1819
Torres/
Haley
Date
Time Station
18:00 AT0003-
Lat
North
Long
West
Depth
meters
Observers
1540
Hubbard
San Clemente fault
14SS
23:00 AT0003-
Pull apart basin
320
15CTD
AT0003-
04.177'
1170
31.048'
San Clemente fault
Goldfinger/
16SS
1-Apr
2:30
AT0003-
Legg
Pull-apart basin
32 °
04.177'
17MC
AT0003-
117 °
31.048'
1540
San Clemente fault
Moser
Goldfinger/
18SS
Legg
6:00 AT0003- Exposed scarp fault. Recover
19AD3537 landers. Dive terminated early
due to ground problems in the
sub
32 °
13.061'
1170
1783
42.373'
Legg/
de Angelis
Recovered transponders
17:00 AT000320SS
19:30
2-Apr
Transit to whale site, Seabeam
in transit
Goldfinger/
Legg
Calibrate net at whale site
2:00 AT0003-
At the entrance to the canyon.
32 ° 36'
118 ° 06.0'
2048
Deploy elevator
32 °
25.830'
118 °
08.540'
1904
32 °
118 °
1902
25.830'
08.540'
Moser
21 MC
6:00
8:00
AT0003- San Clemente whale
22AD3538
17:00 AT0003-
North San Clemente fault
Goldfinger/
23SS
23:00 AT0003-
Miller/
Hinen
Legg
North San Clemente fault
32048.19'
2:00 AT000325CTD
North San Clemente fault
32039.60'
AT0003-
North San Clemente fault
118015.16'
1060
Hubbard
118008.9'
2040
Hubbard
24CTD
3-Apr
5:00
Goldfinger/
26SS
8:00
AT0003-
egg
San Clemente whale
32 °
25.830'
27AD3539
7
118 °
08.540'
1902
Miller/PIT
Date
Time Station
3-Apr
15:30
Lat
North
Long
West
North San Clemente fault
Goldfinger/
28SS
7:30
Observers
Recover transponders
16:30 AT0003-
4-Apr
Depth
meters
Legg
At sea buoy
3. GEOPHYSICAL SURVEY
The geophysics objectives of the cruise were to survey active faulting in the
California Continental Borderland using SeaBeam swath bathymetry and 3.5 KHz
subbottom profiling combined with ground truth examination of recent seafloor faulting
using DSV ALVIN. The focus of the survey was on the San Clemente fault zone,
although regional coverage to include other Inner Borderland faults was accomplished.
During this cruise, we acquired multibeam coverage over several active segments of the
San Clemente fault zone stretching from the southeast tip of San Clemente Island to the
Descanso Plain area west of Ensenada, Baja California, Mexico. Combined with swath
bathymetry from previous cruises, and existing SIO archive swath bathymetry, we
compiled nearly complete swath coverage of a 225 km length of the San Clemente fault
zone. These data show abundant evidence of active faulting including seafloor scarps up
to 1500 meters high (Fortymile Bank) with remarkably linear traces, typical of vertical
strike-slip faulting. Right fault step-overs of fault scarps are characterized by basins and
troughs, whereas left step-overs are characterized by ridges or broad anticlines,
confirming the right-slip fault character. High-resolution seismic profiles (3.5 KHz)
acquired allow identification of prominent acoustic horizons that may be mapped
throughout the region and may allow determination of age of faulting. Other areas of
active faulting identified by the swath bathymetry include the San Diego Trough where a
low, linear scarp was mapped.
4. WATER COLUMN PROGRAM
During the AT0003 cruise, we deployed 5 CTD casts and collected water from 12 of
the 24 bottles mounted on the R/VAtlantis rosette. The primary emphasis in station
selection was to determine whether the observed or predicted venting along the San
Clemente fault zone could be mapped by anomalies in the methane and barium content of
the water column. Generally, the CTD's were deployed as part of the night program,
which also included multicoring and geophysical surveys. Samples were collected from
the rosette for shipboard analysis of methane; and post-cruise analyses of nutrients, trace
elements, carbon and oxygen isotopes, and methane oxidation rates. A detailed listing of
the stations, sample depths and methane contents is given in Table 2, the hydrocast
stations are depicted in Figure 1.
8
Table 2. Hydrocast data
Station
AT00034CTD
Lat.
North
Long.
3212.8
11743.2
Depth
(m)
(nM)
02
(ml/L)
1
1801
2.8
0.629
2
1795
3
28.9
6
1790
1785
1780
1775
7
8
1771
1765
9
13
1750
1700
1500
500
1.2
2.1
1.0
1
1804
2.0
2
1804
1800
1800
1795
1795
1790
1790
1785
1785
1780
1780
1775
1775
1770
1770
1765
1765
1760
1760
1755
1700
1700
2.2
2.7
0.0
Bottle
West
4
5
10
11
AT00039CTD
32 12.6
11743.2
3
4
5
6
7
.8
9
10
11
13
14
15
16
17
18
19
20
21
22
23
24
9
CH4
ECO2
(mM)
Comments
#2 Niskin did not
trip
0.9
1.5
3.4
0.9
2.2
1.8
16.8
8.6
9.3
7.5
1.9
7.5
3.0
8.0
2.4
5.5
1.2
0.670,
0.685,
0.644
Station
AT000315CTD
Lat.
North
Long.
West
3204.2
117 31.0
Bottle
Depth
(m)
(nM)
1
1496
1.9
2
1496
3
24
1494
1494
1492
1492
1490
1490
1488
1488
1486
1480
1480
1475
1475
1470
1470
1465
1465
1300
1300
1000
1000
1
1040
13.2
2
1035*
1030
1020
1010
1000
990
980
950
900
800
600
400
0.0
5.8
4
5
6
7
8
9
10
11
13
14
15
16
17
18
19
20
21
22
23
AT000324CTD
32 48.19
118 15.16
3
4
5
6
7
8
9
10
11
13
14
10
CH4
02
(ml/L)
ICO2
(mM)
0.585,
0.570,
0.562
0.0
33.4
1.2
11.6
4.5
2.6
1.1
15.1
2.6
19.1
5.3
1.2
0.9
1.6
0.7
1.5
2.4
1.0
10.9
0.0
19.3
0.364,
0.371,
0.433
2.410
Comments
Station
AT000325CTD
Lat.
Long.
North
West
32 39.60
118 08.90
Bottle
Depth
(m)
(nM)
1
1990
0.2
2
0.1
5
1850
1750
1650
1550
6
1500
7
1500
8
1500
9
1500
3
4
CIA,
02
(ml/L)
ZC02
(mM)
Comments
0.706,
0.661,
0.810
2.371
Possible
contamination in 02
flask #T31(.810)
0.2
0.4
0.6
Niskin #s 6-9 for
Chi's cubitainers.
Niskin #s 6-9 for
Chi's cubitainers.
Niskin #s 6-9 for
Chi's cubitainers.
Niskin #s 6-9 for
Chi's cubitainers.
.4.1 Methane Analyses
Methane was analyzed using a McAuliffe extraction of methane in water into
headspace and subsequent injection into a gas chromatograph (GC) with flame ionization
detection (FID). For all CTD samples, 100 ml of water were drawn from each Niskin
into a 140m1 syringe to which 40 ml of UHP helium was added. The samples were then
shaken on a wrist-action shaker for 5 minutes. For all CTD samples, the gaseous
headspace was injected into the 10-cc loop of the GC, prior to injection into a HayeSep Q
column. Samples were calibrated against a 10 ppm or 1000 ppm methane in helium
standard, depending upon sample methane concentrations. Methane peak areas were
integrated using Peak Simple software directly interfaced with a SRI Model 8610 gas
chromatograph.
4.1.1.Preliminary Results
Station AT0003-04CTD exhibited typical ocean water methane concentrations of 1 to
3 nM at all depths except for a one-point sharp maximum of 28.9 nM at a depth of 1790
meters. AT0003-09CTD showed slightly elevated methane concentrations (5 to 9 nM)
below 17000 meters. AT0003-15CTD also exhibited elevated methane concentrations
below 1300meters with a maximum of 33,4 nM at 1492 meters. Stations AT000324CTD and AT0003-25CTD, located along the north section of the san Clemente fault,
were characterized by typically low ambient open ocean methane concentrations
throughout most of the water column. However, AT0003-24CTD show higher methane
levels in the upper water column at 400 meters, and an increase in methane
concentrations at depths greater than 1030 meters, from non-detectable (<1nM) to 13.2
nM by 1040 meters. AT0003-25CTD showed no anomalous methane values, with
methane levels less than 2 nM throughout the water column.
11
4.2 Methane oxidation
Samples for methane oxidation were collected only from 8 depths on Station
AT0003-25CTD. These samples were incubated in 14ml septum vials with no headspace
to which dissolved 14CH4 was added at various times ranging from 2 to 8 hours. At the
end of each incubation time, methane oxidizers were killed by the addition of 6N NaOH,
which stopped all methane oxidation activity and converted all 14C02 produced by
methane oxidation to carbonate. This allowed for transfer of samples to 20m1 vials
without loss of label carbon for safe transport to a shore-based lab (Humbolt State
University) for further analyses. Samples will be then transferred to 100 ml serum bottle
equipped with baskets containing a Whatman GF/C filter soaked in betaphenylethylamine. Upon acidification with ION sulfuric acid and shaking, all 14-C
carbonate will be quantitatively transferred to the filter. The filter will then be placed on
a scintillation vial to which 10 ml of scintillation cocktail has been added, and the activity
will be counted on a Packard Model 1600 liquid scintillation counter. Acidified samples
will be filtered through a 0.22 u filter to determine 14-C cell carbon production.
5. MULTICORE PROGRAM
During the nigh program of cruise AT0003, we successfully deployed the OSU
multicorer on 5 stations (Table 3, Figure 1), with the aim of complementing the data
obtained with the Alvin push cores at the vent sites, and to trace the effect of barium
discharge at the seeps on a basin-wide scale.
Table 5. Multicore station summary
Date
Time
Station
Lat
Long
North
West
Core tube number
W.D
(m)
1
29Mar
30Mar
3:00
3:00
AT0003- Multicore deployed
2MC at base of the
escarpment, 5 Km
from seeps. Only
recovered 5 of the 8
cores. Core #8 was
lost on deck.
32
13.455
AT0003- Over the scarp, on a
6MC small topographic
high near the top of
the scap. Probably
some turbidite
deposits
32 13.4
117
1847
46.607
M
e
3 4
P N N
W R R
2
t
117
1766
A
r
c
h
P
W
7
8
L
o
s
1
A
r
c
h
/
i
s
e
d
v
6
B
i
o
t
e
P
o
F
o
B
S
A
i
r
o
o
r
a
e
d
1
i
r
c
h
s
m
o
v
e
i
g
m
e
t
y
n
y
12
F
o
r
a
m
h
42.5
5
t
i
Date Time Station
Lat
North
1-Apr 3:00 AT0003 Multicore 10 km
-12MC from seep, not on
turbidite fan
2-Apr 2:30 AT0003 Pull-apart basin, as
-17MC close to the scarp
Long
West
32
117
10.725 48.734
32
117
Core tube number
W.D
(m)
1897
2
3
4
7
P
P
B
5
F
6
S
S
A A
e
o
W
i
o
e
r
r
d
r
o
r
d
c
c
i
m
o
a
i
h
m
m
i
e
i
v
h
i
e
l
o
g
n
t
y
n
e
e
t
y
1
2
P
8
1540
04.177 31.048
s
t
4
5
6
7
P
F
A
S
A A
W
o
r
e
r
r
r
c
d
c
c
o
a
h
i
h
s
m
h
i
1
-21MC the canyon;
r
i
m
i
v
e
i
v
t
e
n
e
e
2
118 2048
06.0
v
t
y
32 36
v
3
o
as possible
3-Apr 2:00 AT0003 At the entrance to
8
1
3
P
4
5
7
8
P
A A A
S
W
6
r
r
r
e
compressional
r
c
c
c
d
section of the fault
o
h
h
h
s
i
i
i
m
i
v
v
e
v
e
e
n
Same location as
McManus cores in
o
t
y
1992 and 1995 .
e
i
t
W.D.= water depth; N.R. = not-recovered; P.W.= pore water samples
5.1 Pore water analyses
Pore waters were extracted by sectioning and centrifuging sediment slices (7-10,000
rpm). Cores for pore water analyses were processed at in situ temperatures under a
nitrogen atmosphere. Cores were typically sectioned directly into acid-cleaned centrifuge
tubes. Tubes were filled sequentially to full volume (50 cc) and sediment depths are
back-calculated based on the volume removed and the area of the core liner (72.6 cm2).
Pore water samples were filtered (0.45 µm filter, under a nitrogen atmosphere) into HClleached bottles. For those samples stored for trace element analysis, samples were
subsequently acidified with triple-distilled 6N HCI. A total of 5 sediment cores were
processed for pore waters collected using the multi-corer. Pore waters were analyzed
aboard ship for pH,'CO2, sulfides, and amonium. Samples for porosity and nutrients
were shipped for nutrient and porosity analyses immediately after the cruise. Results of
pore water chemical analyses are given in Appendix 1.
13
5.2 Methane
For multicore samples, cores were sectioned at 2-cm intervals after the first 1 cm.
Sediment samples for methane analysis were taken using a 3-ml disposable syringe with
the tip cut off. Methane concentrations were determined only for one multicore
deployment (AT0003-02MC). The sediment plug taken as described below was placed in
a 60-ml serum bottle containing 10 ml of distilled water. Immediately following the
addition of sediment, the serum bottles were sealed with a blue butyl rubber stopper and
crimp sealed with an aluminum seal. Blanks were also prepared consisting of 10 ml
distilled water with no sediment added. Sealed bottles were shaken on a wrist-arm shaker
for a minimum of 5 minutes. After shaking, the gaseous headspace was withdrawn using
a 60-m1 syringe equipped with a stopcock and a 18-gauge needle. Withdrawn gas was
simultaneously replaced with distilled water using another 60-ml syringe and 18-gauge
needle. The extracted gas was then injected into a 0.1 or 10 cc loop on the GC (see
section 4.1).
5.2.1 Preliminary Results
The uppermost 6 cm of the sediment showed non-detectable methane levels. Below 6
cm, methane concentrations in the sediment increased to an approximately constant level
of 1,800 nmoles CH4 ml-' of sediment. Methane data is given in Appendix 1
5.3 Methane oxidation
Samples for methane oxidation were taken for the same core described above for
methane analysis. Sediment samples were taken using a 3-ml disposable syringe with the
tip cut off from the surface of the core (0 to 1 cm) and every 2-cm section thereafter. 0.5
cc sediment subsamples were then added to 7-mi septum vials to which previously
degassed (using UHP NO seawater was added to each vial under no headspace was
present prior to addition of radiolabeled methane. Methane oxidation samples were
returned to Humboldt State University for subsequent extraction of all 14CO2 and 14C-cell
carbon using liquid scintillation counting as described above (Section 4.2).
