37. depositional and diagenetic behavior of barium in … · ductivity in deep-sea environments....

Pisciotto, K. A., Ingle, J. C, Jr., von Breymann, M. T., Barron, J., et al., 1992Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 127/128, Pt. 1

37. DEPOSITIONAL AND DIAGENETIC BEHAVIOR OF BARIUM IN THE JAPAN SEA1

M. T. von Breymann,2 H. Brumsack,3 and K. C. Emeis4

ABSTRACT

The barium distribution in sediments and pore fluids from five sites drilled in the Japan Sea have been used to illustrate thegeochemical behavior of this element as it pertains paleoproductivity reconstructions, diagenetic remobilization, and bariteprecipitation in authigenic fronts.

Sites where sulfate is depleted in the pore fluids also show high concentrations of dissolved barium, reflecting dissolution ofbiogenic barite. The high rate of sedimentation at Sites 798 and 799 results in a rapid sulfate depletion, which in turn leads tobarite dissolution and reprecipitation in diagenetic fronts. The dissolved barium distribution at these sites has been used to quantifythe rate of barite dissolution; we estimate a first-order rate constant for barite dissolution to be 2 × lO^/s at Site 799 and 2 ×10"7/s at Site 798.

Authigenic barite has been documented in sediments from Site 799 at 323 meters below seafloor by scanning electronmicroscopy and X-ray fluorescence analysis. These results indicate barite precipitation in a diagenetic front near the zone ofsulfate depletion by upward migration of dissolved barium and downward diffusion of sulfate. Barite precipitation has also beeninferred at Sites 796 and 798 based on sedimentary and dissolved barium distributions.

Sulfate is not depleted in the pore fluids of Site 794. The lack of diagenetic remobilization of biogenic barium at this sitepreserves the high barium signal associated with the high-productivity sequences deposited during the late Miocene to Pliocene.Significantly, the organic carbon distribution does not indicate high accumulation rates during the periods of high opal and bariumdeposition. Instead, higher organic carbon accumulations are recorded in the Quaternary and middle Miocene sequences; intervalsthat are also characterized by deposition of siliciclastic turbidites. The presence of a terrestrial component in the organic carbonrecord renders barium a more useful indicator than organic carbon for paleoproductivity reconstructions in this marginal sea.

INTRODUCTION

Geologic and Oceanographic Setting

The Japan Sea is a large backarc basin with water depths in excessof 3500 m, separated from the Pacific Ocean by shallow bathymetricsills of less than 150 m below sea level (mbsl). The objective ofdrilling in the Japan Sea during Legs 127 and 128 of the OceanDrilling Program (ODP) was to determine the style and dynamics ofmarginal sea formation and the parallel Oceanographic evolution ofthe sea (Fig. 1). Table 1 summarizes the location, water depth, andaverage sedimentation rates at the sites used in this study. Figure 2illustrates the changes in sedimentation rate with depth a these sites.

The sedimentary sequences overlying basement rocks in the JapanSea show distinct regional similarities that record the major tectonicand paleoceanographic changes during the evolution of the basin (Fig.3; Tamaki, Pisciotto, Allan, et al., 1990; Ingle, Suyehiro, von Brey-mann, et al., 1990). Delta-front sands and siltstones rich in plant debriswere deposited during the initial backarc rifting and basin subsidencein the early Miocene. Basin subsidence accelerated during the middleto late Miocene accompanied by widespread deposition of diatoma-ceous muds at bathyal depths. These deposits reflect increasing ratesof primary productivity in the Japan Sea, which probably resultedfrom climatic cooling and a decrease in the flux of terrigenoussediments to the deepening basinal areas. The diatom flux to thesediments decreased during the Pleistocene, indicating lower produc-tivity in the surface waters concurrent with a major progradation ofsubmarine fans and deposition of coarse siliciclastic sequences.

Pisciotto, K. A., Ingle, J. C, Jr., von Breymann, M. T., Barron, J., et al., 1992. Proc.ODP, Sci. Results, 127/128, Pt. 1: College Station, TX (Ocean Drilling Program).

2 Ocean Drilling Program, Texas A&M University, 1000 Discovery Drive, CollegeStation, TX 77845-9547, U.S.A. (Present address: GEOMAR, 1-3 Wischhofstrasse,D-2300 Kiel, Federal Republic of Germany.)

3 Geochemisches Institut, Goldschmidtstrasse 1, D-3400 Goettingen, Federal Repub-lic of Germany.

4 Geologisch-Palaontologisches Institut, Universita^ Kiel, Olshausenstrasse 40/60,D-2300 Kiel, Federal Republic of Germany.

Lower productivity during this period probably reflects changes inthe Oceanographic regime of the basin. The topographic isolation andsevere winter climate of the modern Japan Sea leads to the formationof cold low-salinity water in its northern reaches. This high-densitywater, termed the Liman current, sinks as it travels southward andcreates a convection system that maintains a cold, homogeneous, andwell-oxygenated water mass at all depths below 300 m (Ingle, 1975a;Worthington, 1981).

Lithofacies recovered during drilling correspond to lithologicaland faunal sequences onshore (Ingle, 1975b; Iijima et al., 1988,Takayasu and Matoba, 1976; Ikebe and Maiya, 1981). All observa-tions demonstrate that the Japan Sea experienced wide extremes oftemperature, productivity, and circulation since the time of its forma-tion. The sites drilled in this marginal sea offer a good opportunity tostudy paleoproductivity variations that result from tectonically andeustatically controlled changes in basin geometry and gateways, aswell as from changes in global and local climatic patterns (e.g.,Matoba, 1984). The problem of estimating paleoproduction fromclassical biogenic indicators (organic matter, opal, and calcium car-bonate) is that the bottom-arriving flux of these components is highlydependent on water column characteristics. These indicators arestrongly affected by degradation in the water column, at the sedimentwater interface and by sediment diagenesis. For this reason, currentresearch has placed importance on establishing and calibrating newproductivity indicators (Jumars et al., 1989) in the hope that theseparameters will provide the much needed support for accurate esti-mates of paleocycling of organic carbon and silica.

Barium as an Indicator of Paleoproductivity

Particle fluxes of barium and organic carbon in sediment-trapsamples are being explored as means to establish a link betweenprimary productivity and the barium flux to the ocean floor (Dymondet al., in press). Sediment-trap data support inferences of a biogenicsource for this element based on barium enrichment in sedimentsunderlying the equatorial divergence in the Pacific and Indian oceans(Goldberg and Arrhenius, 1958;Gurvichetal, 1978). Scientific effort

651

M. T. VON BREYMANN, H. BRUMSACK, K. C. EMEIS

45:

40°N

130°E 140°

Figure 1. Map of the Japan Sea showing locations of sites from Ocean Drilling Program Leg 127 (dots) andLeg 128 (circled dots), and Deep Sea Drilling Project Leg 31 (squares). Site 794 was occupied on both Legs127 and 128. Bathymetry in meters.

has recently been directed toward the use of barium for paleopro-ductivity reconstructions. For example, Schmitz (1987) used the distri-bution of nonclastic barium in sediments from the Indian Ocean to tracethe northward movement of the Indian plate across the high-productivityequatorial divergence zone. Also, Shimmield and Mowbray (1991) andWeedon and Shimmield (1991) have shown an enhanced increase insedimentary concentrations of biogenic barium during interglacial pro-ductivity maxima in sediments from the Owen Ridge beneath the zoneof monsoonal upwelling in the Arabian Sea. These observations are takenas an indication of enhanced ocean fertility associated with strongmonsoon circulation during interglacial episodes.

