27. miocene benthic foraminifer oxygen and carbon … · 2006. 9. 22. · duncan, r. a., backman,...

Duncan, R. A., Backman, J., Peterson, L. C , et al., 1990Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 115

27. MIOCENE BENTHIC FORAMINIFER OXYGEN AND CARBON ISOTOPES,SITE 709, INDIAN OCEAN1

Fay Woodruff,2 Samuel M. Savin,3 and Linda Abel3

ABSTRACT

The benthic isotopic record of Miocene Cibicidoides from Site 709 provides a record of conditions in the IndianOcean at a depth of about 3200 mbsf. As expected, the record qualitatively resembles those of other Deep Sea DrillingProject and Ocean Drilling Program sites. The data are consistent with the scenario for the evolution of thermohalinecirculation in the Miocene Indian Ocean proposed by Woodruff and Savin (1989). Further testing of that scenario, how-ever, requires isotopic data for Cibicidoides from other Indian Ocean sites. There is a correlation between 513C values ofCibicidoides and planktonic:benthic (P:B) ratios of Site 709 sediments, implying a causal relationship between the cor-rosiveness of deep waters and concentration of CO2 derived from oxidation of organic matter.

INTRODUCTION

In this paper, we report the results of oxygen and carbon iso-topic analyses of the tests of Miocene benthic foraminifers fromOcean Drilling Program (ODP) Site 709. Site 709 is located nearthe summit of the Madingley Rise in the western Indian Ocean.Present-day water depth is 3041 m. Back-tracked Miocene depthsof the site are between about 2550 and 2900 m, making it thedeepest Indian Ocean site for which Miocene benthic isotopedata are available.

Woodruff and Savin (1989) presented a global synthesis ofMiocene benthic foraminiferal carbon isotopic data and inter-preted directions of deep- and intermediate-water flow from vari-ations in 513C values of the tests. They concluded that early Mi-

, ocene thermohaline circulation was very different from that oftoday. They proposed that during early Miocene time a plumeof warm, saline water from the Tethys entered the northern In-dian Ocean in the region of the Red Sea and Persian Gulf. Thisplume would have sunk to intermediate depths in the IndianOcean, entraining warm surface water as it sank and forming awater mass they called Tethyan Indian Saline Water (TISW). TheTISW would have flowed southward to high southern latitudeswhere it would have welled up into the circumantarctic surfacecirculation. There, they proposed, it would have become refrig-erated and sunk to the ocean bottom, flowing northward in theAtlantic, Pacific, and Indian oceans analogous to modern Ant-arctic Bottom Water (AABW). Thus, the proposed Tethyan out-flow water and the resulting TISW would have played an earlyMiocene role similar in some respects to that of North AtlanticDeep Water (NADW) in the modern ocean.

Of all benthic foraminiferal taxa commonly used in isotopicreconstructions of oceanographic conditions, carbon isotopicratios of the genus Cibicidoides appear to reflect the 513C valuesof dissolved HCO3 in seawater at the sediment-water interfacemost closely (Duplessy et al., 1984; Shackleton et al., 1984;Savin and Woodruff, 1990, unpubl. data, and others). Mioceneisotopic data are available for only a few sites in the IndianOcean and most of the available data are for Oridorsalis umbo-

1 Duncan, R. A., Backman, J., Peterson, L. C , et al., 1990. Proc. ODP, Sci.Results, 115: College Station, TX (Ocean Drilling Program).

2 Department of Geological Sciences, University of Southern California, LosAngeles, CA 90089, U.S.A.

3 Department of Geological Sciences, Case Western Reserve University, Cleve-land, OH 44106, U.S.A.

natus (Vincent et al., 1985). It is critical to the testing of ourearly Miocene scenario, or any other model of Miocene thermo-haline circulation, to enlarge the data base of isotopic composi-tions of Miocene Cibicidoides from the Indian Ocean. This briefpaper represents a small step toward compilation of that database.

METHODS AND PROCEDURESBenthic foraminifers were prepared for isotopic analysis fol-

lowing procedures described by Woodruff and Savin (1989).Preparation of CO2 for isotopic analysis was done with a modi-fied version of the technique of Epstein et al. (1951). These modi-fications are especially useful in the analysis of small (< 500 ̂ ig)samples of CaCO3.

