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Fig. 3. Phosphorus speciation data. The non-reactive (i.e., detrital) P fraction ranges from <1% to 42% of total P, but a majority of units (11 of 18) yield values between 10 and 20%. The mean (+1 s.d.) TOC content of each unit is shown to the right; note that many of these are not organic-rich facies (i.e., mean TOC<1%). “P-undiff” represents undifferentiated, non-organic reactive P in unit 11. Data sources: (1—2) Filippelli and Delaney (1996); (3) Tamburini et al. (2002); (4, 8, 16) Berner et al. (1993); (5—6) Schenau et al. (2005); (7) Schenau and De Lange (2001); (9) Eijsink et al. (2000); (10) Slomp et al. (2004); (11) Filipek and Owen (1981); (12) Delaney and Anderson (2000); (13) Tamburini et al. (2003); (14-15) Ruttenberg and Berner (1993); (17) Vink et al. (1997); (18) Filippelli (2001). LJ. Algeo, E. Ingall / Palaeogeography, Palaeoclimatology, Palaeoecology 256 (2007) 130-15:

Figure 3 Phosphorus speciation data. The non-reactive (i.e., detrital) P fraction ranges from <1% to 42% of total P, but a majority of units (11 of 18) yield values between 10 and 20%. The mean (+1 s.d.) TOC content of each unit is shown to the right; note that many of these are not organic-rich facies (i.e., mean TOC<1%). “P-undiff” represents undifferentiated, non-organic reactive P in unit 11. Data sources: (1—2) Filippelli and Delaney (1996); (3) Tamburini et al. (2002); (4, 8, 16) Berner et al. (1993); (5—6) Schenau et al. (2005); (7) Schenau and De Lange (2001); (9) Eijsink et al. (2000); (10) Slomp et al. (2004); (11) Filipek and Owen (1981); (12) Delaney and Anderson (2000); (13) Tamburini et al. (2003); (14-15) Ruttenberg and Berner (1993); (17) Vink et al. (1997); (18) Filippelli (2001). LJ. Algeo, E. Ingall / Palaeogeography, Palaeoclimatology, Palaeoecology 256 (2007) 130-15:

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Fig. 1. Sedimentary P cycle model (e.g., Froelich et al., 1988; Glenn et al., 1994; Jarvis et al., 1994; Féllmi, 1996; Filippelli, 2002). Under oxic bottomwaters (left), redox cycling of Fe within the sediment facilitates retention of remineralized organic P. P that is initially sorbed onto Fe-oxyhydroxides subsequently may be fixed in authigenic carbonate fluorapatite phases as Ca** and F diffuse into the sediment. Under anoxic bottomwaters (right), the lack of ferric iron phases allows most remineralized P to diffuse out of the sediment. SWI = sediment—water interface.
Fig. 1. Sedimentary P cycle model (e.g., Froelich et al., 1988; Glenn et al., 1994; Jarvis et al., 1994; Féllmi, 1996; Filippelli, 2002). Under oxic bottomwaters (left), redox cycling of Fe within the sediment facilitates retention of remineralized organic P. P that is initially sorbed onto Fe-oxyhydroxides subsequently may be fixed in authigenic carbonate fluorapatite phases as Ca** and F diffuse into the sediment. Under anoxic bottomwaters (right), the lack of ferric iron phases allows most remineralized P to diffuse out of the sediment. SWI = sediment—water interface.