There is still no consensus as to the mode of barium enrichmentin conjunction with primary productivity. Barite crystals do notappear to be actively secreted by planktonic organisms. Instead, asyngenetic origin during aggregation, settling, and decay of siliceousmatter has been shown in suspended barium (Bishop, 1988) andsediment-trap samples (Dymond et al., in press). The systematicdecrease in the organic carbon to barium ratio of organic debris withincreasing water depth observed in sediment traps is thought to be aconsequence of the simultaneous uptake of barium with the decom-positional loss of organic matter. This phenomenon is reflected inbarium distributions of sediments from a variety of upwelling andnon-upwelling areas (von Breymann et al., in press).

The enrichment of barium during transport through the watercolumn constitutes an advantage for the reconstruction of paleopro-ductivity in deep-sea environments. Paleoproductivity in these areasis difficult to assess with conventional biogenic indicators becausegreat water depths result in significant losses of these tracers duringtransit from the sea surface to the sediments. The advantage in using

barium accumulation for estimating ocean fertility is the fact that it issignificantly less labile than organic matter, opal, and calcium car-bonate. Comparison between the rain rates of particulate barium tothe seafloor with burial rates indicate that between 30% and 60% ofthe barium is preserved, depending on the sediment mass accumula-tion rate (MAR) (Dymond et al., in press).

On the other hand, diagenetic redistribution of barium in anoxicsystems presents a problem for the application of this element toestimates of biogenic flux. Dissolved barium distributions in porefluids of the Peru margin (von Breymann et al., 1990b) and Gulf ofCalifornia (Brumsack, 1986) sediments indicate barite dissolution inintervals depleted in interstitial sulfate. Upward diffusion of dissolvedbarium results in local barite precipitation in sediments near thetermination of the sulfate-reducing zone.

In this study we have examined the barium record in Japan Seasediments to evaluate the deposition of biogenic barium in relation toproductivity changes. Sites where sulfate is exhausted in the sedi-ments have been used to quantify the rate of dissolution of barite, andits reprecipitation in diagenetic fronts.

METHODS

Sediment samples were obtained aboard the JOIDES Resolution,freeze-dried, and ground. The organic carbon content of the sedimentswas determined aboard ship by a Carlo Erba elemental analyzer(Tamaki, Pisciotto, Allan, et al., 1990; Ingle, Suyehiro, von Brey-mann, et al., 1990). Barium and aluminum concentrations weremeasured in samples from Sites 794, 796, 798, and 799 by neutronactivation analysis (INAA) at the Texas A&M University Nuclear

652

BARIUM IN THE JAPAN SEA

Table 1. Location, water depth, and average sedimentation rates for ODPsites in the Japan Sea.

Site

794795796798799

Latitude(N)

40° 11.4'43°59.2'42°50.9'37°O2.3'39° 13.2'

Longitude(E)

138° 13.9'I38°58.O'I39°24.7'134°48.0'133°52.0'

Water depth(m)

285033002571

9032084

Sedimentation rate(m/m.y.)

355040

120127

Location

Yamato BasinJapan BasinJapan BasinOki RidgeKita-Yamato Trough

Note: Data from Tamaki, Pisciotto, Allan, et al. (1990) and Ingle, Suyehiro, von Breymann, et al(1990).

Science Center. The counting was performed using a germanium-lith-ium gamma-detector, coupled with a pulse-height multichannel ana-lyzer. The precision of the analysis is better than 5%. Abarite layer atSite 799 was identified by scanning electron microscopy (SEM) andX-ray fluorescence (XRF) analysis performed at the Universityd'Orleans, France.

Interstitial fluids were collected by pressure filtration. The samplehandling and analytical techniques used are those described inGieskes and Peretsman (1986). Sulfate was measured aboard ship byion chromatography using a 0.25:50 dilution of the sample withnanopure water. Barium was determined in the pore waters by ICP-AES on 1:10 or 1:100 dilutions of the pore water with deionized water.Calibration solutions were made by spiking a 3% NaCl solution(sulfate-free) with the appropriate amounts of barium. The accuracywas tested by analyzing acid digestions of international standardrocks; precision of the method is better than 5%.

RESULTS AND DISCUSSION

Barium and aluminum concentrations in sediments from Sites794, 796, 798, and 799 are given in Table 2. The downcore distribu-tions of these elements and organic carbon are illustrated in Figure 4.Results from the analysis of dissolved sulfate and barium in theinterstitial fluids are shown in Table 3 and Figure 5.

Barium as a Recorder of Productivity in the Japan Sea:Site 794

In pelagic environments particulate barium fluxes are usuallydominated by biogenic sources, although detrital aluminosilicates andhydrothermal processes may also constitute a source for this elementin marine sediments (Dymond, 1981; Dymond et al., in press). In theJapan Sea nonmarine volcaniclastic and hydrothermal deposits arecommon only for the period following its initial rift (early Miocene).Barium minerals of volcanic and hydrothermal origin have beenobserved in these sequences (Pouclet et al., this volume). We havetherefore restricted our study to sediments younger than the middleMiocene, a sequence that is mostly composed of terrigenous andbiogenic constituents (Ingle, Suyehiro, von Breymann, et al., 1990;Tamaki, Pisciotto, Allan, et al., 1990). By considering only sedimentswith a detrital or biogenic barium source, we can use a simplenormative correction for the detrital fraction; an approach that hasbeen successfully used for a variety of areas and sediment types(Dymond, 1981; Leinen and Pisias, 1984, Dymond et al., 1984). Inthis manner, the biogenic fraction (Babio) may be estimated by

Babi0 = Batotal - (Altotal × Ba/Aldetrital). (1)

This approximation assumes that all the aluminum is of detrital origin.As suggested by Dymond et al. (in press), we have utilized a barium toaluminum ratio of the detrital particles of 0.0075. This average value wascalculated using various compilations of elemental abundances in crustalrocks (Taylor, 1964; Rosier and Lange, 1972). Results from barium andaluminum fluxes in settling particles indicate that variations from the

100

200

CO

E

GL

CDQ

400

300

500 "

600

Figure 2. Age vs. depth relationships from the late Miocene to the present atthe Japan Sea drill sites used in this study. Data from Tamaki, Pisciotto, Allan,et al. (1990) and Ingle, Suyehiro, von Breymann, et al. (1990).