Samples weighing between a few tens of micrograms and 1 mgwere placed in a miniaturized Rittenberg tube (Fig. 1) with 0.5 mlof 100% phosphoric acid. The tubes were evacuated overnight,and then placed in a thermostated water bath at 25°C. No morethan 24 hr before the CO2 was to be collected, the Rittenbergtube was tipped, which allowed the acid to contact the CaCO3.After a reaction time of 2-24 hr at 25°C, the tube was plungedinto a Dewar flask containing a slush made from a mixture ofethanol and finely ground dry ice. The tube, still in the Dewar,was then attached directly to a mass spectrometer sample inletsystem of our own design, and the CO2 was distilled into thevariable volume inlet where it was frozen with liquid N2 and an-alyzed isotopically.

This technique yields cleaner CO2 and isotopic analyses ofsmall samples of higher precision than we could obtain withmore conventional multistage cryogenic distillation procedures.We routinely achieved precision of 518O and 513C analyses ofbetter than 0.1%o with samples weighing as little as 150 fig.

RESULTS

Isotopic Time SeriesIsotopic results, as well as planktonic:benthic (P:B) ratios of

samples from Holes 709A and 709B are tabulated in Table 1.Isotopic data are plotted as a function of depth (meters belowsea floor [mbsf]) in Figures 2a and 2b. At this time only a fewbiostratigraphic ages of Miocene Site 709 samples have been de-termined. We have assigned ages based upon correlations be-tween oxygen and carbon isotopic curves from Holes 709A and709B and those of high-resolution Pacific 18O and 13C recordsfor which there are well-determined nannofossil, radiolarian, dia-tom, and planktonic foraminifer datums (Woodruff and Savin,

519

F. WOODRUFF, S. M. SAVIN, L. ABEL

70 mm

• 45mm J

Figure 1. Miniature Rittenberg tube used for reaction of small carbon-ate samples. The lower portion of the vessel fits easily inside a standard265-ml Dewar.

unpubl. data). The ages of datums we used are based on thoselisted in Barron et al., 1985. The early Miocene isotopic pat-terns are not sufficiently distinct to permit their use for makingage assignments. We have a high degree of confidence in theages of the middle Miocene section between 119 and 150 mbsffrom Holes 709A and 709B. We correlated sediments at a depthof 132.5 mbsf from Hole 709A with those from 136 mbsf inHole 709B as well as sediments from a depth of 151.5 mbsf atHole 709A with those at 150.5 mbsf at Hole 709B. Thus, thesection from Hole 709A fills a gap that we think resulted fromsediment missing between Cores 115-709B-15H and -16H. Agedeterminations based upon the isotopic record and also uponbiostratigraphy (Backman, Duncan, et al., 1988; Rio et al., thisvolume; Johnson, this volume) are indicated in Figure 2; age de-terminations based on the isotopic record are listed in Table 2.Biostratigraphic age datums from Backman, Duncan, et al.(1988) that appear compatible with the isotopic data are listedin Table 3.

Backman, Duncan, et al. (1988) inferred from whole-coremagnetic susceptibility profiles that the early Miocene sectionfrom 163.3 to 168.0 mbsf in Hole 709B is a repetition of the in-terval immediately overlying it. The isotopic patterns (Fig. 3)are consistent with, but do not require, this interpretation. Core115-709B-20H (177.6-187.2 mbsf) was not recovered.

Qualitatively, the major features of the oxygen and carbonisotopic records resemble those of other Miocene sites. Thesewill not be detailed here. Mean 518O and

MIOCENE BENTHIC FORAMINIFER 18O AND 13C ISOTOPES

Table 1. Oxygen and carbon isotope ratios of Miocene benthic foraminifers from Site 709Aand 709B.

Core, section,interval (cm)

115-709 A-

14H-5, 2-514H-5, 50-5314H-5, 94-9714H-6, 1-414H-6, 50-5314H-6, 100-10314H-7, 3-614H-7, 47-50

15H-1, 5-815H-1, 50-5315H-1, 101-10415H-2, 2-515H-2, 50-5315H-2, 94-97

15H-3, 2-515H-3, 2-515H-3, 50-5315H-3, 50-5315H-3, 100-10315H-4, 2-515H-4, 50-5315H-4, 94-9715H-5, 2-515H-5, 50-53

15H-5, 94-9715H-6, 2-5

15H-6, 50-5315H-6, 100-103

15H-7, 2-5

15H-7, 50-52

16H-1, 2-5

16H-1, 50-53

16H-1, 94-97

16H-2, 2-5

16H-2, 50-5216H-2, 94-97

16H-3, 2-5

16H-3, 50-5316H-3, 101-104

16H-4, 2-5

16H-4, 50-5316H-4, 102-105

16H-5, 2-516H-5, 2-516H-5, 50-5316H-5, 94-97

16H-6, 2-516H-6, 53-5616H-6, 100-10316H-7, 2-516H-7, 50-5317H-1, 50-53

17H-1, 100-103

17H-2, 4-7

Depth(mbsf)

