35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN...

16
Prell, W. L., Niitsuma, N., et al., 1991 Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 117 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC MATTER FROM SITES 724 AND 725, OMAN MARGIN 1 Alfred N. N. Muzuka, 2 Stephen A. Macko, 2 ' 4 and T. F. Pedersen 3 ABSTRACT Stable isotopic compositions of carbon and nitrogen and organic carbon content of sediments ranging from the Pli- ocene to the Pleistocene-Holocene in age from the Oman Margin (ODP Sites 724 and 725) are reported. In general, the organic carbon content is greater than 2% at Site 724. Prior to the Pleistocene-Holocene at this site, sediments with higher content of organic matter were deposited owing to favorable preservation conditions and/or higher productivity. In the Pleistocene, lower amounts of organic matter have been preserved; this material generally has more enriched ni- trogen isotopic compositions. This may indicate intensification of the Oxygen Minimum Zone and denitrification with the onset of the Pleistocene. A correlation of carbon isotope content of these sediments with oxygen isotope stages at Site 724 indicates an enrichment in 13 C during glacial events. Based on the stable isotope evidence of both carbon and nitrogen, there does not appear to be major input of terrigenous-derived allochthonous material in this marine environ- ment. The timing and extent of monsoon winds on the productivity of this region are not evident, but require further studies for collaborative interpretation of small-scale features in the isotopic and carbon content of this environment. INTRODUCTION One of the primary goals of drilling in the western Arabian Sea during Ocean Drilling Project Leg 117 was to determine the history of monsoon variability by studying the fluctuations in oceanic circulation and productivity as preserved in the sedi- mentary record. The effects of land mass altitude, atmospheric circulation, and glacial events on the initiation and magnitude of the monsoons need to be incorporated into paleoclimatic models. Holes were drilled at 12 sites on the Indus Fan, the Owen Ridge, and the Oman Margin. This paper presents stable carbon and nitrogen isotope analyses on the sediment organic matter from two of the Oman Margin sites (Fig. 1). The sites which were studied, 724 and 725, are located on the continental margin of Oman in water depths of 592.8 m and 311.5 m, respectively. In addition to the primary objectives of this leg, these sites were drilled to obtain high resolution infor- mation to establish the relationships among the intensity and timing of monsoons, the productivity of the region, and the fluctuation and effects of the oxygen minimum zone (OMZ) on the preservation and diagenesis of organic matter in sediments below an upwelling area. The amount and type of organic matter produced in the up- welling zone is a product of oceanic circulation, water column concentrations of nutrients, and the hydrographic regime (Zahn and Pedersen, this volume). The amount of organic matter pro- duced over time should be related to the development of re- gional upwelling, which depends directly on the intensity of monsoon winds. The present productivity in the upwelling zone of the Arabian Sea may be as much as 30 times the amounts commonly observed in the oceans of the world (Romankevich, 1984). The historical changes in the intensity of monsoon winds are likely to have affected the distribution and quantity of or- 1 Prell, W. L., Niitsuma, N., et al., 1991. Proc. ODP, Sci. Results, 117: Col- lege Station, TX (Ocean Drilling Program). 2 Department of Earth Sciences, Memorial University, St. John's, Newfound- land A1B 3X5, Canada. 3 Department of Oceanography, University of British Columbia, Vancouver, British Columbia V6T 1Y1, Canada. 4 Present address: Department of Environmental Sciences, University of Vir- ginia, Charlottesville, VA 22903, U.S.A. garlic matter produced in upwelling regions. During interglacial periods, southwest monsoon winds are thought to have been strong, resulting in enhanced upwelling whereas upwelling tended to be weak during glacial events (Prell and Curry, 1981; Rossi- gnol-Strick, 1983; Prell and van Campo, 1986; Prell and Kutz- bach, 1987). The record of these variations may be preserved in the organic matter found in sediments beneath areas influenced by upwelling (Muller and Suess, 1979; Muller et al., 1983). Upwelling zones may vary spatially as well as temporally, com- plicating an interpretation of the organic sedimentary record (Reimers and Suess, 1983; ten Haven et al., 1989). The preserva- tion of organic material in the sediments is also affected by hy- drographic regime, particle size, oxidant content, and sedimen- tation rate (Emerson and Hedges, 1988; Calvert and Pedersen, in press). The isotopic composition of organic matter in sediments has been used to suggest the influence of glacial episodes on marine sequences (Parker et al., 1972; Macko, 1989). To use stable iso- tope compositions to interpret input into the sedimentary re- cord, the organic matter incorporated in sediments must reflect the original source carbon or nitrogen. Organic materials in the marine environment may originate in the photic zone, or in nearshore environments as terrigenous debris, or as a mixture of these two sources. This study uses organic carbon and nitro- gen stable isotope compositions to delineate the origin of or- ganic matter in sediments from the western Arabian Sea. In numerous studies of marine environments, the relative contributions of terrigenous and marine inputs have been esti- mated from stable carbon isotope compositions. For example, in the Gulf of Mexico, surficial sediments contain increasing amounts of the heavier isotope of carbon ( 13 C) with increasing distance from land, and suggest a decreasing terrigenous carbon influence (Sackett and Thompson, 1963; Hedges and Parker, 1976; Gearing et al., 1977). In the deltas of both the Pedernales in Venezuela (Eckelmann et al., 1962) and Niger rivers (Gearing et al., 1977), woody fragments and more finely disseminated terrestrial plant debris give a clear terrigenous isotopic signature to deltaic sediments. In more northern Arctic environments, the transport of terrigenous material may be more extensive. In the Beaufort Sea, lateral transport of terrestrial debris is enhanced by ice-rafting (Gearing et al., 1977). These variations in source are recorded in the sedimentary record of a region. In the Gulf 571

Transcript of 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN...

Page 1: 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC ... tion of organic material in the sediments is also affected

Prell, W. L., Niitsuma, N., et al., 1991Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 117

35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC MATTERFROM SITES 724 AND 725, OMAN MARGIN1

Alfred N. N. Muzuka,2 Stephen A. Macko,2 '4 and T. F. Pedersen3

ABSTRACT

Stable isotopic compositions of carbon and nitrogen and organic carbon content of sediments ranging from the Pli-ocene to the Pleistocene-Holocene in age from the Oman Margin (ODP Sites 724 and 725) are reported. In general, theorganic carbon content is greater than 2% at Site 724. Prior to the Pleistocene-Holocene at this site, sediments withhigher content of organic matter were deposited owing to favorable preservation conditions and/or higher productivity.In the Pleistocene, lower amounts of organic matter have been preserved; this material generally has more enriched ni-trogen isotopic compositions. This may indicate intensification of the Oxygen Minimum Zone and denitrification withthe onset of the Pleistocene. A correlation of carbon isotope content of these sediments with oxygen isotope stages atSite 724 indicates an enrichment in 13C during glacial events. Based on the stable isotope evidence of both carbon andnitrogen, there does not appear to be major input of terrigenous-derived allochthonous material in this marine environ-ment. The timing and extent of monsoon winds on the productivity of this region are not evident, but require furtherstudies for collaborative interpretation of small-scale features in the isotopic and carbon content of this environment.

INTRODUCTION

One of the primary goals of drilling in the western ArabianSea during Ocean Drilling Project Leg 117 was to determine thehistory of monsoon variability by studying the fluctuations inoceanic circulation and productivity as preserved in the sedi-mentary record. The effects of land mass altitude, atmosphericcirculation, and glacial events on the initiation and magnitudeof the monsoons need to be incorporated into paleoclimaticmodels. Holes were drilled at 12 sites on the Indus Fan, theOwen Ridge, and the Oman Margin. This paper presents stablecarbon and nitrogen isotope analyses on the sediment organicmatter from two of the Oman Margin sites (Fig. 1).

The sites which were studied, 724 and 725, are located on thecontinental margin of Oman in water depths of 592.8 m and311.5 m, respectively. In addition to the primary objectives ofthis leg, these sites were drilled to obtain high resolution infor-mation to establish the relationships among the intensity andtiming of monsoons, the productivity of the region, and thefluctuation and effects of the oxygen minimum zone (OMZ) onthe preservation and diagenesis of organic matter in sedimentsbelow an up welling area.

The amount and type of organic matter produced in the up-welling zone is a product of oceanic circulation, water columnconcentrations of nutrients, and the hydrographic regime (Zahnand Pedersen, this volume). The amount of organic matter pro-duced over time should be related to the development of re-gional upwelling, which depends directly on the intensity ofmonsoon winds. The present productivity in the upwelling zoneof the Arabian Sea may be as much as 30 times the amountscommonly observed in the oceans of the world (Romankevich,1984). The historical changes in the intensity of monsoon windsare likely to have affected the distribution and quantity of or-

1 Prell, W. L., Niitsuma, N., et al., 1991. Proc. ODP, Sci. Results, 117: Col-lege Station, TX (Ocean Drilling Program).

2 Department of Earth Sciences, Memorial University, St. John's, Newfound-land A1B 3X5, Canada.

3 Department of Oceanography, University of British Columbia, Vancouver,British Columbia V6T 1Y1, Canada.

4 Present address: Department of Environmental Sciences, University of Vir-ginia, Charlottesville, VA 22903, U.S.A.

garlic matter produced in upwelling regions. During interglacialperiods, southwest monsoon winds are thought to have beenstrong, resulting in enhanced upwelling whereas upwelling tendedto be weak during glacial events (Prell and Curry, 1981; Rossi-gnol-Strick, 1983; Prell and van Campo, 1986; Prell and Kutz-bach, 1987). The record of these variations may be preserved inthe organic matter found in sediments beneath areas influencedby upwelling (Muller and Suess, 1979; Muller et al., 1983).Upwelling zones may vary spatially as well as temporally, com-plicating an interpretation of the organic sedimentary record(Reimers and Suess, 1983; ten Haven et al., 1989). The preserva-tion of organic material in the sediments is also affected by hy-drographic regime, particle size, oxidant content, and sedimen-tation rate (Emerson and Hedges, 1988; Calvert and Pedersen,in press).

