The effectiveness and utility of soil chronofunctions is examined in the light of existing pedogenic theory. Statistical treatments applied in chronofunction research are reviewed, including linear transformations of raw data, which may improve the utility of the chronofunction. We advocate using a particular statistical model only if it can be justified based on our current understanding of the functioning of the pedologic system. We emphasize the potential difficulties of using linear chronofunction methods; simple linear and logarithmic functions are not always the best option for chronofunctions. Hyperbolic, polynomial or nonlinear functions might improve not only the fit of the chronofunction but also advance our understanding of the pedologic system.When the chronofunction explaining the most variance is not best suited to a process-based understanding of pedogenic theory, other functions with slightly smaller r2 values that have been judged suitable by a priori reasoning or theory might better reflect the functioning of the pedologic system. We justify limited extrapolation of some chronofunctions to time zero and discuss how this can be useful in the identification of pedogenic thresholds and 'step functions'. Interpretation of the Y-intercept of chronofunctions can, at times, aid our understanding of the soil system near time zero and be useful in the identification of the existence and timing of thresholds.

on four terraces near Lake Michigan to assess rates of podzolization and changes in soil properties with age. The terraces .ung"d i;ug. from 3000 b 10000 BP. Each surface was systematically samplei to determine tfr" r?OA pto"nt", which was then described and sampled. Quantities of.OC' Fe, anO Al in the B horizons of rirodal ioils increased with soil age. Silt content of surface horizons also increased with age, possibly due to eolian input or physical weathering' For weighted profile and B horizon Al and Fe uu.rug"t inO a variety of soil development indices, a single logarithmic model generally gave the trighest siatistical signihiance of the three chronofunction models used. All pedons i"*pf"O fiif.O to ctaisity as Podzols, dut the oldest two met the criteria for the Spodosol order' Thus' more than 4000, but lesi than 10 000, years are required for the development of a spodic horizon in Michigan.

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