131.8132.3132.7133.31133.80134.30134.83135.3

135.55136.00136.51137.02137.501137.94

138.52138.52139.00139.00139.50140.02140.50140.94141.52142.00

142.54143.02

143.50144.00

144.52

145.00

145.22

145.70

146.14

146.72

147.20147.64

148.22

148.70149.21

149.72

150.20150.72

151.22151.22151.70152.20

152.70153.23153.73154.22154.70155.3

155.9

156.5

Species

Cibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergi

+ C. lamontdohertyiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides lamontdohertyiCibicidoides kullenbergi

+ C. lamontdohertyiCibicidoides lamontdohertyiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides lamontdohertyiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergi

+ C. lamontdohertyiCibicidoides kullenbergiCibicidoides kullenbergi

+ C. sp. S + C. trinitatensisCibicidoides kullenbergiCibicidoides kullenbergi

+ C. lamontdohertyi + C. trinitatensisCibicidoides kullenbergi

+ C. lamontdohertyiCibicidoides kullenbergi

+ C. sp. SCibicidoides kullenbergi




+ C. sp. S + C. lamontdohertyiCibicidoides kullenbergiCibicidoides wuellerstorfi





+ C. lamontdohertyiPlanulina renziCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergi

+ C. lamontdohertyiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergi

+ Planulina renziCibicidoides kullenbergi


+ Planulina renzi

518O

.59

.69

.44

.76

.54

.78

.76

.53

1.761.861.751.701.741.73

:

:

.99

.79

.99'.12.67.83.84.89.59.72

1.751.44

1.761.34

1.54

1.50

1.65

1.42

1.46

1.66

1.191.37

1.87

1.711.73

1.98

1.521.86

1.501.701.641.86

1.601.691.531.801.511.87

1.87

1.64

S13C

0.751.010.590.860.670.800.730.31

0.880.850.770.560.810.78

0.640.650.860.700.870.900.721.531.641.84

1.761.80

1.631.59

1.58

1.58

1.54

1.25

1.20

1.51

0.970.99

1.08

0.971.03

1.10

0.810.80

0.850.760.760.85

0.660.790.700.690.451.02

1.11

0.91

P:Bratio

371796351365230430484103

1801452081505229

74749595

102201154167106137

390545

566404

461

493

181

696

294

465

416199

241

557131

519

347423

249249189273

278287227157111

521


Table 1 (continued).


115-709B-

7H-2, 75-807H-4, 70-75

7H-5, 125-130

8H-2, 25-30

8H-4, 70-758H-5, 125-1309H-2, 25-309H-4, 70-75

9H-5, 125-13010H-2, 25-30

10H-4, 70-7510H-5, 125-13011H-2, 25-3011H-2, 25-3011H-2, 25-3011H-2, 25-3011H-4, 25-30

11H-4, 70-7511H-6, 25-3011H-6, 25-3011H-6, 25-3012H-2, 25-30

12H-3, 70-7512H-4, 25-3012H-7, 25-3013H-1, 75-8013H-1, 125-13013H-2, 25-3013H-2, 75-8013H-2, 125-13013H-3, 25-3013H-3, 70-7513H-3, 70-7513H-3, 75-8013H-3, 75-8013H-3, 125-13013H-4, 25-3013H-4, 75-8013H-4, 125-13013H-4, 125-13013H-5, 25-3013H-5, 25-3013H-5, 75-8013H-5, 75-8013H-5, 75-8013H-5, 125-13013H-6, 25-3013H-6, 75-8013H-6, 125-13013H-7, 25-3014H-1, 75-80

