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Filippelli, Gabriel M; Delaney, Margaret Lois (1995): Phosphorus geochemistry of eastern equatorial Pacific Ocean sediments. PANGAEA,, Supplement to: Filippelli, GM; Delaney, ML (1995): Phosphorus geochemistry and accumulation rates in the eastern equatorial Pacific Ocean: results from Leg 138. In: Pisias, NG; Mayer, LA; Janecek, TR; Palmer-Julson, A; van Andel, TH (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 138, 757-767,

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We determined phosphorus (P) concentrations in Leg 138 sediment samples from Sites 844, 846, and 851, using a sequential extraction technique to identify the P associated with five sedimentary components. Total concentrations of P (sum of the five components) ranged from 4 to 35 µmol P/g sediment, with mean values relatively similar between the three sites (11, 14, and 12 for Sites 844,846, and 851, respectively). Authigenic/biogenic P was the most important component in terms of percentage of total P (about 75%), with iron-bound P (13%), adsorbed P (2%-9%), and organic P (4%) of secondary importance; detrital P was a minor P sink (1%) in these sediments. Profiles of adsorbed P and iron-bound P show decreasing concentrations with age, indicating that these components have been affected by diagenesis and reorganization of P. A peak in iron-bound P may reflect higher fluxes of hydrothermally derived Fe to eastern equatorial Pacific Ocean sediments from 11 to 8 Ma. Lower detrital P values for western Site 851 reflect a greater distance of this site from a terrigenous source area, compared to that of Sites 844 and 846.
Phosphorus mass accumulation rates (P-MARs; units of µmol P/cm**2/k.y.) were calculated using total P concentrations (not including the minor and oceanically unreactive detrital P component) and sedimentation rates and dry-bulk densities averaged over time intervals of 0.5 m.y. P-MARs generally decrease from 17 Ma to the present. Eastern transect Sites 844 and 846 display a decrease in P-MARs from about 30 to 10 in the interval from 17 to 8 Ma, while western transect Site 851 is highly variable during this interval. P-MARs increase to about 45 and stay relatively high from 8 to 6 Ma, then decrease toward the present to some of the lowest values of the record (about 10). The general trend of high P-MARs at about 6 Ma and decreasing values toward the present is correlated with other geochemical and sedimentary trends through this interval and may reflect (1) a change in net sediment and P burial, (2) a reorganization of fluxes with no change of net burial, or (3) a combination of the two.
Median Latitude: 2.532253 * Median Longitude: -97.290173 * South-bound Latitude: -3.094930 * West-bound Longitude: -110.571800 * North-bound Latitude: 7.921310 * East-bound Longitude: -90.480760
Date/Time Start: 1991-05-11T10:24:00 * Date/Time End: 1991-08-09T06:00:00
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