Alkenone Ol3C as a Proxy for Past PCO, in Surface Waters
473
Material and Methods
Gravity core GeoB 10 16-3 was retrieved from
11°46.2'S, 11 °40.9'E (3410 m water depth) in the
Samples
eastern Angola Basin (Wefer et al. 1988) and has
been stored at a temperature of 4°C. For 8 13 C
The surface sediments for this study were obtained measurements on the C'7:2 alkenone, we re-samwith box and multiple corers from the South pled the core about 6 years after its recovery. The
Atlantic continental margins in the Angola Basin, chronostratigraphy of the core is based on
Cape Basin and Brazil Basin during RV "Meteor" the 8 18 0 record of the planktonic foraminifera
cruises M6/6, MI6/2, M20/2, M22/2, M23/2 and Globigerinoides ruber (pink) (Schneider et al.
M23/3 (http://www.pangaea.de). Figure 1 and 1995). The 8 13 C content of bulk organic matter
Table 1 show the study areas and the core posi- and sea surface temperatures (SST) derived from
tions. Samples for organic geochemistry were taken alkenone analyses were taken from MUller et al.
from the box core surfaces (0-1.5 cm) immediately (1994). Average phosphate concentration of the
after recovery using 10 cm' plastic syringes, sealed upper water column (0-50 m) at each of our stawith electrical tape and kept at 4°C until being tions was calculated from annual mean data ofthe
freeze-dried and ground in an agate mortar in the World Ocean Atlas (1994) obtained via Internet
home laboratory. Surface slices of multicores (0-1 (http://ferret.wrc.noaa.gov./fbinlclimate_server).
cm) were kept deep-frozen at -18°C and later proc- The pre-industrialPC0 2 in surface waters was esessed in the same way as the box-core samples. timated by substracting 70 ppmv (increase since the
Position
LAT LONG Water
Bulk- Alk.enone/i\'N
SST Pre-indo [CO,(aq)]pre.iNi Alkenone [PO']II.50m
depth
/i 13 C
/i 13 C
PCO,
EP
[0]
[0]
[m] [%oPDB] [%oPDB]
[%0 air] [0C] [Jlatm]
[JlM]
[%oPDB] [Jlmolll]
GeoB 1008-6
-6.59 10.32 3100
-21.80
-23.14
6.87
25.5
311
8.9
12.84
0.62
GeoB 1016-3 -11.59 11.70 3410
-20.47
-23.48
7.80
25.1
324
9.4
13.15
0.65
GeoB 1703-5 -17.45 11.02 1769
-19.95
-23.83
5.49
19.6
296
9.9
12.88
0.88
GeoB 1706-1 -19.56 11.18 980
-20.16
-23.48
4.81
18.1
285
10.0
12.34
0.90
GeoB 1711-2 -23.32 12.38 1964
-20.18
-23.90
5.81
18.3
283
9.9
12.80
0.77
GeoB 1719-5 -28.93 14.17 1024
-19.59
-24.75
6.22
17.5
274
9.8
13.59
0.44
GeoB 1508-1
5.33 -34.03 3685
-18.94
-25.11
6.30
27.1
289
8.0
15.08
0.22
GeoB 1515-2
4.24 -43.67 3125
-19.02
-25.04
6.13
26.7
287
8.0
14.95
0.24
GeoB 1503-2
2.31 -30.65 2298
-18.33
-24.99
7.15
26.7
302
8.4
14.90
0.16
Geob 1505-3
2.27 -33.01 3703
-18.88
-25.12
6.98
26.3
302
8.5
14.99
0.18
GeoB 2215-8
0.01 -23.49 3711
-18.84
-24.50
7.64
26.7
317
8.8
14.39
0.14
GeoB 1501-1
-3.68 -32.01 4258
-19.05
-25.37
8.31
25.2
319
9.0
15.24
0.18
GeoB 1903-1
-8.68 -11.84 3161
-25.74
10.09
24.9
320
9.3
15.48
0.22
GeoB 2125-2 -20.82 -39.86 1542
-20.34
-25.80
6.78
25.2
313
9.1
15.58
0.13
GeoB 2102-1 -23.98 -41.20 1805
-20.63
-25.60
6.48
24.7
313
9.2
15.36
0.17
Table 1. Positions and water depths of surface sediments used in this study. Also listed are bulk OIlC (Fischer et al.
1998), alkenone 013C, bulk sediment olsN (Holmes et al. 1996, 1998; and unpubl. data), the sea surface temperatures
(SST) derived from alkenone analyses (Sclmeider et al. 1995; MUller et al. 1998), pre-industrial PC0 2 and [CO,(aq)]
calculated from modem data (Weiss et al. 1992), alkenone e p and [PO,]o_som (World Ocean Atlas 1994; http://
ferret. wrc.noaa.gov .Ifbinlclimate _server).