14H-1, 125-13014H-1, 125-13014H-2, 25-30

14H-2, 75-80

14H-2, 125-130

14H-3, 25-3014H-3, 70-7514H-3, 75-80

14H-3, 125-13014H-4, 25-30

14H-4, 75-80

14H-4, 125-130

Depth(mbsf)

54.257.2

59.2

61.9

66.968.971.976.5

78.382.7

86.288.292.392.392.392.395.3

95.898.398.398.3

102.0

104.0105.0109.2110.6111.1

112.15112.65113.15113.60113.60113.65113.65114.1114.7115.1115.6115.6116.1116.1116.6116.6116.6117.1117.6118.1118.6119.1120.3

120.8120.8121.3

121.8

122.3

122.8123.2123.3

123.8124.3

124.8

125.3

Species

Cibicidoides wuellerstorfiC. wuellerstorfi

+ C. kullenbergi + Planulina bradyiC. wuellerstorfi

+ Planulina bradyiCibicidoides kullenbergi

+ C. wuellerstorfiCibicidoides wuellerstorfiCibicidoides wuellerstorfiCibicidoides wuellerstorfiCibicidoides rugosa

+ C. kullenbergiCibicidoides wuellerstorfiCibicidoides wuellerstorfi

+ C. rugosaCibicidoides wuellerstorfiCibicidoides kullenbergiOridorsalis umbonatusCibicidoides wuellerstorfiCibicidoides sp. BPlanulina bradyiCibicidoides kullenbergi

+ C. wuellerstorfi + C. sp. BCibicidoides wuellerstorfiOridorsalis umbonatusCibicidoides wuellerstorfiCibicidoides kullenbergiC. wuellerstorfi

+ Planulina bradyiCibicidoides wuellerstorfiCibicidoides wuellerstorfiCibicidoides kullenbergiCibicidoides wuellerstorfiCibicidoides wuellerstorfi

Cibicidoides wuellerstorfiCibicidoides wuellerstorfiCibicidoides kullenbergiCibicidoides wuellerstorfiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides wuellerstorfiCibicidoides wuellerstorfiCibicidoides wuellerstorfiCibicidoides wuellerstorfiCibicidoides kullenbergiCibicidoides wuellerstorfiCibicidoides lamontdohertyiCibicidoides wuellerstorfiCibicidoides lamontdohertyiCibicidoides kullenbergiCibicidoides wuellerstorfiCibicidoides wuellerstorfiCibicidoides wuellerstorfiCibicidoides wuellerstorfiCibicidoides wuellerstorfiCibicidoides wuellerstorfiCibicidoides wuellerstorfi

+ C. sp. C + C. kullenbergiCibicidoides wuellerstorfiCibicidoides lamontdohertyiCibicidoides wuellerstorfi

+ C. kullenbergiCibicidoides kullenbergi

+ C. wuellerstorfiCibicidoides kullenbergi

+ C. lamontdohertyiCibicidoides lamontdohertyiOridorsalis umbonatusCibicidoides kullenbergi


+ C. wuellerstorfiCibicidoides kullenbergi

+ C. wuellerstorfi + C. lamontdohertyiCibicidoides kullenbergi

518O

2.632.84

2.62

2.73

2.682.742.712.89

2.812.66

2.612.662.972.532.572.982.67

2.533.082.592.672.51

2.722.552.782.682.49

2.522.392.582.522.632.482.562.322.532.462.562.332.622.372.572.652.332.382.592.342.382.372.33

2.502.572.29

2.56

2.60

2.662.652.36

2.492.51

2.49

2.28

513C

0.030.37

0.24

0.16

-0 .120.220.270.29

0.050.04

0.710.54

-1 .100.120.150.781.10

1.110.420.760.630.94

0.600.700.720.540.59

0.700.560.450.900.860.780.930.800.710.770.620.860.600.930.670.780.721.141.051.210.970.941.56

0.990.720.67

0.92

0.82

0.81-0 .85

0.78

0.990.95

0.99

1.05

P:Bratio

167244

357

57

2743425

262

8757

231175289289289289250

221270270270301

670329202

7413538374380

490490

696941

113335858

14014014814814875

353272266303601

114114386

302

309

372210127

142322

481

198

522




115-709B- (Cont.)