5.4 Foraminifera
A total of 4 multicores were used in sampling for microscopic foraminifera. The
fifth multicore was not used in sampling due to a shortage of bottles. Aside from the last
coring site sampled, each core was sliced up into 1/2cm intervals for the first 6cm and
then at l cm intervals from 6-12cm. The fourth multicore (17MC) was sliced in 1 cm
intervals for the first 12cm. A piston and measuring rings aided in this process. From
each slice the sediment was placed into 125ml nalgene bottles labeled with coring site
and centimeter depth from core. After 12cm was reached the core was sliced into 4cm
intervals, except for the first multicore (2MC) which was sliced into 6cm intervals, and
stored in ziploc bags. After all samples were taken formalin containing rose bengal was
added, about a half an inch per bottle, to preserve and stain the forams. Samples
collected for these studies are listed in Table 5.
14
Table 5. Samples collected for foraminifer studies.
Station: AT0003-2MC-5
Date: Mar-28, 2000
Core Diameter: 9.5cm
Number of Samples: 22
Sample Depths: 0-6cm at 0.5cm intervals
6-12cm at lcm intervals
12cm-bottom at 6cm intervals
Station:AT 0003-6MC-5
Date: Mar-29, 2000
Core Diameter: 9.5cm
Number of Samples: 24
Sample Depths: 0-6cm at 0.5cm intervals
6-12cm at 1cm intervals
12cm-bottom at 4cm intervals
Station: AT 0003-12MC-5
Date: Mar-31, 2000
Core Diameter: 9.5
Number of Samples: 27
Sample Depths: 0-6cm at 0.5cm intervals
6-12cm at lcm intervals
12cm-bottom at 4cm intervals
Station: AT 0003-17MC-4
Date: Apr-1, 2000
Core Diameter: 9.5
Number of Samples: 20
Sample Depths: 0-6cm at 0.5cm intervals
6-12cm at lcm intervals
12cm-bottom at 4cm intervals
5.5 Sediment provenance studies
Five cores were collected with the objective of identifying the sediment provenance,
and to establish possible connections among the sub-basins. The sediments will be
analyzed for Sm/Nd isotopes, mayor and trace element composition and sediment
magnetic properties by Elena Centeno-Garcia at UNAM.
15
6. ALVIN OPERATIONS
6.1 Introduction
We had a total of 8 Alvin dives, 6 on the San Clemente escarpment, and 2 on the San
Clemente basin, at the whale-fall site. The location and a summary for each dive is given
in Table 6.
Table 6. Dive summary
Number Site
3532
NE end of
scarp
3533
NE end of
scarp
3534
NE end of
scarp
Launch
position
Summary
32° 13.197'
117 43.029'
Alvin has ground probles. Aborted dive at 500m
32 ° 13.197'
117 ° 43.029'
Deployed benthic lander. Sampled barite from the
seafloor and 2 Niskins. Alvin had problems with
propulsion and ballast control, which made the
operations very difficult and slow.
32 ° 13.197'
117 ° 43.029'
Checked placement and seal of lander; deployed
benthic barrel; took 2 Niskin samples near benthic
barrel site; collected barite and tubeworms, took 8
push cores near barrel site; conducted survey at
various locations along scarp; retrieved lander and
benthic barrel.
3535
NE end of
32 ° 13.197'
scarp to the 117043.029'
cove
Deployed benthic barrel, near tube worms and clam
shells. Collected 2 Niskins. Push Cores were taken
zero meters from the barrel (4); one meter from the
barrel (5); and at the bottom of the scarp (5).
Transit to Shelter Cove along fault scarp. Several
grab samples were taken along transit. Benthic
barrel was picked up before returning to the surface.
3536
NE of cove 32 ° 12.779'
Deployed barrel on clam site at the base of the slope
which appears to reflect a different type of venting.
Deployed the landers on worm-rich site and
background station. Sampled surface sediments and
clams.
117 ° 42.237'
3537
NE of cove 32 ° 13.061'
117 ° 42.703'
Surveyed scarp from starting point to site of red
lander; surveyed numerous terraced scarps at depths
ranging from 1778 to 1800 meters; collected barites
and tubeworms from two sites; collected Niskin
water samples and pushcores from red lander site;
retrieved red and brown landers from previous dive.
Dive curtailed due to unidentified grounding
problems.
16
Number Site
3538
Whale fall
35 39
Whale fall
Launch
position
32 ° 25.83'
118 ° 08.54'
32'25.83'
118 ° 08.54'
Summary
Located elevator and tripped the first Niskin (#5).
The brown lander was deployed next to the elevator,
with some problems with visibility due to
suspended sediments. Had difficulty releasing the
elevator due to low visibility, and problems with the
lander removal. Searched for whale, when it was
located we tripped the second Niskin (#3), and then
deployed the second lander. 13 push cores taken
near the whale. Biological samples were taken from
the whale carcass and surounding area.
Collected sediments and biological samples. Took
video transects from the whale carcass. Recovered
landers.
6.2 Navigation
During this cruise we utilized the ACNAV long baseline navigation system, using
two nets of two acoustic transponders each. This nets allowed tracking of ALVIN's
position from the support ship and from within the submersible. ALVIN is equipped with
an in-hull navigation transceiver which allows the submersible to utilize the long baseline
transponder net to navigate independently of ATLANTIS and thus more accurately (<5
meters). This transceiver is capable of transmitting on any one frequency and receiving
on any four frequencies between 5.0 and 15.0KHz in 100 Hz steps. The acoustic travel
times measured by this transceiver are fed to the ALVIN computer for further
interpretation and display.
The acoustic transmitter/receiver (Benthos 455 ASP) on the ATLANTIS receives 16
of the 17 frequencies from 7.0 to 15.0 KHz simultaneously with 500 Hz spacing
(normally no reception on 12.5 KHz). Additionally, it can interrogate on 16 frequencies
(excluding 12.5 KHz). This system can provide precision navigation of the support ship
with an accuracy of within 10 meters relative to the transponder net. The uncertainty is
primarily due to errors inherent in the system such as imprecise sound velocity
information and instability of the transponder moorings. However, since these errors are
relatively constant for a particular net, the precision of the system is quite good and a
repeatability of 5 meters can be expected. The preferred baseline distance between
transponders is approximately 1.5 times the site depth, and reliable fixes may generally
be obtained at distances up to one baseline length away from any two transponders. The
Alvin positions are given on XY coordinates relative XY origins, which for this cruise
were located at 32° 12.0'N and 117° 44.0'W for the seep sites, and at 32° 25.0'N and
118° 10.O'W for the whale site.
Unfortunately, during this cruise, we only had navigation data from Alvin in 1 out of
the six dives at the seep sites, which resulted in a less-than satisfactory situation during
the geological surveys of the scarp. The two dives at the whale site had reliable ALVIN
XY readings.
6.3 Geological surveys
ALVIN dives at the "Seeps" site near Navy submarine fan examined the steep-sloped
17
scarp along the San Clemente fault and found geologically youthful, vertical, fault scarps
that ranged in height from several centimeters to a few meters. Different ages of faulting
were apparent based upon the degree of bioturbation and degradation of the scarp surface,
with some scarps very young showing minor biotic activity and others older being
covered by burrows and some mud drape. Other areas of active faulting identified by the
swath bathymetry include the San Diego Trough where a low, linear scarp was mapped.
Further indication of youthful fault activity was the abundant evidence of fluid venting
along the young scarps. Venting evidence included barite precipitates along the faults,
and chemosynthetic organisms such as tube worms and clams found only along the fault
traces. Evidence of venting from Navy Fan strata exposed by vertical separation of the
active scarps was also abundant. The active fault scarps exposed a probable HolocenePleistocene boundary evidenced by a color change in the sediments from olive green
(Holocene) to gray (Pleistocene). Several scarps appeared to have single-event offsets,
based on the even bioturbation vertically on the scarp face. Multiple events would show
vertical zonation of bioturbation as has been observed on active scarps on the Oregon
margin. Active scarps with the characteristics observed were probably formed during
earthquakes of M>6.0.
6.4 Bottom sampling
6.4.1 Authigenic barites
A prominent feature of the seeps along the San Clemente escarpment is the formation
of extensive deposits of barium sulfate along the escarpment wall. These deposits are
observed as large blocks on the seafloor, and serve, in some instances as anchor for
tubeworm thickets. We sampled these deposits during 3 of the dives to the seeps.
Sample descriptions are given in Table 7.
Table 7. Barite samples collected
Alvin
dive #
Dive Sample Description
station
#
AT00033AD3533
1
2
3
4
5
Samples recovered from exposed
deposits on the scarp wall. No
tubeworms associated with these,
but seemed to harbor enhanced
benthic fauna (sampled by Bob
Alvin
X
Alvin
Y
Depth
meters
1490
2188
1812
1530
2194
1796
Miller). All samples are very
dark brown. Samples 1 to 3 to
OSU. #4 Rosa Prol-Ledezma,
and #5 for methane oxidation
(Marie de Angelis)
AT00037AD3534
11
1
Yellow piece, with small calm
shell cemented in it. Sample
collected near tubeworm clumps
18
Alvin
dive #
AT000319AD3537
Dive Sample Description
station
#
1
1
1
2
1
3
1
4
3
5
3
6
3
7
3
8
Very white and crumbly
precipitate with some dark spots
on bottom surface. Bob Miller
will use it to try to develop
tubeworm communities near the
whalewhale
Piece with lots of living creatures
in it. To Bob Miller for biologic
studies
Mixed pieces
2 Pieces with distinct color
zonations. To Jim McManus
Piece with only few white
surfaces. Probably higher Fe/Mn
Very white sample with only
FEW dark zones. It was attached
to tube worms on Lander RED
site
Very white sample with only
FEW dark zones. It was attached
to tube worms on Lander RED
site
Very white sample with only
FEW dark zones. It was attached
to tube worms on Lander RED
Alvin
X
Alvin
Y
Depth
meters
2085
1916
1794
2085
1916
1794
2085
2085
1916
1916
1794
1794
2555
1563
1817
2555
1563
1817
2555
1563
1817
2555
1563
1817
site
6.4.2 Alvin push cores
We collected 11 Alvin push cores for pore water analysis, methane and methane
oxidation evaluations, foraminifer and biology studies, as described in the sections below.
Detail descriptions of the collection sites and sampling scheme are included in each dive
summary (Appendix 1).
6.4.2.1 Pore water analysis Samples for pore water analysis were obtained by
centrifugation, as described in Section 5.2.
6.4.2.2 Methane analyses.
ALVIN pushcore samples were analyzed for methane as described for the multicore
samples in section 5.2. For pushcore samples, cores were sectioned at 2-cm intervals after
the first 1 cm. Sediment samples for methane analysis were taken using a 3-ml
disposable syringe with the tip cut off. Methane concentrations were determined for
pushcores on the following dives: 7AD3534 (core #8; 0 meters from tubeworm thicket),
10AD3535 (core # 4b; 1 meter from benthic barrel, core # 8, base of scarp), 13AD3536
19
(core #17b; 1 meter from barrel, core #2; background), 17AD3537 (core #10; base of
tubeworm thicket, core #4b; 1 meter from tubeworm thicket), 22AD3538 (core #2; edge
of whale cargo net).
The sediment plugs were placed in a 60-m1 serum bottle containing 10 ml of distilled
water. Immediately following the addition of sediment, serum bottle were sealed with a
blue butyl rubber stopper and crimp sealed with an aluminum seal. Blanks were also
prepared consisting of 10-ml of distilled water with no sediment added. Sealed bottles
were shaken on a wrist-arm shaker for a minimum of 5 minutes. After shaking, the
gaseous headspace was withdrawn using a 60-m1 syringe equipped with a stopcock and a
18-gauge needle. Withdrawn gas was simultaneously replaced with distilled water using
another 60-m1 syringe and 18-gauge needle. The extracted gas was then injected into a
0.1 or 10 cc loop on the GC.
No detectable methane was found in either core from dive 3535 or dive 3538. For all
other cores, methane concentrations were low to non-detectable in the first 2 to 10 cm of
the sediment and then increased to levels of 970 to 30,000 nmoles CH4 ml` sediment by
10 to 18 cm depth. Highest methane values in sediment were observed in cores from
dive 3537.
6.4.2.3 Methane oxidation.
Samples for methane oxidation were taken on the same cores as described above for
methane analysis. Sediment samples were taken using a 3-ml disposable syringe with the
tip cut off from the surface of the core (0 to 1 cm) and every 2-cm section thereafter. 0.5
cc sediment subsamples were added to 7-ml septum vials to which previously degassed
(using UHP N2) seawater was added to each vial under no headspace was present prior to
addition of radiolabeled methane. Methane oxidation samples were returned to
Humboldt State University for subsequent extraction of all 14CO2 and 14C-cell carbon
using liquid scintillation counting as described above.
6.4.2.4 Foraminifera.
A total of 7 push cores were used in sampling for microscopic foraminifera. Aside
from the last two push cores sampled, each core was sliced up into 1/2cm intervals for the
first 6cm and then at lcm intervals from 6-12cm. The last two push cores sampled, both
from AD3537, were sliced in lcm intervals for the first 12cm. A piston and measuring
rings aided in this process. From each slice the sediment was placed into 125ml nalgene
bottles labeled with coring site and centimeter depth from core. After 12cm was reached
the core was sliced into 4cm intervals and stored in ziploc bags. After all samples were
taken formalin containing rose bengal was added, about a half an inch per bottle, to
preserve and stain the forams. Samples are summarized in Table 8.
Table 8. Samples for foraminifer studies.