0.0075 value will introduce a 15% error in samples with 30% detritalbarium, and thus equation 1 can predict the biogenic fraction withsufficient accuracy in locations where the detrital contribution is lessthan 30% of the total rain (Dymond et al., in press). Figure 6 showsthe result of this calculation at Site 794, which indicates that duringthe late Miocene high-productivity intervals the detrital fraction isindeed less than 30% of the total barium content.

We have compared the organic carbon to biogenic barium in theJapan Sea sediments with those expected from the organic carbon andbarium fluxes observed in other parts of the ocean. Dymond et al. (inpress) have shown that systematic variations of the Corg/Ba ratio inthe particle rain can be estimated as a function of water depth, andthat site-to-site changes in the decrease rate of the Corg/Ba values withdepth seem to be related to the dissolved barium content of deep water.We have selected their relationship for the Equatorial Pacific and thepresent water depth of the Japan Sea sites to estimate the organiccarbon to barium rain ratio in the Japan Sea from the late Miocene tothe present. The Equatorial Pacific data was selected because theestimated deep-water barium content at this location (110 µm/kg,

653


Table 2. Concentration of barium and aluminumin sediments from Sites 794,796, 798, and 799.

Table 2 (continued).

Core, section,interval (cm)

127-794A-

1H-2, 100-1022H-3, 100-1024H-5, 100-1015H-5, 100-1017H-2, 100-1029H-2, 101-10212H-2, 100-10215H-2, 100-10117X-5, 100-10119X-5, 100-10121X-5, 80-8223X-5, 100-10226X-5, 100-10230X-2, 100-10235X-2, 100-1019R-1,57-5813R-1, 118-12016R-1,64-6620R-1,44-4624R-3, 70-72

127-796 A-

1H-1, 58-611H-1, 64-671H-2, 40-421H-3, 0-52H-5, 0-53H-2, 80-814H-5, 109-1118H-5, 49-5012X-5, 80-8218X-2, 99-10119X-2, 99-10122X-2, 98-10126X-2, 87-8815R-2, 83-8520R-1, 114-116

128-798B-

Depth(mbsf)

2.5010.8032.8042.3056.8075.81

104.30132.80156.50175.50194.70214.20243.20277.60324.70376.57415.68443.84482.44524.30

0.580.641.902.109.20

15.0029.2958.1991.90

148.69158.29187.18225.87293.63340.94

Al(%)

8.078.048.617.969.107.076.973.945.465.794.264.683.635.637.592.944.243.633.717.24

8.457.587.577.447.716.747.857.705.576.124.387.706.345.823.83

Ba(ppm)

720980840

1260950940

1470306023203030250019301220311014101480980

13902540

740

520860900860

2680125019601160440315270540270240500


2H-4, 4-94H-4, 59-616H-4, 4-97H-4, 50-5513H-4, 74-7914H-4, 62-6717X-4, 28-3522X-4, 17-2227X-4, 15-2032X-4, 70-7538X-4, 31-3343X-4, 50-5549X-4,112-11453X-4, 95-977R-1,58-60

128-799B-

1H-1,44^92H-4, 74-783H-2, 10-154H-2, 20-255H-2, 20-256H-2, 20-257H-2,40-448H-2, 70-749H-2, 30-3510H-2, 25-3011H-2, 20-2512H-2, 20-2513H-2, 26-3114H-6, 30-3516H-2, 60-6517H4, 40-4518H-6, 40-4520H-4, 20-2522X-6, 34-3829X-2, 25-3035X-2, 66-7039X4, 40-4445X4, 44-4950X-2, 88-92

Depth(mbsf)

13.8432.3950.7460.36

118.63127.12156.19205.27253.65301.2358.71407.21465.69504.15407.38

0.446.44

12.3022.0031.6041.2051.0060.9070.1079.6589.2098.90

108.56124.30137.90150.40163.10179.20201.64252.65309.46350.80405.84454.68

Al(%)

7.837.936.087.936.637.004.435.036.094.526.77

10.008.367.476.49

5.737.426.467.667.934.597.445.174.197.207.167.017.187.547.753.973.517.003.102.992.663.622.125.86

Ba(ppm)

6301064622687749834666846

1064773882

1085958

128522440

943850

1091708946

10981094903

1126115522161728117415921485511720474193411528871846248227162261

Dymond et al., in press) best approximates the barium content ofPacific water entering the Japan Sea through the Tsushima Strait(109-115 µm/kg, GEOSECS, 1987; Lea and Boyle, 1989). Theresults of our approximation are shown in Table 4. If we consider thedifference in preservation of barium to organic carbon as a functionof mass accumulation rates (Dymond and Lyle, in press; Dymond etal., in press), we can arrive at a first-order estimate of the organiccarbon to barium expected in the sediments from biogenic sources(Fig. 7). As stated before, these estimates are a function of water depth,deep-water barium concentration and mass accumulation rates. Al-though these estimates do not consider any diagenetic remobilizationof either organic carbon or barium, they are useful in delineating theeffect of water depth on the accumulation of barium relative to organiccarbon, consistent with results from sediment-trap deployments. En-hanced barium to organic carbon in deep-water areas has been re-corded in the Peru slope relative to the highly productive shelf areas(von Breymann et al., in press). The difference in the organic carbonto barium ratios between Site 798 (903 mbsl) and the other sites drilledat water depths greater than 2000 m is apparent in Figure 7. Further-more, the excess barium in samples from Sites 796 and 799 is likelyto represent precipitation of authigenic barite in diagenetic fronts.

The dissolved barium and sulfate distributions in Figure 5 showbarium remobilization at all sites where sulfate is depleted by bacterialdegradation of organic matter. This remobilization reflects dissolutionof microcrystalline barite and will be discussed in more detail in thefollowing sections. Only at Site 794 is sulfate not depleted in the pore

waters (Fig. 5) and, therefore, we constrained the paleoproductivityreconstructions to this site.

Site 794 lies along the eastern margin of the Japan Sea on a gentle,north-dipping slope that forms the northeastern margin of the YamatoBasin (Fig. 1). Figure 8 shows the accumulation of biogenic barium andorganic carbon as a function of depth. The lithologic column also includedin this figure clearly shows an increase in diatomaceous componentsduring the high-productivity interval from 100 to 400 m below seafloor(mbsf). The barium signal is enhanced relative to carbon at the bathyaldepths of Site 794. More significantly, the organic carbon distributiondoes not indicate high accumulation rates during periods of high opal andbarium deposition. Instead, higher organic carbon accumulations arerecorded in the Quaternary and middle Miocene sequences (Fig. 8). Themiddle Miocene period is characterized by hemipelagic claystones,gravity-flow tuffs, and minor glauconite deposited at upper bathyaldepths. During the late Pliocene to Holocene period, when diatomaceoussedimentation stopped, the propagation of submarine fans led to theaccumulation of massive and laminated hemipelagic sediments (Tamaki,Pisciotto, Allan, et al., 1990). This association suggests an allochthonoussource for the organic-rich deposits during these periods, reflectingsediment transport from shelf or terrestrial sources. A high terrestrialcomponent above 100 and below 400 mbsf was inferred by shipboardorganic geochemists based on elemental and Rock-Eval analysis ofsediments at this site (Tamaki, Pisciotto, Allan, et al., 1990).

