DSDP 273-Site

Alt, J.C. and Honnorez, J. (1984) Alteration of the upper oceanic crust, DSDP site 417 mineralogy and chemistry. Contr. Mineral. Petrol, 87, 149-169. 

Fig. 4.3. (A) Composite multispecies benthic foraminiferal Mg/Ca records from three deep-sea sites DSDP Site 573, ODP Site 926, and ODP Site 689. (B) Species-adjusted Mg/Ca data. Error bars represent standard deviations of the means where more than one species was present in a sample. The smoothed curve through the data represents a 15% weighted average. (C) Mg temperature record obtained by applying a Mg calibration to the record in (B). Broken line indicates temperatures calculated from the record assuming an ice-free world. Blue areas indicate periods of substantial ice-sheet growth determined from the S 0 record in conjunction with the Mg temperature. (D) Cenozoic composite benthic foraminiferal S 0 record based on Atlantic cores and normalized to Cibicidoides spp. Vertical dashed line indicates probable existence of ice sheets as estimated by (2). 3w, seawater S 0. (E) Estimated variation in 8 0 composition of seawater, a measure of global ice volume, calculated by substituting Mg temperatures and benthic 8 0 data into the 8 0 paleotemperature equation (Lear et al., 2000).

Miller, K.G., Feigenson, M.D. and Wright, J.D. (1991) Miocene isotope standard section, DSDP Site 608 An evaluation of isotope and biostratigraphic resolution. Paleoceanography, 6, 33-52. 

Shackleton, N.J. and Kennett, J.P. (1975a) Paleotemperature history of the Cenozoic and the initiation of Antarctic glaciation oxygen and carbon isotope analyses in DSDP Sites 277, 279, and 281. Initial Reports of the DSDP, 29, Washington, D.C. U.S. Gov. Printing Office, pp. 743-755. 

Staudigel H, Plank T, White B, Schmincke H-U (1996) Geochemical fluxes during seafloor alteration of the basaltic upper oceanic crust DSDP Sites 417 and 418. In Subduction Top to Bottom. Bebout GE, Scholl DW, Kirby SH, Platt JP(eds), AGU, Washington DC, p 19-37 Suman DO, Bacon MP (1989) Variations in Holocene sedimentation in the North American Basin determined by °Th measurements. Deep Sea Res 36 869-787... 

Figure 11. (a) Late Pleistocene 5 Ca record based on measiwe-ments of G. sacculifer (from Nagler et al. 2000). The inferred variations of temperature are similar to diose inferred from variations of Mg/Ca in die same sediment core, (b) Plio-Pleistocene record of seawater b Ca based on bulk coccolith ooze from DSDP Site 590B in the soudiwestem Pacific (Tasman Sea). The 2.5 m.y. record shows only small variations of 5 Ca. The seawater curve is constructed assuming that the fractionation between seawater and bulk sediment remained constant. The decrease of S Ca at ca. 0.7 Ma could reflect cooling rather than a change in the seawater 5 Ca. 

Deniel D, Vidal P, Fernandez A, LeFort P, Peucat JJ (1987) Isotopic study of the Manaslu granite (Himalaya, Nepal) inference on the age and source of Himalayan leucogranites. Contrib Mineral Petrol 96 78-92 DePaolo DJ (1986) Detailed record of the Neogene Sr isotopic evolution of seawater from DSDP Site 590B. Geology 14 103-106... 

Fig. 3.22 6 C records ot total dissolved CO2 from pore waters of anoxic sediments recovered in various DSDP sites (after Anderson and Arthur 1983)...

October 19,1988), in addition to biogenic dominance in ocean hydrates (Dillon and Max, 2000), with sporadic mixtures of biogenic and thermogenic gas in Alaska, Russia, offshore Canada, and the Gulf of Mexico. It is possible to have both means (in place generation and fast fluxes) of supplying biogenic gas, indicated by Kvenvolden et al. (1984) and Kvenvolden and Claypool (1985) at DSDP Site 570 in the Middle America Trench. 

Rocks with a composition similar to the Mid-Ocean Ridge Basalts have been recovered from the Vavilov basin (ODP Site 655 and DSDP Site 373)... 

MORB-type DSDP Site 373 7.3 to 4.1 - Basaltic lavas forming the... 

Rapid increases in the interstitial water concentrations of dissolved strontium with increasing burial depth of deep-sea carbonate sediments have been interpreted as evidence of the recrystallization reaction (Baker et al., 1982 Elderfield et al., 1982 Gieskes, 1983). Figure 8.17 shows an example of interstitial-water profiles of dissolved alkaline-earth species from a carbonate nanno-fossil ooze from the Ontong Java Plateau (DSDP site 288 5°58 S, 161°50 E). At this site calcium and magnesium concentrations are linearly correlated, and their gradients are governed by chemical reactions deep in the sediment column. 