Station: AT0003-7AD3534-PC-13
Date: Mar-29, 2000
Core Diameter:
Number of Samples: 17
Sample Depths: 0-6cm at 0.5cm intervals
6-10cm at lcm intervals
10-10.5cm
20
Station AT0003-10AD3535-PC-13
Date: Mar-30, 2000
Core Diameter:
Number of Samples: 19
Sample Depths: 0-6cm at 0.5cm intervals
6-12cm at lcm intervals
12-15cm
Station: AT0003-10AD3535-PC-16
Date: Mar-30, 2000
Core Diameter:
Number of Samples: 19
Sample Depths: 0-6cm at 0.5cm intervals
6-12cm at 1 cm intervals
12-16cm
Station: AT0003-13AD3536-PC-14
Date: Mar-31, 2000
Core Diameter:
Number of Samples: 19
Sample Depths: 0-6cm at 0.5cm intervals
6-12cm at lcm intervals
12-14cm
Station: AT0003-13AD3536-PC-18
Date: Mar-31, 2000
Core Diameter:
Number of Samples: 19
Sample Depths: 0-6cm at 0.5cm intervals
6-12cm at lcm intervals
12-13cm
Station: AT0003-19AD3537-PC-4
Date: Apr-1, 2000
Core Diameter:
Number of Samples: 12
Sample Depths: 0-11cm at lcm intervals
11-13cm
Station: AT0003-13AD3536-PC-14b
Date: Apr-1, 2000
Notes:
solid debris in the topmost two
samples
Core Diameter:
Number of Samples: 14
Sample Depths: 0-12cm at lcm intervals
12-16cm
16-19cm
21
6.4.3 Bottom water samples
Two to four (1.71) Niskin bottles were mounted on Alvin, on the starboard side of the
sampling basket, with the purpose of sampling bottom water at the seep sites. Data from
these samples are listed in Table 9.
Table 9. Water samples collected by Niskin bottles during Alvin
dives.
Sample ID
EC02
pH
(mM)
02
CH4
NH4
(mill)
(uM)
AT0003-3AD 3533
Niskin 2
AT0003-3AD 3533
Niskin 6
2.405
7.60
1.675
(nM)
nd
2.406
7.60
1.419
nd
0.0
AT0003-7AD-3534
Niskin 5
AT0003-7AD-3534
Niskin 6
2.385
7.57
1.496
0.2
0.0
2.377
7.58
1.550
0.100
0.0
AT0003-10AD-3535
Niskin 3
AT0003-1 OAD-3535
Niskin 5
AT0003-1OAD-3535
2.360
7.57
1.461
28.5
0.0
2.393
7.56
1.536
12.1
0.0
2.388
7.61
1.453
5.3
0.0
1.535
15.2
0.0
4.6
Niskin 6
AT0003-13AD 3536
Niskin 3
2.413
AT0003 -19AD-3537
Niskin 2
AT0003 -19AD-3537
Niskin 3
AT0003 - 19AD-3537
Niskin 5
AT0003 - 19AD-3537
2.466
7.35
0.1
0.2
2.391
7.57
0.2
0.0
2.409
7.61
0.2
0.0
2.420
7.59
0.2
0.0
Niskin 6
6.4.4 Benthic Barrel (OSU)
The OSU benthic barrel is a cylindrical chamber with a large opening at the bottom
and a small opening at the top. The barrel is designed to sample sites that have active
fluid flow, by placing the barrel over a vent site thereby channeling the effluent from the
seafloor into a semiclosed environment. The bottom of the barrel is open and can be
pushed into the sediments to assure a seal over the vent sites. The barrel encloses 0.26 m2
of the bottom surface area and has an internal displaceable volume of 180 1. The internal
volume of the barrel is initially flooded with ambient seawater and is slowly replaced by
venting fluids. Six Niskin water bottles (1.7 L) are mounted vertically around a
cylindrical polycarbonate frame, and they are tripped sequentially by a motor located in
22
the center of the frame. Changes in the concentration of dissolved components in the
sequentially timed water samples are then used to calculate their flux rates (Carson et al.,
1990). The exhaust port at the top of the chamber is designed to accept a thermistor
flowmeter. A complete description of this instrument and its operation can be found in
Linke et al., 1994. This instrument was deployed three times during this cruise. The data
collected during these deployments is summarized in Table 10.
Table 10: Analysis of samples from barrel deployments
Deployment AT0003-7AD3534
Barrel deployed on the scarp immediately adjacent to tubeworm thicket.
X=1534
Y=2200
Z=1796
Bottle#
Time since
engagement
Oxygen
(mill)
ECO2
(mM)
(nM)
CH4
Notes
(minutes)
1
5
1.947
2.382
8.1
no sub
2
10
1.965
2.390
7.6
nav.
3
23
79
108
144
1.995
2.121
1.990
1.999
2.386
2.378
2.381
2.360
7.3
4
5
6
7.5
7.7
Deployment AT0003-10AD3535
Barrel deployed next to tube worms and clam shels on the escarpment
X=1526
Y=2211
Z=1805
Bottle#
Time since
engagement
(minutes)
Oxygen
ECO2
CH4
(mill)
(mM)
(nM)
Notes
1
5
1.842
2.39
351
no sub
2
10
1.854
2.379
568
nav.
3
23
59
2.385
2.392
2.439
2.403
3670
4
5
83
1.847
see book
1.439
6
143
1.721
28800
22700
Deployment AT0003-13AD3536
Barrel deployed at the base of the scarp over small patch of living clams
X=2618
Y=1375
Z=1848
Bottle#
Oxygen
ECO2
CH4
(mill)
(mM)
(nM)
1
Time since
engagement
(minutes)
0
1.731
2.391
4.7
good sub
2
1
1
4
1
5
1
2.7
5.0
47.6
64.9
6
1
2.384
2.376
2.381
2.385
2.375
nav.
3
1.644
1.696
1.701
1.698
1.786
23
Notes
6.4. 5. Benthic landers
We deployed a singular incubation chamber similar to that designed by Berelson and
Hammond (1986), both at the seep sites as well as on background stations on the San
Clemente whale fall. This lander design is relatively simple. It has an aluminum frame,
PVC-constructed chamber, a stirring motor, and gasket material for sealing the chamber
lid to the chamber. Nine samples are to be collected during incubation-including one for.
bottom water; however during these deploymnets we did not always collect all nine
samples due to technical problems with the firing of the syrin ges. Samples are collected
at preprogrammed times via a computer housed inside a pressure case. Sample collection
is initiated by an electrical signal originating from the computer (i.e. a burn wire).
Chamber volume will be determined by analysis of CsCl concentration, which was
injected as "tracer" spike of known concentration in all deployments. The benthic landers
were deployed at seep sites, at the base of the escarpment and on the San Clemente basin.
Preliminary results from these deployments are listed in Table 11.
Table 11: Results from lander deployments
DEPLOYMENT: AT0003-07AD-3533-BROWN
Lander deployed near tube worm thicket on the scarp wall
Date Time Mrs
Deployment
date
Sample
3/28/00
AT003-7AD-
28-
3534-1R
Mar
Recovery date
3/29/00
ECO2
pH
mm
AT003-7AD-
28-
3534-2R
Mar
AT003-7AD-
28-
3534-3R
Mar
AT003-7AD-
29-
3534-4R
Mar
2.332
7.604
02
.t M
NH4
75
0.0
Comments
µM
1730
0
2030
3
did not fire
2330
6
did not fire
230
9
2.243
7.561
69
0.0
AT003-7AD-
29-
530
12
did not fire
3534-5R
Mar
29Mar
830
15
did not fire
AT003-7AD-
29-
1130
18
did not fire
3534-7R
Mar
1430
21
AT003-7AD3534-6R
AT003-7AD-
29-
3534-8R
Mar
2.359
24
7.517
51
1.6
DEPLOYMENT: AT0003-13AD-3536-BROWN
Landerdeployed at the base of the scarp on a "background" site
Deployment
date
Sample
Date Time Hrs EC02
pH
mm
3/31/00
AT003-13AD3536-1B
Recovery date AT003-13AD3536-2B
4/1/00
AT003-13AD3536-3B
AT003-13AD3536-4B
AT003-13AD3536-5B
AT003-13AD3536-6B
AT003-13AD3536-7B
AT003-13AD3536-8B
31-
Mar
31Mar
31Mar
1-
02
NH4
µM
µM
1530
0
2.324
7.571
58
1830
3
-0.001
7.573
191
DID NOT FIRE
2130
6
2.308
7.566
87
0:30
9
2.347
7.578
62
3:30
12
2.339
61
Tube
disconnected
Tube
disconnected
Tube
disconnected
630
15
2.362
46
930
18
2.363
7.556
1230
21
2.367
7.57
53
ECO2
ECO2
pH
Apr
1-
Apr
1-
Comments
Apr
1-
Apr
1-
Tube
disconnected
Apr
DEPLOYMENT: AT0003-13AD-3536-RED
Lander deployed at tubeworm
site on the scarp wall
Deployment
date
3/31/00
Sample
AT003-13AD3534-1R
Recovery date AT003-13AD3534 -2R
4/1/00
AT003-13AD3534-3R
AT003-13AD3534-4R
AT003-13AD3534-5R
AT003-13AD3534-6R
AT003-13AD3534-7R
AT003-13AD3534-8R
Date Time Hrs
H
mm
L
pH
from
mm
CO2
02(uM)
vials
31-
1530
0
2.342
2.361
7.592
7.498
56
1730
2
2.347
2.331
7.573
7.52
54
1930
4
0.009
0.026
7.307
7.699
261
2130
6
2.297
7.558
0:30
9
2.054
2.280
7.577
7.478
73
330
12
2.209
2.321
7.573
7.478
57
630
15
2.367
7.573
930
18
2.373
7.578
Mar
31-
Mar
31-
Mar
31-
62
Mar
1-
Apr
1-
Apr
1-
18
Apr
1-
Apr
25
2.378
7.525
26
DEPLOYMENT: AT0003-22AD-3538-BROWN
Lander deployed at San Clemente Basin, whale site
Deployment
date
Sample
Date Time Hrs
EC02
pH
mM
AT003-22AD3538-1B
Recovery date AT003-22AD3538-2B
4/3/00
AT003-22AD3538-3B
AT003-22AD3538-4B
AT003-22AD3538-5B
AT003-22AD3538-6B
AT003-22AD3538-7B
AT003-22AD3538-8B
4/2/00
2-
02
NH4
µM
µM
1530
0
2.387
7.496
26
0.0
1830
3
2.381
7.576
69
0.0
2130
6
2.374
7.574
78
0.0
0:30
9
2.381
7.582
51
0.0
3:30
12
0.031
7.889
630
15
2.381
7.598
47
0.0
930
18
2.390
7.569
61
0.0
1230
21
2.390
7.582
44
0.0
EC02
pH
02
µM
NH4
Comments
Apr
2-
Apr
2-
Apr
3-
Apr
3-
0.6
Apr
3-
02 Greater
than120 uM
Apr
3-
Apr
3-
Apr
DEPLOYMENT: AT0003-22AD-3538-RED
Lander deployed on San Clemente Basin
Deployment
date
Sample
AT003-22AD3538-1R
Recovery date AT003-22AD3538 -2R
4/3/00
AT003-22AD3538-3R
AT003-22AD3538-4R
AT003-22AD3538-5R
AT003-22AD3538-6R
AT003-22AD3538-7R
AT003-22AD3538-8R
4/2/00
Date Time Hrs
mm
2-
Comments
µM
1530
0
2.389
7.58
56
0.0
Apr
2-
1830
2
2.379
7.57
59
0.0
Apr
2Apr
2130
4
2.161
7.59
105
0.0
60
0.0
3-
0:30
6
2.356
7.57
Apr
3Apr
3:30
9
2.350
7.57
3-
630
12
2.378
7.57
57
0.0
930
15
2.385
7.57
74
0.0
1230
18
2.403
7.57
44
0.0
0.0
Apr
3-
Apr
3-
Apr
26
02 No sample
APPENDIX 1
MULTICORE LOGS AND PORE WATER DATA
TABLE 3: MULTICORE STATION SUMMARY
DATE
29-Mar
TIME
STATION
3:00 AT0003-2MC
Let
Long
north
west
Multicore deployed at base of the 32 13.455 117 46.607
Depth
meters
1847
Cor e Tube Number
escarpment, 5 Km from seeps.
Only recovered 5 of the 8 cores.
Core #8 was lost on deck
30-Mar
3:00 AT0003-6MC
3:00 AT0003-12MC
117 42.5
B
r
t
e
N
A
r
N
A
0
P
r
o
r
r
I
hC
a
m
s
S
e
v
d
e
L
o
s
t
S
A
i
e
d
0
i
r
c
h
I
m
e
I
i
e
r
0
32 10.725 117 48.734
B
F
0
r
a
m
s
i
w
a
t
v
e
e
r
S
P
o
e
0
r
e
B
0
F
0
d
W
i
A
r
c
a
I
r
m
h
i
t
a
m
s
i
e
o
9
e
t
n
v
e
s
I
t
o
g
n
V
t
e
1897
P
r
0
s
32 04.177 117 31.048
At the entrance to the canyon;
32 36
compressional section of the
fault Same location as McManus
cores in 1992 and 1995.
