Rates of formation of modern phosphorite off western Mexico

Schuffert, Jeffrey D; Jahnke, Richard A.; Kastner, Miriam; Leather, Jim; Sturz, Anne Aleda; Wing, Michael R.

doi:10.1016/0016-7037(94)90227-5

Cited by 74 publications

(33 citation statements)

References 44 publications

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“…In BC451 and BC455, J P is lower than J P(F) ( Table 6). A similar difference between interstitial phosphate and fluoride removal fluxes was observed by Schuffert et al (1994) for sediments off western Mexico. The F flux into the sediment probably provides the best direct measure for francolite precipitation rates, because seawater is the dominant source for F in marine sediments (Froelich et al, 1983).…”

Section: Authigenic Apatite Formationsupporting

confidence: 77%

“…In situ phosphogenesis, therefore, seems more important than the contribution of reworked phosphogenetic material. The calculated downward fluxes of phosphate and fluoride for BC484 (Table 6) are similar to estimates for modern phosphorite formation (Froelich et al, 1988;Schuffert et al, 1994). We conclude that the high phosphorus content is the result of both redeposition of phosphatised particles and high rates of in situ phosphogenesis.…”

Section: Redepositionsupporting

confidence: 71%

“…High francolite contents just below the sediment water interface as observed in BC484 have previously been documented for the continental margins of Peru (Burnett et al, 1982;Froelich et al, 1988), western Mexico, Baja California Schuffert et al, 1994Schuffert et al, , 1998, Namibia (Thomson et al, 1984), Eastern Australia ) and western India (Rao and Lamboy, 1996). Many of these phosphorite deposits have been identified as lag deposits (Kolodny, 1981;Garrison and Kastner, 1990).…”

Section: Phosphorite Formation In Bc484mentioning

confidence: 75%

“…Phosphorites have been found worldwide in numerous geological formations (e.g. Filippelli and Delaney, 1994;Föllmi, 1996;Trappe, 1998), but their recent formation is a relatively rare phenomenon Thomson et al, 1984;Froelich et al, 1988;Heggie et al, 1990;Schuffert et al, 1994Schuffert et al, , 1998. In addition to upwelling areas, phosphogenesis has been recognised in sediments of shallow continental margins (Ruttenberg and Berner, 1993;Reimers et al, 1996;Louchouarn et al, 1997), the continental slope underlying low productivity areas (Slomp et al, 1996) and in deep-sea sediments (Lucotte et al, 1994;Filippelli and Delaney, 1996).…”

Section: Introductionmentioning

confidence: 99%

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Phosphogenesis and active phosphorite formation in sediments from the Arabian Sea oxygen minimum zone

2000

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In this study, porewater chemistry, solid-phase analysis and microscopic observations were combined to evaluate phosphogenesis in three boxcores located within the intensive oxygen minimum zone of the Arabian Sea. Three parameters, namely a decrease of the dissolved phosphate and fluoride concentrations with depth, saturation with respect to carbonate fluorapatite, and the presence of a solid-phase Ca-phosphate mineral, all indicate that phosphogenesis is currently taking place at all three sites. Authigenic apatite precipitation rates vary between 0.076 and 1.04 mmolP cm Ϫ2 yr Ϫ1 , and are of the same order of magnitude as reported for other high productivity areas. Precipitation of an intermediate precursor precedes francolite formation in the continental slope sediments on the Karachi Margin. Results of a diagenetic P model indicate that phosphogenesis is induced by high rates of organic matter degradation. Dissolution of fish debris is likely to provide a substantial additional source of phosphate. Redox iron cycling does not influence phosphogenesis in these environments. Model results suggest that sediment mixing is essential in promoting early diagenetic phosphogenesis. The highest rate of francolite formation was observed in a boxcore taken on the Oman Margin, where it contributes to the formation of a Holocene phosphorite deposit. This observation contrasts with previous reports of only old phosphorites in this area. Phosphorites are presently forming on the Oman Margin as a result of: (a) deposition of older, reworked material from the continental shelf, which has undergone an earlier phase of phosphogenesis; (b) a high input of reactive P (fish debris and degradable organic matter); (c) a relatively low sediment accumulation rate; and (d) the absence of winnowing on this location. Holocene phosphorite deposits may be less common on the Oman Margin than in other coastal upwelling areas because of the narrowness of the shelf and the steepness of the slope, which limit the area where phosphorite formation may occur. ᭧