14H-5, 25-30

14H-5, 125-130

14H-6, 25-30

14H-6, 75-80

14H-6, 125-130

14H-7, 25-30

15H-1, 75-8015H-1, 125-13015H-2, 25-30

15H-2, 70-7515H-2, 125-13015H-3, 25-3015H-3, 70-7515H-3, 75-8015H-3, 125-13015H-3, 125-13015H-4, 25-3015H-4, 25-3015H-4, 75-8015H-4, 125-13015H-5, 23-3015H-5, 25-3015H-5, 75-80

15H-5, 125-13015H-6, 25-30

15H-6, 70-7515H-6, 125-130

15H-7, 25-3016H-1, 25-3016H-1, 25-30

16H-1, 75-8016H-1, 125-13016H-1, 125-13016H-2, 25-3016H-2, 25-3016H-2, 70-7516H-2, 125-13016H-3, 25-3017H-2, 70-7518H-1, 25-30

18H-1, 75-8018H-1, 125-13018H-2, 25-3018H-2, 70-7518H-2, 125-130

18H-3, 25-30

18H-3, 75-80

18H-3, 125-130

18H-4, 25-3018H-5, 25-3018H-6, 25-3018H-7, 25-3019H-1, 25-3019H-1, 25-3019H-1, 75-80

19H-1, 125-13019H-2, 25-3019H-2, 25-3019H-2, 70-75

Depth(mbsf)

125.7

126.8

127.2

127.8

128.3

128.7

130.0130.5130.9

131.5132.0132.4132.9133.0133.5133.5133.9133.9134.5135.0135.4135.4136.0

136.5136.9

137.5138.0

138.4139.2139.2

139.7140.2140.2140.6140.6141.1141.7142.1149.3158.5

159.0159.5160.0160.5161.0

161.5

162.0

162.5

163.0164.5166.0167.5168.2168.2168.7

169.2169.7169.7170.2

Species

Cibicidoides kullenbergi+ C. wuellerstorfi

Cibicidoides kullenbergi+ C. wuellerstorfi

Cibicidoides kullenbergi+ C. wuellerstorfi + C. lamontdohertyi

Cibicidoides kullenbergi+ C. wuellerstorfi + C. lamontdohertyi

Cibicidoides wuellerstorfi+ C. kullenbergi

Cibicidoides wuellerstorfi+ C, kullenbergi

Cibicidoides kullenbergi + C. sp. CCibicidoides kullenbergiCibicidoides kullenbergi

+ C. lamontdohertyi + Planulina bradyiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiPlanulina bradyiCibicidoides kullenbergiOridorsalis umbonatusCibicidoides kullenbergiCibicidoides lamontdohertyiCibicidoides kullenbergiOridorsalis umbonatusCibicidoides kullenbergiCibicidoides kullenbergi


+ C. lamontdohertyi + Planulina renziCibicidoides kullenbergiCibicidoides kullenbergi

+ C. lamontdohertyiCibicidoides kullenbergiOridorsalis umbonatusCibicidoides kullenbergi

+ C. lamontdohertyiCibicidoides kullenbergiCibicidoides kullenbergi > 250 fimCibicidoides kullenbergi < 250 ^mCibicidoides kullenbergiPlanulina renziCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiOridorsalis umbonatusCibicidoides kullenbergi

+ Planulina renziCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergi




+ C. lamontdohertyiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides lamontdohertyiCibicidoides kullenbergiCibicidoides kullenbergi

+ C. lamontdohertyiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides lamontdohertyiCibicidoides lamontdohertyi

618O

2.12

2.22

2.38

2.25

2.11

2.13

:::

.66

.70

.69

.50

.84

.19

.32

.562.001.822.291.802.151.902.101.751.47

1.521.80

1.821.75

1.761.761.48

1.491.771.801.261.491.611.781.602.271.76

1.681.371.681.651.78

1.78

1.86

1.79

1.471.531.701.751.891.741.82

1.851.761.651.76

513C

1.65

1.79

1.01

1.19

1.25

1.80

1.381.331.19

1.561.461.411.081.351.111.470.941.531.121.080.271.030.57

0.640.70

0.600.79

0.880.051.06

1.341.381.491.351.661.711.931.700.170.67

0.830.630.450.620.71

0.73

0.75

0.84

0.720.490.770.750.730.830.57

0.610.770.710.57

P:Bratio

591

1294

398

390

423

579

200

442

75

152

7070

262262

65

233433

70

247

30

256498498

146437437

9191

482435496297195

230113111196320

137

263

597

18363

117132162162151

883232

352

523




Depth(mbsf) Species

115-709B-(Cont.)