The isotopic composition of organic matter in sediments hasbeen used to suggest the influence of glacial episodes on marinesequences (Parker et al., 1972; Macko, 1989). To use stable iso-tope compositions to interpret input into the sedimentary re-cord, the organic matter incorporated in sediments must reflectthe original source carbon or nitrogen. Organic materials in themarine environment may originate in the photic zone, or innearshore environments as terrigenous debris, or as a mixtureof these two sources. This study uses organic carbon and nitro-gen stable isotope compositions to delineate the origin of or-ganic matter in sediments from the western Arabian Sea.

In numerous studies of marine environments, the relativecontributions of terrigenous and marine inputs have been esti-mated from stable carbon isotope compositions. For example,in the Gulf of Mexico, surficial sediments contain increasingamounts of the heavier isotope of carbon (13C) with increasingdistance from land, and suggest a decreasing terrigenous carboninfluence (Sackett and Thompson, 1963; Hedges and Parker,1976; Gearing et al., 1977). In the deltas of both the Pedernalesin Venezuela (Eckelmann et al., 1962) and Niger rivers (Gearinget al., 1977), woody fragments and more finely disseminatedterrestrial plant debris give a clear terrigenous isotopic signatureto deltaic sediments. In more northern Arctic environments, thetransport of terrigenous material may be more extensive. In theBeaufort Sea, lateral transport of terrestrial debris is enhancedby ice-rafting (Gearing et al., 1977). These variations in sourceare recorded in the sedimentary record of a region. In the Gulf

571

Page 2: 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC ... tion of organic material in the sediments is also affected

A.N.N. MUZUKA, S. A. MACKO, T. F. PEDERSEN

19°N

18C

17*

16C

15°

I ... ..

ArabiaINDIA

OMAN MARGIN

SITES

56°E 57° 58*

Figure 1. Map showing locations of Leg 117 sites in this study.

of Mexico, variations downcore have been correlated with gla-cial and interglacial episodes which are related to sea level low-ering and the increasing influence of the Mississippi River onmarine deposits (Parker et al., 1972; Newman et al., 1973). Inenvironments which are dominated by marine productivity, otherenvironmental parameters such as temperature, growth rate, spe-cies distribution, and CO2 availability may affect carbon iso-topic compositions (Sackett et al., 1965; Degens et al., 1968;Gearing et al., 1977; Fontugne and Duplessy, 1978,; 1981; De-gens, 1969). In Baffin Bay and the Labrador Sea (ODP Leg 105)and in the Weddell Sea (ODP Leg 113), large-scale changes inδ13C were interpreted to be strongly influenced by variations inmarine planktonic productivity, and by the effect of ice-rafteddebris on the overall accumulation of organic matter in sedi-ments of the region (Macko, 1989; Macko and Pereira, 1990).Such variability would impact the organic isotopic record pre-served in a sediment (Macko et al., 1987b). In this present study,it is less likely that certain of these variables will significantlyimpact the carbon isotopic compositions. For example, enhancedisotopic fractionation of carbon at low temperature and thestrong influence of terrestrial debris are not expected owing tothe warm waters and the lack of significant rivers in the region.

61

Temporal variation in river outflow and eolian inputs couldhave introduced measurable amounts of organic matter of ter-rigenous origin at specific times in the past, particularly duringmonsoon maxima.

Stable nitrogen isotopes are also useful indicators of thesources of organic material in marine sediments. Peters et al.(1978) used nitrogen isotope compositions to evaluate the rela-tive contributions of terrigenous and marine inputs into a sedi-ment. Because the major sources of nitrogen in terrestrial sys-tems (N2 via nitrogen fixation) are isotopically distinct from ma-rine nitrogen (nitrate through nitrate reduction), these sourcesmay be resolved in most environments. Further, in purely ma-rine environments, the processes through which phytoplankton(or bacteria) incorporate nitrogen may be resolved if one caneliminate sources of nitrogen from land. The process of nitro-gen fixation has a small isotopic fractionation associated withthe utilization of molecular nitrogen. Such a process is easilydistinguished from the more common mode of nitrate reductionin which phytoplankton fully utilize dissolved nitrate and reflectits isotopic signature (Macko et al., 1984). When algae are onlyable to use a portion of the dissolved nitrate, depleted 15N val-ues may be evident, reflecting the isotopic fractionation associ-

572

Page 3: 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC ... tion of organic material in the sediments is also affected

ISOTOPIC COMPOSITIONS OF CARBON AND NITROGEN OF ORGANIC MATTER

ated with that reduction (Macko et al., 1987a). Such changesmay then be useful in the interpretation of the paleoceano-graphic record of an area. The organic matter in sediments de-posited during periods of higher productivity, in which phyto-plankton fully utilized the oceanic nitrate, may be more en-riched in 15N than sediments associated with lower productivityin which larger fractionations occur.

However, the situation is complicated by factors which in-clude microbial action, denitrification, diagenesis, and recyclingof organics. Variations in isotopic signature may occur as a re-sult of deamination reactions associated with organic rich mate-rials (Wada, 1980; Zieman et al., 1984; Sigleo and Macko, 1985;Libes and Deuser, 1988). Such processes of alteration may be es-pecially important in changing isotopic signatures below the eu-photic zone (Altabet and McCarthy, 1986). Highly enriched iso-topic compositions of nitrogen were observed in particulate ma-terial of the Indian Ocean; these enrichments were attributed todiagenetic effects in the water column (Saino and Hattori, 1980).With extensive denitrification of dissolved nitrate, the residualnitrate may become highly enriched in 15N (Cline and Kaplan,1975; Liu, 1979). This remaining nitrate may serve as a nitrogensource for primary production, and if fully utilized, would beisotopically reflected in the newly produced organic matter.

METHODS

Sediment samples collected for isotope analysis were initiallyfrozen. In this study, sampling frequency was typically five sam-ples per 1 m interval, with the sample representing a homoge-nate of a 2 cm section of core. A large number of these samplesthawed during shipment from the vessel to the laboratory (lower180 m of Hole 724C and the samples from Site 725). These sam-ples were refrozen upon receipt and maintained at - 10°C untilprocessing. Samples were dried at 40° C and then acidified with30% HC1 to remove carbonate. The carbonate-free residue waswashed of all salts, because of the high carbonate content, anddried. A portion of the dried material was then weighed andcombusted in quartz for 1 hr at 850°C in the presence of puri-fied cupric oxide wire and high purity granular copper (Mackoet al., 1984). The N2 and CO2 gases obtained were cryogenicallyisolated from other combustion products and analyzed on aV.G. Micromass PRISM stable isotope ratio mass spectrometer.On the basis of replicate analyses of samples, the reproducibil-ity in combustion and measurement is within ± 0.2‰. Isotopedata are reported relative to standard materials as:

δ x E = pie

L standard103

where X is the isotope of the element E and R is the abundanceratio of the heavy to light isotope; the standard for 15N is atmo-spheric nitrogen and the standard for carbon is the ChicagoPDB. For routine measurement, samples are analyzed vs. a lab-oratory secondary standard tank of either pure nitrogen or car-bon dioxide gas. The organic carbon content was determined onthe carbonate-free residue as volume of the carbon dioxide gasreleased in the combustion. The organic carbon percentages(Table 1) are not corrected for carbonate content of the sedi-ment.

RESULTS

Site 724

At Site 724, sampling was undertaken for high resolutionanalysis with 811 isolates being characterized from one hole(Hole 724C). This sampling allowed for resolution of fluctua-tions to be observed on the order of 1400-5700 yr at the esti-mated sedimentation rate ranges of 142-35 m/m.y. The homog-

Table 1. Stable isotope organic geochemis-try results.

Core andsection

117-724C-

1H-11H-11H-11H-11H-11H-11H-11H-21H-21H-21H-21H-21H-22H-2H-2H-2H-2H-]2H-2H-]2H-22H-22H-22H-22H-22H-22H-32H-32H-32H-32H-32H-32H-32H-32H-42H-42H-42H-42H-42H-42H-42H-52H-52H-52H-52H-52H-52H-52H-52H-62H-62H-62H-62H-62H-62H-62H-72H-72H-72H-73H-13H-13H-13H-13H-13H-13H-13H-23H-23H-23H-23H-23H-23H-23H-3

Depth(mbsf)

0.220.420.620.821.021.221.241.621.822.022.222.422.582.873.023.423.623.824.024.224.424.625.025.225.425.625.826.026.226.426.626.827.027.227.427.627.828.028.228.428.628.829.029.229.429.629.82

10.0210.2210.4210.6210.8211.0211.2211.4211.6211.8212.0212.2212.4212.4212.6212.8213.0213.2213.4213.6213.8214.0214.2214.4214.6214.8215.0215.22

δ 1 5N

8.16.08.10.97.36.15.56.46.07.86.54.5

10.16.25.97.95.65.8

10.16.26.45.96.96.66.67.26.52.26.0

10.811.06.24.76.6

10.78.49.48.39.08.1

10.09.4

10.77.0

11.05.6

10.47.8

15.96.6

10.511.19.4

11.56.68.7

12.27.95.59.28.84.96.6

12.58.08.34.45.86.16.6

12.513.210.110.29.2

δ1 3C

-20.0-20.2-19.6-19.5-19.5-19.2-19.1-18.5-19.3-18.8-19.0-18.4-19.0-20.0-20.8-19.0-19.3-20.1-20.0-23.0-21.7-21.1-20.2-21.7-21.9-20.0-20.6-22.2-19.4-19.7-19.3-19.8-19.6-19.7-19.5-19.4-19.9-19.8-19.9-19.9-19.5-20.1-19.2-20.6-20.0-21.0-20.3-19.6-19.8-20.1-19.6-19.6-19.5-20.0-19.9-20.7-19.5-20.8-19.7-19.4-19.6-19.5-19.5-19.5-20.1-19.5-19.5-19.8-20.0-19.9-19.4-19.8-19.8-19.6-19.5

<%C

6.16.52.52.31.41.20.81.41.73.32.73.32.61.31.23.11.13.44.90.81.02.24.31.81.42.70.70.31.11.71.61.62.13.62.34.05.32.43.43.64.53.42.83.91.62.02.81.10.81.10.81.41.41.51.74.12.91.91.52.23.32.61.82.14.61.51.91.92.80.81.31.21.31.51.9

573

Page 4: 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC ... tion of organic material in the sediments is also affected

A.N.N. MUZUKA, S. A. MACKO, T. F. PEDERSEN

Table 1 (continued). Table 1 (continued).