Fig. 2. (A) Co,9:P ratios of modern marine sediments (open triangles; median values given by solid stars). The Redfield ratio of 106:1 is shown for reference. Sediment C,,9:P ratios are mostly <50:1 in oxic—suboxic environments and ~ 50—300 in anoxic environments. The range of observed deepwater redox conditions for each environment is given at the right. (B) Relationship of C,,9:P ratios to deepwater redox status. Boxes represent the median (+1 s.d.) for Co,g:P ratios and the full range of observed redox conditions. Dashed diagonal line is a best-fit regression through the data, excluding the two Effingham Inlet data points (*=0.95, p(«)<0.01). Data sources: Hirst (1974), Suess (1981), Calvert and Price (1983), Skei (1986), Francois (1987), Froelich et al. (1988), Brumsack (1989), Lyons (1992), Ruttenberg et al. (1997), Yarincik (1997), Bianchi et al. (2000), Emeis et al. (2000), Anderson et al. (2001), Emelyanov (2001), Filippelli (2001), and Ingall et al. (2005). LJ. Algeo, E. Ingall / Palaeogeography, Palaeoclimatology, Palaeoecology 256 (2007) 130-155
Fig. 2. (A) Co,9:P ratios of modern marine sediments (open triangles; median values given by solid stars). The Redfield ratio of 106:1 is shown for reference. Sediment C,,9:P ratios are mostly <50:1 in oxic—suboxic environments and ~ 50—300 in anoxic environments. The range of observed deepwater redox conditions for each environment is given at the right. (B) Relationship of C,,9:P ratios to deepwater redox status. Boxes represent the median (+1 s.d.) for Co,g:P ratios and the full range of observed redox conditions. Dashed diagonal line is a best-fit regression through the data, excluding the two Effingham Inlet data points (*=0.95, p(«)<0.01). Data sources: Hirst (1974), Suess (1981), Calvert and Price (1983), Skei (1986), Francois (1987), Froelich et al. (1988), Brumsack (1989), Lyons (1992), Ruttenberg et al. (1997), Yarincik (1997), Bianchi et al. (2000), Emeis et al. (2000), Anderson et al. (2001), Emelyanov (2001), Filippelli (2001), and Ingall et al. (2005). LJ. Algeo, E. Ingall / Palaeogeography, Palaeoclimatology, Palaeoecology 256 (2007) 130-155
Corg:P ratios for Phanerozoic anoxic marine facies Table 1
Corg:P ratios for Phanerozoic anoxic marine facies Table 1
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“ Corg and P values are given as the mean of the sample set plus or minus one standard deviation. B Corg:P molar ratios are given as the median of the sample set with the standard deviation range (i.e., 16th—84th percentiles) in parentheses; these statistics are used in preference to the mean anc standard deviation in order to avoid the influence of extreme values on the latter. © Corg:P ratios given separately for type II and type III organic matter, or for black shale (BS) and gray shale (GS) facies.
“ Corg and P values are given as the mean of the sample set plus or minus one standard deviation. B Corg:P molar ratios are given as the median of the sample set with the standard deviation range (i.e., 16th—84th percentiles) in parentheses; these statistics are used in preference to the mean anc standard deviation in order to avoid the influence of extreme values on the latter. © Corg:P ratios given separately for type II and type III organic matter, or for black shale (BS) and gray shale (GS) facies.
Fig. 4. Median Co,:P ratios from 91 “formation-studies” of 58 different Phanerozoic organic-rich facies (Table 1). For each unit, the median Co,.:P ratio was calculated in preference to the mean to avoid undue influence by outliers. Two Late Permian units with C,,9:P ratios <10 are not shown but are included in calculations of the linear regression (dashed line), running mean (solid line), and standard deviation range (shaded). Trend line calculations are based on logarithms of median C,,,:P ratios. The linear regression line shows that C,,9:P ratios have declined on average by a factor of four from the Cambrian (~ 260:1) to the Recent (~ 65:1). The running mean curve demonstrates the existence of coherent secular variation in the dataset. The Redfield ratio of 106:1 is shown for reference. The timescale used is that of Gradstein et al. (2004).
Fig. 4. Median Co,:P ratios from 91 “formation-studies” of 58 different Phanerozoic organic-rich facies (Table 1). For each unit, the median Co,.:P ratio was calculated in preference to the mean to avoid undue influence by outliers. Two Late Permian units with C,,9:P ratios <10 are not shown but are included in calculations of the linear regression (dashed line), running mean (solid line), and standard deviation range (shaded). Trend line calculations are based on logarithms of median C,,,:P ratios. The linear regression line shows that C,,9:P ratios have declined on average by a factor of four from the Cambrian (~ 260:1) to the Recent (~ 65:1). The running mean curve demonstrates the existence of coherent secular variation in the dataset. The Redfield ratio of 106:1 is shown for reference. The timescale used is that of Gradstein et al. (2004).
Fig. 5. Phanerozoic atmospheric pO, models. The model of the present study (thick line) was generated by inversion and scaling of the Phanerozoic Co,9:P curve (Fig. 4). The curve is anchored to the present atmospheric Oy level of 21% (horizontal line), and Phanerozoic variation is maximized consonant with range constraints imposed by (1) diffusion modeling of Late Ordovician and Late Devonian soils (arrows with “G”; Yapp, 1996), (2) fossil charcoal occurrences, which require Oz levels >13% for sustained combustion (diamonds; Chaloner, 1989; Robinson, 1989), and (3) spontaneous ignition of wood at O, levels of ~35% (Chaloner, 1989; Wildman et al., 2004). Four published atmospheric pO2 models are shown for comparison (thin lines; Berner and Canfield, 1989; Berner et al., 2000; Bergman et al., 2004; Berner, in press).
