Sakurajima-Satsuma (Sz-S) and Noike-Yumugi (N-Ym) tephras: new tephrochronological marker beds for the last deglaciation, southern Kyushu, Japan

• Published in: Quaternary International
• Main Authors: Moriwaki, Hiroshi, Suzuki, Takehiko, Murata, Masanori, Ikehara, Minoru, Machida, Hiroshi, Lowe, David J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2011
• Subjects: marine core; tephra; tephrochronology; identification; last deglaciation; southern Kyushu; IMTIMATE; Greenland; ice core; NGRIP
• Online Access: https://hdl.handle.net/10289/5278; https://doi.org/10.1016/j.quaint.2011.03.046

Two prominent tephras, Sakurajima-Satsuma (Sz-S) erupted from Sakurajima volcano and Noike-Yumugi (N-Ym) erupted from Kuchierabujima Island, provide new key marker beds for dating and synchronizing palaeoenvironmental and archaeological records in the last deglaciation in southern Japan. These tephras were identified on the basis of glass major-element compositions in two distal areas, a marine core (IMAGES MD98-2195) in the northern part of the East China Sea and on the central part of Tanegashima Island, and related their stratigraphic positions to the marine oxygen isotope-based chronology. In MD98-2195, Sz-S, 0.8 cm in thickness at 9.12 m depth and N-Ym, 3 cm in thickness at 9.30 m depth, are both white, vitric, ash-grade tephras. On Tanegashima Island, Sz-S, 10 cm in thickness and N-Ym, 3 cm in thickness, are stratigraphically constrained by well-characterised marker tephras Kikai-Akahoya (7,300 cal BP) and Aira-Tn (29,000 cal BP). Sz-S is rhyolitic and homogeneous on the basis of glass major-element compositions assayed by electron microprobe. Pumiceous glass shards predominant in distal Sz-S tephra indicate that it derived from pumice fall units that correspond to pumiceous and phreatomagmatic fine ash units constituting proximal Sz-S tephra. N-Ym is rhyolitic and glass major-element analyses reveal compositional diversity between units, suggesting that the lower and middle tephra units dispersed to the east, whereas the upper unit was dispersed north to north-west from the vent. Stratigraphically, Sz-S occurs at around the start of the late-glacial reversal (cooling) in oxygen isotope records of MD98-2195, corresponding to the end of GI-1 and the start of GS-1 in the ice-core events of NGRIP (GICC05), consistent with a terrestrial age of ˜12,800 cal BP. Based on the oxygen isotope stratigraphy, the tephra identified in the core as N-Ym at 9.30 m depth is close to the end of Greenland GI-1 and hence has an age of ˜13,000 cal BP, but on Kuchierabujima Island it has an age based on ¹⁴C assay of charcoal of ...