19H-2, 70-7519H-2, 125-13019H-2, 125-13019H-3, 25-3019H-3, 25-3019H-3, 25-3019H-3, 75-8019H-3, 125-13019H-4, 25-3019H-4, 75-8019H-4, 125-13019H-5, 25-3019H-5, 25-3019H-5, 75-8019H-5, 75-8019H-5, 125-13019H-5, 125-13019H-6, 25-3019H-6, 75-8019H-6, 125-13019H-7, 27-3021H-1, 25-3021H-1, 25-3021H-1, 75-8021H-1, 125-13021H-2, 25-3021H-2, 25-3021H-2, 75-8021H-2, 125-13021H-3, 25-30

21H-3, 75-8021H-3, 123-128

21H-4, 25-30

21H-4, 75-8021H-4, 125-130

21H-5, 25-30

21H-5, 25-3021H-5, 75-8021H-6, 25-3021H-6, 75-8021H-7, 15-20

22H-1, 25-3022H-1, 75-8022H-1, 125-130

22H-2, 25-3022H-2, 75-8022H-2, 125-13022H-3, 75-80

170.2170.7170.7171.2171.2171.2171.7172.2172.7173.2173.7174.2174.2174.7174.7175.2175.2175.7176.2176.7177.2187.4187.4187.9188.4188.9188.9189.4189.9190.4

190.9191.4

191.9

192.4192.9

193.4

193.4193.9194.9195.4196.4

197.0197.5198.0

198.5199.0199.5200.5

Cibicidoides kullenbergiCibicidoides kullenbergiCibicidoides lamontdohertyiCibicidoides sp. CCibicidoides kullenbergiCibicidoides lamontdohertyiCibicidoides sp. SCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiOridorsalis umbonatusCibicidoides kullenbergiCibicidoides lamontdohertyiCibicidoides kullenbergiCibicidoides lamontdohertyiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides sp. SCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides lamontdohertyiCibicidoides lamontdohertyiCibicidoides kullenbergiCibicidoides lamontdohertyiCibicidoides kullenbergiCibicidoides lamontdohertyiPlanulina renziCibicidoides kullenbergi

+ C. lamontdohertyi + Planulina renziCibicidoides lamontdohertyiCibicidoides lamontdohertyi


+ C. lamontdohertyiCibicidoides lamontdohertyiCibicidoides kullenbergi

+ Planulina renziCibicidoides lamontdohertyi

+ C. kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides lamontdohertyi

+ C. kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergi

+ Planulina renziCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergiCibicidoides kullenbergi

P:Bratio

2.061.832.031.731.801.862.012.102.061.851.612.081.902.092.071.961.871.651.551.901.692.092.031.961.882.321.992.151.711.93

1.841.81

1.73

2.121.64

2.01

2.181.882.122.001.98

1.741.711.50

1.661.611.661.65

3.770.890.580.760.720.820.930.890.900.650.58

-0.100.980.910.900.740.680.480.570.860.661.50

:

:

:

:

.19

.30

.34

.64

.47

.50

.21

.57

.06

.42

1.30

1.400.90

1.30

.46

.35

.53

.12

.09

1.051.181.14

0.890.580.620.72

3529898646464

1601891381221146767

105105229229185108409372210210178124387387280432822

223162

185

551278

273

273440234305206

231135161

264288147218

which the corrosiveness of Miocene intermediate and deep wa-ter are low may be intervals in which the waters have decreasedconcentrations of CO2 formed by oxidation of organic matter.Conversely, periods of poorer carbonate preservation may havebeen ones in which the concentration of respiratory CO2 in deepand intermediate water was higher.

CONCLUSIONSThe benthic isotopic record of Miocene Cibicidoides from

Site 709 provides a record of oceanographic conditions at thatlocation throughout the epoch. As expected, the record qualita-tively resembles those of other DSDP and ODP sites. The dataare consistent with the scenario for the evolution of thermoha-line circulation in the Miocene Indian Ocean proposed by Wood-ruff and Savin (1989). Further testing of that scenario, however,

requires isotopic data from other sites as well as resolution ofthe reasons for variability in interspecific differences between518O and 513C values of different benthic taxa, especially Cibici-doides and Oridorsalis, from the same sample.

