Pedogenic correlation of lateritic river terraces in central Taiwan

Abstract The Pakua, Chushan and Touliu terraces are three groups of lateritic river terraces resulting from different fluvial systems in central Taiwan. Their geomorphic features do not enable regional correlations to be made. In this study, an alternative scheme based on the quantification of a pedogenic development is proposed for this correlation. Four soil pedons from the Chushan and Touliu terraces are classified as Ultisols (CS-1, CS-2 and TL-1) and an Inceptsol (TL-4) following the Soil Taxonomy . An additional six soil pedons, including an Oxisol (PK-1), Ultisols (PK-2, -3, -4 and -5), and an Inceptsol (PK-6), from the Pakua terraces were included from a previous study [Tsai, H., Huang, W.S., Hseu. Z.Y., Chen, Z.S., 2006. A river terrace soil chronosequence of the Pakua tableland in Taiwan. Soil Science 171, 167–179.]. The weighted mean profile development indices (WPDI) for the pedons suggest a chronological order of I (PK-1), II (PK-2), III (PK-3), IV (PK-4, CS-1 and TL-1), V (PK-5 and CS-2), VI (PK-6) and VII (TL-4). The correlation suggests the Chushan and Touliu terraces correspond to the same surface of an anticline, separated by the Chinshui River. Surface deformation reflects the growth of the underlying structure in which uplift folding occurred in the hinge zone and tilted to the east along the fold limb, as a result of the southern extension of the Pakua anticline. However, the different geometries on both the surface and subsurface from southern Pakua Anticline indicate a mechanism of fault-bend folding for Touliu Hill.