FIGURE 3. Concentration relationships between organic carbon and phosphorus, and organic carbon and nitrogen.
From the following article:
Geochemical evidence for terrestrial ecosystems 2.6 billion years ago
Yumiko Watanabe, Jacques E. J. Martini and Hiroshi Ohmoto
Nature 408, 574-578(30 November 2000)
doi:10.1038/35046052
a, Organic-carbon/phosphorus relationship in bulk-rock samples; b, organic-carbon/nitrogen relationship in bulk-rock samples and in kerogen-enriched fractions. These latter fractions are what remains after the carbonates, silicates and oxides in the rock samples have been dissolved by hydrochloric and hydrofluoric acids.