i
r
S
e
t
A
r
c
h
v
e
1540
P
P
o
o
r
r
e
o
s
w
a
i
t
t
e
r
2:00 AT0003-21MC
A
o
w
a
t
3-Apr
i
F
0
e
A
n
Pull-apart basin, as close to the
scarp as possible
8
P
m
e
2:30 AT0003-17MC
7
6
1766
d
i
2-Apr
5
o
M
e
t
h
a
n
e
Over the scarp, on a small
32 13.4
topographic high near the top of
the scap. Probably some turbidite
deposits
Multicore 10 km from seep, not
on turbidite fan
4
P
r
c
h
1-Apr
3
2
1
118 06.0
NOTES: NR= not recovered;
Porosity samples taken to LLO
Methane analyses and pore water extraction conducted onboard;
Forams samples and archive cores taken to OSU;
-Samples procesed for biology to U. Hawaii;
Sediment analyses for provenance studies to be conducted by Elena Centeno Garcia at UNAM
A
F
0
r
a
m
s
r
c
S
e
d
A
A
r
c
i
r
c
h
m
h
I
v
e
n
v
v
e
t
e
e
h
I
2048
P
P
o
o
r
r
e
0
s
i
t
S
e
d
W
A
r
c
A
r
c
a
h
h
r
c
h
t
I
I
i
e
v
v
v
m
a
n
r
e
e
e
t
A
PORE WATER ANALYSES FOR MUL71CORE SAMPLES
STATION AT0003-02MC
Tube#
Sample# vol of mud
7-Depth
Depth
(cm)
1
2
3
4
5
6
7
8
9
1 0
11
12
13
14
15, 16
17, 18
19, 20
21, 22
23, 24
2MC-OW
2MC-1
2MC-2
2MC-3
2MC-4
2MC-5
2MC-6
2MC-7
2MC-8
2MC-9
2MC-10
2MC-11
2MC-12
2MC-13
'2MC-14
2MC-15
2MC-16
2MC-17
2MC-18
2MC-19
35
35
50
50
50
50
50
50
50
50
50
50
50
50
100
100
100
100
100
STATION AT0003-06MC
Tube#
Sample# vol of mud
1, 2
6MC-1
6MC-2
6MC-3
5
6MC-4
6
6MC-5
7
6MC-6
8
6MC-7
9
6MC-8
10
6MC-9
11
6MC-10
12
6MC-11
13
6MC-12
14, 15
6MC-13
16, 17
6MC-14
18, 19
6MC-15
20, 21, 22 6MC-16
23, 24
6MC-17
3
4
74
50
50
50
50
50
50
50
50
50
50
50
100
100
100
150
100
0.48
0.96
1.65
2.34
3.03
3.72
0.24
0.72
ECO2
pH
NH4
(uM)
7.510
7.480
7.466
7.582
7.464
7.502
7.546
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.5
1.7
5.3
8.3
9.4
12.4
15.3
20.4
7.571
23.1
27.9
(mM)
2.370
2.478
2.511
1.31
2.492
2.00
2.69
3.37
4.06
4.75
5.44
6.13
6.82
2.561
2.579
2.556
2.556
2.613
2.626
2.562
2.649
7.51
2.631
11.98
13.36
14.74
16.12
8.20
8.88
9.92
11.29
12.67
14.05
15.43
2.656
2.657
2.693
2.696
2.729
2.789
7.537
7.556
Depth
Depth
ECO2
pH
NH4
(cm)
0.51
1.36
2.05
2.74
3.43
4.12
4.81
5.50
6.18
6.87
7.56
8.25
9.28
10.66
12.04
13.76
15.48
(mM)
2.471
2.581
7.565
4.00
2.50
1.50
2.50
7.50
11.25
12.80
15.25
18.25
4.41
5.10
5.79
6.47
7.16
7.85
8.54
9.23
10.61
1.02
1.71
2.40
3.09
3.77
4.46
5.15
5.84
6.53
7.22
7.91
8.60
9.97
11.35
12.73
14.79
16.17
2.771
2.612
2.663
2.623
2.659
2.717
2.714
2.771
2.729
2.753
2.848
2.864
7.491
7.537
7.514
7.512
7.505
7.505
7.502
7.507
7.529
7.531
29.1
(uM)
7.541
7.611
7.541
7.483
7.461
7.449
7.422
7.425
2.831
7.410
7.435
7.422
7.439
7.500
2.981
7.461
19.00
27.00
27.80
34.00
38.25
42.25
STATION AT0003-12MC
Tube#
Sample# vol of mud
JDepth
Depth
(cm)
1
2
3
4
5
6
7
8
9
1 0
11
12
13
14
15
16
17, 18
19, 20
21, 22
23, 24
12MC-OW
12MC-1
12MC-2
12MC-3
12MC-4
12MC-5
12MC-6
12MC-7
12MC-8
12MC-9
12MC-10
12MC-11
12MC-12
12MC-13
12MC-14
12MC-15
12MC-16
12MC-17
12MC-18
12MC-19
12MC-20
37
37
50
50
50
50
50
50
50
50
50
50
50
50
50
50
100
100
100
100
STATION AT0003-17MC
Tube#
Sample# vol of mud
0.51
1.02
1.71
2.40
3.09
3.77
4.46
5.15
5.84
6.53
7.22
0.25
0.76
1.36
2.05
2.74
3.43
4.12
4.81
8.60
9.28
9.97
10.66
12.04
13.42
14.79
16.17
5.50
6.18
6.87
7.56
8.25
8.94
9.63
10.32
11.35
12.73
14.10
15.48
Depth
Depth
7.91
(cm)
1
2
3
17MC-OW
17MC-1
17MC-2
17MC-3
4
5
6
7
8
9
10
11
12
13
14
15,16
17, 18
17MC-4
17MC-5
17MC-6
17MC-7
17MC-8
17MC-9
17MC-10
17MC-11
17MC-12
17MC-13
17MC-14
17MC-15
38
38
50
50
50
50
50
50
50
50
50
50
50
50
100
100
0.52
1.05
1.74
2.42
3.11
3.80
4.49
5.18
5.87
6.56
7.25
7.93
8.62
9.31
10.69
12.07
0.26
0.79
1.39
2.08
2.77
3.46
4.15
4.83
5.52
6.21
6.90
7.59
8.28
8.97
10.00
11.38
ICO2
(mM)
pH
2.367
2.483
2.485
2.543
2.572
2.603
2.633
2.630
2.648
2.660
2.674
2.673
2.710
2.696
2.718
2.684
2.715
2.760
2.764
2.809
2.834
7.566
7.488
7.491
7.541
7.479
7.478
7.476
7.496
7.499
7.503
7.486
7.511
7.518
7.531
7.523
7.568
7.521
7.558
7.55
7.545
NH4
(uM)
0
2.154
2.154
0.615
0
0
0
1.231
8.41
6.359
10.462
11.487
.20.718
20.718
20.718
23.795
26.872
28.923
32
35.59
NH4
EC02
(mM)
pH
2.389
2.433
2.477
2.498
7.549
7.524
7.522
0
0
0
7.531
0.778
2.613
2.640
2.690
2.718
2.742
2.764
3.085
7.509
7.464
7.447
7.439
7.44
7.422
7.422
7.422
7.423
7.434
7.442
7.473
2.444
2.821
2.870
2.871
2.870
2.854
(uM)
9.111
13.778
20.444
24.889
30.444
36.56
39.333
43.78
47.111
51.556
59.333
19, 20
21, 22
23, 24
17MC-16
17MC-17
17MC-18
100
100
100
STATION AT0003-21 MC
Tube#
Sample# vol of mud
13.44
14.82
16.20
12.75
14.13
Depth
Depth
15.51
(cm)
2.900
2.960
3.016
7.495
7.495
7.505
ICO2
(mM)
pH
64.889
70.444
83.778
NH4
(uM)
APPENDIX 2
ALVIN DIVE LOGS
Alvin Dive Log
Dive number:
3533
San Clemente scarp
Area:
Date:
Bottom time:
Pilot:
Port observer:
Starbord observer:
Origin of XY coord.:
28 March 2000
2.5 hrs
Blee Williams
Marta Torres
Chris Goldfinger
32° 12'N; 117° 44'W
Objectives:
Survey of north section of scarp at 1800 m; search for evidence of active
fluid venting (live clam colonies, tube worms). Deploy benthic lander at
the base of the scarp. Deploy benthic barrel on a clam bed on scarp. Take
push cores near tube worm thicket- 8 in all. Sample active fluid vents with
Niskin bottle. Sample clams and tube worms
Summary:
Deployed benthic lander. Sampled barite from the seafloor and 2 Niskins.
Alvin had problems with propulsion and ballast control, which made the
operations very difficult and slow.
Time
X
Y
11:55
12:29 1591 1852
13:25
13:30
13:43
13:49
13:58
14:00
14:28
15:07
15:11
Alvin launched
307 m from target bearing 350, at 700 in water depth
Alvin on bottom, but no nav data on sub, water depth 1809 in
Soft sediment with bioturbation and white starfish
Bottom of the slope. Observed disarticulated shells and tube
worms
Area with few tube worm fields, not too steep. Prepare to deploy
lander at 1795 in
Fire Niskin #2 as bottom water sample over the lander site.
Observe benthic fauna: large anemone, white starfish, seaspider,
lots of bioturbation
Lander on the seafloor
Lander tipped over. Observed that motor still turning
Redeployed lander, approximately 1 meter from thicket. Flasher
still flashing. All systems in lander seem to still operate normally.
Sub experiencing problems with ballast control. No nav data either
Heading 130 at 1800 in contour past more clam shells, galatea
crab. Left animal community. Observe break in slope. More clam
shells on bottom
Heading 310 water depth 1794
Water depth 1812. Upslope due north. Bottom very lumpy, lots of
15:12
15:24
15:26
15:34
15:39
15:44
bioturbation, lots of shrimp. Holothurians
Heading 025 directly upslope. Lots of holothurina tracks,
gastropods
Trip Niskin #6 in clear water
Barite on the seafloor on port side. Beautiful community, cannot
get video because sub had propulsion problems and we are running
out of time. Sampled barite, nice big piece.
More barite deposits with living things on them indicative of food
source. Tried to sample holothurian but got too cloudy and the
pilot had trouble with sub controls
Bridge call to terminate dive
All weights away. Tried to fire the remaining Niskins on the way
up, but pilot could not see them with camera. End of dive
Sheets
BOTTOM SEDIMENT SAMPLE SUMMARY SHEET
AT0003-49
AD 3533
CRUISE:
STATION
DATE
Dive
3/28/00
Time
Type
Depth
X
Y
OBSERVERS
Torres/Goldfinger
PILOT
SITE
Blee Williams
seep © 1800m on northern end of scarp
Lat
Long
Comments
Station
1
13:49
N
1806
1540
2196
32°13.188'N
117°43.020'W
bottomwater over lander site
2
14:28
L
1808
1537
2195
32°13.188'N
117°43.020'W
lander app. 1 m from thicketbarite. All lander systems looked OK
3
15:24
N
1812
1490
2188 32°13.184'N
117°43.052'W
Clear water over barite concentration
with lots of benthic life
TYPE:
BC=BENTHIC CHAMBER
APC=ALVIN PUSH CORE
N=NISKIN BOTTLE
BB=BENTHIC BARREL
GR=GRAB SAMPLE
*Note: Alvin had no navigation - the ositions and depths are from ships ACNAV
Page 1
Alvin Dive Log
Dive number:
Area:
Date:
Bottom time:
Pilot:
Port observer:
Starbord observer:
Origin of XY coord.:
3534
San Clemente scarp
29 March 2000
5.5 hours
Bob Brown
Mark Legg
Marie de Angelis
32° 12'N; 117°44'W
Objectives:
Retrieve lander from dove 3533; deploy benthic barrel near barite deposit or
tubeworm thicket. Take push cores at 0 meters and 1 meter from tubeworm
thicket; collect barite, clams and tubeworms; conduct a survey from seep site
southeast towards "cove" at 1800 meters and return along 1750 meters; return
to seep site; take Niskin samples, retrieve lander and benthic barrel.
Summary:
Checked placement and seal of lander; deployed benthic barrel; took 2 Niskin
samples near benthic barrel site; collected barite and tubeworms, took 8 push
cores near barrel site; conducted survey at various locations along scarp;
retrieved lander and benthic barrels.
Time X
08:27
08:33
09:57
09:58
10:07
10:35
10:55
11:16
11:20
11:25
11:28
11:32
11:36
11:43
11:50
12:00
Y
Alvin launched
Commence dive
Start video taping
°
Arrived at bottom; 53 m from target, bearing 326; depth 1799 m; many brittle
stars, isolated tubeworms but no thickets
Sighted lander on a slight slope; checked seal on both sides with 3-chip camera;
depth 1796 m
Found good tubeworm thicket with relatively good slope for benthic barrel
placement; sampled water with Niskin #5 (furthest aft); 1796 meters; benthic
barrel deployed immediately adjacent to tubeworm thicket.
Benthic barrel engaged. Lander bears 150 from barrel; both lander and benthic
barrel in sight
Began pushcore sampling starting from large tubeworm thicket with yellow and
white tubeworms. Pushcore #2 (forward, furthest port) taken at base of
tubeworm thicket (0 meters).
Push core #13 (aft, furthest port) (0 meters from thicket), 1796 meters;
repositioned submersible
Push core #5 (forward, 2nd from port) 0 meters from thicket, 1796 meters
Push core #14 (aft, 2nd from port) 0 meters from thicket, 1796 m
Push core #8 (forward, 2nd from starboard), 0 meters from thicket, 1796
meters
Push core #15 (aft, 2nd from starboard), 1 meter from thicket, 1796 meters
Push core #10 (forward, furthest starboard), 1 meter from thicket, 1796 meters
Push core #17 (aft, furthest starboard), 1 meter form thicket, 1796 meters
Began collections of tubeworms and barite immediately in front of push core
locations; used clam scoop to retrieve barite pieces which were too crumbly to
pick up by manipulator; benthic barrel forward of this location at bearing of
035; sponges noted on a large number of tubeworms - took digital stills of
12:04
12:29
12:33
12:45
13:03
13:21
13:25
13:43
13:50
14:50
14:52
14:59
15:25
15:33
some. Pilot noted that Niskins may have muddy bottoms due to contact with
bottom
Change video tapes
Began survey SE along 1800 contour. Set still camera at 60 sec auto trigger
Reached crest of ridge along scarp
Heading upslope; mud, mud, more mud with sprinkling of brittle stars
Turned northwest at heading of 320; 1740 meters; mud and more mud
Heading straight north; more mud
Skeleton (raffish???) observed off port side; took digital stills; mud continues
Commenced turn west heading 220; lots o' mud
Strange seafloor object, small green cylinders arranged in pattern like a skeleton
Returned to lander site; took water sample with Niskin #6 near barrel
approximately SW of barrel along same depth contour, 1794 meters
Benthic barrel recovered, 1795 meters; note: benthic barrel rolled downslope
around 20 meters.
Lander recovery begun, 1796 meters
Lander recovery complete
Left bottom
Sheets
Bottom sample record
AT0003
AD 3534
CRUISE:
STATION
DATE
Dive
3/28/00
Time
Type
Dept h
X
Y
10:35
N
1805
1536
2199
OBSERVERS
deAn elis/Le
PILOT
SITE
Bob
seeps
Station
1
2
3
4
5
6
7
8
9
10
11
12
10:54
11:16
11:20
11:25
11:28
11:32
11:36
11:43
11:50
12:00-12:28
14:50
BB
1534
2200
APC
no nav
no nav
no nav
no nav
no nav
no nav
no nav
no nav
no nav
no nav
no nav
no nav
no nav
no nav
1533
1530
1535
2197
2194
2207
APC
APC
APC
APC
APC
APC
APC
Cfi
N
1805
1805
1815
TYPE.
