The role of tephras in developing a high-precision chronostratigraphy for palaeoenvironmental reconstruction and archaeology in southern Kyushu, Japan, since 30 cal. BP: an integration

Abstract

Tephras are important for the chronostratigraphy of palaeoenvironmental and archaeological records in southern Kyushu because numerous tephra beds enable these records to be connected and dated precisely using tephrochronology. A regional tephra-based framework or lattice for the past 30,000 calendar (cal.) years is proposed in the style of recent INTIMATE projects elsewhere. We review stratigraphic, compositional, age, and distributional data for a range of tephras, and comment on the relationship of several marker tephras to distinct palaeoenvironmental and cultural events in the southern Kyushu region since 30,000 cal. BP. More than 90 visible tephra beds are recorded, deriving from Kakuto, Aira, Ata, and Kikai volcanic centres, which incorporate large calderas, and the Tokara volcanic islands. The tephra record is underpinned by two widespread tephras, Aira-Tn tephra (AT; ca. 30,000 cal. BP), and Kikai-Akahoya tephra (K-Ah; ca. 7,300 cal. BP). In addition to AT and K-Ah, locally-distributed marker tephra beds are related to the chronostratigraphy of terrestrial and marine palaeoenvironments including sea-level and coastal environments, vegetation, and culture. Some tephras, notably AT, K-Ah, and Sakurajima-Satsuma tephra (Sz-S, ca. 12,800 cal. BP), have been recognized in marine and laminated lake sediments and hence dated with high precision, thereby facilitating correlation of those records to global high-resolution ice, marine, and terrestrial stratotypes. Sz-S is a useful isochron for the last deglaciation in southern Kyushu. Our integrated regional chronostratigraphic model for southern Kyushu, founded by tephras (and with further potential via systematic identification of cryptotephras), will enable change in regional palaeoenvironments and culture to be evaluated in national and global contexts.