Using Carbon Isotope Equilibrium to Screen Pedogenic Carbonate Oxygen Isotopes: Implications for Paleoaltimetry and Paleotectonic Studies

Figure 7

Plots of δ¹⁸O_carb versus Δ¹³C. (a) This panel shows data from Hyland and Sheldon [28]. Using the Δ¹³C screening criteria outlined in the text, 18 of 24 carbonates formed in equilibrium. By removing the nonequilibrium carbonates from consideration, the range of δ¹⁸O_carb values drops to ~6.5‰ from ~11‰. Using the global δ¹⁸O lapse rate of Poage and Chamberlain [18], this would reflect a difference of ~1.6 km between the estimates of paleoelevation. (b) This panel shows the data from Gutierrez and Sheldon [27]. Using the Δ¹³C screening criteria outlined in the text, nine of ten carbonates formed in equilibrium. The dashed line in both panels represents the empirically observed mean Δ¹³C value of +15.62‰; the solid lines represent ±2σ (2.22‰).

(a)

(b)