Core andsection

Depth(mbsf)

117-724C-(Cont.)

3H-33H-33H-33H-33H-33H-33H-43H-43H-43H-43H-43H-43H-43H-53H-53H-53H-53H-53H-53H-53H-53H-63H-63H-63H-63H-63H-63H-63H-73H-73H-73H-74H-]4H-14H-:4H-i4H-]4H-14H-]

[

I1IIII

4H-14H-24H-24H-24H-24H-24H-24H-24H-34H-34H-34H-34H-34H-34H-34H-34H-44H-44H-44H-44H-44H-44H-44H-54H-54H-54H-54H-54H-54H-54H-54H-64H-64H-64H-64H-64H-64H-«

15.4215.6215.8216.2216.4216.6216.8217.0217.2217.4217.6217.8218.0218.2218.4218.6218.8219.0219.2219.4219.6219.8220.0220.2220.4220.6220.8221.0221.2221.4221.6221.8221.8021.9222.1222.3222.5222.7222.9223.1223.3223.5223.7223.9224.1224.3224.5224.7224.9225.1225.3225.5225.7225.9226.1226.3226.5226.7226.9227.1227.3227.5227.7227.9228.1228.3228.5228.7228.9229.1229.3229.5229.7229.9230.1230.3230.52

5 1 5 N

11.35.4

11.29.75.2

15.111.512.310.08.95.5

10.47.65.87.74.39.4

12.69.45.69.4

12.48.69.8

10.610.612.69.17.62.29.98.7

12.89.7

11.912.36.1

10.49.0

10.811.411.210.710.99.38.68.85.2

14.010.79.6

10.512.411.39.88.79.19.18.4

10.04.66.57.96.5

10.94.17.2

14.011.810.39.2

12.516.013.09.37.89.9

δ1 3c

-19.5-19.8-19.3-21.4-19.4-20.0-19.5-19.6-20.1-21.3-19.8-19.7-19.0-19.5-20.0-19.6-19.7-19.5-19.6-19.8-19.6-20.1-19.8-20.8-19.6-20.5-20.0-19.4-19.6-19.9-19.5-20.5-20.4-20.5-20.2-19.9-20.1-20.1-20.1-19.5-20.3-20.1-20.0-19.5-19.4-21.1-20.2-21.1-22.6-19.2-21.4-20.1-19.6-19.8-19.4-20.4-20.0-19.8-20.0-19.6-20.0-21.3-21.1-20.7-20.5-20.3-20.5-20.1-21.5-22.2-21.0-24.7-21.0-23.6-23.5-20.0-20.2

%C

1.72.91.95.22.30.91.31.62.51.61.51.72.22.22.92.32.01.71.91.91.92.73.62.73.53.64.02.11.92.52.83.71.62.21.71.22.63.64.12.13.13.72.32.92.71.51.61.00.41.20.31.62.42.63.32.65.83.32.82.43.33.35.06.12.40.14.20.80.90.80.80.20.50.91.32.21.9

Core andsection

Depth(mbsf)

117-724C-(Cont.)

4H-74H-74H-74H-75H-15H-5H-5H-5H-5H-5H-5H-25H-25H-25H-25H-25H-25H-35H-35H-35H-35H-35H-35H-35H-45H-45H-45H-45H-45H-45H-45H-55H-55H-55H-55H-55H-55H-55H-65H-65H-65H-65H-65H-65H-65H-75H-75H-715H-76X-16X-6X-6X-6X-6X-6X-6X-6X-26X-26X-26X-26X-26X-26X-26X-36X-36X-36X-36X-36X-36X-36X-36X-46X-46X-46X-^

30.8831.0831.2831.4831.2831.4231.6232.0232.2232.4232.6232.8233.0233.4233.6233.8234.0234.4234.6234.8235.0235.2235.4235.4635.4836.0236.2236.4236.6236.8237.0237.2237.4237.6238.0238.2238.4238.6238.8239.0239.2239.4239.6239.8240.0240.2240.4240.6240.8240.8441.0241.2241.4241.6241.8242.0242.2242.4242.6242.8243.0243.2243.4243.6243.8244.0244.2244.4244.6244.8245.0245.2245.4245.6245.8246.02

δ 1 5 N

11.410.79.26.05.49.5

11.211.38.05.67.9

11.911.111.810.214.38.5

15.514.15.3

10.511.910.014.25.87.2

12.56.87.97.18.59.6

11.06.8

12.611.810.49.8

15.313.812.911.913.212.111.99.3

12.311.011.711.79.79.49.6

11.111.19.69.8

13.08.7

11.510.08.59.9

11.311.614.77.4

11.28.19.8

11.511.112.29.78.2

10.8

δ1 3c

-20.1•– 19.8-19.7-20.1-20.0-20.1-20.2-20.2-20.1-20.7-20.3-20.3-20.8-21.0-20.6-19.5-19.8-19.8-20.1-19.4-19.9-18.5-19.8-19.3-19.5-19.6-18.8-20.1-19.7-19.4-19.6-18.5-19.5-20.2-19.6-19.9-19.6-19.9-19.9-20.0-18.8-21.9-23.3-20.3-19.4-19.9-20.0-19.6-19.6-20.8-21.4-20.4-19.9-19.8-19.5-19.9-19.9-22.6-20.7-20.6-21.5-20.3-19.9-20.3-20.0-20.1-19.2-20.3-19.8-19.4-19.7-18.9-20.3-19.6-19.4-19.8

<%C

2.22.02.22.32.31.51.52.02.12.23.52.21.60.80.61.61.71.31.01.10.92.32.42.02.23.04.24.23.73.04.52.63.53.23.33.43.83.03.03.83.41.92.42.42.13.01.71.62.13.23.45.13.62.82.22.74.01.85.14.21.31.22.52.31.91.92.31.72.92.62.12.01.33.53.15.7

574

Page 5: 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC ... tion of organic material in the sediments is also affected

Table 1 (continued).

Core and Depthsection (mbsf) δ1 5N δ1 3C %C

117-724C-(Cont.)

6X-4 46.22 10.9 -19.6 4.36X-4 46.42 5.4 -19.7 3.16X-4 46.62 8.4 -20.0 2.56X-5 46.82 9.7 -20.1 2.46X-5 47.02 7.1 -20.2 2.66X-5 47.22 11.3 -20.7 3.46X-5 47.42 12.5 -20.0 1.86X-5 47.62 7.7 -20.2 2.36X-5 47.82 12.4 -19.8 1.66X-5 48.02 11.2 -20.6 1.76X-5 48.22 12.0 -19.2 1.66X-6 48.42 6.1 -20.6 2.66X-6 48.62 10.2 -19.6 2.26X-6 48.82 10.8 -21.2 4.06X-6 49.02 9.3 -19.9 1.86X-6 49.22 10.3 -19.2 1.27X-1 50.72 12.5 -21.0 6.27X-1 50.92 9.8 -20.9 5.27X-1 51.12 10.0 -20.4 2.57X-1 51.32 11.1 -20.9 5.27X-1 51.52 10.3 -20.8 3.67X-1 51.72 5.5 -20.2 2.27X-1 51.92 8.0 -20.1 1.47X-2 52.12 9.6 -20.2 1.77X-2 52.32 10.0 -20.2 2.07X-2 52.52 4.5 -20.5 1.67X-2 52.72 8.1 -19.9 1.27X-2 52.92 4.5 -19.0 1.07X-2 53.12 16.9 -20.0 1.67X-2 53.32 12.0 -20.6 1.17X-3 53.52 8.1 -19.5 0.87X-3 53.72 13.1 -20.2 1.07X-3 53.92 10.2 -20.6 1.37X-3 54.32 12.6 -20.2 1.87X-3 54.52 7.8 -20.2 2.17X-3 54.72 6.1 -20.1 3.07X-3 54.92 9.9 -19.8 3.17X-4 55.12 6.9 -21.2 3.87X-4 55.32 11.9 -20.4 4.47X-4 55.52 11.0 -20.1 5.17X-4 55.72 11.9 -20.8 4.37X-4 55.92 9.7 -22.9 2.57X-4 56.12 5.7 -19.4 2.87X-4 56.32 8.6 -21.5 4.67X-5 56.72 6.7 -20.4 2.97X-5 56.92 7.5 -20.3 3.37X-5 57.12 9.1 -20.6 3.77X-5 57.32 11.3 -20.6 2.27X-5 57.52 9.3 -17.7 1.97X-5 57.72 10.1 -20.5 1.97X-5 57.92 8.3 -19.8 2.17X-6 58.12 9.0 -20.3 2.77X-6 58.32 12.3 -19.3 2.87X-6 58.52 8.2 -20.1 2.67X-6 58.72 8.9 -20.1 3.58X-1 60.22 18.9 -20.2 4.18X-1 60.42 6.2 -21.1 4.18X-1 60.62 6.7 -20.7 4.98X-1 60.82 5.7 -20.4 3.68X-1 61.02 5.4 -20.5 4.78X-1 61.22 8.2 -20.3 3.38X-1 61.42 8.7 -20.2 3.38X-1 61.62 6.1 -20.9 4.78X-2 61.82 8.8 -19.9 5.78X-2 62.02 8.9 -20.1 3.58X-2 62.22 4.7 -20.5 3.68X-2 62.42 6.4 -21.0 5.28X-2 62.62 16.4 -20.5 4.58X-2 62.82 5.8 -20.7 4.78X-2 63.02 4.9 -19.0 1.48X-3 63.22 4.4 -19.3 1.18X-3 63.42 6.3 -19.2 1.38X-3 63.62 10.7 -18.9 1.18X-3 63.82 11.0 -20.1 2.38X-3 64.02 12.9 -19.5 1.28X-3 64.22 11.2 -19.5 1.5