The presence of a terrestrial signal is a well known problem inassessing paleoproductivity from the organic carbon record. Based on

654


SITE 794

(Yamato Basin)

WD=2811m

SITE 795

(Japan Basin)

WD = 3300 m

SITE 796

(Okushiri Ridge)

WD = 2571 m

SITE 797

(Yamato Basin)

WD = 2862 m

SITE 798

(Oki Ridge)WD=903m

SITE 799

(Kita-Yamato Trough)WD=2084m

0m

100

200

300

400

500

600

700

800

900

1000

N•Bioclastic

»andPebbly

claystonβ

Figure 3. Summary stratigraphic columns for the Japan Sea sites drilled during Legs 127 and 128. WD = water depth. Modified from Tamaki,Pisciotto, Allan, et al. (1990) and Ingle, Suyehiro, von Breymann, et al. (1990).

655


Barium (ppm) Aluminum (%) Organic carbon (%)

2 0 0 0 4 0 0 0 2 4 6 8 1 0 0 1 2 3 4 5

Barium (ppm) Aluminum (%) Organic carbon (%)

0 7 0 0 1 4 0 0 4 6 8 1 0 1 2 0 1 2 3 4 5

100

200

300

600

500

600

0 1 0 0 0 2 0 0 0 3 0 0 0 3 4 5 6 7 8 9 0 I 2 3

100

200

300

400

500

0 3 0 0 0 6 0 0 0 2 4 6 8 1 0 0 1 2 3 4 5

Figure 4. Downcore distribution of barium, aluminum, and organic carbon in the sediments from Sites 794,796,798, and 799.

the distribution of biomarkers, Prahl and Muehlhausen (1989) havesuggested that marine sediments contain more than 20% land-derivedorganic carbon, even in sediments distant from land. Organic-rich tur-bidite sequences reflecting redeposition of land- or shelf-derived organiccarbon have been identified in a wide range of marine settings (e.g.,Adams, 1990; Prahl and Muehlhausen, 1989). The large input ofnonpelagic organic carbon associated with these deposits signifi-cantly affect the paleoproductivity estimates because they do notreflect changes in ocean fertility of the overlying waters. The low-re-action kinetics of the terrestrial material further hinder paleoproduc-tivity estimates based exclusively on the organic carbon distribution.Site 794 provides an example of a system where the barium distribu-tion constitutes a significantly better proxy indicator for paleoproduc-tivity reconstructions than organic carbon.

Diagenetic Remobilization of Barium: Sites 798 and 799

The high barium concentrations in the interstitial waters of all sitesexcept Site 794 reflect dissolution of some of the biogenic barite under

conditions of sulfate depletion (Fig. 5). Dissolved interstitial sulfategradients are plotted as a function of the bulk sedimentation rates inFigure 9. This empirical relationship, described by Berner (1980),results from the interaction of sulfate diffusion, bacterial sulfatereduction rates, and sediment accumulation rates. These processeshave been thoroughly discussed by Murray et al. (this volume) andCraig et al. (this volume). The rate of barium dissolution, however, isnot positively correlated with the rate of sulfate consumption (Fig. 9).In order to estimate the dissolution rates at each site, we must concernourselves with the degree of saturation of the pore fluids with respectto barite because the upward migration of dissolved barium results inthe precipitation of particulate barite near the end of the sulfate-re-duction zone. The free-ion concentrations of barium and sulfate wereestimated using a modified version of MINEQL (Westall et al., 1987),as described by von Breymann et al. (1990a). The ion activity product(IAP) was compared with the barite solubility at 25 °C and 300atmospheres (atm) (Kd 300 = 2.3 × I0"10). This value was estimated byusing the solubility product at 25°C and 1 atm (Kd, = 1.1 × I0"10)given by Church and Wolgemuth (1972), a knowledge of the relative

656


Ba (µli)

200

600

400 •

8 |4 20 0 I0 20 30 0 I0 20 30 0 I0 20 30

S04(mM) S04(mM) S04(mM) S04(mM)

10

S04(mM)

Figure 5. Downcore distribution of dissolved barium and sulfate in the pore fluids of sites drilled in the Japan Sea. Note the difference in scales. Sulfate data

are fromTamaki, Pisciotto, Allan, et al. (1990), and Ingle, Suyehiro, von Breymann, et al. (1990).

A Barium (ppm)

0 2000

B Barium detrital fraction (%)

4000 0 20 40 60 80 100

σ

o

T3•σ

0

100

- 200

- 300

- 400

- 500

600

σ

3criS)

Figure 6. A. Partitioning between detrital (shaded) and biogenic components of the barium content in the sediments at Site 794 vs.depth. B. The detrital fraction expressed as a percentage of the total barium content vs. depth. The detrital fraction was calculatedusing equation 1.

657


Table 3. Dissolved sulfate and barium concentrationsin pore fluids.



127-794A-

1H-3, 145-1502H-3, 145-1503H-5, 145-1454H-4, 145-1505H-4, 145-1506H-4, 140-1456H-4, 145-1507H-4, 145-1508H-4, 145-1509H-4, 140-14510H-l,0-1010H-4, 145-15012H-4, 140-14512H-4, 145-15013H-l,0-1015H-4, 140-14516X-1.0-1019X-4, 140-14522X-4, 140-14525X-4,140-14529X-4, 140-14529X-4, 145-15033X-2, 140-14533X-2, 145-15036X-4, 140-14536X-4, 145-150

127-794B-

12R-1, 145-15012R-2, 145-15015R-1, 145-15018R-4, 145-15021R-3, 145-15024R-2, 140-145

127-795 A-

1H-4, 145-1502H-4, 145-1503H-4, 145-1504H-4, 145-1505H-4, 145-1506H-4, 145-1507H-4, 145-1508H-4, 145-1509H-4, 145-15010H-1, 145-15012H-4, 140-14512H-4, 145-15015H-4, 145-15018H-4, 140-14518H-4, 145-15021X-4, 145-15025X-3, 140-14525X-3, 145-15029X-2, 145-15030X-2, 145-15031X-4, 145-15034X-5, 145-15035X-2, 145-15037X-1, 138-143

127-795B-

1R-1, 140-14510R-4, 140-14510R-4, 145-15013R-2, 140-14513R-2, 145-15016R-1, 145-15019R-1, 140-14519R-1, 145-150

Depth(mbsf)

4.4511.2523.7531.7541.2550.7050.7560.2569.7579.2082.8088.75

107.70107.75111.30136.20139.80174.40203.40232.40271.30271.35306.20306.25337.80337.85

406.35407.85435.25468.55496.15523.50

5.9515.2524.7534.2543.7553.2562.7572.2581.7586.75

110.20110.25138.75158.80158.85187.55224.80224.85262.45272.25285.05315.35320.55338.28

366.60457.90457.95483.90483.95511.15540.10540.15

so4(mM)

