Late Holocene Geomorphological Development of Beach Ridge Ranges in the Central Part of Ise Plain, Central Japan

Abstract

A total of three to four beach ridges occurred along the coast in the central part of the Ise Plain (between the Tanaka River and Anotsu River) in central Japan. We conducted an array-coring survey, radiocarbon dating, and diatom fossil analysis of alluvium distributed on the north side of the Shitomo River. Four beach ridges, BR I–IV, numbered landward to seaward, occurred in this area. Based on the results of the survey and analyses, the late Holocene environmental changes in the back marsh and interridge marsh of the beach ridges were reconstructed. The geomorphological development processes of the beach ridges were as follows. BR I started to form around 7,000calBP and finished ca. 5,700–6,000calBP. BR II occurred around 3,300calBP and was completed ca. 2,700calBP. The complete timing of BR III is thought to be around 1,500–2,200calBP from the results of archeological excavations at BR III. In the lower Kumozu River lowland south of the study area, there is no beach ridge corresponding to BR I near the Shitomo River. This discordance in the geomorphological development of the primary barrier was likely caused by regional differences in the buried planation surface and river power. In contrast, between 1,500calBP and 3,000calBP, the complete timing of BR II and III in the study area corresponded to BR I and II of the lower Kumozu River lowland, respectively. This accordance indicates that the secondary barriers developed nearly uniformly over a wide area of the central part of the Ise Plain during this period.