Table 1 (continued).

Core and Depthsection (mbsf) δ1 5N δ1 3C %C

117-724C-(Cont.)

8X-3 64.42 6.2 -19.6 1.88X-3 64.62 11.2 -20.3 4.38X-4 64.82 4.3 -19.7 4.08X-4 65.02 4.7 -20.4 2.88X-4 65.22 6.8 -20.3 3.88X-4 65.42 8.3 -19.4 3.18X-4 65.62 7.1 -20.7 5.18X-4 65.82 7.0 -21.2 5.98X-4 66.02 5.7 -21.7 6.58X-5 66.22 7.0 -23.5 12.98X-5 66.42 9.0 -21.2 6.58X-5 66.62 11.4 -20.5 6.08X-5 66.82 10.4 -20.9 6.08X-5 67.02 12.6 -20.0 2.58X-5 67.22 12.6 -21.0 1.28X-5 67.42 6.1 -20.1 1.78X-5 67.62 14.0 -18.7 1.68X-6 67.82 11.6 -22.0 2.98X-6 68.02 4.6 -20.2 3.88X-6 68.22 7.5 -19.9 3.99X-1 70.02 12.5 -20.1 4.09X-1 70.22 12.4 -19.8 4.49X-1 70.42 8.2 -19.9 3.09X-1 70.62 2.8 -21.3 1.39X-1 70.82 6.5 -20.5 3.69X-1 71.02 9.5 -19.9 5.09X-1 71.22 8.3 -20.4 4.49X-2 71.42 7.7 -20.8 3.99X-2 71.62 8.9 -20.2 2.09X-2 71.82 6.0 -21.4 3.39X-2 72.02 13.0 -19.8 4.49X-2 72.22 12.0 -19.9 3.39X-2 72.42 5.4 -21.0 3.49X-2 72.62 8.5 -21.6 2.49X-3 72.82 12.6 -20.4 4.39X-3 73.02 7.1 -19.9 3.89X-3 73.42 4.1 -20.4 3.49X-3 73.62 7.6 -20.2 4.09X-3 73.82 6.9 -21.9 5.29X-3 74.02 10.4 -22.0 6.49X-3 74.22 11.3 -21.2 5.49X-3 74.42 4.7 -21.8 8.89X-4 74.62 12.2 -21.2 6.89X-4 74.82 7.1 -23.0 3.69X-4 75.02 9.9 -21.5 4.39X-4 75.22 9.8 -20.8 4.89X-4 75.42 11.9 -20.7 5.09X-5 75.82 10.8 -19.6 3.19X-5 76.02 2.8 -20.2 2.49X-5 76.22 10.6 -20.5 3.29X-5 76.42 16.4 -20.5 3.89X-5 76.82 10.7 -20.5 4.39X-5 77.02 9.2 -20.9 3.09X-5 77.22 4.6 -22.3 2.59X-6 77.42 7.1 -20.9 3.39X-6 77.82 11.5 -20.5 3.79X-6 78.02 5.9 -20.8 3.09X-6 78.42 9.3 -20.2 3.29X-6 78.62 7.8 -21.4 3.09X-7 78.82 12.8 -19.4 1.010X-1 79.42 10.0 -21.0 7.710X-1 79.62 8.3 -21.3 7.410X-1 79.82 8.8 -21.9 6.310X-1 80.02 15.2 -21.3 6.510X-1 80.22 9.3 -21.5 5.110X-1 80.42 10.5 -21.5 6.710X-1 80.62 10.7 -20.9 7.410X-1 80.82 8.2 -20.3 5.710X-2 81.02 9.2 -21.3 8.010X-2 81.42 8.8 -20.8 5.310X-2 81.62 10.6 -20.7 4.910X-2 82.02 9.7 -20.8 4.410X-2 82.22 9.8 -21.1 7.310X-3 82.42 9.0 -20.3 5.610X-3 82.62 13.9 -20.4 5.1

ISOTOPIC COMPOSITIONS OF CARBON AND NITROGEN OF ORGANIC MATTER

Page 6: 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC ... tion of organic material in the sediments is also affected

A.N.N. MUZUKA, S. A. MACKO, T. F. PEDERSEN

Table 1 (continued). Table 1 (continued).

Core andsection

Depth(mbsf)

117-724C-(Cont.)

10X-310X-310X-310X-310X-310X-410X-410X-410X-410X-410X-510X-510X-510X-510X-510X-510X-CC10X-CC11X-111X-111X-111X-111X-111X-111X-211X-211X-211X-211X-211X-211X-211X-311X-311X-311X-311X-311X-311X-311X-411X-411X-411X-411X-411X-511X-511X-511X-511X-511X-511X-611X-611X-611X-611X-611X-711X-712X-12X-12X-12X-12X-12X-12X-12X-112X-212X-212X-212X-212X-212X-312X-312X-312X-312X-312X-:1

82.8283.0283.2283.4283.8284.2084.4284.6285.0285.2285.4285.6285.8286.2286.4286.6286.7786.9789.0289.2289.4289.6289.8290.0290.6290.8291.0291.2291.4291.6291.8292.0292.2292.4292.8293.0293.2293.4293.8294.0294.2294.4294.6295.0295.2295.4295.8296.0296.2296.6296.8297.4297.6097.8298.0298.2298.6298.8299.0299.4299.6099.80

100.22100.44100.62100.82101.04101.22101.42101.62101.82102.42102.62102.82103.02

δ1 5N

10.611.211.27.4

12.09.8

10.713.65.9

11.19.79.18.88.57.86.35.46.69.16.79.04.28.29.47.78.9

10.211.79.06.7

10.05.87.59.29.5

11.07.07.67.57.07.27.27.66.09.29.09.9

12.26.19.67.58.18.98.97.3

10.99.17.96.37.67.65.69.2

11.98.19.3

10.48.77.0

10.46.97.17.84.87.3

δ1 3C

-21.1-21.0-20.8

-21.2-20.0-20.6-20.2-20.2-22.1-20.2-20.8-21.6-21.3-21.4-20.5-20.7-20.8-21.0-22.1-20.6-20.3-19.8-20.5-19.9-20.1-19.8-20.0-19.7-20.2-20.2-19.1-19.8-19.8-19.7-20.2-20.2-19.8-19.9-20.3-19.4-20.2-19.8-19.8-20.7-19.6-20.2-19.9-21.3-20.3-20.1-20.6-21.8-20.5-21.6-21.4-20.4-20.2-19.5-19.7-20.1-19.8-19.7-19.7-20.8-20.6-20.0-24.4-20.7-19.9-19.9-19.7-19.8-19.8-19.9

2.73.93.6

2.43.82.83.50.31.62.63.25.04.04.63.51.72.54.24.33.92.63.46.32.63.73.85.14.64.14.45.35.03.98.47.56.35.75.95.14.43.84.04.45.06.38.45.25.84.55.65.77.89.57.56.99.85.14.53.96.14.75.96.96.54.64.99.53.32.12.42.33.93.97.7

Core andsection

Depth(mbsf)

117-724C-(Cont.)