18.40

17.30

16.4020.9014.0014.70

20.9013.9018.0015.0010.8010.209.30

13.3013.70

13.6016.2015.2011.5011.30

20.9017.2013.109.406.404.302.401.000.000.00

0.000.00

0.000.60

0.500.500.000.200.200.402.10

0.00

0.000.00

0.40

Ba(µM)

0.400.330.330.290.33

0.360.360.440.47

0.51

0.51

0.69

0.690.730.73

0.840.73

0.69

0.73

0.800.471.570.73

0.40.40.50.70.91.74.5

42.0364437728

910800

306

538

895400

715230

145

605120


22R-2, 84-8925R-1, 140-14525R-1, 145-15028R-2, 140-14528R-2, 145-15031R-5, 143-150

127-796 A-

1H-1,50-551H-2, 55-602H-4, 145-1502H-4, 145-1503H-1, 140-1453H-1, 145-1504H-5, 145-1505H-5, 145-1506H-6, 140-1456H-6, 145-1508H-5, 93-989X-2, 140-14511X-1, 145-15014X-2, 140-14514X-2, 140-14517X-2, 140-14517X-2, 145-15021X-4, 140-14521X-4, 145-15024X-1, 140-14524X-1, 145-150

127-796B-

1R-2, 145-15012R-1, 140-14512R-1, 145-15015R-2, 140-14515R-2, 145-150

127-797B-

1H-2, 140-1452H-4, 145-1503H-5, 145-1504H-4, 145-1505H-4, 145-1506H-4, 145-1507H-4, 145-1508H-4, 145-1509H-4, 140-1459H-4, 140-14510H-4, 140-14512H-4, 140-14515H-4, 140-14518H-4, 140-14518H-4, 145-15021X-4, 140-14521X-4, 145-15024X-5, 140-14524X-5, 145-15027X-6, 145-15028X-1, 145-15030X-1, 145-15031X-4, 140-14532X-3, 145-15033X-2, 140-14534X-2, 145-15037X-4, 140-14537X-4, 145-15040X-1, 56-6140X-1, 61-6647X-3, 140-15049X-3, 145-15051X-4, 140-14551X-4, 145-150

Depth(mbsf)

570.04598.10598.15628.60628.65661.93

0.502.059.159.15

14.1014.1529.6539.1550.1050.1558.6361.6079.75

110.50110.50139.40139.45180.90180.95205.50205.55

2.95263.70263.75294.20294.25

2.9011.8522.8530.8540.3549.8559.3568.8578.3078.3087.80

106.80135.30163.80163.85191.40191.45221.70221.75252.35254.55273.95288.10296.35304.40314.15346.20346.25369.86369.91440.60459.95480.80480.85

so4(mM)

0.90

0.00

0.00

10.109.802.302.300.400.400.000.000.000.000.400.000.90

1.304.902.805.404.80

21.4021.70

12.1017.3018.2013.6013.90

24.0018.6015.6013.9012.5010.709.408.707.607.506.106.104.503.703.302.702.702.302.001.703.500.900.300.602.001.102.904.000.100.602.903.504.905.00

Ba(µM)

11590.0

56.0

5.9

1.4489

6211034896

65724144111624.3

6.1

4.4

1.0

1.3

1.2

1.3

0.20.30.30.30.40.40.50.5

0.50.60.81.9

2.7

4.27.6

17.711.4

26.944.212.2

4.8

85.2

1.0

0.8

658




127-797C-

5R-2, 145-150

128-798B-

IH-l, 125-1311H-2, 3 5 ^ 11H-2, 127-1331H-3, 100-1061H-4, 125-1312H-1,45-512H-3,45-513H-4, 85-914H-7, 56-615H-4, 140-1506H-4, 45-557H-3, 140-1509H-3, 123-13314H-7, 123-13315H-5, 140-15021X-6, 140-15030X-2, 140-15042X-5, 140-150

128-799 A-

2H-1, 145-1503H-4, 135-1405H-4, 140-1456H-3, 140-1459H-3, 140-14512H-4, 140-14515H-4, 140-14515H-4, 140-14521X-4, 140-14533X-5, 140-14539X-3, 140-14545X-3, 140-14548X-2, 140-145

128-799B-

7R-2, 140-15012R-3, 140-15016R-3, 140-150

Depth(mbsf)

524.95

1.251.852.774.005.759.85

12.8523.7536.9642.7050.5959.9878.57

133.13140.08199.21280.10398.85

2.8516.5535.8543.9072.70

103.10132.00132.00190.00295.30350.30408.30435.80

502.60552.30591.00

so4(mM)

9.00

25.1024.4021.5017.7012.000.600.300.100.000.000.300.100.400.000.000.000.000.00

19.602.900.000.000.000.100.000.000.200.200.200.300.20

0.000.000.00

Ba(µM)

0.6

0.0

13.1

121

143

139

582785582

0.05.1

257347572783

1189123813872192159323112138

80712751273

Note: Sulfate data from Tamaki, Pisciotto, Allan, et al. (1990)and Ingle, Suyehiro, von Breymann, et al. (1990).

change of molal volume (-40.6 cm3/mole), and the formulation ofOwen and Brinkley (1941).

Figure 10 illustrates the degree of saturation of the pore fluids withrespect to barite. We may assume that the main processes affectingthe distributions of dissolved barium in the unsaturated pore fluidsare ion diffusion and barite dissolution. With these assumptions wemay estimate the rate of dissolution by using the general diageneticequation (Berner, 1980). We may further assume a first-order reac-tion, independent of the reactive barium concentration, as a firstapproximation for the purpose of mathematical modeling. The ratelaw for barite dissolution should then be of the form

= km{C - (2)

where C = concentration of dissolved barium; C = asymptotic con-centration attained at infinite depth—it can be but it is not necessarilythe dissolved barium at saturation with barite; and km = rate constant.

The dissolution profiles may be characterized by the standardvertical diffusion model of Berner (1980). Further assuming that (1)there is no barite precipitation above the saturation zone, (2) compac-

co-Q

TOuo

EroenL-

o

/\\\\\v794, 796, 799 r

0 1000 2000 3000 4000

Biogenic barium (ppm)

5000

Figure 7. Organic carbon vs. biogenic barium. The solid lines represent theCOIB/Babio burial ratios estimated using the algorithms of Dymond et al. (in press)and Dymond and Lyle (in press). These ratios are a function of water depth; arelationship that is apparent in the difference in Corg/Babio between Site 798 (973mbsl) and the other sites drilled in water depths greater than 2000 m. Samples thatshow a high enrichment of barium relative to the burial ratio (Sites 796 and 799)are likely to represent the precipitation of authigenic barite in diagenetic fronts.

tion and water flow are slow compared to pore-water diffusion, and(3) steady state diagenesis, then

Ds ( 2 C/ z2) -W( Cß z) + km(C -Q = (3)

where D^ = whole sediment diffusion coefficient for barium, taken asapproximately equal to 8 × 10~6 cm2 s-l (Li and Gregory, 1974);z = depth, and W = sedimentation rate.