Correlation between 513C values of Cibicidoides and P:B ra-tios at Site 709 suggests that Miocene intervals of poorer car-bonate preservation at Site 709 are also intervals of increasedconcentration of respiratory CO2 in intermediate and deepwaters.

ACKNOWLEDGMENTSWe thank the staff of the Ocean Drilling Program for their

cooperation in providing the samples necessary for this study.This work was supported by National Science Foundation GrantNos. OCE-8800449 (F.W.) and OCE-8800472 (S.M.S.).

524

S'8O


8I3C

3.0 2.5 2.0 1.5 1-0 0.5

loo

rse

a i

I- Q

to

me

tei

no

120-

130-

140-

150-

160-

170-

, . , i 1 . , , i 1

<

i i i 1 i i i i 1 i i i i

709 A

^P

-0.5 0.0 0.5 1.0 15 2.0

- Q

100-

I 10-

120-

130-

140 -

150-

160-

170-

180-

190-

200-

-0.5 0.0 0.5 1.0 1.5 2.0i i i i I i i i i I i i i i I i i i i I i i '

709 B

3.0 2.5 2.0 1.5 1.0 0.5

Figure 2. A. The 518O and 513C values of Cibicidoides from the Miocene section of Hole 709A. Inferredages are shown. B. The 618O and 513C values of Cibicidoides from the Miocene section of Hole 709B. Iso-topically derived ages (see text and Table 2) are underlined. Other ages are inferred from biostratigraphicdata sources listed in Table 3.

525


Table 2. Age determina-tions for Hole 709Bbased on the isotopicrecord (see text).

Depth(mbsf)

83-86120124129132133146

Age(Ma)

6.011.813.414.314.715.015.6

REFERENCES

Backman, J., Duncan, R. A., et al., 1988. Proc. ODP, Init. Repts., 115:College Station, TX (Ocean Drilling Program).

Barron, J., Keller, G., and Dunn, D. A., 1985. A multiple microfossilbiochronology for the Miocene. In Kennett, J. P. (Ed.), The MioceneOcean: Paleoceanography and Biogeography. Mem. Geol. Soc. Am.,163:21-36.

Duplessy, J . -C, Shackleton, N. J., Matthews, R. K., Prell, W. L., Rud-diman, W. F., Caralp, M., and Hendy, C. H., 1984. 13C record ofbenthic foraminifera in the last interglacial ocean: implications forthe carbon cycle and the global deep water circulation. Quat. Res.,21:225-243.

Epstein, S., Buchsbaum, S. R., Lowenstam, H. A., and Urey, H. C ,1951. Carbonate-water isotopic geothermometer. Geol. Soc. Am.Bull., 62:417-426.

Haq, B. U , Worsley, T. R., Burckle, L. H., Douglas, R. G., Keigwin,L. D., Opdyke, N. D., Savin., S. M., Sommer, M. A., Vincent, E.,and Woodruff, F., 1980. Late Miocene carbon-isotopic shift andsynchroneity of some phytoplanktonic biostratigraphic events. Geol-ogy, 8:425-431.

Miller, K. G., and Katz, M., 1987. Oligocene to Miocene benthic fora-miniferal and abyssal circulation changes in the North Atlantic. Mi-cropaleontology, 33:130.

Savin, S. M., and Woodruff, F., 1990. Isotopic evidence for temperatureand productivity in the Tertiary oceans. In Burnett, W. C , andRiggs, S. R. (Eds.), Phosphate Deposits of the World: Genesis ofNeogene to Recent Phosphorites (Vol. 3): Cambridge (CambridgeUniv. Press), 241-259.

Shackleton, N. J., Hall, M. A., and Boersma, A. J., 1984. Oxygen andcarbon isotope data from Leg 74 foraminifers. In Moore, T. C , Jr.,Rabinowitz, P. D., Init. Repts. DSDP, 74: Washington (U.S. Govt.Printing Office), 599-612.

Vincent, E., Killingley, J. S., and Berger, W. H., 1982. The magnetic ep-och-6 carbon shift: a change in the oceans C13/C12 ratio. Mar. Mi-cropaleontol., 5:185-203.

, 1985. Miocene oxygen and carbon isotope stratigraphy of thetropical Indian Ocean. In Kennett, J. P. (Ed.), The Miocene Ocean:Paleoceanography and Biogeography. Mem. Geol. Soc. Am., 163:103-130.