12X-412X-412X-412X-412X-412X-412X-512X-512X-512X-512X-512X-512X-612X-612X-612X-612X-612X-612X-612X-712X-713X-113X-113X-113X-113X-113X-113X-213X-213X-213X-213X-213X-213X-213X-313X-313X-313X-313X-313X-313X-413X-413X-413X-413X-413X-413X-513X-513X-513X-513X-513X-513X-613X-613X-613X-613X-613X-613X-713X-713X-714X-114X-114X-114X-114X-114X-214X-214X-214X-214X-314X-314X-314X-314X-4

103.42103.62103.82104.02104.22104.42104.62105.02105.22105.42105.62105.82106.23106.42106.62106.82107.02107.22107.42107.62107.82108.32108.52108.72108.92109.10109.52109.92110.12110.32110.52110.72110.94111.12111.32111.72111.92112.12112.32112.52112.92113.12113.32113.52113.72113.92114.32114.52114.72115.14115.32115.52115.92116.10116.32116.52116.72116.92117.32117.52117.72117.82118.40118.67118.81119.02119.42119.60120.02120.38120.87121.63121.81122.02122.42

δ1 5N

11.28.98.78.87.96.46.8

10.57.19.29.27.74.54.85.98.78.97.17.67.26.98.76.68.67.37.98.67.6

10.37.69.27.97.75.55.5

10.09.07.58.58.98.59.17.8

11.010.19.78.79.67.37.35.45.46.57.75.85.76.65.87.67.67.4

10.88.61.09.09.6

10.28.48.87.06.47.1

10.26.88.5

δ1 3C

-19.7-21.1-20.1-20.6-20.0-20.1-20.0-20.1-20.5-20.2-20.3-20.5-20.3-20.2-20.4-20.6-20.7-19.9-20.0-20.4-20.1-20.3-22.2-20.0-22.0-22.1-20.9-21.9-20.3-19.8-20.4-21.2-20.5-20.0-20.3-20.1-20.3-20.5-21.9-22.1-20.3-20.8-20.5-20.2-20.6-20.3-20.1-19.9-22.5-20.0-21.9-20.6-20.1-20.2-20.5-20.3-20.7-22.5-20.5-20.0-22.2-20.2-20.3-20.2-20.9-20.1-20.1-20.4-21.3-20.4-21.6-20.3-20.4-20.5-20.9

%C

6.03.84.54.87.78.99.65.07.24.55.83.33.84.85.25.46.36.58.27.76.57.98.1

11.47.36.17.15.78.47.29.06.68.47.16.57.55.78.86.38.5

11.18.48.28.9

12.77.06.17.54.26.66.35.56.08.07.33.45.53.97.25.14.77.57.16.46.65.37.15.74.87.25.16.85.76.55.7

576

Page 7: 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC ... tion of organic material in the sediments is also affected

ISOTOPIC COMPOSITIONS OF CARBON AND NITROGEN OF ORGANIC MATTER

Table 1 (continued). Table 1 (continued).

Core and Depthsection (mbsf)

117-724C-(Cont.)

14X-4 122.6214X-4 122.8214X-4 123.0214X-4 123.4214X-4 123.6214X-fH×-lH×-l14X-!14X-i14X-f

i 123.82i 124.23> 124.42> 124.62i 125.02i 125.22

14X-6 125.4214X-6 125.6215X-15X-15X-15X-15X-15X-;15X-:

127.42127.62128.02128.20128.60

! 129.02! 129.22

15X-2 129.6515X-:15X-:i5x-:15X-:15X-:15X-:15X-:15X-:15X-:15X-̂15X-̂15X-<15×-i15X-f15X-515X-f15X-515X-515X-!15X-!15X-(15X-<15X-(i5X-ei5X-e15X-"15X--15X--!16X-116X-116X-116X-116X-116X-116X-116X-216X-216X-216X-216X-216X-216X-216X-316X-316X-316X-316X-316X-316X-416X-416X-416X-416X-416X-416X-4

t 129.831 130.42

130.601 130.841 131.00I 131.20\ 131.43

131.52131.60

\ 132.00t 132.45I 132.61

133.42133.80134.00134.20134.40134.65134.74134.82

» 135.00135.22135.40

» 135.72135.94136.42136.62136.75137.02137.22137.42137.62137.82138.02138.42138.62138.82139.02139.22139.42139.60139.82140.02140.22140.62140.82141.02141.22141.60141.82142.02142.22142.40142.60142.82

δ1 5N

7.47.96.67.59.37.56.89.78.07.67.89.54.66.37.87.46.25.75.45.85.76.05.46.97.16.16.16.15.36.16.86.27.54.13.74.26.54.84.87.48.35.66.37.27.06.77.77.95.65.03.47.37.97.26.16.26.07.67.55.46.05.55.86.05.94.04.54.96.67.17.15.54.75.95.55.4

δ1 3C

-20.7-23.0-22.4-22.8-20.0-20.5-20.4-20.5-20.2-22.0-20.0-20.0-20.4-21.0-21.9-22.1-20.9-21.1-21.2-20.7-20.3-20.1-21.0-20.2-21.4-20.4-20.8-21.5-20.7-21.0-20.6-20.7-20.3-20.4-19.9-20.7-21.5-20.2-21.5-21.6-21.6-20.1-21.7-21.4-21.1-20.7-22.8-21.9-23.0-21.7-22.3-21.7-19.7-22.6-21.2-22.7-22.1-21.7-21.0-20.9-21.3-21.6-21.3-23.0-20.9-20.7-20.2-20.8-20.0-21.2-22.8-22.0-20.6-20.4-20.6-20.5

<VoC

5.83.84.43.35.25.23.74.15.85.94.13.02.64.53.64.75.44.03.34.34.44.94.05.34.04.64.23.43.64.34.06.23.11.83.03.67.85.63.46.0

10.24.94.25.55.15.54.54.85.0

12.49.89.6

10.28.18.17.49.58.39.16.75.75.46.45.26.97.55.96.36.37.04.95.19.56.87.98.7

Core andsection

Depth(mbsf)

117-724C-(Cont.)

16X-516X-516X-516X-516X-516X-516X-516X-616X-616X-616X-616X-616X-616X-616X-716X-716X-717X-117X-117X-117X-117X-117X-217X-217X-217X-217X-317X-317X-317X-317X-317X-317X-317X-317X-417X-417X-417X-417X-417X-517X-517X-517X-517X-517X-517X-517X-617X-617X-617X-617X-618X-118X-118X-118X-118X-118X-118X-118X-118X-218X-218X-218X-218X-218X-318X-318X-318X-318X-318X-318X-318X-418X-418X-418X-418X-4

143.07143.23143.40143.62144.02144.22144.42144.62144.82144.98145.22145.42145.62145.82146.02146.22146.42146.62146.82147.02147.22148.02148.20148.42148.62148.81149.62149.82150.02150.22150.42150.62150.82151.02151.20151.42151.48152.22152.42152.62152.82153.02153.22153.42153.62153.82154.22154.42154.62154.82155.02156.32156.52156.72156.92157.12157.32157.52157.68157.92158.10158.72158.92159.12159.32159.52159.72159.92160.12160.32160.52160.95161.12161.32161.72161.92

δ1 5N

6.65.57.35.36.75.25.84.15.83.55.25.15.35.63.96.54.58.26.27.97.96.56.38.2

10.37.95.68.56.76.88.16.24.46.66.66.87.49.17.26.94.48.37.19.16.18.99.9

14.010.57.58.37.57.37.36.85.91.57.67.56.57.27.06.56.04.97.08.09.27.46.16.97.55.77.59.55.7

δ1 3C

-20.7-21.3-21.1-20.4-20.4-20.6-20.3-20.8-22.7-20.3-20.9-20.7-20.6-21.0-20.9-21.0-21.0-19.8-19.7-20.5-19.7-19.9-19.7-19.7-20.1-22.5-21.0-20.1-22.4-20.0-20.0-20.2-21.2-19.7-21.7-19.9-19.9-19.9-21.3-19.9-20.2-20.2-21.8-20.2-21.0-20.2-20.2-20.0-20.6-20.4-20.2-20.2-20.8-20.4-20.7-20.3-20.3-20.8-20.6-20.8-20.6-20.1-20.1-20.9-21.0-20.5-20.9-22.1-20.3-20.9-19.9-20.1-21.5-21.0-19.9-20.5

%C

5.55.25.47.97.97.48.04.14.96.46.96.96.76.43.96.55.97.06.47.17.27.57.57.99.34.38.69.18.2

11.910.810.39.98.26.48.28.86.06.99.3

10.96.35.05.65.95.66.16.03.37.34.16.87.77.36.36.66.16.27.89.46.55.66.16.47.55.9

10.69.2

10.07.34.75.06.76.64.06.2

577

Page 8: 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC ... tion of organic material in the sediments is also affected

A.N.N. MUZUKA, S. A. MACKO, T. F. PEDERSEN

Table 1 (continued).

Core and Depthsection (mbsf) δ 1 5N δ 1 3C %C

117-724C-(Cont.)