For boundary conditions, we will take for z = 0, C = Csw (thebarium concentration in seawater), and for z = , C - C . Integratingover depth we obtain

z-Co (4)

Because C » Csw, and if the reaction rate constant is high relativeto the accumulation rate, equation 4 can be simplified to

C = Coo exp z - Co (5)

Only at Sites 798 and 799 the dissolved barium profiles allow usto estimate the value for C . From the best fit of equation 5 to thedata (assuming C = 1250 µM, Fig. 11) we estimate the rate constantfor barite dissolution to be 2 × 10^/s at Site 799 and 2 × 10~7/s at Site798. The difference in the rate constants might be due to site-to-sitevariations in the kinetics, lack of steady-state conditions or it mayindicate that the reaction rate is dependent on the concentration of"reactive" biogenic barite, a value that is approximately 3 times largerat Site 799 than at Site 798 (Fig. 7).

Because the highest reported sedimentation rates at the sites is 120m/m.y. (Ingle, Suyehiro, von Breymann, et al., 1990), we can show that

AkJ>s > > 6 × I0"14 cm2/s2 > > 1.5 × 10~17 cm2/s2 > > W2, (6)

satisfying the condition required to simplify equation 4.

659


n -u

100-

g 200-E

J" 300-

400-

500-

Age

Qu

ater

nary

late

M

ioce

ne

Plio

cene

mid

dle

Mio

cene

Lithology

V1 W

V

V

VIVV

t/VV

VfVV

vvVIVVvvVt/VVIVVI/VV

VtvV/vV

Silty clay

Diatomooze

Siliceousclaystone

TuffClaystone

Uni

tJ

1

II

III

IVV

Bab j 0 MAR Corg MAR

(mg/cm2/kyr) (mg/cm2/kyr)

12 0 100 200Figure 8. Accumulation of biogenic barium and organic carbon at Site 794. The lithologic column (from Tamaki, Pisciotto, Allan, etal., 1990) illustrates the increase in diatomaceous components during the high-productivity interval between 100 and 400 mbsf. Thehigh accumulation rates of carbon in the Quaternary and middle Miocene sequences are thought to represent a terrestrial source (Tamaki,Pisciotto, Allan, et al., 1990); this interval is characterized by the deposition of siliciclastic turbidites.

Diagenetic Barite

As indicated previously, barite precipitation is thought occur inthat section of the sediments where there is sufficient sulfate to causesupersaturation of this mineral. Authigenic precipitation in "baritefronts" near the end of the sulfate reduction zone has been inferredbased on the barium distributions in sediments and pore fluids(Brumsack, 1986; von Breymann et al., 1990b). At Site 799 weidentified a layer of barite crystals (Fig. 12) which may correspondto an authigenic precipitate in a "barite front." This layer has a lightgreen color and a fine and smooth appearance. SEM analysis ofSample 128-799B-36X-5,23-26 cm (323.2 mbsf), revealed the pres-ence of barite crystals 3 to 6 mm in length (Fig. 13). X-ray diffracto-grams indicate that barite is the main crystalline phase in this layer.

Precipitation of barite at Sites 798 and 799 occurs by upwarddiffusion of barium and downward sulfate diffusion. Sulfate frac-tionation during bacterial decomposition of organic matter results ina dissolved sulfate reservoir enriched in the heavy 34S isotope(Goldhaber and Kaplan, 1980), so the authigenic barites should beisotopically heavy relative to crystals formed in modern seawater.

Sakai (1971) reported the presence of barite concretions enriched in34S in sediments from banks in the Japan Sea. We postulate that themechanism for barite remobilization during diagenesis in sulfate-de-pleted environments is indeed the mechanism leading to the formationof the deposits reported by Sakai (1971).

SUMMARY

The barium distribution in the Japan Sea drill sites permits a goodoverview of the geochemical behavior of this element as it pertainspaleoproductivity reconstructions, diagenetic remobilization and bar-ite precipitation in authigenic barite fronts (Fig. 14). The simultaneousuptake of barium by settling particles, coupled with the decomposi-tion of organic matter during transport through the water column,results in an enhanced C0Ig/Ba ratio at Site 798 (903 mbsl) relative to thesites drilled at greater water depths.

The rate of sediment accumulation has a twofold effect on thebarium distributions. First, the degree of preservation of the bariumrain seems to be a function of sediment-accumulation rates (Dymondet al., in press). Second, higher sedimentation rates result in more rapid

660


ECD</)

CD

UCD

T3CD

4—>

CO

2 •

795

-a—794

796

798

799 •

_

Table 4. Estimated organic carbon to biogenic-barium ratios.

20 40 60 80 100 120 140

Site

794795796798799

Water depth(m)

285033002571903

2084

MAR average(g/cm2/1000 yr)

47564

(Corg/BaW

25-3423-3428-3964-7433^5

(C O T g /Ba) b u r i e db

1110123016

aEstimated using alogarithms obtained from sediment-trap deployments in theequatorial Pacific, from Dymond et al. (in press).

kRatio includes a correction for the different preservation of these parameters asa function of sediment-accumulation rates. (Corg/Ba)buried values were estimatedassuming 20% preservation of the organic carbon (from Dymond and Lyle,1990) and 55% preservation for barium (Dymond et al., in press).

CDT3

TOQQ

40

30 •

cu 20 -

10 -

20

- • - 796

- • - 795

• 1 ' •

_

-

799

798

40 60 80 00 120 140

Sedimentation rate (m/m.y.)

Figure 9. Dissolved interstitial sulfate gradients vs. bulk sedimentation ratesfrom the sites drilled in the Japan Sea (upper). This empirical relationship,described by Berner (1980), illustrates the influence of sedimentation rate onthe preservation of organic matter. Dissolved interstitial barium gradients vs.bulk sedimentation rates for the sites where sulfate is depleted in the pore fluids(Sites 795,796,798, and 799) (lower). Note that the dissolved barium gradientsin these sites do not correspond to the sulfate gradients; rather, the higher valuesare observed at the sites with slower rates of sedimentation.

burial and better preservation of metabolizable organic compounds,enabling these organic substances to reach the sulfate reduction zone(Berner, 1980; Reimers and Suess, 1981). Sulfate consumption in turnpromotes dissolution of biogenic barite, as indicated by high levelsof dissolved barium in the pore fluids. Upward diffusion of dissolvedbarium results in local barite precipitation near the termination of thesulfate reduction zone, as illustrated in Figure 15.

Results from sediment fluxes of particulate barium indicate that thiselement may be useful as a proxy indicator for ocean fertility (Dymond etal., in press). The barium distribution at Site 794 appears to reflect highlevels of primary productivity in the Japan Sea from the late Miocene tothe Pliocene. The high rate of barium accumulation corresponds to thewidespread deposition of diatom-rich sediments, indicative of high pro-ductivity during this time. Quaternary eustatic variations in sea level, inconcert with tectonically emplaced shallow sills, resulted in the topo-graphic isolation of the sea, a condition that is in part responsible for thelower productivity of the modern Japan Sea. The present deep-waterformation in the northern reaches of the basin leads to a homogenouswell-oxygenated basin, a setting that is very different from the upwellingregime that resulted in a high-productivity environment from the lateMiocene to Pliocene times.