BC=BENTH IC CHAMBER
APC=ALVIN PUSH CORE
BB=BENTHIC BARREL
N=NISKIN BOTTLE
Lat
Long
Comments
Niskin #5, furthest aft, prior to BB deployment near
benthic barrel deployment site
on slope; u slo e & adjacent to tubeworm thicket
core #2 forward; furthest port, Om from thicket
core #13 aft; furthest port, Om from thicket
core #5 forward; 2nd from port, Om from thicket
core #14 aft; 2nd from port, Om from thicket
core #8 forward; 2nd from stbd, Om from thicket
core #15 aft; 2nd from stbd, Om from thicket
core #10 forward; furthest stbd, 1 m from thicket
core #17 aft; furthest stbd, lm from thicket
collected tubeworms, barite crumbs
Niskin #6 furthest forward; near BB-at some depth SW
GRRAB SAMPLE
Note: 1. All nav points are ACNAV from ship - no sub fixes
2. All samples were taken within a few meters of each other
Page 1
Alvin Dive log
Dive Number:
Area:
3535
San Clemente scarp
Date:
30 March 2000
Pilot:
Port Observer:
Starboard Observer:
Start Location:
Bruce
Chris Goldfinger
Bronwen Cumberland
X: 1528
Y: 2209
Z: 1797
Waypoint:
Summary:
X: 2780
Y: 1347
Found location to deploy Benthic barrel, near tube worms and clam shells. Before
placing barrel, 2 Niskins were fired. Four Push Cores were taken zero meters from
the barrel. Five Push Cores were taken one meter from the barrel. An additional
five Push Cores were taken at the bottom of the scarp, about 30 meters from the
barrel. Transit to Waypoint #2 (Shelter Cove) to explore area. Several grab samples
were taken along transit. Traversed along fault scarp. Drove down to bottom of
cove. One Niskin was fired, while returning to the barrel site. Benthic barrel was
picked up, before returning to the surface.
Time
08:00
09:15
09:22
09:23
09:26
09:32
09:45
09:47
09:56
10:00
10:08
10:12
10:17
10:19
10:28
10:30
Alvin free of ship
40 meters from surface; video tapes started
Reach bottom
Depth: 1808 meters
Surface gives vector 024 for 60 miles; begin traverse
Reach barrel target site; big thickets of tube worms, disattriculated clam shells,
scattered gastropods; depth: 1805 meters
Fired Niskin Bottle (#3)
Fired Niskin Bottle (#5); wait for sediment to clear before deploying barrel
Barrel deployed (next to a cluster of tube worms)
Barrel started; digital picture taken of barrel
Push core taken 0 meters from barrel - first port-side tube; not filled
Push core taken 0 meters from barrel - second port-side tube
Push core taken 0 meters from barrel - third port-side tube (marked #4)
Push core taken 0 meters from barrel - fourth port-side tube (marked #6)
Push core taken 1 meter from barrel - fifth port-side tube (marked #18); cores taken
from port side; digital picture taken of site
Push core taken 1 meter from barrel - sixth port-side tube (marked #16)
10:34
10:37
10:40
10:45
11:06
11:09
11:12
11:15
11:19
11:20
11:24
11:32
11:49
11:53
12:03
12:06
12:17
12:23
12:32
12:34
12:41
12:44
12:46
12:50
12:59
13:00
13:07
13:10
Push core taken 1 meter from barrel - seventh port-side tube (marked #4B or #46?);
core contains clamshell
Push core taken 1 meter from barrel - eigth port-side tube; core contains clamshell
Push core taken 1 meter from barrel - ninth port-side tube;
Attempted to take a low-temperature reading, but were unable to free temperature
probe ; window temperature is 2.6oC
Depth: 1815 meters; -30 meters downhill from barrel site at bottom of scarp; push
cores taken at this site, from starboard side
Push core taken - tenth port-side tube (marked #8B)
Push core taken - eleventh port-side tube
Push core taken - twelve port-side tube (marked #13)
Video tapes changed
Push core taken - thirteenth port-side tube (marked #15)
Push core taken - tube farthest starboard, inboard row (marked #14?)
Decide to save two push cores; prepare for departure to Shelter Cove
Driving 124, along base of scarp; Depth - 1799 meters; received range and bearing
from surface - 1500 meters from plunge pool
Crossed an Alvin track - perpendicular to course; continue to drive along scarp at
125; scarp is heavily sedimented, no sign of seeps or active scarp
Find small area of clams, two worm clump (sparse)
View outcrop: striking 130, exposed bedding, possible fault scarp exposure
Passed scarp exposure (-im in height), some fresh slumping, horizontal bedding,
lighter colored horizon at base of slope (probably Holocene), along fault trend
View of Holocene fault scarp on 3-Chip camera; lower, lighter horizon may be
Pleistocene
Continue to take pictures of Holocene fault scarp (possible Pleistocene base); View
in pan and tilt camera: where the scarp is slumping off, the slump blocks are
breaking off in little sheets parralel to the main scarp - it looks sheared
In video: shearing; Have not seen striations along scarp to indicate fault motion;
Grap Sample: placed in smaller (port-side) box, two clay chunks from near base of
scarp; Continue driving 130, continue to see discontinuous bits of scarp
Pass another small patch of scarp
Pass another small patch of scarp, appears hummocky
Stopped at vertical outcrop, light and dark bands, no apparent associated venting,
(several meters high, 300 meters, 131, from Waypoint 2)
Continue driving: begin to see vertical steps down to the southeast
Clams, clumps of tube worms; Depth of 1823; sparse, but more clams than at
previous sites
Stopped 120 meters from the corner (according to SeaBeam) of Shelter Cove;
Outcropping bedding in gullies trending perpendicular to fault
Grab Sample: taken from vertical wall, placed in white box
Sitting at fault scarp, vertical bedding or jointing striking N40W magnetic(Brunton),
30 -40 degree angle to the trend of the slope; trend of slope appears to be (locally)
170; either shearing or jointing (because bedding looks close to horizontal); Digital
picture #19 taken directly along trend of joints/shears; Vertical shears off-setting
wall; wall begins to wrap around to the east
13:19
13:23
13:25
13:33
13:43
13:47
13:55
14:00
14:06
14:13
14:28
14:42
14:48
15:31
15:36
15:46
Follow wall along heading of 090 (heading into Shelter Cove); dead clams
Passed a possible bullet
Major vent site at corner of Shelter Cove (bacteria, tube worms, clams)
Wall of barite (several meters high); Depth: 1794; trend is almost N-S
Heading 110, back down into plunge pool; crossing step-downs, perpendicular to
our course (to the east) trending 020
Driving 110, vertical drop-off, all is trending NE
Possible bottom of Shelter Cove; Depth: 1850 meters
Turned around, driving 290 (out of Shelter Cove)
Gully running N-S; bearing to Waypoint 2 (to Shelter Cove entrance) is 280, range
of 200m
Bedding has a gentle east dip, 200 meters from Waypoint 2
Passed another barite outcrop; Depth: 1812 meters; Driving 310
Fire Niskin #6 (in open water column, during transit back to barrel site)
Heading 300; Depth 1814 meters
Reached the barrel; there seems to be silty water venting out of the push core holes
Recovered barrel
Begin ascent to surface; Depth 1783 meters
Sheetl
Bottom sam pie record
CRUISE:
STATION
DATE
Dive
AT0003
AD 3535
OBSERVERS
PILOT
Bruce
3/30/00
SITE
scarp
Type
Depth
x
Y
9:45
9:47
9:56
10:08
10:12
10:17
10:19
10:28
10:30
10:34
10:17
11:09
11:12
11:15
11:20
11:24
12:34
1525.7
1525.7
1525.8
1524.9
1525.9
1524.6
1525.5
1524.5
2210.9
2210.9
2211.9
2211.6
2210.9
2211.1
2211.3
2210.1
2210.7
2212.4
2207.6
2198.9
2199.1
2199.1
2199.9
2199.1
GR
1805
1805
1805
1805
1805
1805
1805
1805
1805
1805
1805
1815
1815
1815
1815
1815
1790
13:07
GI
1816
2554.5
1540.3
1812
2554.2
2163.3
1540.8
1799.1
Time
Goldfin er/Cumberland
Let
Long
Comments
Station
1
2
3
4
5
6
7
8
9
10
11
12
13
14
13:10
14:42
TYPE:
APC=ALVIN PUSH CORE
BB=BENTHIC BARREL
Note: Alvin had no navi
1525.1
1525.0
1525.6
1499.5
1499.1
1498.8
1498.3
1498.6
2219.4
Niskin #3
Niskin #5
Barrel deployed
Push core # , Om from barrel - not filled
#9, Om from barrel
#4, Om from barrel
#6, Om from barrel
#18, 10m from barrel
#16, 1m from barrel
#4b, 1m from barrel, contains clamshells
1m from barrel
#8b, background, bottom of scarp
background, bottom of scarp
#13, background
#15, background
#14, background
Two clay chunks from near base of scarp
Clay from vertical wall, on white box
Digital picture
Niskin #6 - open water column
1778.1
BC=BENTHIC CHAMBER
N=NISKIN BOTTLE
GR=GRAB SAMPLE
tion - the positions and depths are from ship's ACNAV
Page 1
Alvin Dive Log
Dive number:
3536
San Clemente scarp
Area:
Date:
Bottom time:
Pilot:
Port observer:
Starbord observer:
Origin of XY coord.:
31 March 2000
5.5 hours
Bob Walters
Marta Torres
Brian Haley
32° 12'N; 117° 44'W
Objectives:
Deploy barrel on seeps near the cove on scarp. Retrieve landers
from the elevator and deploy one at a seep site, and another on
background sediments. Sample sediments,clams and barite from the
instrumented sites. Survey the cove if time permits.
Summary:
Deployed barrel on clam site at the base of the slope which appears
to reflect a different type of venting. Deploy the landers on wormrich site and background station. Sampled surface sediments and
clams.
Time
08:00
08:02
08:37
09:32
X
Y
2766 1429
10:18
10:23
2644 1427
2571
1420
10:26
10:28
10:34
10:48
10:51
2575
2575
2581
2646
2675
1438
1438
1509
1455
1451
11:06
2774 1444
28:09 1458
11:19
2849 1449
11:49
2618 1375
11:57
Latched sealed
Alvin launced at 1803 m altitude
Alvin @ 600 m
Arrived at bottom; sloping seafloor, with barite exposed at the
seafloor. Heading 275, target at 70 m. However the target is on
Winfrog, and Alvin's nav is offset from this reading. Decided to
approach the search following the scarp.
c/c due west for 100 m.
c/c heading 90 towards the scarp. Smooth sediment with lots of
bioturbation.
Statring upslope, not very steep yet. Shell debris and Galatea crab
Rocky outcrop at 1844m. Small tube worm patches ahead.
More shell shot and tube worms. c/c 130
c/c 110
1819 m. Found Niskin bottels at the seafloor. Realized they
belong to us and must have fallen from the basket. Retrieve
Niskins, and continue search for the tube worms site following
scarp.
1815 m. Clear fault trace at the bottom of the scarp, which we
follow into the cove
Fault trace still at 1815 m, turning starboard to the other end of the
cove. Big gastropod.
c/c to to restart the search for the seeps again from the norhteast.
1830 m.
Found a clam site at the bottom of the scarp. Several dead shells
and few live ones indicative of active venting. The area looks good
for barrel deployment. Tripped Niskin forward on port side, and
deploy barrel.
Engage Barrel
12:04
12:08
12:14
12:26
13:10
13:20
13:26
13:34
13:39
13:45
13:55
14:19
14:24
14:29
14:30
14:40
14:46
14:47
2618 1375
Push core #9 and #10 on sediments app. 1 meter from the barrel on
clam field.
2623 1377 Sample clams and mud in biobox. Bob Thinks he got about 2
clams. Water depth 1848m.
Elevator at 120m heading 345.
2696 1505 Found elevator at 1809m
Elevator off. Heading for X=2555, Y=1540 at 260. No altimeter
and very cloudy
Bob got altimeter to work. Start to pump water to compensate for
added weight to the sub
2538 1467 Heading 260
2530 1473 Slope raising gradualy. 1847 in
2541 1540 Clams and tubeworms at 1825m
2552 1562 Tubeworms and barites on slope
2554 1566 Positioned Red lander on a sediment patch surrounded by lots of
big thickets of tubeworms at 1814m. Evidence of extensive barite
formation. Good video of tubeworms. Lander's pinch plate looks
fine, chamber is buried and motor is truning. Cannot see the door.
Sediment claoud to thick to see enough to core or sample barites.
2551 1473 Back to the base of the scarp at 1844. Looking for a background
site for brown lander. Pumping water.
2554 1464 1846 in. Waiting for mud to settle before deploying lander. There
is no current whatsoever, mud cloud just hangs on. Brian
observes a few dead tubeworms near the deployment site
2556 1461 Deployed Brown lander at 1845m. Could not see much.
Push core #18 app. 1 meter from lander
2553 1460 Push core #14b, 1 meter from lander at 1847m.
Too cloudy to continue sampling. head 100 towards the barrel.
14:48
2574 1444
2589 1439
14:53
2611 1430
Still on the flats looking for a location to sample more background
sediment.
Push cores 4,16,2 on background sediment at 1844. Barrel target
at 51 m heading 180.
14:58
2621
1846m
14:59
15:10
15:14
15:26
15:28
15:30
15:31
2621 1387
2618 1383
2618 1383
1408
2605 1372
1846m
Strobe on sight
Push core #18, 1 in from bareel. Fell on basket
Push cores #3,#17,#14,#15 all collected 1 m from barrel at 1848m
Retrieve the barrel. Too murky to ake digital picture.
Barrel in basket
Tripped last Niskin at barrel site. Too muddy.
Weights away. End of dive
BOTTOM SEDIMENT SAMPLE SUMMARY SHEET
AT0003-49
13AD 3536
31-Mar-00
CRUISE:
STATION
DATE
Type
Time
Dive
OBSERVERS
Torres/Haley
PILOT
Bob
San Clemente scarp
SITE
Depth
X
Y
Let
Comments
Long
Station
1
1149 N
1848
2618
1375 32-12.744'N
117-42.334'W
Niskin #6 forward on port side 0
barrel site
2
1157 63
1847
2618
1375 32-12.744'N
117-42.334'W
Deployed 0 site on bottom, on a
clam field, with only a few living
individuals; no tubeworms or
barite
3
1204 APC
1848
2618
1375 32-12.744'N
117-42.334'W
push core #9; 1m from barrel on
clam field
4
1204 APC
1848
2618
1375 32-12.744'N
117-42.334'W
push core #10; 1m from barrel
on clam field
5
1208 G
1848
2623
1377 32-12.744'N
117-42.334'W
sampled clams in biobox
6
1355 L
1814
2554
1566 32-12.847'N
117-42.375'W
7
1429 L
1845
2556
1461 32-12.790'N
117-42.373'W
positioned lander on sed patch
surrounded by tubeworm
thickets; evidence of barite
formation
brown lander on bottom of scarpbackground site
8
1430 APC
1845
2556
1461 32-12.790'N
117-42.373'W
9
1440 APC
1847
2553
1460 32-12.790'N
117-42.373'W
10
1453 APC
1844
2611
1430 32-12.774'N
117-42.338'W
#4 background seds
11
1453 APC
1844
2611
1430 32-12.774'N
117-42.338'W
#16 background sods
12
1453 APC
1844
2611
1430 32-12.774'N
117-42.338'W
#2 background seds
13
1510
APC
1848
2618
1383 32-12.748'N
117-42.334'W
14
1514 APC
1848
2618
1383 132-12.748'N
117-42.334'W
#18, 1m from barrel- core fell on
basket- lost
#3, 1m from barrel, clam field
push core #18, 1m from landerbackground
#14b, 1m from landerbackground
Alvin Dive Log
Dive number: 3537
Area: San Clemente scarp
Date:
01 April 2000
Bottom time:
Pilot:
Port observer:
Starbord observer:
Origin of XY coord.:
4.5 hours
Dudley
Mark Legg
Marie de Angelis
Objectives:
Survey scarp to southeast to cove along 1810 in contour; measure strike/slip; collect
clams, tubeworms and barite; collect Niskin water samples at red lander site (from
dive 3436), tubeworms and barite; collect pushcores at 0 and 1 meter from
tubeworm thicket; retrieve red lander; retrieve brown lander (from dive
3436).Retrieve lander from dive 3533
Summary:
Surveyed scarp from starting point to approxialmatelt site of red lander; surveyed
numerous terraced scarps at depths ranging from 1778 to 1800 meters; collected
barites and tubeworms from two sites; collected Niskin water samples and pushcores
from red lander site; retrieved red and brown landers from previous dive. Dive
curtailed due to unidentified grounding problems.
