Subtropical Soil Chronosequence on Holocene Marine Terraces in Eastern Taiwan

Th e Coastal Range in eastern Taiwan is characterized by rapid uplift at a rate of about 5 mm yr −1 because of active arc-continent collision since the Mio-Pliocene. Th e Coastal Range includes three main levels of Holocene marine terraces, labeled the fi rst, second, and third levels descending to the coast. Th e soils that have developed on the terraces provide a chronosequence for pedogenic studies. Th irteen soil pedons formed from conglomerate associated with tuff were sampled along three transects in the central and southern part of the eastern coast of Taiwan near the localities of Chang-Bin, Cheng-Gong, and Du-Lan. Th e soils of the oldest terrace (fi rst level) are mainly Typic Hapluderts with one Typic Hapludoll; the soils of the intermediate terrace (second level) are Vertic or Typic Hapludolls; and the soils of the youngest terrace (third level) are Typic Udipsamments. Th e degree of development of these soils can be determined from horizon index (HI), weighted profi le development index (WPDI), weighted mean profi le (WMP) clay, WMP silt, WMP sand, and WMP cation exchange capacity with correlation coeffi cients (r) >0.6 by linear or logarithmic functions. Comparisons of the chronofunctions based on WMP clay data in subtropical and Mediterranean climates suggest that climatic conditions not only control weathering intensity but also infl uence rates of soil development. Th e pedogenic evidence in this study supports the correlation of terraces suggested by previous geomorphic and tectonic studies. Th e anomalous, relatively weaker degree of soil development on the oldest terrace at Du-Lan supports the conclusion that uplift rates in the Du-Lan area are greater than at Chang-Bin and Cheng-Gong.