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Section: Authigenic Apatite Formationsupporting

confidence: 77%

Section: Redepositionsupporting

confidence: 71%

Section: Phosphorite Formation In Bc484mentioning

confidence: 75%

Section: Introductionmentioning

confidence: 99%

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Phosphogenesis and active phosphorite formation in sediments from the Arabian Sea oxygen minimum zone

2000

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“…High subsurface porewater phosphate concentrations observed in continental slope sediments often cannot be explained exclusively by phosphate release from organic matter degradation or iron oxide reduction (Froelich et al 1988;Van Cappellen and Berner 1988;Schuffert et al 1994). Some of these high porewater phosphate concentrations, therefore, have been attributed to the dissolution of fish debris (Suess 1981;Van Cappellen and Berner 1988).…”

Section: Yrmentioning

confidence: 99%

A novel chemical method to quantify fish debris in marine sediments

Schenau

Lange

2000

Limnology & Oceanography

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Burial of fish bones, which consist primarily of hydroxyapatite, has been recognized as a mechanism to remove reactive phosphorus from the oceans. In this study, a new method is presented, which differentiates P associated with biogenous apatite (P fish ) from other P fractions. The method, consisting of a sequential chemical extraction with 2 M NH 4 Cl, has been successfully tested on standard materials. It enables us, for the first time, to quantify fish debris in sediment records and to assess their importance for the marine phosphorus cycle.The NH 4 Cl extraction has been applied to sediment samples from the Arabian Sea. Preservation of fish debris is significantly higher in sediments located above 1,200 m water depth than it is for deeper sediments. The distribution of P fish contents in surface sediments is predominantly governed by the extent of fish debris regeneration, which is related to differences in water depth and sedimentation rates. In addition, a good correlation between high sedimentary P fish contents and low oxygen bottom water concentrations suggests that the presence of the intense oxygen minimum zone may account for the enhanced preservation of fish debris in continental slope sediments.

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Sampling pore water at a centimeter resolution in sandy permeable sediments of lakes, streams, and coastal zones

Anschutz

Charbonnier

2020

Limnology & Ocean Methods

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Concentration gradients in the solid fraction and pore water of modern sediments allow to identify benthic biogeochemical processes and the associated fluxes. Gradients are often obtained from layers sampled below the sediment–water interface from sediment cores. Numerous examples in the literature show results from cores collected in impermeable porous sediments, but very few from permeable sediment cores. Indeed, the acquisition of vertical profiles in sandy permeable sediments with a spatiotemporal resolution equivalent to that of muddy sediments is a challenge. We present here a simple protocol that allows sampling of sandy sediments and their interstitial waters with a vertical resolution of 1 cm. This method is suitable for shallow environments, such as intertidal zones, lakes, lagoons, and stream beds. The method is based on rapid conditioning of hand‐collected cores. The cores are pre‐cut lengthwise. Immediately after recovery, they are laid horizontally, opened, and sliced. Interstitial water is collected by centrifugation on site shortly after cutting the core with tubes equipped with a 0.2 μm membrane. Optimally, 30 min is sufficient between core collection and conditioning of 12 sections of a 20‐cm long core. The examples shown indicate that the method is reproducible. Reduced dissolved compounds such as Fe(II), Mn(II), and NH4+ show profiles without significant oxidation. At the time of core cutting, small volumes of pore water are seeping out of the core, but for sediments with a permeability of up to 10−10 m2, this seepage does not disturb the shape of the pore‐water profiles.

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Rates of formation of modern phosphorite off western Mexico

Cited by 74 publications

References 44 publications

Phosphogenesis and active phosphorite formation in sediments from the Arabian Sea oxygen minimum zone

Phosphogenesis and active phosphorite formation in sediments from the Arabian Sea oxygen minimum zone

A novel chemical method to quantify fish debris in marine sediments

Sampling pore water at a centimeter resolution in sandy permeable sediments of lakes, streams, and coastal zones

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