Time
X
08:02
09:21
09:23
09:31
09:45
09:48
09:55
09:59
10:04
10:06
10:12
10:16
10:16
2016
2056
1915
1919
1935
2021
2021
2015
1827
1944
1938
1907
1882
1799
1779
1805
1841
1848
10:19
10:20
10:24
10:31
10:34
2159
2158
2034
2040
2059
2084
2088
2119
2144
2148
1977
2097
2086
Y
1862
1861
1895
1909
1910
Commence dive
Arrived at bottom; depth = 1783 meters
Started video; depth = 1788 meters
Sloping bottom about 10-20 degrees declivity; Depth = 1790.5 in
Started survey; steep downslope to starboard; 1792 meters
Moving downslope; 1796 meters
Small tubeworm cluster; 1810 meters (Port side); heading 170
Tubeworms and clam debris; 1818 meters; heading 178
Sharp dropoff to starboard; 1831 meters
Turning upslope at a heading of 040
Clams and shell debris; 1818 meters
Large barite chimneys, tubeworm thickets; 1799 meters
Bacterial mat on sediment; more barite formations and tubeworm thickets;
1797 meters
Scarp sighted; 1788 meters
Scarp height approximately 2 meters on port side; 1787 meters
Scarp peters out; 1784 meters
Barite chimneys, barite boulder out port side (about 1 meter across)
Scarp pictures using digital camera; 1796 meters
2072
2081
2085
2085
1934
10:57 2085
11:01 2129
1916
1869
11:03 2167
1843
2174
2228
2236
2316
1833
1779
1778
1770
2511
1646
10:37
10:40
10:43
10:55
11:05
11:07
11:08
11:14
11:17
11:19
11:24
11:30
11:35
11:38
11:39
1921
1916
1916
2562 1580
2583 1563
2600 1544
11:42 2620
1544
11:44 2631
1554
11:48 2651
1546
12:14
12:31 2562
12:34
12:35 2562
1457
1453
12:39 2558 1461
12:47 2559 1456
12:49 2553
12:56 2555
1491
1563
12:57 2555
1563
12:59 2552
1565
13:02 2552
1564
Head upslope, 10 meters shallower, then back around to find scarp
Barite, tubeworms; 1793 meters
Collected tubeworms and barite; no clams; 1794 meters
Tripped aft Niskin (#6) at same location at which tubeworms and barite were
collected
Heading 135; moving towards red lander site
More barite, tubeworms and clam debris observed; 1794 meters; outside
35mm still camera (STBD) set to 30 sec firing rate
Arcuate fractures noted in sediment, concave downslope; steep dropoff to
starboard; 1791 meters
Head 180 downslope
Small scarp, 5-10 cm high; 1799 meters
Moving upslope diagonally
Reacquired scarp, strike about 120-125; 1778 meters
More sediment cover on scarp, irregular exposure
No more scarp?
Swapped out video.
Heading downslope; flat on top; steep downslope to starboard; 1778 meters
Scarp reacquired; approximately 1 meter high; 1798 meters
Fractures noted; 1797 meters
Terraced scarps parallel to above scarp; approximately 2 to 3 meters high
with overhangs; 1801 meters
Submersible facing scarp; video and stills; sub-horizontal lineations--grooves
or bedding?; 1800 meters
Another scarp to starboard (downslope) approximately 1 meter high; 1792
meters
Another scarp downslope; 1796 meters; electrical ground problem;
submersible stopped; navigation lost; video stopped
Navigation system back on
Looking for lander
Restart video
Brown lander found; Niskin #3, second from aft; water turbid at time of
sampling; 1846 meters
Retrieved brown lander; heading due north to red lander site
Mini scarp observed; much barite forming very rough topography; 1839
meters
Barite rubble continuous from previous location; 1836 meters
Arrive at red lander site; took 2 Niskin water samples with two furthest
forward Niskins (#2, #5) near red lander; 1817 meters
Push core taken at base of tubeworm thicket; core #6 starboard core inside
basket; 1817 meters
Push core taken at base of tubeworm thicket; core #10 far starboard core
outside basket; 1817 meters
Push core taken at base of tubeworm thicket; core #4 second from starboard
core outside basket; 1817 meters
13:05 2552
13:06 2550
13:11 2550
13:15 2548
13:28 2551
13:44 2549
13:48
13:53 2549
Push core taken at base of tubeworm thicket; core #9 fourth from starboard
core outside basket; 1817 meters; push core #15 no good
1565 Push core taken at base of tubeworm thicket; core #2 fifth from starboard
core outside basket; 1817 meters
1565 Push core taken at base of tubeworm thicket; core #17 sixth from starboard
core outside basket; 1817 meters
1565 Push core taken approximately 1 to 2 meter form base of tubeworm thicket;
core #146 far port core, 1818 8th from port core, 1818 meters; 6th core form
port lost its valve; swapped video tape
1568 Retrieved red lander; 1814 meters
1566 Tubeworm and barite collection in far port box; 1817 meters
Video shut down
1566 Leaving bottom; navigation system off
1563
Sheetl
Bottom sample record
CRUISE:
STATION
DATE
AT0003
AD 3537
OBSERVERS
PILOT
deAn ells/Le
Dudley
4/l/00
SITE
scarp
Time
Type
Depth
x
Y
1
10:55
N
1794
2085
1916
#6, same location as barite/tubeworms, aft Niskin
2
12:35
N
1845
2562
1453
#3, 2nd aft, water cloudy/muddy
3
12:56
N
1817
2555
1563
#2, 2nd forward
3
12:56
N
1817
2555
1563
#5, forward, Niskin, near lander red
3
12:57
APC
1817
2555
1563
#6, stbd in basket, base of tb thicket
3
12:59
APC
1817
2552
1565
#10, far stbd outside basket, base of tb thicket
3
13:02
APC
1817
2552
1564
#4, 2nd from stbd out, base of tb thicket
3
13:05
APC
1817
2552
1563
#9, 4th from stbd, base of tb thicket #15 NG
3
13:06
APC
1817
2550
1565
#2, 5th from stbd, base of tb thicket
3
13:11
APC
1817
2550
1565
#17, 6th from stbd, base of tb thicket right at base
3
13:15
APC
1818
2548
1565
#146, 2nd from far port, lm away
3
13:18
APC
1818
2548
1566
#8, 3rd from port, 1m away to 2 m
3
13:19
APC
1818
2548
1566
#3, 4th from port, lm away, all
3
13:20
APC
1818
2549
1565
#176, 5th from port, lm away, 6th from port
3
13:22
APC
1817
2548
1566
#16, 7th from port, lost valve
Dive
Let
Comments
Long
Station
1
-
barite/scarp
2 - brown lander
3 - red lander
;W,
I
BC=BENTHIC CHAMBER
APC=ALVIN PUSH CORE
N=NISKIN BOTTLE
BB=BENTHIC BARREL
GR--GRAB SAMPLE
*Note: Alvin had no navigation - the positions and de the are from ship's ACNAV
Page 1
Sheetl
Bottom sam pie record
CRUISE:
STATION
DATE
AT0003
AD 3538
OBSERVERS
4/2/00
SITE
PILOT
x
Y
Lat
Bob Miller/Eric H
Blee Williams
San Clemente Whale fall
Comments
Long
Time
Type
Depth
1
9:57
N
1902
2317.6 1621.3
#5, tripped before lander deployed
2
10:00
BC
1902
2317.6 1621.3
stirrer may not be working
3
12:29
N
1906
2331
1498
4
12:31
BC
1906
2331
1498
AOK
5
13:15
APC
1906
2331
1498
#3, 0" from ed a of cargo net
6
APC
1906
2331
1498
#2, 0" from edge of cargo net
7
APC
1906
2331
1498
#16, 0" from edge of cargo net
8
APC
1906
2331
1498
#10, 0" from edge of cargo net
9
APC
1906
2331
1498
#4b, 0" from edge of cargo net
Dive
Station
APC
1906
2331
1498
#9- 6" from net
11
13:31
APC
1906
2331
1498
#8- 0" from net
12
13:35
APC
1906
2331
1498
#14b, 1m from whale
13
APC
1906
2331
1498
#4, 1m from whale
14
APC
1906
2331
1498
#6, 1m from whale
10
15
13:40
APC
1906
2331
1498
#17, 1m from whale
16
13:45
APC
1906
2331
1498
#18, 3m from whale
APC
1906
2331
1498
#17b, 3m from whale
17
18
14:57
1906
2331
1498
whale bone (1)
19
15:35
1902
no nav
no nav
box core
TYPE:
BC=BENTHIC CHAMBER
APC=ALVIN PUSH CORE
N=NISKIN BOTTLE
BB=BEM HIC BARREL
GR=GRAB SAMPLE
"Note: Alvin had no navigation - the positions and depths are from ship's ACNAV
Page 1
Sheets
Bottom sample record
AT0003
AD 3539
CRUISE
STATION
DATE
OBSERVERS
PILOT
SITE
4/3/00
Bob Miller/Mark Drewe
Bob Brown
San Clemente Whale
Time
Type
Depth
1
10:07
N
1906
Om, port most core, inside row
2
10:18
BC
1906
1m, port most core, outside
3
10:18
N
1906
#9, 1 m
4
10:38
BC
1894
next after 9, 3m
5
APC
1894
#16, 3m
6
APC
1894
#15, 3m
Dive
Y
X
Let
Long
Comments
Station
7
10:42
APC
#14b, 9m
8
APC
#2, 9m
9
APC
#17
10
10:35
APC
1895
2192
1456
#3, bkgd
11
APC
#4b, bk d
12
APC
#4, bk d
13
13:25
BC
stirring, pinch plate open, door closed (syringe
not fully drawn)
14
14:12
door closed, pinch It., closed, can't see stirrer,
BC
all syringes drawn
TYPE
BC=BENTHIC CHAMBER
APC=ALVIN PUSH CORE
N=NISKIN BOTTLE
BB=BENTHIC BARREL
GR=GRAB SAMPLE
*Note: Alvin had no navigation - the positions and depths are from ship's ACNAV
Page 1
APPENDIX 3
ALVIN PUSH CORES:
LOGS, PORE WATER, AND METHANE DATA
PUSH CORES LOG
CRUISE:
STATION
DATE
Dive
Station
AT0003-49
7AD3534
OBSERVERS
SITE
deAn elis/Le
scarp-seeps
29-Mar-00
Push core
number
Lat
Long
Length
Analyses/scientist
sample site
description
(cm)
13
32-13.1904'N
117-43.0226'W
17.5
forams
by tube worms
lost vaccuum- only mud
14
32-13.1904'N
117-43.0226'W
17.5
pore water
by tube worms
lost lid- 2 layers mud
8
32-13.1904'N
117-43.0226'W
21.5
Marie
by tube worms
lost lid
10
32-13.1904'N
117-43.0226'W
22.5
porewater
by tube worms
mud and water
15
32-13.1904'N
117-43.0226'W
23
Elena
1m away from worms
tan/brown mud and water
17
32-13.1904'N
117-43.0226'W
14
Bob Miller
1m
away from worms
starfish on to
PUSH CORES LOG
CRUISE:
STATION
DATE
Dive
Station
AT0003-49
10AD3535
OBSERVERS
SITE
Goldfin er/Cumberland
San Clemente Escarpment
Analyses/scientist
sample site
30-Mar-00
Push core
number
Lat*
Long*
Length
description
(cm)
9
32 13.1904'N
117 43.0226'W
27.5
Bob Miller
Om
4
32 13.1904'N
117 43.0226'W
27.5
pore water
Om
grey with dark bands
6
32 13.1904'N
117 43.0226'W
22
Bob Miller
Om
olive top/grey bottom- starfish
18
32 13.1904'N
117 43.0226'W
25.5
porewater
1m
olive top/grey bottom
16
32 13.1904'N
117 43.0226'W
23
forams
1m
olive top/grey bottom
4b
32 13.1904'N
117 43.0226'W
26.5
Marie
1m
clam- rust colored spots
17
32 13.1904'N
117 43.0226'W
25.5
Bob Miller
1m
clam and starfish
2
32 13.1904'N
117 43.0226'W
28
Elena
1m
olive/grey- worm
8b
32 13.1904'N
117 43.0226'W
24
Marie
80 m
yellowish grey
17b
32 13.1904'N
117 43.0226'W
28
Bob Miller
80 m
yellowish grey
13
32 13.1904'N
117 43.0226'W
20.5
forams
80 m
yellowish grey
15
32 13.1904'N
117 43.0226'W
28.5
Bob Miller
80 m
yellowish grey
14
32 13.1904'N
117 43.0226'W
26.5
80 m
olive top/grey bottom
ore water
re
with dark bands
PUSH CORES LOG
CRUISE:
STATION
DATE
AT0003-49
10AD3536
SITE
Goldfin er/Cumberland
San Clemente Escarpment
Analyses/scientist
sample site
OBSERVERS
31-Mar-00
