Indian Ocean sediment

Seawater. A half dozen analyses of Mo isotopes in the Pacific, Atlantic and Indian oceans, covering depths to -3000 m (Barling et al. 2001, Siebert et al. 2003), reveal two important facts. First, there is no detectable 5 Mo variation in the oceans with location or depth. Second, d Mo in the oceans is similar to the heaviest of euxinic sediments, and is heavier than in igneous rocks or ferromanganese sediments by -1.5%o and -2%o, respectively. A uniform isotopic composition in the oceans is consistent with the 10 -1 O " year ocean residence time. The explanation for the heavy isotopic composition is discussed further below. 

Phosphorites (manne apatites) are dense, hght-brown-to-black concretions, ranging in size from sands to nodules and irregular masses. Phosphorites have been found off Argentina, Chile, Japan, Mexico, Peru, South Africa, and Spain, and several islands in the Indian Ocean. Some also have been found off the west coast of North America and on the eastern North American continental shelf These deposits occur where water upwelling transports phosphorus and where the rate of sedimentation is slow. The... 

Chernova, T.G., Rao, P.S., Pikovskii, Yu.I., Alekseeva, T.A., Nagender Nath, B., Ram-alingeswara Rao, B., Rao, Ch.M., 2001. The composition and the source of hydrocarbons in sediments taken from the tectonically active Andaman Backarc Basin, Indian Ocean. Mar. Chem. 75, 1-15. 

Figure 2.14. The log of dissolution rate in percent per day versus the log of (1-fi). A = whole Indian Ocean sediment dissolved in deep-sea sediment pore water B = whole Pacific Ocean sediment dissolved in Atlantic Ocean deep seawater C = whole Atlantic Ocean sediment dissolved in Long Island Sound seawater (Morse and Berner, 1972) D = > 62 pm size fraction of the Indian Ocean sediment dissolved in Atlantic Ocean deep seawater, E = the 125 to 500 pm size fraction of Pacific Ocean sediment dissolved in Atlantic Ocean deep seawater F = 150 to 500 pm Foraminifera dissolved in the Pacific Ocean water column. (After Morse, 1978.)...

The distribution of CaC03 in Indian Ocean basin sediments has been examined by Kolia et al. (1976). Their plot of surface sediment carbonate distribution is presented in Figure 4.19. Again the first order control of carbonate... 

Further processes leading to the chemical stabilization of these periplatform metastable carbonates and chalk formation have been documented by Malone et al. (1989) for carbonate sediments found at ODP site 716, Maldives Archipelago, Indian Ocean. This site, one of only a few such periplatform sites drilled by the ODP, represents a reasonably continuous recovery of sediments deposited at a nearly constant sedimentation rate. 

Figure 8.20. Generalized relationship between Sr and Na in CaC03 for periplatform carbonate sediments at ODP site 716, Maldives Archipelago, Indian Ocean. In general, Sr and Na concentrations in the carbonate phase decrease with increasing burial depth at this site. (After Malone et al., 1990.)...

Malone M.J., Baker P.A. and Burns S.J. (1989) Geochemistry of periplatform carbonate sediments ODP Site 716 Maldives Archipelago, Indian Ocean (in press). 

Peterson L.C. and Prell W.H. (1985a) Carbonate dissolution in recent sediments of the eastern equatorial Indian Ocean Preservation patterns and carbonate loss above the lysocline. Mar. Geol. 64, 259-290. 

Raghukumar, C. Raghukumar, S. (1998). Barotolerance of fungi isolated from deep-sea sediments of the Indian Ocean. Aquatic Microbial Ecology, 15, 153-63. 

Figure 15. The measured rate of dissolution (Rm) per gram of calcium carbonate, divided by the initial rate of dissolution (Rr) vs. the percent of the calcium carbonate which has dissolved. Runs were carried at Q = 0.40.1.O.S. = Indian Ocean sediment, P.O.S. = Pacific Ocean sediment (after Ref. 30).

The material used by Morse was "whole Indian Ocean sediment" which is largely of biogenic origin. It is expected that the reacting surface area is considerably less than the BET surface area used by Morse to normalize rate. This may also explain some of the disparity between calculated and observed rates (Table III). 

The Indian Ocean has sedimentation rates ranging between those of the Pacific and the Atlantic Ocean. 

Fig. 10. Map of the Atlantic and Indian Ocean with manganese nodule fields (hatched) and limits of sedimentation rate 30 mm/1000 years (pointed). The arrows indicate the direction of higher sedimentation rates. The data are taken from Lisitzin and Dreyfus et al. . They are inadequate because measurements on the ocean floor are scarce. The map only illustrates that oceans with lower sedimentation rates contain larger fields of manganese nodules and vice versa...

During an extended station in a Trichodesmium bloom in the Indian Ocean, sediment trap material from that station clearly reflected diazotrophic input, compared to stations away from the bloom (Capone et al., 1998). Another example was observed during the massive bloom of R. intracellularis within H. hauckii off the NE coast of South America (Carpenter et al., 1999). Suspended particles and zooplankton collected within the bloom were depleted in reflecting the dominant contribution of N2 fixation to the planktonic N budget. 

Figure Distribution of (%o vs. air) in surface sediments of the North Indian Ocean...

Gaye-Haake, B., Lahajnar, N., Emeis, K. C., Unger, D., Pdxen, T., Suthhof, A., Ramaswamy, V., Schulz, H., Paropkari, A. L., Guptha, M. V. S., and Ittekkot, V. (2005). Stable nitrogen isotopic ratios of sinking particles and sediments from the northern Indian Ocean. Mar. Chem. 96, 243-255. 

Rehkamper M. and Hofmann A. W. (1997) Recycled ocean crust and sediment in Indian Ocean MORB. Earth Planet Sci. Lett. 147, 93-106. 

Anderson R. N., Hobarth M. A., and Langseth M. G. (1979) Geothermal convection through oceanic crust and sediments in the Indian Ocean. Science 204, 828-832. 

Koning E., Brummer G.-J., van Raaphorst W., van Bennekom J., Helder W., and van Iperen J. (1997) Settling dissolution and burial of biogenic silica in the sediments off Somalia (northwestern Indian Ocean). Deep-Sea Res. II 44, 1341-1360. 

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