18X-4 162.12 5.7 -19.9 11.418X-5 162.32 7.2 -20.0 10.618X-5 162.52 6.1 -20.5 6.418X-5 163.12 6.5 -21.4 6.118X-5 163.32 5.7 -19.9 2.118X-5 163.72 6.5 -20.4 6.218X-6 163.92 8.3 -20.2 4.018X-6 164.12 5.8 -20.0 4.018X-6 164.52 5.9 -20.2 3.618X-6 164.72 5.3 -20.1 6.318X-6 164.92 6.2 -19.7 4.318X-6 165.12 5.2 -20.0 4.019X-1 166.09 6.8 -20.2 9.119X-1 166.31 6.7 -20.2 8.919X-1 166.50 5.5 -20.3 6.419X-1 167.14 7.2 -20.2 5.919X-1 167.32 6.7 -19.9 8.619X-2 167.52 6.3 -21.2 6.719X-2 167.72 5.7 -19.9 7.719X-2 167.92 5.2 -20.6 5.919X-2 168.12 5.8 -20.3 4.119X-2 168.25 7.3 -20.5 7.919X-2 168.52 6.7 -21.2 1.019X-2 168.72 7.4 -19.6 8.220X-1 175.54 8.4 -19.7 5.420X-1 175.72 5.5 -19.7 8.820X-1 175.92 8.2 -19.3 6.620X-1 176.36 8.9 -19.7 5.520X-1 176.52 5.2 -20.3 6.920X-1 176.74 8.3 -19.7 6.120X-1 176.92 6.1 -20.0 5.120X-2 177.12 8.6 -20.0 11.020X-2 177.32 8.8 -19.7 8.120X-2 177.72 5.4 -19.7 7.320X-2 178.12 9.4 -20.0 5.720X-2 178.36 6.5 -21.2 4.520X-3 178.52 4.7 -20.3 3.820X-3 178.72 7.5 -19.9 3.920X-3 178.92 7.5 -19.8 4.420X-3 179.29 7.7 -20.7 6.220X-3 179.52 6.3 -19.8 7.920X-3 179.72 5.6 -21.7 6.720X-3 179.92 6.9 -20.2 11.620X-4 180.12 11.3 -20.4 10.720X-4 180.32 7.4 -20.8 5.720X-4 180.52 8.7 -20.4 7.620X-4 180.72 6.2 -20.5 2.820X-4 181.12 3.7 -20.5 3.020X-4 181.32 5.6 -19.5 3.320X-5 181.52 3.6 -19.4 4.420X-5 181.72 9.4 -19.4 4.520X-5 181.92 7.6 -19.4 5.020X-5 182.12 5.3 -19.5 5.520X-5 182.32 6.4 -19.3 5.820X-5 182.52 6.4 -19.6 7.720X-5 182.72 4.4 -19.3 5.520X-5 182.92 7.4 -19.5 5.920X-6 183.12 6.1 -19.9 9.920X-6 183.32 4.9 -20.4 11.120X-6 183.52 7.7 -20.6 11.420X-6 183.72 5.5 -20.5 18.220X-6 183.92 5.6 -22.5 8.221X-1 185.22 7.2 -20.9 10.921X-1 185.62 5.4 -20.5 10.521X-1 185.85 5.8 -22.0 6.321X-1 186.02 7.8 -19.8 11.121X-1 186.22 10.7 -20.4 8.721X-1 186.42 9.3 -20.5 7.521X-1 186.62 10.5 -20.5 8.621X-2 186.82 13.3 -21.4 17.221X-2 187.02 6.2 -20.0 7.221X-2 187.22 5.0 -21.6 5.521X-2 187.42 7.3 -21.2 6.221X-2 188.02 7.6 -21.4 8.921X-3 188.22 8.3 -19.9 14.521X-3 189.02 9.4 -19.8 14.0

Table 1 (continued).

Core and Depthsection (mbsO δ 1 5N δ 1 3C %C

117-724C-(Cont.)

21X-3 189.22 8.0 -20.5 9.621X-4 189.82 6.6 -22.5 4.921X-4 190.02 5.9 -20.8 9.221X-4 190.22 7.1 -20.0 9.821X-4 190.42 7.2 -20.2 11.922X-1 194.82 3.9 -20?3 9.722X-1 195.02 7.6 -21.0 12.122X-1 195.42 6.5 -20.5 13.022X-1 195.62 6.8 -19.7 14.022X-1 195.82 6.8 -19.7 9.622X-1 196.02 8.4 -20.2 9.622X-1 196.22 6.4 -19.8 6.722X-2 196.40 7.1 -19.9 5.122X-2 196.62 6.2 -20.7 8.122X-2 196.82 6.1 -20.1 10.222X-2 197.02 5.9 -20.6 12.622X-2 197.22 7.0 -19.8 10.922X-2 197.42 7.5 -20.4 11.522X-2 197.62 4.8 -22.1 9.922X-3 197.82 7.5 -21.0 9.722X-3 198.02 3.9 -21.0 8.922X-3 198.22 8.9 -19.3 13.322X-3 198.42 5.6 -19.2 4.622X-3 198.62 7.6 -19.9 12.822X-3 198.82 7.8 -20.9 10.822X-3 199.02 6.5 -20.6 12.622X-3 199.22 7.6 -21.1 10.922X-4 199.42 6.9 -18.9 9.822X-4 199.65 7.4 -19.9 14.122X-4 199.86 7.8 -19.9 11.322X-4 200.42 7.6 -20.5 11.122X-4 200.62 7.0 -18.6 12.822X-5 200.82 6.2 -20.1 11.522X-5 201.82 7.4 -19.9 10.522X-5 201.83 7.2 -20.4 12.422X-5 202.28 6.4 -20.8 13.022X-6 203.22 6.9 -21.1 15.922X-6 203.62 6.7 -20.3 7.822X-7 203.82 6.4 -20.2 8.722X-7 203.97 6.9 -20.3 9.8

117-725C-

1H-1 0.20 6.9 -20.7 1.31H-1 0.40 9.8 -19.4 1.01H-1 0.60 8.2 -22.8 1.01H-1 0.80 11.8 -19.5 0.71H-1 1.20 10.9 -19.5 0.51H-2 1.40 11.3 -19.8 0.61H-2 1.60 7.7 -20.1 1.01H-2 1.80 12.2 -19.4 0.61H-2 2.00 14.0 -19.2 0.51H-2 2.20 15.7 -19.1 0.81H-2 2.37 11.3 -18.9 0.81H-2 2.60 9.9 -18.8 0.91H-3 3.00 11.6 -18.8 1.41H-3 3.20 5.9 -18.7 1.01H-3 3.40 13.7 -19.0 0.91H-3 3.60 8.9 -18.6 0.71H-3 3.80 7.2 -20.7 0.91H-3 4.00 10.7 -18.7 1.21H-3 4.20 15.1 -18.5 1.31H-4 4.60 16.0 -19.0 1.21H-4 4.80 12.3 -19.1 1.21H-4 5.20 8.5 -19.0 0.91H-4 5.40 6.8 -19.1 1.31H-4 5.60 5.5 -19.0 1.51H-4 5.80 14.5 -19.3 1.01H-5 6.20 5.5 -19.5 0.91H-5 6.40 9.6 -18.7 0.81H-5 7.00 16.6 -20.1 1.31H-5 7.20 14.8 -19.5 0.91H-5 7.40 13.1 -19.2 0.61H-6 7.80 6.4 -19.4 0.81H-6 8.00 4.6 -20.7 0.62H-1 9.00 11.3 -20.3 0.5

Page 9: 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC ... tion of organic material in the sediments is also affected

ISOTOPIC COMPOSITIONS OF CARBON AND NITROGEN OF ORGANIC MATTER

Table 1 (continued). Table 1 (continued).

Core andsection

Depth(mbsf)

117-725C-(Cont.)

2H-12H-12H-12H-12H-22H-22H-22H-22H-22H-22H-32H-32H-32H-32H-32H-32H-32H-32H-42H-42H-42H-42H-42H-42H-52H-52H-52H-52H-52H-52H-62H-62H-62H-62H-62H-62H-62H-72H-72H-73H-13H-13H-13H-13H-13H-23H-23H-23H-23H-33H-33H-33H-33H-33H-43H-43H-43H-43H-43H-53H-53H-53H-53H-53H-53H-53H-53H-63H-63H-63H-63H-63H-73H-73H-7

9.609.80

10.0010.2010.6010.8011.2011.4011.6011.8012.0012.2012.4012.6012.8013.0013.2013.4013.6013.8014.0014.2014.6014.8015.0015.2015.4015.6016.0016.4016.6016.8017.0017.2017.4017.6017.8018.0018.2018.4018.6018.8019.0019.4020.0020.2021.0021.2021.4021.6021.8022.0022.6022.8023.2023.6023.8024.0024.2024.6024.8025.0025.2025.4025.6025.8026.0026.2026.6026.8027.0027.4027.6027.8028.00

δ 1 5N

11.312.111.17.8

12.78.89.45.6

15.211.014.514.49.44.9

13.515.212.011.18.47.2

13.313.37.5

14.410.011.113.814.09.9

11.77.38.8

14.111.85.75.36.56.2

13.114.217.015.113.113.311.210.016.713.615.012.013.312.613.711.213.612.111.712.711.610.611.114.910.812.913.514.310.114.313.910.514.913.115.412.314.1

δ1 3C

-19.6-19.8-19.9-20.3-19.9-19.9-19.6-20.8-19.9-20.0-20.3-19.0-20.4-20.1-19.4-19.8-18.9-19.4-19.6-19.5-19.7-20.1-19.8-20.0-19.7-19.6-18.1-20.0-19.3-19.0-18.6-20.0-19.3-19.8-20.4-17.6-19.6-20.5-20.2-19.9-20.0-20.1-20.0-19.8-19.1-19.9-20.1-20.1-20.2-22.5-20.1-20.4-20.1-20.6-19.9-18.8-19.9-19.6-19.9-19.7-20.1-20.0-19.3-20.1-20.6-21.1-20.1-20.8-20.8-20.0-20.2-20.3-21.9-20.1-21.8

%C

1.01.11.21.12.01.80.81.20.90.80.60.80.90.81.21.61.61.41.31.21.41.70.51.01.11.51.02.01.11.50.90.50.50.70.70.60.80.70.60.70.60.60.71.00.71.30.70.60.60.50.80.70.60.70.80.71.20.60.90.71.21.01.30.90.51.30.90.71.40.90.70.90.50.80.8

Core andsection

Depth(mbsf)

117-725C-(Cont.)

3H-74X-14X-14X-14X-14X-14X-24X-24X-24X-24X-24X-24X-34X-34X-34X-3

28.2028.7028.9029.3029.5029.7030.1030.5030.7030.9031.1031.3031.5031.7031.9032.10

δ 1 5N

15.010.014.710.412.210.95.3

10.310.012.812.08.2

14.58.3

10.311.3

δ1 3C

-21.2-25.0-23.7-23.4-24.2-25.6-21.9-21.6-22.7-20.5-21.6-19.8-20.6-20.4-21.6-20.4

%C

1.10.20.40.40.40.20.71.50.52.11.11.01.31.00.50.3

enized sample interval of 20 mm would include 140-570 yr ofsediment influx to the ocean floor. Organic carbon content ofthe acidified residue of the sediments is seen to increase drasti-cally with depth. Highest values occur in the Pliocene, reachinga maximum of 18.2% at a depth of approximately 180 m. Asharp decline in the organic content occurs toward the Pliocene-Pleistocene boundary (near 130 m) with an increase above thatboundary. From 80 m to the surface of the core, a nearly con-stant amount of 2%-3% of the residue could be identified asorganic carbon. The lowest amounts of carbon are observedduring this period, at 0.2%. The levels of carbon are noted tobe much lower during the Pleistocene-Holocene section of thecore, but are still much above the world average for typical car-bon content of marine sediments. The average carbon contentmeasured on these samples was 4.9% with a standard deviationof 2.9%, (Fig. 2).