Lat
Long
9
32-12.744'N
117-42.334'W
20.5
Bob Miller
barrel
10
32-12.748'N
117-42.334'W
20.5
Bob Miller
barrel
18
32-12.748'N
117-42.334'W
18.5
forams
back round
14b
32-12.748'N
117-42.334'W
22
porewater
background
4
32-12.748'N
117-42.334'W
20
Bob Miller
background
16
32-12.748'N
117-42.334'W
20.5
Elena
back round
15
32-12.748'N
117-42.334'W
15
Bob Miller
barrel
14
32-12.748'N
117-42.334'W
19.5
forams
barrel
17b
32-12.748'N
117-42.334'W
19
Marie
barrel
17
32-12.748'N
117-42.334'W
20.5
Bob Miller
barrel
3
32-12.748'N
117-42.334'W
23
porewater
barrel
2
32-12.748'N
117-42.334'W
19.5
Marie
back round
Dive
Push core
Station
number
Length
cm
description
PUSH CORES LOG
STATION
DATE
AT0003-49
19AD3537
1-A r-00
Dive
Push core
Station
number
CRUISE:
OBSERVERS
deAn elis/Le
SITE
Lat
Long
Length
Analyses/scientist
sample site
description
(cm)
3
9
32 12.847'N
117 42.375'W
20.5
Bob Miller
Om
olive/brown mud
3
4
32 12.847'N
117 42.375'W
20.5
Bob Miller
Om
olive/brown mud- no water
3
10
32 12.847'N
117 42.375'W
18.5
forams
Om
light brown mud
3
6
32 12.847'N
117 42.375'W
22
porewater
Om
- light brown mud
3
4B
32 12.847'N
117 42.375'W
20
Bob Miller
1m
dark brown, black, green
3
16
32 12.847'N
117 42.375'W
20.5
Elena
1m
dark brown, black, green
3
17
32 12.847'N
117 42.375'W
15
Bob Miller
Om
grey/green
3
2
32 12.847'N
117 42.375'W
19.5
forams
Om
green/brown mud
3
14B
32 12.847'N
117 42.375'W
19
Marie
1m
green/brown mud
3
8
32 12.847'N
117 42.375'W
20.5
Bob Miller
1m
olive mud
3
3
32 12.847'N
117 42.375'W
23
orewater
1m
olive mud with dark spots
3
17B
32 12.847'N
117 42.375'W
19.5
1m
olive mud with dark spots
Marie
PUSH CORES LOG
AT0003-49
STATION 22AD3538
DATE
2-A r-00
CRUISE:
Dive
Station
OBSERVERS
Heinen/Miller
SITE
San Celmente whale carcass
Analyses/scientist
sample site
description
Lat
Long
4B
32 26'N
118 09'W
19
Bob Miller
Om from whale
olive/black spots
10
32 26'N
118 09'W
24
Bob Miller
Om from whale
olive/black spots
16
32 26'N
118 09'W
23
Bob Miller
Om from whale
olive/black spots
2
32 26'N
118 09'W
24
Marie
Om from whale
olive/black spots with grey mid
3
32 26'N
118 091W
25
porewater
Om from whale
olive with grey middle
4
32 26'N
118 09'W
23.5
Bob Miller
1m from whale
murky water
14B
32 26'N
118 09'W
21.5
Bob Miller
1m from whale
olive mud
8
32 26'N
118 091W
20.5
Bob Miller
Om from whale
olive mud- surface stirred up
9
32 26'N
118 09'W
17
Bob Miller
Om from whale
olive/grey
17B
32 26'N
118 09'W
22.5
Bob Miller
3m from whale
olive/grey
15
32 26'N
118 09'W
23.5
Bob Miller
3m from whale
starfish on top
17
32 26'N
118 09'W
23.5
porewater
1m from whale
good surface
6
32 26'N
118 09'W
20.5
Bob Miller
1m from whale
bad surface
Push core
number
Length
cm
PORE WATER ANALYSES OF PUSH CORE SAMPLES
STATION AT0003-7AD3534-PC10
Tube#
vol of mud
Sample#
Depth
(cm)
7AD-PCIO-OW
7AD-PCIO-1
7AD-PC10-2
3,4,5
6,7
7AD-PCIO-3
8,9
7AD-PC10-4
10,11 12 7AD-PC10-5
13,14
7AD-PC10-6
7AD-PC10-7
15,16
17
7AD-PC10-8
1,2
r
70
150
100
100
150
100
100
50
STATION AT0003-7AD3534-PC14
vol of mud
Sample#
8 9,10
7AD-PC14-OW
7AD-PC14-1
7AD-PC14-2
7AD-PC14-3
7AD-PC14-4
35
50
50
50
STATION AT0003-10AD3535-PC14
Tube#
vol of mud
Sample#
1
2
3
4
5
6,7
8
9
10
11,12
13,14
15,16
17,18
10AD-PC14-OW
IOAD-PC14-1
10AD-PC14-2
10AD-PC14-3
10AD-PC14-4
10AD-PC14-5
IOAD-PC14-6
10AD-PC14-7
10AD-PC14-8
10AD-PC14-9
10AD-PC14-10
IOAD-PC14-11
IOAD-PC14-12
10AD-PC14-13
35
35
50
50
50
50
50
50
50
50
50
50
50
STATION AT0003-10AD3535-PC18
Tube#
vol of mud
Sample#
1,2
3
4,5
6,7
8,9
10,11
12,13
14,15
16,17
18
IOAD-PC18-OW
10AD-PC18-1
10AD-PC18-2
10AD-PC18-3
IOAD-PC18-4
10AD-PC18-5
IOAD-PC18-6
IOAD-PC18-7
IOAD-PC18-8
IOAD-PC18-9
IOAD-PC18-10
35
35
50
50
50
50
50
50
50
50
STATION AT0003-10AD3535-PC4
Tube#
Sample#
vol of mud
1,2
3,4
5,6
7,8
10AD-PC4-OW
10AD-PC4-1
10AD-PC4-2
10AD-PC4-3
1OAD-PC4-4
35
35
50
50
Depth
(cm)
ECO2
mM
0
2.201
2.487
6.63
9.64
12.65
17.17
20.18
23.19
24.70
1.05
4.37
8.13
11.14
14.91
18.67
21.69
23.95
Depth
Depth
(cm)
(cm)
0
2.11
0
0
1.05
2.56
4.07
5.57
0.53
Depth
Depth
(cm)
(cm)
1.81
3.31
4.82
0
0
1.05
2.11
3.61
0.53
1.58
2.86
4.37
5.87
7.38
8.89
10.39
11.90
13.40
5.12
6.63
8.13
9.64
11.14
12.65
14.16
15.66
17.17
18.67
14.91
16.42
17.92
pH
1.241
7.469
7.611
7.670
7.748
7.617
7.500
7.466
7.558
12.3
52.6
81.4
99.5
126.3
213.4
348.5
434.9
ECO2
mM
H
NH4
uM
2.020
2.390
2.596
2.703
2.903
8.036
7.514
7.444
7.509
7.543
0.7
19.9
39.0
78.6
163.1
E0O2
mM
pH
NH4
uM
2.014
2.320
2.462
2.537
2.564
2.564
2.570
2.582
2.565
2.575
2.581
2.540
2.578
2.622
7.97
7.57
7.46
7.46
7.47
7.52
7.53
7.53
7.52
7.53
7.58
7.64
7.65
7.67
2.664
2.597
2.615
2.811
3.090
3.203
Depth
Depth
2.099
2.468
2.695
2.784
2.778
2.773
2.865
3.034
3.169
3.461
7.92
7.49
7.46
6.63
8.13
9.64
11.14
12.65
14.16
(cm)
0.000
0.53
1.58
2.86
4.37
5.87
7.38
8.89
10.39
11.90
13.40
ECO2
mM
pH
(cm)
0.00
1.05
Depth
Depth
ECO2
(cm)
0.00
1.05
(cm)
0.000
0.53
1.58
2.86
4.37
(mm)
2.214
2.441
2.517
2.470
2.534
2.11
3.61
5.12
2.11
3.61
5.12
NH4
uM
7.41
7.40
7.45
7.43
7.50
7.54
7.36
0.7
1.9
0.0
2.7
16.1
20.3
25.6
29.8
31.4
33.5
36.6
39.8
42.9
52.9
H2S
uM
0
2
2
2
3
2
3
4
5
Notes
H2S
Notes
uM
0
0
0
0
H2S
Notes
uM
0
0
0
0
0
0
0
0
0
0
0
0
0
NH4
uM
H2S
0.72
2.42
29.8
65.6
80.3
98.5
137.2
0
0
0
0
0
H Samples too warm (30 C
H Samples too warm (30 C)
H Samples too warm (30 C)
H Samples too warm (30 C)
Notes
uM
0
0
0
0
19
91
H
NH4
H2S
(UM)-
7.755
7.493
7.445
7.459
7.587
0.21
6.11
15.1
0
0
50.8
52.9
0
0
0
Notes
9,10,11
12,13
14,15
16,17,18
19,20
10AD-PC4-5
10AD-PC4-6
10AD-PC4-7
10AD-PC4-8
10AD-PC4-9
50
50
50
50
50
STATION AT0003-13AD3536-PC17B
Tube#
vol of mud
Sample#
13AD-PC17b-OW
13AD-PC17b-1
3
13AD-PC17b-2
4
13AD-PC17b-3
5,6
13AD-PC17b-4
13AD-PC17b-5
7,8
13AD-PC17b-6
9,10
13AD-PC17b-7
11 12
13,14,15 13AD-PC17b-8
12
35
35
50
50
50
50
50
50
STATION AT0003-13AD3536-PC3
Tube#
vol of mud
Sample#
13AD-PC3-OW
13AD-PC3-1
2
13AD-PC3-2
13AD-PC3-3
3
4
13AD-PC3-4
5
13AD-PC3-5
6
13AD-PC3-6
7
13AD-PC3-7
8,9
13AD-PC3-8
13AD-PC3-9
10,11
12,13
13AD-PC3-10
14,15 16 13AD-PC3-11
1
35
35
50
50
50
50
50
50
50
50
50
STATION AT0003-19AD3537-PC16
Tube#
Sam le#
vol of mud
1,2
3,4
5,6
7,8
9,10 11
12,13
19AD-PCI6-OW
19AD-PC16-1
19AD-PC16-2
19AD-PC16-3
19AD-PC16-4
19AD-PC16-5
19AD-PC16-6
35
35
50
50
50
50
STATION AT0003-19AD3537-PC2
Tube#
vol of mud
Sample#
19AD-PC2-OW
19AD-PC2-1
19AD-PC2-2
3
19AD-PC2-3
4,5
19AD-PC2-4
6,7
8,9
19AD-PC2-5
10,11
19AD-PC2-6
12,13,14 19AD-PC2-7
1,2
35
35
50
50
50
50
50
STATION AT0003-22AD3538-PC17
Tube#
vol of mud
Sample#
1,2
3
4
22AD-PC17-OW
22AD-PC17-2
22AD-PC17-3
22AD-PC17-4
35
50
50
6.63
8.13
9.64
11.14
12.65
5.87
7.38
8.89
10.39
11.90
2.537
2.577
2.564
2.829
3.041
7.629
7.549
7.673
7.621
7.665
7-Depth
Depth
(cm)
0.000
0.53
E0O2
mM
pH
(cm)
0.00
1.05
2.11
3.61
1.58
5.12
6.63
8.13
9.64
11.14
2.86
4.37
5.87
7.38
8.89
10.39
Depth
Depth
(cm)
0.00
1.05
(cm)
0.000
0.53
2.11
3.61
1.58
2.86
4.37
2.386
2.457
2.560
2.636
2.671
2.819
2.894
3.018
3.205
E0O2
mM
2.355
2.429
2.444
2.533
2.611
2.675
3.017
3.825
5.480
7.342
9.115
9.859
7.63
7.54
7.55
7.56
7.64
7.75
7.78
7.83
7.88
7.526
7.433
7.416
7.455
7.569
7.684
7.769
8.026
7.775
8.019
Depth
ECO2
mM
pH
2.327
2.349
2.495
2.579
3.232
6.978
9.516
7.61
7.51
7.41
5.12
6.63
8.13
(cm)
0.000
0.53
1.58
2.86
4.37
5.87
7.38
Depth
Depth
ICO2
pH
(cm)
0.00
1.05
mM
5.12
6.63
8.13
9.64
(cm)
0.000
0.53
1.58
2.86
4.37
5.87
7.38
8.89
Depth
Depth
(cm)
0.00
1.05
2.56
4.07
(cm)
0.000
0.53
1.81
3.31
NH4
uM
0
H2S
9.52
16.8
30.2
61.6
94.5
128.5
158.5
0
0
0
0
0
9
7.60
7.74
7.74
7.70
7.58
7.56
7.47
7.38
7.78
7.49
7.52
7.55
NH4 No Sample
81
Notes
uM
0
36
51
63.8
139.3
278.2
576.1
845.6
1048
1248
NH4
uM
0.94
4.83
22.6
59.8
249.3
NH4
uM
0.0
4.3
25.9
70.4
125.9
197.6
249.3
H2S
uM
0
0
0
0
0
0
0
H2S
off scale greater than 900 uM
off scale greater than 900 uM
H2S
Notes
uM
0
0
0
0
0
0
0
0
uM
0
0
0
7.87
7.54
0.0
7.51
0.2
0.0
Notes
64
1150
1614
H2S
2.172
2.389
2.538
2.522
NH4 Not enough sample
uM
0
0
0
0
uM
H
Notes
148
423
1107
1327
1155
NH4
ECO2
mM
7.56
1
0
0.00
4.86
5.90
17.8
Depth
2.11
3.61
53
7.606
7.531
(cm)
0.00
1.05
2.135
2.495
2.590
2.738
2.809
2.926
3.109
3.383
179.8
227.2
NH4
uM
5.87
7.38
8.89
10.39
11.90
13.40
2.11
3.61
0
pH
5.12
6.63
8.13
9.64
11.14
12.65
14.16
15.66
14.91
71.1
104.5
0
NH4 off scale, > than 900 uM
Notes
NH4 no Sample
5
6,7
8,9
10,11
12,13
14,15
16,17
22AD-PC17-5
22AD-PC17-6
22AD-PC17-7
22AD-PC17-8
22AD-PC17-9
22AD-PC17-10
22AD-PC17-11
50
50
50
50
50
50
50
5.57
7.08
8.58
10.09
11.60
13.10
14.61
4.82
6.33
7.83
9.34
10.84
12.35
13.86
2.588
2.656
2.727
2.668
7.54
7.54
7.59
7.66
7.60
7.66
Depth
ICO2
pH
(cm)
0.00
0.53
mM
0.0
1.8
10.7
18.6
26.4
26.4
43.2
0
0
0
0
0
0
0
*There is no sam le #1
STATION AT0003-22AD3538-PC3
Tube#
Sam le#
vol of mud
1,2
3
4
5,6
7,8
9,10
11,12
13,14
15,16
22AD-PC3-OW
22AD-PC3-1
22AD-PC3-2
22AD-PC3-3
22AD-PC3-4
22AD-PC3-5
22AD-PC3-6
22AD-PC3-7
22AD-PC3-8
22AD-PC3-9
35
50
50
50
50
50
50
50
50
ZDe th
(cm)
0.00
1.05
2.56
4.07
5.57
7.08
8.58
10.09
11.60
13.10
1.81
3.31
4.82
6.33
7.83
9.34
10.84
12.35
2.134
2.402
2.437
2.476
2.461
2.404
2.459
2.605
2.729
2.750
7.73
7.58
7.58
7.56
7.54
7.66
7.58
7.60
7.61
7.72
NH4
uM
H2S
0.0
0.0
0.2
2.8
8.0
11.6
12.2
29.0
52.9
74.2
0
0
0
0
0
uM
0
0
0
0
0
Notes
METHANE ANALYSES OF PUSH CORE SAMPLES
STATION AT0003-7AD3534-PC8
(0 meters from tubeworm bush)
Depth
CH4
(cm)
0.5
2
4
6
8
10
(ul/ml)
12
32.3
27.5
22.2
46.4
STATION AT0003-7AD3536-PC2
(background, scarp base)
Depth
CH4
(cm)
(ul/ml)
0.5
2
4.7
4
6
8
2.5
1.3
2.4
10
12.5
4.1
1.8
STATION AT0003-7AD3536-PC17B
(1 m from benthic barrel site, clams)
Depth
CH4
(cm)
(ul/ml)
0.5
2
1.8
4
6.2
6
8
10
12
8.1
19
35.8
54.8
STATION AT0003-7AD3537-PC4B
(I m from tubeworm bush, Mn layer)
Depth
CH4
(cm)
0.5
2
4
6
8
(ul/ml)
0.0046
0.105
0.18
0.473
11
14
17
19
21
0.677
6.66
18.2
60.6
APPENDIX 4
ABSTRACTS SUBMITTED TO AGU FALL MEETING 2000
SPECIAL SESSION: Geochemical, biological and tectonic interactions in the
Southern California Borderlands. San Francisco, CA, Dec. 2000
ABSTRACTS SUBMITTED TO AGU FALL MEETING 2000.