Fig. 5. Phanerozoic atmospheric pO, models. The model of the present study (thick line) was generated by inversion and scaling of the Phanerozoic Co,9:P curve (Fig. 4). The curve is anchored to the present atmospheric Oy level of 21% (horizontal line), and Phanerozoic variation is maximized consonant with range constraints imposed by (1) diffusion modeling of Late Ordovician and Late Devonian soils (arrows with “G”; Yapp, 1996), (2) fossil charcoal occurrences, which require Oz levels >13% for sustained combustion (diamonds; Chaloner, 1989; Robinson, 1989), and (3) spontaneous ignition of wood at O, levels of ~35% (Chaloner, 1989; Wildman et al., 2004). Four published atmospheric pO2 models are shown for comparison (thin lines; Berner and Canfield, 1989; Berner et al., 2000; Bergman et al., 2004; Berner, in press).
Fig. 6. Silurian—Carboniferous atmospheric pO, and the “Devonian charcoal gap.” Atmospheric pO, curves are from Fig. 5. Fossil charcoal records: (1) Platyschima Shale Member, Downton Castle Formation (Glasspool et al., 2004); (2) Ditton Formation (Edwards and Axe, 2004); (3) Duncannon Member, Catskill Formation (Cressler, 2001); (4) Hangenberg Sandstone (Rowe and Jones, 2000); (5) Berea Sandstone (Beck et al., 1982); (6) Cementstone Group (Scott et al., 1985); (7) Horton Group (Falcon-Lang, 2000); (8) Moyny Limestone (Falcon-Lang, 1998); (9) Upper Shalwy Beds (Nichols and Jones, 1992); (10) Strathclyde Group (Scott and Jones, 1994); (/7) Namurian B units, Staffordshire, England (Scott et al., 1997). The presence of fossil charcoal implies atmospheric O2 levels >13% for sustained combustion of plant tissue; soil diffusion modeling imposes an O» minimum of 8% for the Late Devonian (arrow with “G”; Yapp, 1996). Inset at top: stratigraphic trends in inertinite and vitrinite abundances in the Famennian Ohio Shale and Early Tournaisian Sunbury Shale (Rimmer et al., 2004).
Fig. 6. Silurian—Carboniferous atmospheric pO, and the “Devonian charcoal gap.” Atmospheric pO, curves are from Fig. 5. Fossil charcoal records: (1) Platyschima Shale Member, Downton Castle Formation (Glasspool et al., 2004); (2) Ditton Formation (Edwards and Axe, 2004); (3) Duncannon Member, Catskill Formation (Cressler, 2001); (4) Hangenberg Sandstone (Rowe and Jones, 2000); (5) Berea Sandstone (Beck et al., 1982); (6) Cementstone Group (Scott et al., 1985); (7) Horton Group (Falcon-Lang, 2000); (8) Moyny Limestone (Falcon-Lang, 1998); (9) Upper Shalwy Beds (Nichols and Jones, 1992); (10) Strathclyde Group (Scott and Jones, 1994); (/7) Namurian B units, Staffordshire, England (Scott et al., 1997). The presence of fossil charcoal implies atmospheric O2 levels >13% for sustained combustion of plant tissue; soil diffusion modeling imposes an O» minimum of 8% for the Late Devonian (arrow with “G”; Yapp, 1996). Inset at top: stratigraphic trends in inertinite and vitrinite abundances in the Famennian Ohio Shale and Early Tournaisian Sunbury Shale (Rimmer et al., 2004).
Fig. 7. (A) Model of feedbacks between the marine P cycle and atmospheric pO . Cycle I represents the “productivity-anoxia feedback” and cycle II the “C,,g burial-pO. feedback” (see text for discussion). (B) Characteristic spatio-temporal scales of operation of these feedbacks. Differences in scale between cycles | and II imply that marine anoxic events should be self-reinforcing on sub-million-year timescales and self-limiting on multi-million-year timescales.
Fig. 7. (A) Model of feedbacks between the marine P cycle and atmospheric pO . Cycle I represents the “productivity-anoxia feedback” and cycle II the “C,,g burial-pO. feedback” (see text for discussion). (B) Characteristic spatio-temporal scales of operation of these feedbacks. Differences in scale between cycles | and II imply that marine anoxic events should be self-reinforcing on sub-million-year timescales and self-limiting on multi-million-year timescales.
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