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Fig. 4. Graphs showing variability associated with chronosequence analysis. (a) Plot of the relation between age estimate (ka) and horizon values of tiron-extractable Si (%) for pedons in Cajon Pass (CP) and San Timoteo Badland (STB) study areas. The results are arranged by surface, with the designation of CP or STB as modifiers to the surface designation (i.e., CP Qoac is the Qoac surface in Cajon Pass). The values for the Cajon Pass horizons are shown with a closed diamond, while San Timoteo soil horizon values are shown using an open diamond. Mean values for each pedon (sometimes more than one per surface) are plotted with a large "X" symbol. The data shown for each surface are from the following pedons: Surface CP Qoac: Pedon SB1; Surface STB Q1: Pedon STC 7; Surface CP Qoad: Pedon RW 11; Surface STB Q2: Pedons STC 9, RC 6; Surface STB Q3: Pedons RC 2, STC 10, STC 6. (b) Horizon values of Feo/Fed ratios for the soils in the Eastern Transverse Range chronosequence (McFadden, 1982; McFadden and Hendricks, 1985). (c) Horizon values of Feo/Fed ratios for the Cajon Pass chronosequence (McFadden and Weldon, 1987).
