This paper reviews geomorphological and geological studies along the Sanriku coast, Japan, and presents issues and projections for interpretation of the earthquake cycle. Crustal movement trend on a timescale of 10³-10⁴ years, estimated from analyses of incised valley fill succession, indicates a subsidence trend along the southern part of the coast and a relatively uplifting trend along the northern part. On the other hand, height distribution and age of Pleistocene marine terrace show uplifting trend on a timescale of 10⁵ years along the northernmost part of the Sanriku coast. However, chronology of marine terraces along other parts of the coast has not progressed until now because of lack of tephra layering. In addition, distribution of flat surfaces previously interpreted as marine terraces is fragmentary along the southern Sanriku coast. These geomorphological and geological studies suggest that the Sanriku coast should be segmented into multiple deformation areas when assessing crustal deformation related to a megathrust earthquake. For the segmentation of crustal deformation area, continuing analyses of incised valley fill succession and reconsideration of the origin and chronology of flat surfaces previously interpreted as marine terraces are needed. OSL dating method is expected to clarify the formation age of marine terraces distributed along the Sanriku coast.

Sediment transport and landform development caused by Southeast Asian rivers undergo dramatic seasonal changes due to distinct monsoon and dry climate conditions. Though their spatiotemporal scale is several orders smaller, the changes are similar to the river response to long-term basal level changes during the Quaternary Period, offering many suggestions to characterize river behavior. However, only limited numbers of studies have been conducted on this matter. In addition, it is important for flood damage mitigation in areas along the rivers to understand seasonally sensitive characteristics of fluvial plains in terms of sediment transport processes. In this context, introducing research conducted in Cambodia and the Philippines, this paper discusses the importance of scientifically interpreting phenomena in land areas, such as floods, fluvial sediment transport, and historical development of fluvial plains, from the Quaternary viewpoint, and of understanding diverse human involvements in the dynamic water environment in order to contribute to constructing safe and stable communities.

This paper reviews recent (from 2000 to 2016) progress in cold region Quaternary science studies undertaken by Japanese researchers in domestic and overseas sites. Studies on glacial processes, periglacial processes, and landslide processes have progressed during the past 17 years, and many peer-reviewed papers have been published in national and international journals. However, the current robust growth does not seem likely to continue for the next several decades due to aging and depopulation of researchers in this field. In addition, it was found that the Quaternary Research (Daiyonki-kenkyu), a periodical journal of the Japan Association for Quaternary Research (JAQUA), has not been chosen by researchers as a venue for publishing research papers. A major structural reform of JAQUA seems to be necessary. Outreach and educational programs are also required to attract new members to JAQUA.

We conducted diatom analysis, pollen analysis, and radiocarbon dating of a black mud layer with an altitude of about 5m located in the coastal area of Kyotango City, Kyoto Prefecture, Japan. Radiocarbon age of the tree fossil in this layer was older than 43,500yBP. Pollen analysis reconstructed cool-temperate deciduous broad-leaved forests accompanied with Cryptomeria japonica and Pinus, but some pollen grains of evergreen Quercus subgenus Cyclobalanopsis were also detected. The fossil diatom assemblage, mainly composed of brackish species with the dominance of Pseudopodosira kosugii, suggests that the layer was deposited on a salt marsh around the high tide level of a river mouth mudflat. This is the first report of P. kosugii from the Pleistocene series of the Japan Sea Coast.