Figure 8.17. Interstitial water chemistry of sediments at DSDP site 288. A. Ca2+ and Mg2+ concentration-depth profiles. B. Sr2+ concentration-depth profile. C. Sr/Ca ratio in carbonates black dots, observed pluses calculated from interstitial water data and distribution coefficients. Lithology 1A, pyrite-bearing, foram-nanno ooze IB, bioturbated nanno ooze 1C, nanno-foram chalks and oozes. (After Gieskes, 1983.)...

Heat flow affects the rate of alteration of pelagic ooze to chalk the higher the temperature, the greater the degree of cementation of the sediment. This effect on the ooze/chalk transition has been convincingly demonstrated by Wetzel (1989) in a study of compositionally similar pelagic carbonate sediments at DSDP sites 504 and 505 located south of the Costa Rica Rift zone. 

Table 8.4 Thermal conditions at DSDP sites 504 and 505, south of the Costa Rica Rift zone, eastern Pacific Ocean. (After Wetzel, 1989.)...

Figure 8.18. Porosity-depth relations at DSDP sites 504 and 505. Thin line, porosity determinations on ship-board black dots, porosity determinations from samples tested in laboratory dark thick line, best fit to the data. Notice porosity gradient is steeper at the high heat flow site 504 than at the "cooler site 505. (After Wetzel, 1989.)...

Wetzel (1989) calculated the volume of calcite cement at the two DSDP sites. The results of these calculations are shown in Figure 8.19. It can be seen that the calculated rate of increase of cement volume with increasing depth at the high heat flow area of site 504 is greater than that of the low heat flow site 505. 

These differences in the physical properties of pelagic calcareous sediments at DSDP sites 504 and 505 are a result of the temperature difference between the two sites. A more rapid decrease in diagenetic potential is favored by increasing sediment temperature. The rates of the diagenetic solution-precipitation reactions are increased because of the higher temperature (Baker et al 1980), and the accompanying increased concentrations of ions involved in cementation (Mottl et... 

Dolomite rhombs have been observed on smear slides of sediments from several DSDP sites, and the occurrence of dolomite in these sediments has been documented quantitatively by Lumsden (1988). Deep-marine dolomite averages about 1 wt % in all sampled DSDP sediments throughout post-Jurassic time. The dolomite is nonstoichiometric, averaging 56 mole % CaC03 (Figure 8.24), and has a crystal size and appearance similar to that of supratidal dolomite. Lumsden (1988) concludes that most is an early chemical precipitate from seawater. He estimated that about 10% is detrital, but he advocates that more criteria are needed to distinguish dolomite formed in cold, deep marine waters from that formed in supratidal deposits before this estimate can be substantiated. 

Wetzel A. (1989) Influence of heat flow on ooze/chalk cementation Quantification from consolidation parameters in DSDP sites 504 and 505 sediments. J. Sediment. Petrol. 59, 539-547. 

Hart S. R. and Staudigel H. (1986) Ocean emst vein mineral deposition Rb/Sr ages, U-Th-Pb geochemistry, and duration of circulation at DSDP Sites 261, 462, and 516. Geochim. Cosmochim. Acta 50, 2751-2761. 

Staudigel H., Hart S. R., Schmincke H. U., and Smith B. M. (1989) Cretaceous ocean crust at DSDP sites 417 and 418 Carbon uptake from weathering versus loss by magmatic outgassing. Geochim. Cosmochim. Acta 53, 3091-3094. 

Staudigel H., Plank T., White W. M., and Schmincke H.-U. (1996) Geochemical fluxes during seafloor alteration of the upper oceanic crust DSDP sites 417 and 418. In SUBCON Subduction from Top to Bottom (eds. G. E. Bebout and S. H. Kirby). American Geophysical Union, Washington, DC, vol. 96, pp. 19-38. 

The Ontong Java plateau (OJP) in the western Pacific (Figure 1) has been tectonically uplifted and exposed along its south eastern margin, at the Solomon Islands arc, mostly on the Islands of Maliata and Santa Isabel. In contrast to the CCOP, which has numerous exposed sections, these are currently the only known subaerial exposures of the OJP. The rest of our knowledge of the OJP comes from a series of drill holes DSDP Site 289 and OOP Sites 803 and 807 (Mahoney et al. 

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