The enhanced accumulation of biogenic barium in sediments of lateMiocene to Pliocene age at Sites 794, 798 and 799 is illustrated inFigure 16. We have shown that barium remobilization and barite precipi-

-9

co •

200 -

400-

600

IAP ×

) 10

ft'

W

> -

10

20 3j

: >

794

-9IAP × 10

60 120

IAP × 10

60 120 0

-9IAP x 10

10 20 30 0

1

Ba (µM)

2 0

If

n

D

1 ' I

\

798i i i

i

•

1000Ba(µM)

200 0 600Ba(µM)

1200 0 2000Ba(µM)

4000

Figure 10. Comparison of the estimated ion activity product (IAP) for barite (squares) with the value for the solubility constant at 25°C and 300 atm (indicatedby arrows). The dissolved barium concentration is shown for comparison (line without symbols).

661


tation at Site 799 results in samples highly enriched in bariumrelative to sediments at Site 794, as illustrated by the solid symbolsin Figure 16. If we ignore samples that lie within these barite-fociwe can see a good correspondence in the accumulation rates ofbiogenic barium at both Sites 799 and 794. At Site 798 the sedimentsequence recovered was much younger than that at Sites 794 and799; however, the general distribution indicate a similar behavior inthe barium accumulation. These observations indicate that eventhough diagenetic remobilization does alter the original bariumsignal, this element may still be useful for paleoproductivity recon-structions as long as care is taken in interpreting the barium recordin environments depleted of sulfate.

ACKNOWLEDGMENTS

We are very thankful to A. Pouclet for the identification of the baritelayer found at Site 799, as well as for the XRF and SEM analysis of thismineral. In addition we acknowledge the scientific, technical and crewmembers of ODP Legs 127 and 128 for their helpful assistance duringboth cruises. Financial funding was provided by grants from theJOI/USSAC support program to M. T. von Breymann and from theGerman ODP/SPP (German Science Foundation) to H. J. Brumsack.

REFERENCES

Adams, J., 1990. Paleoseismicity of the Cascadia subduction zone: evidencefrom turbidites off the Oregon-Washington margin. Tectonics, 9:569-583.

Berner, R. A., 1980. Early Diagenesis: A Theoretical Approach: Princeton(Princeton Univ. Press).

Bishop, J. K., 1988. The barite-opal-organic carbon association in oceanicparticulate matter. Nature, 24:341-434.

Brumsack, H. J., 1986. The inorganic geochemistry of Cretaceous black shales(DSDP Leg 41) in comparison to modern upwelling sediments from the Gulfof California. In Summerhayes, C. P., and Shackleton, N. J. (Eds.), NorthAtlantic Paleoceanography. Spec. Publ.—Geol. Soc. Am., 21:447-462.

Church, T. M., and Wolgemuth, K., 1972. Marine barite saturation. EarthPlanet. Sci. Lett., 15:35-44.

Dymond, J., 1981. Geochemistry of Nazca plate surface sediments: an evalu-ation of hydrothermal, biogenic, detrital and hydrogenous sources. InKuhn, L. D., Dymond, J., Dash, E. J., and Hussong, D. M. (Eds.), NazcaPlate: Crustal Formation and Andean Convergence. Mem.—Geol. Soc.Am., 154:33-174.

Dymond, J., and Lyle, M., in press. Particle fluxes in the ocean and implica-tions for sources and preservation of ocean sediments. In Hay, W. W. (Ed.),Geomaterial Fluxes, Glacial to Recent. Nat. Res. Counc, Washington,D.C. (Nat. Acad. Sci. Press).

Dymond, J., Lyle, M., Finney, B., Piper, D. Z., Murphy, K., Conard, R., andPisias, N., 1984. Ferromanganese nodules from MANOP Sites H, S, andR: control of mineralogical and chemical composition by multiple accre-tionary processes. Geochim. Cosmochim. Acta, 48:931-949S

Dymond, J., Suess, E., and Lyle, M., in press. Barium in deep sea sediment: ageochemical indicator of paleoproductivity. Paleoceanography.

GEOSECS, 1987. Atlantic, Pacific and Indian Ocean Expeditions. Shore-based Data and Graphics (Vol 7). Nat. Sci. Found., Washington, D.C.

Gieskes, J. M., and Peretsman, G., 1986. Water chemistry procedures aboardJOIDES Resolution—some comments. ODP Tech. Note, 5.

Goldberg, E. D., and Arrhenius, G.O.S., 1958. Chemistry of Pacific pelagicsediments. Geochim. Cosmochim. Acta, 13:153-212.

Goldhaber, M. B., and Kaplan, I. R., 1980. Mechanisms of sulfur incorporationand isotope fractionation during early diagenesis in sediments of the Gulfof California. Mar. Chem., 9:95-143.

Gurvich, Y. G., Bogdanov, Y. A., andLisitzin, A. P., 1978. Behavior of bariumin Recent sedimentation in the Pacific. Geokhim., 3:359-374. (In Russian)

Iijima, A., Tada, R., and Watanabe, Y, 1988. Developments of Neogenesedimentary basins in the northeastern Honshu arc with emphasis onMiocene siliceous deposits. /. Fac. Sci., Univ. Tokyo, 21:417-466.

Ikebe, Y, and Maiya, S., 1981. Akita and Niigata areas. In Tsuchi, R. (Ed.),Neogene of Japan—Its Biostratigraphy and Chronology: Shizuoka(Kurofume Printing), 68-75.

Ingle, J. C , Jr., 1975a. Pleistocene and Pliocene planktonic foraminifera fromthe Sea of Japan, Leg 31, Deep Sea Drilling Project. In Karig, D. E., Ingle,J. C , Jr., et al., Init. Repts. DSDP, 31: Washington (U.S. Govt. PrintingOffice), 693-702.

, 1975b. Summary of late Paleogene-Neogene stratigraphy, paleo-bathymetry, and correlations, Philippine Sea and Sea of Japan region. InKarig, D. E., Ingle, J. C , Jr., et al., Init. Repts. DSDP, 31: Washington (U.S.Govt. Printing Office), 837-855.

Ingle, J. C, Jr., Suyehiro, K., von Breymann, M. T, et al., 1990. Proc. ODP,Init. Repts., 128: College Station, TX (Ocean Drilling Program).

Jumars, P. A., Altenbach, A. V., de Lange, G. J., Emerson, S. R., Hargrave, B.T, Muller, P. J., Prahl, F. G., Reimers, C. E., Steiger, T, and Suess, E.,1989. Transformation of seafloor arriving fluxes into the sedimentaryrecord. In Berger, W. H., Smetaceck, V, and Wefer, G. (Eds.), Productivityof the Ocean: Present and Past. Dahlem Workshop, Life Sci. Res. Rep.,44:291-311.