Woodruff, F., and Savin, S. M., 1989. Miocene deep-water oceanogra-phy. Paleoceanography, 4:87-140.

Date of initial receipt: 15 June 1989Date of acceptance: 20 December 1989Ms 115B-147

Table 3. Hole 709B Biostratigraphic age datums from Backman, Duncan, et al. (1988), Rioet al. (this volume), and Johnson (this volume) that are consistent with the isotopic data.

Depth(mbsf)

Age(Ma) Datum Zonal boundary

53.3-54.856.3-57.860.8-63.066.5-68.068.0-77.689.5-92.590.2-91.9

105.8-107.3107-116107-116

109.1-111.1112.7-114.2114.2-115.7

119126.5-127.7

141164.6

169.8-169.9192.2-193.5

4.65.05.45.45.86.46.57.38.69.98.9

10.010.811.813.915.217.617.524.3

Ceratolithus rugosus (N)(B)Ceratolithus acutus (N)(B)Discoaster quinqueramus (N)(T)Acrobotrys tritubus (R)Pulleniatina primalis (F)(B)Stichocorys delmontensis to S. peregrina (R)Amaurolithus primus (N)(B)Discoaster quinqueramus (N)(B)Neogloquadrina acostaensis (F)(B)Globorotalia siakensis (F)(T)Discoaster hamatus (N)(T)Discoaster hamatus (N)(B)Catinaster coalitus (N)(B)Sphaeroidinella subdehiscens (F)(T)Sphenolithus heteromorphus (N)(T)Orbulina suturalis (F)(B)Catapsydrax dissimilis (F)(T)Sphenolithus heteromorphus (N)(B)Lychnocanoma elongata (R)(B)

CNlOc/CNIOb, NN13/NN12CNlOb/CNIOaCN10a/CN9

N17b/N17a

CN9b/CN9aNN11/NN10N16/N15N15/N14CN8a/CN7, NN10/NN9CN7a/CN6, NN9/NN8CN6/CN5, NN8/NN7N13/N12CN5A/CN4, NN6/NN5N9/N8N7/N6CN3/CN2Zonal base

Notes: F = foraminifer, R = radiolarian, N = nannoplankton, T = range top, and B = range bot-tom.

526


S values

0.3 0 .5 0.7 0.9 I.I 1.3 1.5 1.7 1.9158

170 -I

Figure 3. Detail of the oxygen and carbon isotopic records of Hole 709BCibicidoides over the interval from 155 to 170 mbsf. Backman, Duncan,et al. (1988) inferred from whole-sample magnetic susceptibility datathat the section between 163.3 and 168 mbsf was a repeat of the immedi-ately overlying interval. The isotopic data are consistent with, but donot require, that interpretation. Squares = S18O values, and diamondsindicate 513C values.

Table 4. Mean 518O and


13

0)-Q

log P'B & S I JC

-0.2 0.3 0.8 1.3 1.8 2.3 2.8 3.3

CO

enO

CO

ocr>c>O

UJ

UIO

CL

ID,

DD

Q-

cnO

2 . 8 -

2.7-

2 . 6 -

2 . 5 -

2.4-

2 . 3 -

2 . 2 -

2.1 -

2.0-

1.9-

1 . 8 -

/ . 7 -

1.6-

c

D

0 / ^

0

D

a a

aD

D

aa

aa o

D D0

0 _

D 'nOD

0

D

0 D

D

• • Q0° 0-0J° Dtf M H

8f«°=oosT>

v^ n

3 ° 0 ^ ^

o° a

0 DnD 0

Da

[j D

°̂ ̂ ^^Iri D n

0 0

00

i T

-0.2 0 0 . 2 0 . 4 0 . 6 0.8 I 1.2 1.4 1.6 1.8 2

Cibicidoides O CFigure 5. Scatter plot of 513C values of Cibicidoides vs. the logarithm ofthe P:B ratio (5-point moving average). The regression line is significantat the 99% level.

200

Figure 4. Time-series plot of 513C values of Cibicidoides from Holes709A and 709B (squares) compared with planktonic:benthic ratios ofthe sediment samples (diamonds). P:B ratios are plotted on a logarith-mic scale. Major increases in 513C correspond to increases in P:B ratio.

528

27. miocene benthic foraminifer oxygen and carbon … · 2006. 9. 22. · duncan, r. a., backman,...

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