Subtropical Soil Chronosequence on Holocene Marine Terraces in Eastern Taiwan

Abstract

The 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. The Coastal Range includes three main levels of Holocene marine terraces, labeled the first, second, and third levels descending to the coast. The soils that have developed on the terraces provide a chronosequence for pedogenic studies. Thirteen 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. The soils of the oldest terrace (first 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. The degree of development of these soils can be determined from horizon index (HI), weighted profile development index (WPDI), weighted mean profile (WMP) clay, WMP silt, WMP sand, and WMP cation exchange capacity with correlation coefficients (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 influence rates of soil development. The pedogenic evidence in this study supports the correlation of terraces suggested by previous geomorphic and tectonic studies. The 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.