Palynological Correlation of Lower Sand and Gravel Layer at Naka-ikemi, Fukui Prefecture

Pollen analysis was conducted for samples from the fine sediment parts of the Lower Sand and Gravel Layers under Naka-ikemi, Fukui Prefecture, Japan. Cluster analysis (Ward method) was performed for correlating the pollen assemblages distributed spatially in columnar sections. Six types of fossil pollen assemblage are recognized from the result of cluster analysis. Characteristics of pollen assemblage types are as follows: type C: Cryptomeria pollen dominated with Alnus pollen. type S: Cryptomeria pollen occupied about 90%. type P: Pinaceae (Abies, Tsuga, Picea, Pinus subgen. Haploxylon) pollen dominated with Alnus pollen. Cryptomeria pollen was less than 2.2%. type T: Tsuga and Cryptomeria pollen dominated with Pinaceae pollen. type D: Pollen of deciduous broadleaf trees such as Quercus, Fagus, Ulmus/Zelkova dominated with Alnus pollen. Cryptomeria pollen was less than 7.9%. type A: Alnus and Cryptomeria pollen dominated. Types C, S, T and A are similar in the abundant occurrence of Cryptomeria pollen. Four regional pollen assemblage zones, NKM-I to IV, were established based on the correlation of the pollen assemblages. NKM-I, which was dominated by Cryptomeria pollen (types C, S, T, A), and NKM-II, which was dominated by deciduous broadleaf tree pollen (type D), are correlated to MIS (marine isotope stage) 7. NKM-III, which was dominated by Pinaceae (Abies, Tsuga, Picea, Pinus subgen. Haploxylon) pollen (type P), is correlated to MIS 6. Dominance of Pinaceae pollen indicates a cold and dry climate. NKM-IV, which was dominated by Cryptomeria pollen (types C, A, D), again is correlated to MIS 5.