473
Material and Methods
Gravity core GeoB 10 16-3 was retrieved from
11°46.2'S, 11 °40.9'E (3410 m water depth) in the
Samples
eastern Angola Basin (Wefer et al. 1988) and has
been stored at a temperature of 4°C. For 8 13 C
The surface sediments for this study were obtained measurements on the C'7:2 alkenone, we re-samwith box and multiple corers from the South pled the core about 6 years after its recovery. The
Atlantic continental margins in the Angola Basin, chronostratigraphy of the core is based on
Cape Basin and Brazil Basin during RV "Meteor" the 8 18 0 record of the planktonic foraminifera
cruises M6/6, MI6/2, M20/2, M22/2, M23/2 and Globigerinoides ruber (pink) (Schneider et al.
M23/3 (http://www.pangaea.de). Figure 1 and 1995). The 8 13 C content of bulk organic matter
Table 1 show the study areas and the core posi- and sea surface temperatures (SST) derived from
tions. Samples for organic geochemistry were taken alkenone analyses were taken from MUller et al.
from the box core surfaces (0-1.5 cm) immediately (1994). Average phosphate concentration of the
after recovery using 10 cm' plastic syringes, sealed upper water column (0-50 m) at each of our stawith electrical tape and kept at 4°C until being tions was calculated from annual mean data ofthe
freeze-dried and ground in an agate mortar in the World Ocean Atlas (1994) obtained via Internet
home laboratory. Surface slices of multicores (0-1 (http://ferret.wrc.noaa.gov./fbinlclimate_server).
cm) were kept deep-frozen at -18°C and later proc- The pre-industrialPC0 2 in surface waters was esessed in the same way as the box-core samples. timated by substracting 70 ppmv (increase since the
Position
LAT LONG Water
Bulk- Alk.enone/i\'N
SST Pre-indo [CO,(aq)]pre.iNi Alkenone [PO']II.50m
depth
/i 13 C
/i 13 C
PCO,
EP
[0]
[0]
[m] [%oPDB] [%oPDB]
[%0 air] [0C] [Jlatm]
[JlM]
[%oPDB] [Jlmolll]
GeoB 1008-6
-6.59 10.32 3100
-21.80
-23.14
6.87
25.5
311
8.9
12.84
0.62
GeoB 1016-3 -11.59 11.70 3410
-20.47
-23.48
7.80
25.1
324
9.4
13.15
0.65
GeoB 1703-5 -17.45 11.02 1769
-19.95
-23.83
5.49
19.6
296
9.9
12.88
0.88
GeoB 1706-1 -19.56 11.18 980
-20.16
-23.48
4.81
18.1
285
10.0
12.34
0.90
GeoB 1711-2 -23.32 12.38 1964
-20.18
-23.90
5.81
18.3
283
9.9
12.80
0.77
GeoB 1719-5 -28.93 14.17 1024
-19.59
-24.75
6.22
17.5
274
9.8
13.59
0.44
GeoB 1508-1
5.33 -34.03 3685
-18.94
-25.11
6.30
27.1
289
8.0
15.08
0.22
GeoB 1515-2
4.24 -43.67 3125
-19.02
-25.04
6.13
26.7
287
8.0
14.95
0.24
GeoB 1503-2
2.31 -30.65 2298
-18.33
-24.99
7.15
26.7
302
8.4
14.90
0.16
Geob 1505-3
2.27 -33.01 3703
-18.88
-25.12
6.98
26.3
302
8.5
14.99
0.18
GeoB 2215-8
0.01 -23.49 3711
-18.84
-24.50
7.64
26.7
317
8.8
14.39
0.14
GeoB 1501-1
-3.68 -32.01 4258
-19.05
-25.37
8.31
25.2
319
9.0
15.24
0.18
GeoB 1903-1
-8.68 -11.84 3161
-25.74
10.09
24.9
320
9.3
15.48
0.22
GeoB 2125-2 -20.82 -39.86 1542
-20.34
-25.80
6.78
25.2
313
9.1
15.58
0.13
GeoB 2102-1 -23.98 -41.20 1805
-20.63
-25.60
6.48
24.7
313
9.2
15.36
0.17
Table 1. Positions and water depths of surface sediments used in this study. Also listed are bulk OIlC (Fischer et al.
1998), alkenone 013C, bulk sediment olsN (Holmes et al. 1996, 1998; and unpubl. data), the sea surface temperatures
(SST) derived from alkenone analyses (Sclmeider et al. 1995; MUller et al. 1998), pre-industrial PC0 2 and [CO,(aq)]
calculated from modem data (Weiss et al. 1992), alkenone e p and [PO,]o_som (World Ocean Atlas 1994; http://
ferret. wrc.noaa.gov .Ifbinlclimate _server).