Quantitative identification of lithologic discontinuities (LDs) is essential for the study of pedogenesis. This study examines three representative soils on three landscape positions-summit, upper backslope, and lower backslope-along a toposequence in southern Taiwan. The objectives were to evaluate whether LDs in the residuum of parent material occurred in these soils which formed in a subtropical region of Taiwan and to test the utility of various parameters for the determination of LDs. The depth of LDs was identified by examination of the depth functions of clay-free particle sizes, sand/silt ratios, uniformity value indices, and Ti, Zr, and Ti/Zr ratios. The soils, derived from sandstone and shale, are Typic Paleudults. The results of this study indicated that the recognition of LDs in these soils was difficult in the absence of different particle size distribution in field observations and distinct Ti and Zr elements analysis in laboratory analysis. Pedogenic processes have blurred or destroyed the evidence of such discontinuities. Results indicated that clay-free particle size distributions (Cf-PSDs), sand/silt ratios, and uniformity value (UV) indices are the most useful parameters in identifying the LDs in this toposequence. The depth functions of the contents of Ti and Zr, and the Ti/Zr ratios in the clay-free sand fraction, were unable to identify the discontinuities of parent materials in this site.