Stable carbon isotopic compositions of this material rangedfrom - 17.7‰ to -24.7‰, with an average of -20.4‰ (stan-dard deviation = 0.8‰). The values are fairly constant but havea slight enrichment in the Pleistocene-Holocene section(-20‰) over the Pliocene (-21‰). Certain intervals of ap-proximately 20 m show depletions of about l‰ from the averageabove and below it.

Stable nitrogen compositions of these sediments are highlyvariable, with an average value of 8.9‰, range of 1.0‰-18.9‰,and standard deviation of 2.5‰ (Fig. 3). The Pliocene has themost uniform values, near the average, with more enriched sam-ples noted in the Pleistocene-Holocene. The very surface of thecore had samples which were depleted to near the average. Nostatistically significant correlations (Pearson R) were observedbetween the isotopic compositions nor with the isotopic compo-sitions and the organic carbon content (Fig. 4).

Site 725

Hole 725C was sampled at 200 mm intervals yielding a reso-lution of approximately 1400 yr between samples at the esti-mated sedimentation rate of 143 m/m.y. Each 20 mm sample in-terval which was homogenized therefore represents 140 yr of sedi-mentation. Organic carbon analysis of these samples yieldedamounts approximately 1% less than levels found in the nearsurface portion of Hole 724C, averaging 0.9% ± 0.4%. Valuesranged from 0.2% to 2.1%. The lowest values were observednear the 29 m depth of the core.

Stable isotopic compositions of carbon of the acidified resi-due were similar to the samples of those from 724C, ranging

579

Page 10: 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC ... tion of organic material in the sediments is also affected

A.N.N. MUZUKA, S. A. MACKO, T. F. PEDERSEN

-2ö0

CARBON ISOTOPE VALUES C o / o o l-23 -21 -19 -17

20

40

6 0 -

8 0 -

1 0 0 -

120-

140

160-

180-

200

Figure 2. Site 724 core results: δ13C compositions.

from -17.6‰ to -25.6‰, with an average of -20.1‰± 1.2‰ (Fig. 5). The excursion in percent carbon at 29 m to thelow value of 0.2% matches closely with a change in δ13C to themost depleted values of the samples for this hole. There is anoverall slight (0.5‰) enrichment trend toward the surface of thecore.

Stable nitrogen isotopic compositions are highly variable witha general trend of decreasing enrichment toward the surface(Fig. 6). These samples averaged 11.3‰ ± 3.0‰, and rangedfrom 4.6‰ to 17.0‰. No statistically significant relationshipswere observed between stable nitrogen isotopic compositionsand either carbon isotopes or organic carbon contents of thesamples. A highly significant relationship (Pearson R = 0.326,0.99 level) was observed between organic carbon and carbonisotopic compositions (Fig. 7).

DISCUSSION

There is no evidence of large scale input of terrigenous mate-rial into the area during Pliocene-Pleistocene times. This mostlikely results from the lack of major rivers that could introduceallochthonous land-derived material at great distances off themodern shoreline during periods of low sea level. The large-scale effect of the monsoons on the organic production of thisarea appears to be small relative to inputs derived from marineproduction associated with upwelling. Occasional excursions ofcarbon and nitrogen isotopic compositions to more depletedvalues may result from changes in primary productivity or dia-genetic processes. Further, this indicates no large-scale eoliantransport of land-derived material to the area over Pliocene-Pleistocene time. Delineation of smaller variations in isotopic

580

Page 11: 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC ... tion of organic material in the sediments is also affected

ISOTOPIC COMPOSITIONS OF CARBON AND NITROGEN OF ORGANIC MATTER

NITROGEN ISOTOPE VALUES E o / b o ]

20

40

60

8 0 -

100

120

140

160

180-

200

Figure 3. Site 724 core results: δ15N compositions.

compositions and organic inputs awaits more detailed analysisof these samples and collaborative interpretation of the results.

During glacial periods, the areas surrounding the ArabianSea were drier than during interglacial periods (van Campo etal., 1982; Kolla and Biscaye 1977; Sirocko, 1989 and referencestherein). This decrease in precipitation was coupled with thepresence of shallower continental shelves and is thought to havebeen accompanied by diminished upwelling of deeper, coolerwater. Such a setting could have caused surface water tempera-tures to be variable with season and dissolved carbon dioxideconcentrations to be slightly enriched in 13C from bicarbonate.This scenario would result in organic matter enrichments in 13Cduring glacial periods. An increase in carbon isotopic values isnoted during oxygen isotope Stage II and Stage IV as defined byZahn and Pedersen (this volume).

Very large enrichments in stable nitrogen (+18.9‰) are foundin these sediments. Nitrogen enrichments of similar magnitudehave been previously reported for organic matter undergoing dia-genetic reactions (Saino and Hattori, 1980). That previous studyfocused on a modern, deep-water ocean with a low flux of or-ganic material to the sediments. In a situation more analogousto the present setting, the Peru Upwelling region, differences ofnearly 7‰ have been reported in 15N for surface sediment sam-ples only 5 km apart (Reimers, 1982). In areas associated withan enhanced oxygen minimum, and extensive denitrification,residual nitrate in the water column has been reported to be en-riched up to 16‰ (Cline and Kaplan, 1975). This enrichment in15N, together with the high levels of preservation of organicmatter in the sediments, could explain the heightened levels of15N in the sediments in the present study.

581

Page 12: 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC ... tion of organic material in the sediments is also affected

A.N.N. MUZUKA, S. A. MACKO, T. F. PEDERSEN

ORGANIC CARBON CONTENT

200-

Figure 4. Site 724 core results: organic carbon content.

The δ15N of sediments at Site 725 is on average about 3‰more enriched than those at Site 724, suggesting that the nearershore environment at Site 725 is more impacted by denitrifica-tion, and possibly less fluctuations in the oxygen minimum.The overall increased amount of production, or preservation oforganic material, is evident at the more offshore location in thehigher carbon content of the offshore sediments. It should benoted however that Shimmield et al. (in press) and Calvert andPedersen (in press) have argued that sedimentary organic matteron the Oman Margin shows general indications of being rela-tively poorly preserved at the present time. The magnitude ofthe preserved organic material is similar to that noted by Reimers(1982) for the Peru Upwelling Area. It is of interest that thetrend of enrichment in nitrogen isotopes coincides closely with adecrease in the organic carbon content of the sediments, ob-served following the start of the Pleistocene. This may indicatethat in the Pliocene conditions in the water column were quite

different than in the Pleistocene or Holocene. The productionof organic matter may not have been associated with such an in-tense oxygen minimum as at present or in the Pleistocene, andthat denitrification was not as well established.

SUMMARY

These preliminary analyses on the stable isotopic composi-tions of carbon and nitrogen of organic material from the west-ern Arabian Sea indicate that:

1. The absence of depleted nitrogen and carbon isotope com-positions suggests that there is little evidence for monsoon re-lated deposits in the sediments from the Pliocene and Pleisto-cene at Sites 724 and 725.

2. The preservation and/or production of organic materialsin this environment appears to have changed from the Plioceneto the Pleistocene.

582

Page 13: 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC ... tion of organic material in the sediments is also affected

-760

ISOTOPIC COMPOSITIONS OF CARBON AND NITROGEN OF ORGANIC MATTER

CARBON ISOTOPE VALUES C o / o o ]

-24 -22 -2,0

Figure 5. Site 725 core results: δ13C compositions.

3. The intensity of the oxygen minimum and related denitri-fication activity level may have also increased during the transi-tion from the Pliocene to the Pleistocene.

4. There is a nearshore (Site 725) diminution of productivityand/or preservation, suggested by 15N compositions as com-pared to the offshore location (Site 724).

5. The effect of glaciation on organic matter appears tocause the carbon isotopic compositions to be slightly more en-riched, especially during ice Stages II and IV.

ACKNOWLEDGMENTS

Appreciation is expressed to the crew and scientific party ofODP Leg 117 for the collection of these samples. This researchwas made possible by research grants from NSERC (individualoperating grants and a collaborative special project) and the Pe-troleum Research Fund, administered by the American Chemi-

cal Society (14805-AC2). The comments by two anonymous re-viewers are acknowledged. The laboratory assistance of K. Pul-chan, G. Hartley, P. Harrigan, T. Bieger, and N. Ostrom isgreatly appreciated. We are grateful for support from the Inter-national Centre for Ocean Development for A. Muzuka and toS. Libes for providing us with documents on the Peru UpwellingArea.

REFERENCES

Altabet, M. A., and McCarthy, J. J., 1986. Vertical patterns in 15N nat-ural abundance in PON from the surface waters of warm-core rings.J. Mar. Res., 44:185-201.

Calvert, S. E., and Pedersen, T. F., in press. Organic carbon accumula-tion and preservation in marine sediments: How important is an-oxia? In Whelan, J. K., and Farrington, J. W. (Eds.). Productivity,Accumulation and Preservation of Organic Matter: Recent and An-cient Sediments. New York (Columbia Univ. Press).