Lea, D. W, and Boyle, E. A., 1989. Barium content of benthic foraminiferacontrolled by bottom water composition. Nature, 338:751-753.

Leinen, M., and Pisias, N., 1984. An objective technique for determiningend-member compositions and for partitioning sediments according totheir sources. Geochim. Cosmochim. Acta, 48:47-62.

Li, Y. H., and Gregory, S., 1974. Diffusion of ions in seawater and in deep-seasediments. Geochim. Cosmochim. Acta, 38:703-714.

Matoba, Y, 1984. Paleoenvironment of the Sea of Japan. Benthos '83: Pau(Elf Aquitaine), 409-^14.

Owen, B. B., and Brinkley, S. R., 1941. Calculation of the effect of pressure uponionic equilibria in pure water and in salt solution. Chem. Rev., 29:461^4-64.

Prahl, F. G., and Muehlhausen, L. A., 1989. Lipid biomarkers as geochemicaltools for paleoceanographic study. In Berger, W. H., Smetaceck, V., andWefer, G. (Eds.), Productivity of the Ocean: Present and Past. DahlemWorkshop, Life Sci. Res. Rep., 44:271-289.

Reimers, C. E., and Suess, E., 1981. Spatial and temporal patterns of organicmatter accumulation on the Peru continental margin. In Thiede, J., andSuess, E. (Eds.), Coastal Upwelling (Pt. B): New York (Plenum),311-346.

Rosier, H. J., and Lange, H., 1972. Geochemical Tables: Amsterdam (Elsevier).Sakai, H., 1971. Sulfur and oxygen isotopic study of barite concretions from

banks in the Japan Sea off Northeast Honshu. Geochem. J., 5:79-93.Schmitz, B., 1987. Barium, equatorial high productivity and the northward

wandering of the Indian continent. Paleoceanography, 2:63-77.Shimmield, G. B., and Mowbray, S. R., 1991. The inorganic geochemical

record of the northwest Arabian Sea: a history of productivity variationover the last 400 k.y. from Sites 722 and 724. In Prell, W. L., Niitsuma, N.,et al., Proc. ODP, Sci. Results, 117: College Station, TX (Ocean DrillingProgram), 409-430.

Takayasu, T, and Matoba, Y. (Eds.), 1976. Guidebook for Excursion 1. OgaPeninsula. First Int. Congr. Pacific Neogene Stratigr., Shizuoka (KurofunePrint Co.).

Tamaki, K., Pisciotto, K., Allan, J., et al., 1990. Proc. ODP, Init. Repts., 127:College Station, TX (Ocean Drilling Program).

Taylor, S. R., 1964. Abundance of chemical elements in the continental crust:a new table. Geochem. Cosmochim. Acta, 28:1273-1285.

von Breymann, M. T, Collier, R., and Suess, E., 1990. Magnesium adsorptionand ion exchange in marine sediments: a multicomponent model.Geochim. Cosmochim. Acta, 54:3295-3313.

von Breymann, M. T, Emeis, K. C, and Camerlenghi, A., 1990. Geochemistryof sediments from the Peru upwelling area: results from Sites 680, 685 and688. In Suess, E., von Huene, R., et al., Proc. ODP, Sci. Results, 112:College Station, TX (Ocean Drilling Program), 491-504.

von Breymann, M. T., Emeis, K. C, and Suess, E., in press. Water-depth anddiagenetic constraints in the use of barium as a paleoproductivity indicator.In Summerhayes, C. P., Prell, W, and Emeis, K. C. (Eds.), Evolution ofUpwelling Systems Since the Early Miocene. Geol. Soc London.

Weedon, G. P., and Shimmield, G. B., 1991. Late Pleistocene upwelling andproductivity variations in the northwest Indian Ocean deduced from spec-

662


tral analysis of geochemical data from Sites 722 and 724. In Prell, W. L.,Niitsuma, N., et al., Proc. ODP, Sci. Results, 117: College Station, TX(Ocean Drilling Program), 431^144.

Westall, J. C , Zachary J. L., and Morel, F.M.M., 1987. MINEQL. Acomputer program for the calculation of chemical equilibrium com-position of aqueous systems. Dept, of Chem., Oregon State Univ.,Rep. 86-01.

Worthington, L. V., 1981. The water masses of the World Ocean: some resultsof a fine-scale census. In Warren, B. A., and Wunsch, C. (Eds.), Evolutionof Physical Oceanography: Cambridge (MIT Press), 42-69.

Date of initial receipt: 26 March 1991Date of acceptance: 14 November 1991Ms 127/128B-168

20

25Ba(µM)

500 1000 500

30 LFigure 12. Core photograph of "barite front" layer in Section 128-799B-36X-5,23-26 cm, at 323.2 mbsf. This layer has a light green color and a smoothappearance. Barite was identified by SEM (Fig. 13) and XRF analysis.

300

Figure 11. Dissolved barium vs. depth for samples above barite saturationdepths at Sites 798 and 799 (squares). Solid lines drawn through the data arebest fits to equation 5. See text for details.

663


4

i / j

w •

/̂ v - -

10 µm

Figure 13. SEM photographs of Sample 128-799B-36X-5, 23-26 cm, indicating the presence of barite crystals.

sea level

Bab jo flux

B abibio

30 m/m.y. C(

Cü =120m/m.y

sediment ?

Y7/////////

Site 798

Site 794 Site 799

authigenicbarite

Product Ba MAR Ba MAR

Figure 14. Schematic diagram illustrating the geochemical behavior of barium in the Japan Sea. The water columnfluxes of Corg and Babio are based on data of Dymond et al. (in press) and are reflected in the different Corg/Babio

ratios (open arrows) between Site 798 (903 mbsf) and the sites drilled in water depths greater than 2 km. The highrate of sedimentation at Site 799 (solid arrows) results in sulfate depletion in the pore fluids, which in turn leadsto barite dissolution and reprecipitation in biogenic fronts. Sulfate is not depleted in the pore fluids at Site 794. Thelack of diagenetic remobilization of biogenic barium at this site preserves the high-barium signal associated withthe high-productivity sequences deposited during the late Miocene to Pliocene.

664


Concentration A MAR biogenic barium(|ig/cm2/1000 yr)

a.α>Q

Sulfate reduction zone

"Barite Front"

Sulfate depleted zone

B MAR biogenic barium(µg/cm2/1000 yr)

6000 1200

Figure 15. Schematic diagram illustrating the precipitation of authigenic barite

near the zone of sulfate depletion by upward migration of dissolved barium

and downward diffusion of sulfate.

20

Figure 16. Mass accumulation rates (MAR) of biogenic barium vs. age

(squares) at Site 799 (A) and Site 798 (B). Barium accumulation in the

sediments at Site 794 is shown for comparison (open circles). The solid

symbols represent samples where the high concentrations probably reflect

barium remobilization and reprecipitation in authigenic barite fronts.

665

37. depositional and diagenetic behavior of barium in … · ductivity in deep-sea environments....

Documents