Late Cenozoic Seafloor Spreading in South San Clemente Basin: A Hole
Through the Inner Borderland Lithosphere
Mark R Legg' (714-842-0404; mrlegg@attglobal.net)
Scott White 2 (805-893-2853; white@geol.ucsb.edu)
Ken Macdonald 2 (805-893-2853; ken@geol.ucsb.edu)
'Legg Geophysical, 16541 Gothard St. \#107, Huntington Beach, CA 92647, United
States
2Dept. Geological Sciences, University of California, Santa Barbara, CA 93106,
United States
The California Continental Borderland sustained a complex tectonic evolution from
Mesozoic subduction to modern transform faulting along the San Andreas fault system. A
major Neogene episode of oblique extension resulted from the establishment of the
Pacific-North America plate boundary as the last remnants of the Farallon plate
foundered, fragmented, or became captured by the northwest moving Pacific plate.
Clockwise vertical-axis transrotation of the Western Transverse Ranges and
northwestward transtensional movement of the Outer Borderland above captured
microplates created the Inner Borderland Rift, a zone of ridge-and-basin morphology
floored by former subduction complex, Catalina Schist basement rocks. Although most of
the ridges and elongate basins are northwest-trending, subparallel to the modern San
Andreas transform fault system, South San Clemente Basin in the central part of the
borderland consists of a symmetrical series of north-trending ridges and troughs. This
symmetric topography is considered to represent a horst-and-graben structure developed
within a Neogene rift system. The northern boundary of this major rift system consists of
the N40W trending San Clemente fault, inferred to be a Neogene transform fault that
continues to move at a reduced rate today. The southern boundary consists of northwesttrending, irregular-shaped, steep-walled Animal Basin, which implies the existence of
another Neogene transform fault, herein named the Animal Basin fault zone. The South
San Clemente Basin rift system is considered to represent a Neogene spreading center,
similar to the early formation of rift basins in the Gulf of California. Gross morphology
shows a 45 degree intersection between the rift axis and transform fault, similar to
continental rifts and consistent with the strain axes expected for the northwest-trending
Pacific-North America transform fault plate boundary. Numerous Sea Beam bathymetry
swaths compiled across the region show an overprinting northeast-trending system of
scarps and sub- basins intersecting the San Clemente fault at a 90 degree angle. We
consider that this northeast-trending overprinting morphology represents the initiation of
seafloor spreading within the South San Clemente Basin rift. Data from a prominent
restraining bend structural uplift on the San Clemente fault suggests that active extension
of the rift may have continued into Quaternary time. Magnetic anomaly patterns along the
Pacific seafloor to the west of the borderland suggest that seafloor spreading on the active
East Pacific Rise ceased 12-17 Ma at this latitude, and the major opening of the Gulf of
California transform fault and rift system occurred about 5-6 Ma. Persistence of rifting
and possible seafloor spreading in the South San Clemente Basin rift perhaps more than 4
Myr later suggests that microplate capture left important lithospheric holes that have long
term affects on the overall plate boundary evolution.
New Mapping and Submersible Observations of Recent Activity on the San
Clemente Fault
Chris Goldfinger' (541-737-5214; gold@oce.orst.edu)
Mark Legg 2 (714-842-0404; mrlegg@attglobal.net)
Marta Torres' (541-737-2296; mtorres@oce.orst.edu)
'Oregon State University, Ocean Admin Bldg 104, Corvallis, OR 97331, United
States
2Legg Geophysical, 5952 Brassie Cr., Huntington Beach, CA 92649-2748, United
States
Three recent cruises to the southern San Clemente fault in the southern California
borderland focused on active tectonic and bio-geologic processes associated with this
major offshore fault system. We have combined new multibeam data collected in 19982000 with existing multibeam and sounding data to produce a new bathymetric grid for
the southern borderland. The new grid reveals both broad and fine scale tectonic
geomorphic relationships along the San Clemente, San Diego Trough and other fault
systems. The dominant dextral nature of the borderland faults is revealed by offset
drainages, offset basement highs, and the numerous restraining and releasing bends that
control the vertical tectonics on both fine and regional scales. For example, San Clemente
Island itself is offset right laterally some 40 km from the submerged Fortymile Bank to
the east. On a smaller scale, numerous restraining and releasing bends control the
development of related folds along the San Clemente fault. Polyphase deformation is
apparent along the fault where one restraining bend is undergoing active uplift as
indicated by shifting channels and Holocene-Pleistocene growth strata. Superimposed on
this uplift are four smaller restraining-releasing bend pairs, mirroring the larger uplift at a
smaller scale. Several late Pleistocene regional stratigraphic marker beds can be
correlated to nearby ODP sites where the have been dated. These markers allow
kinematic modeling to determine the slip-rate of the fault, work presently in progress. At
outcrop scale, ALVIN observations of the San Clemente fault on the northern flank of
Navy Fan reveal a recent Holocene scarp 0.3-1.5 m in height. The scarp is a single event
scarp, indicated by the lack of multiple slope breaks and uniform "weathering" and
bioturbation. The lightly bioturbated fresh scarp offsets Holocene and late Pleistocene
strata, indicating a Holocene event that likely had a magnitude greater than 6.
Barite deposits on the San Clemente fault zone reflect fluid flow through
stratigraphically controlled high permeability zones within Navy Fan sediments.
Sonya Newell' (541-737-2296; newells@ucs.orst.edu)
Marta Torres' (541-737-2902; mtorres@oce.orst.edu)
James McManus2 (218-726-7384, jmcmanus@d.umn.edu)
Ahmed Rushdi' (541-737-2741; arushdi@oce.orst.edu)
'COAS, Oregon State University, 104 Ocean Admin Bldg, Corvallis OR
97331, United States.
2Large Lakes Observatory, University of Minnesota, 10 University Dr, 109
RLB, Duluth MN 58812, United States.
Barite deposits and dense colonies of tube worms were first reported by Lonsdale
(1979) along a young scarp on the San Clemente Fault Zone. Here we present the spatial
distribution of those deposits. Their distribution is consistent with a formation
mechanism whereby barium is remobilized within the Navy fan sedimentary sequence,
followed by transport of Ba-rich fluids along stratigraphically controlled horizons. The
data suggest that the barium source for the deposits is associated with the high
concentration of non-detrital barite buried in the thick sediment sequences of Navy Fan
sediments. Within these sediments barite is remobilized within the anoxic sediment
column. Advective flow drives a significant flux of barium-rich fluids to the seafloor
leading to the formation of barite deposits at the cold vent sites. This mechanism is
similar to that described for barite deposits along the Peru margin and at Monterey Bay
seeps.
The discharge of barium-enriched fluids appears to be limited to the seeps along the
escarpment wall. At the base of the scarp Ba fluxes are low and there was no evidence
for barite deposition; however, fluid seepage of H2S/CH4 bearing fluids was observed at
the base of the scarp. In contrast to sites along the escarpment wall, the fluid discharge at
the foot of the scarp wall is likely to be controlled by the presence of high-permeability
conduits associated with the San Clemente fault. The different fluid composition
suggests a different pathway of fluid migration, as these fluids were not exposed to high
dissolved barium in the sediments.
The biological communites associated with the seeps on the wall are different from
those at the base of the scarp: the chemosynthetic community at the barite-rich sites is
dominated by vestimentifera tubeworms, whereas the sites at the base have no tubeworm
colonies, rather these sites are colonized by vesicomyid clams. These data are another
example of the complex interrelationships between the benthic biota at seep sites and the
geochemical characteristics of the fluid regime.
Effect of benthic biota on methane oxidation rates within upper sediments at
cold seep sites: San Clemente escarpment and Hydrate Ridge.
Marie A de An lis' (707-826-5621; madl @humboldt.edu)
Marta E Torres 2 (541-737-2415; mtorres@oce.orst.edu)
James McManus 3 (218-726-7384; jmcmanus@d.umn.edu)
eg
'Humboldt State University, 1 Harpst Street Dept of Oceanography, Arcata, CA
95521, United States
2COAS, Oregon State University, 104 Ocean Admin Bldg, Corvallis, OR 97331,
United States
3Large Lakes Observatory, University of Minnesota 10 University Dr, 109RLB,
Duluth, MN 58812, United States
Continental shelves have been identified as sites for cold seeps, where release of
fluids and gases from sediments to oceanic bottom water occurs as the result of tectonic
compression of sediments. Frequently, these seeps are characterized by elevated levels of
methane. The quantification of microbial oxidation of methane at seeps is important in
constraining the oceanic methane budget and the amount of methane that may eventually
be released to the atmosphere, where it may contribute to global warming. The control of
microbial methane oxidation rates at seep sites is not well-understood. In order to gain a
better understanding of the role of methane oxidation in determining methane fluxes, we
examined microbial methane oxidation activity in sediments and near-bottom water at: 1)
cold seep sites devoid of gas hydrate (San Clemente escarpment); 2) on seep sites
overlying gas hydrate bearing sediments (Hydrate Ridge); and 3) non-seep sites in East
basin and San Clemente basin. Specific methane oxidation rates (equal to the fraction of
available methane removed per unit time) within surface sediments of seep sites was
orders of magnitude higher than values measured at background stations. At all sites,
methane oxidation rates decreased with depth in the sediments. Within the seeps, the
highest specific methane oxidation rates were recorded at the San Clemente seeps,
reaching values as high as 0.31 per day. These sites were characterized by the presence of
tube worm an clam colonies. On Hydrate Ridge, specific methane oxidation rates in
surface sediments were significantly higher at clam sites (up to 0.30 per day) relative to
bacterial mat sites (up to 0.014 per day). Lower methane activity at mat sites may be due
to lower levels of available methane for methane-oxidizing bacteria due to higher flow
rates and the predominance of gaseous methane (as opposed to dissolved methane)
produced by large-scale decomposition of hydrates Alternatively, methane oxidation rates
at clam sites may be positively affected by different pore water chemistry resulting from
the biopumping action of clams, which generates a downflow of seawater, rich in
electron acceptors such as oxygen and sulfate into the upper sections of the sediment.
Enhanced barium fluxes in the San Clemente basin reflect barium input from
cold seeps along the San Clemente escarpment.
Marta Torres' (541-737-2415; mtorres@oce.orst.edu)
James McManus2 (218-726-7384, jmcmanus@d.umn.edu)
'COAS, Oregon State University, 104 Ocean Admin Bldg, Corvallis OR
97331, United States.
6Large Lakes Observatory, University of Minnesota, 10 University Dr, 109
RLB, Duluth MN 58812, United States.
During an Alvin field program in March 2000 we examined the steep-sloped scarp
along the San Clemente fault and found scarps that ranged in height from several
centimeters to a few meters. Indications of youthful fault activity included fluid venting
and the presence of chemosynthetic organisms such as tube worms and clams found
along the fault traces. A prominent feature of the seeps is the formation of extensive
barite deposits along the escarpment wall (Lonsdale, 1979). These deposits are observed
as large blocks on the seafloor, and serve, in some instances as an anchor for tubeworm
thickets.
Barium fluxes in the San Clemente basin away from the seep sites are as much as a
factor of 4 higher than those from neighboring basins (McManus et al., 1998). These data
indicate that in the San Clemente basin some process other than the rain of material from
the upper water column is contributing barium to the basin inventory. We believe that
these high barium fluxes are due to transport and remobilization of seep-derived barium
sulfate.
Deployments of benthic samplers at the seafloor allowed us to document a flux of
dissolved barium and methane at the seep sites, which reach values as high as high as 5
mmol Ba m-' day' and 280 mmol CH4 m 2 day'. When these Ba-rich fluids are
discharged at seep sites on the escarpment wall, they lead to the precipitation of barium
sulfate at the seafloor. The cold-seep barite is extremely porous and fragile; as we have
observed that microcrystals easily desegregate from the deposits and are transported as
particles within the water column. This process results in a significant flux of seepderived barium sulfate, which is recorded in the large accumulation rates of barium
measured in the San Clemente basin. As this material undergoes diagenetic
decomposition within the sulfate reduction zone, sedimentary barium is remobilized,
diffuses upward, and results in the high benthic barium fluxes recorded away from the
seep sites.
Venting of cold seeps typically occurs in open-ocean waters; thus, the chemical
signature associated with fluid discharge is masked by bottom water advective processes
It has therefore not been possible to unravel the contribution of fluid-seepage to
elemental distributions within the sediment record away from the immediate seep area.
At the San Clemente Fracture Zone fluids are being discharged within one of the basins
of the California Borderlands thus allowing us to evaluate the effect of cold seepage
within a depositional basin.