583

Page 14: 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC ... tion of organic material in the sediments is also affected

A.N.N. MUZUKA, S. A. MACKO, T. F. PEDERSEN

Cline, J. D., and Kaplan, I. R., 1975. Isotope fractionation of dissolvednitrate during denitrification in the eastern tropical North PacificOcean. Mar. Chem., 3:271-299.

Degens, E. T., 1969. Biogeochemistry of stable carbon isotopes. In Eg-linton, G., and Murphy, M.T.J. (Eds.), Organic Geochemistry. NewYork (Springer-Verlag), 304-329.

Degens, E. T., Gaillard, R.R.L., Sackett, W. M., and Hellebust, J. A.,1968. Metabolic fractionation of carbon isotopes in marine plank-ton—I. Temperature and respiration experiments. Deep-Sea Res.,15:1-9.

Eckelmann, W. R., Broecker, W. S., Whitlock, D. W., and Allsup,J. R., 1962. Implications of carbon isotopic composition—of totalorganic carbon of some recent sediments and ancient oils. AAPGBull., 46:699-704.

Emerson S., and Hedges, J. I., 1988. Processes controlling the organiccarbon content of open ocean sediments. Paleoceanography, 3:621-634.

Fontugne, M. R., and Duplessy, J. C , 1978. Carbon isotope ratio ofmarine plankton related to surface water masses. Earth Planet. Sci.Lett., 41:365-371.

, 1981. Organic carbon isotopic fractionation by marine plank-ton in the temperature range — 1 to 31°C. Oceanol. Ada, 4:85-90.

Gearing, P., Plucker, P. F., and Parker, P. L., 1977. Organic carbon sta-ble isotope ratios of continental margin sediments. Mar. Chem., 5:251-256.

Hedges, J. I., and Parker, P. L., 1976. Land derived organic matter insurface sediments from the Gulf of Mexico. Geochim. Cosmochim.Ada, 40:1019-1029.

Kolla, V., and Biscaye, P., 1977. Distribution and origin of quartz in thesediments of the Indian Ocean. J. Sediment. Petrol., 47:642-649.

Libes, S. M., and Deuser, W. G., 1988. The isotope geochemistry ofparticulate nitrogen in the Peru Upwelling Area and the Gulf ofMaine. Deep-Sea Res., 35:517-533.

Liu, K. K., 1979. Geochemistry of inorganic nitrogen compounds intwo marine environments: the Santa Barbara Basin and the oceanoff Peru. [Ph.D. dissert.] Univ. California, Los Angeles.

Macko, S. A. 1989. Stable isotope organic geochemistry of sedimentsfrom the Labrador Sea (Sites 646 and 647) and Baffin Bay (Site 645),ODP Leg 105. In Srivastava, S. P., Arthur, M., et al., Leg 105: Proc.ODP, Sci. Results, College Station, TX, 209-231.

Macko, S. A., Entzeroth, L., and Parker, P. L., 1984. Regional differ-ences in nitrogen and carbon isotopes on the continental shelf of theGulf of Mexico. Naturwissenschaften, 71:374-375.

Macko, S. A., Estep, M.L.F., Hare, P. E., and Hoering, T. C , 1987a.Isotopic fractionation of nitrogen and carbon in the synthesis ofamino acids by microorganisms. Chem. Geol. 65:79-92.

Macko, S. A., and Pereira, C.P.G., 1990. Neogene paleoclimate devel-opment of the Antarctic Weddell Sea region: organic geochemistry.In Barker, P. F., Kennett, J. P., et al., Leg 113: Proc. ODP, Sci. Re-sults, College Station, TX, 881-897.

Macko, S. A., Pulchan, K., and Ivany, D. E., 1987b. Organic geochem-istry of Baffin Island fjords. Sedimentology of Arctic fjords experi-ment. Geol. Surv. Can. Open-File Rept., 1589:1-34.

Muller, P. J., Erlenkeuser, H., and von Grafenstein, R., 1983. Glacial-interglacial cycles in oceanic productivity inferred from organic car-bon contents in eastern North Atlantic sediment cores. In Suess, E.,and Thiede, J. (Eds.) Coastal Upwelling, Part B. Sedimentary Re-cords of Ancient Coastal Upwelling. New York (Plenum Press), 365-398.

Muller, P. J., and Suess, E., 1979. Productivity, sedimentation rate, andsedimentary carbon content in the oceans. 1. Organic carbon preser-vation. Deep-Sea Res., 26A: 1347-1362.

Newman, J. W., Parker, P. L., and Behrens, E. W., 1973. Organic car-bon isotope ratios in Quaternary cores from the Gulf of Mexico.Geochim. Cosmochim. Ada, 37:225-238.

Parker, P. L., Behrens, E. W., Calder, J. A., and Shultz, W., 1972. Sta-ble carbon isotope ratio variations in the organic carbon from Gulfof Mexico sediments. Contrib. Mar. Sci., 16:139-147.

Peters, K. E., Sweeney, R. E., and Kaplan, I. R. 1978. Correlation ofcarbon and nitrogen stable isotope ratios in sedimentary organicmatter. Limnol. Oceanogr., 23:598-604.

Prell, W. L., and Curry, W. B., 1981. Faunal and isotopic indices ofmonsoonal upwelling: Western Arabian Sea. Oceanol. Ada, 4:91-98.

Prell, W. L., and Kutzbach, J. E., 1987. Monsoon variability over thepast 150,000 years. J. Geophys. Res., 92:8411-8425.

Prell, W. L., and van Campo, E., 1986. Coherent response of ArabianSea upwelling and pollen transport to the late Quaternary mon-soonal winds. Nature, 323:526-528.

Reimers, C , 1982. Sedimentary organic matter: distribution and altera-tion processes in the coastal upwelling region off Peru. [Ph.D. dis-sert.] Oregon State Univ.

Reimers, C , and Suess, E., 1983. Spatial and temporal patterns of or-ganic matter accumulation on the Peru continental margin. In Suess,E., and Thiede, J. (Eds.) Coastal Upwelling, Part B. SedimentaryRecords of Ancient Coastal Upwelling. New York (Plenum Press),311-345.

Romankevich, E. A., 1984. Geochemistry of Organic Matter in theOcean. New York (Springer-Verlag).

Rossignol-Strick, M., 1983. African monsoons, an immediate climateresponse to orbital insolation. Nature, 304:46-49.

Sackett, W. M., Eckelmann, W. R., Bender, M. L., and Be, A.W.H.,1965. Temperature dependence of carbon isotope compositions inmarine plankton and sediments. Science, 148:235-237.

Sackett, W. M., and Thompson, R. R., 1963. Isotope organic carboncomposition of Recent continental derived clastic sediments of East-ern Gulf Coast, Gulf of Mexico. AAPG Bull, 147:535-531.

Saino, T., and Hattori, A., 1980.15N natural abundance in oceanic sus-pended particulate matter. Nature, 283:752-754.

Shimmield, G. B., Price, N. B., and Pedersen, T. F., in press. The influ-ence of hydrography, bathymetry and productivity on sediment typeand composition on the Oman Margin and in the Northwest Ara-bian Sea. Geol. Soc. Spec. Pap.

Sigleo, A. C , and Macko, S. A., 1985. Stable isotope and amino acidcomposition of estuarine dissolved colloidal material. In Sigleo,A. C , and Hattori, A. (Eds.). Marine and Estuarine Geochemistry.Chelsea, MI (Lewis Publishers Inc.) 30-48.

Sirocko, F., 1989. Accumulation of eolian sediments in the northwestIndian Ocean: record of the climatic history of Arabia and India.Repts. Geol. Inst. Kiel, 27:1-185 (in German).

ten Haven, L., Farrimond, P., Poynter, J. G., Rullkotter, J., Eglinton,G., and Welte, D. H., 1989. Variations in the composition of extract-able lipids in coastal sediments underlying active upwelling regimes.A study from ODP Legs 108, 112, and 117. 14th Internat. Mtg. onOrg. Geochem. Paris (Abstract).

van Campo, E., Duplessy, J. C , and Rossignol-Strick, M., 1982. Cli-matic conditions deduced from 150-kyr oxygen isotope pollen recordfrom the Arabian Sea. Nature, 296:56-59.

Wada, E. 1980. Nitrogen isotope fractionation and its significance inbiogeochemical processes occurring in marine environments. InGoldberg, E. D., and Horibe, Y. (Eds.). Isotope Marine Chemistry.Uchida Rokakuho Pub., Tokyo, 375-398.

Zieman, J. C , Macko, S. A,, and Mills, A. L., 1984. Role of seagrassesand mangroves in estuarine foodwebs: temporal and spatial changesin stable isotope composition and amino acid content during decom-position. Bull. Mar. Sci., 35:380-392.

Date of initial receipt: 9 October 1989Date of acceptance: 20 February 1990Ms 117B-163

584

Page 15: 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC ... tion of organic material in the sediments is also affected

ISOTOPIC COMPOSITIONS OF CARBON AND NITROGEN OF ORGANIC MATTER

NITROGEN ISOTOPE VALUES E < v o o l

8

3 0 -

Figure 6. Site 725 core results: δ15N compositions.

585

Page 16: 35. STABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS · PDF fileSTABLE CARBON AND NITROGEN ISOTOPE COMPOSITIONS OF ORGANIC ... tion of organic material in the sediments is also affected

A.N.N. MUZUKA, S. A. MACKO, T. F. PEDERSEN

ORGANIC CARBON CONTENT Do/oJ

02 Oδ 10 2 0

10-

nE

3 0 -

I I I I I I I I

Figure 7. Site 725 core results: organic carbon content.

586