Sakurajima-Satsuma (Sz-S) and Noike-Yumugi (N-Ym) tephras: New tephrochronological marker beds for the last deglaciation, southern Kyushu, Japan
Sakurajima-Satsuma (Sz-S) and Noike-Yumugi (N-Ym) tephras: New tephrochronological marker beds for the last deglaciation, southern Kyushu, Japan
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DOI：
10.1016/j.quaint.2011.03.046
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发表时间：
2011-12
影响因子：
2.2
通讯作者：
H. Moriwaki;Takehiko Suzuki;Masanori Murata;M. Ikehara;H. Machida;D. Lowe
中科院分区：
文献类型：
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作者：
H. Moriwaki;Takehiko Suzuki;Masanori Murata;M. Ikehara;H. Machida;D. Lowe
两个突出的火山岩，樱岛-萨摩（Sz-S）从樱岛火山喷发和野池-Yumugi（N-Ym）从Kuchierabujima岛喷发，提供了新的关键标志层的年龄和同步的古环境和考古记录在日本南部的最后一次冰消期。根据东海北方和种子岛中部两个远源区的海相岩芯（IECHMD 982195）的玻璃常量元素组成，对这些火山岩进行了鉴定，并将它们的地层位置与海相氧同位素年代学相关联。在MD 982195中，Sz-S（9.12 m深度处厚度为0.8 cm）和N-Ym（9.30 m深度处厚度为3 cm）均为白色玻璃质火山灰。在种子岛，Sz-S，10厘米厚和N-Ym，3厘米厚，在地层上受到特征良好的标志物tephras Kikai-Akahoya（7300 cal BP）和Aira-Tn（29,000 cal BP）的限制。Sz-S玻璃的主元素组成为流纹状，成分均匀。浮石玻璃碎片主要在远端Sz-S火山点表明，它来自浮石下降单位，对应于构成近端Sz-S火山点的浮石和phreatomagmatic细灰单位。N-Ym是流纹岩和玻璃的主要元素分析揭示了单元之间的成分多样性，这表明下和中火山灰单元分散到东部，而上单元分散从北到西北的通风口。在地层学上，Sz-S出现在MD 982195氧同位素记录中晚冰期逆转（冷却）开始的附近，对应于NGRIP（GICC 05）冰芯事件中GI-1的结束和GS-1的开始，与地球年龄为12，800 cal BP一致。根据氧同位素地层学，在9.30 m深处的岩芯中被鉴定为N-Ym的火山碎屑接近格陵兰GI-1的末端，因此其年龄为13,000 cal BP，而在Kuchierabujima岛上，根据14 C木炭分析，其年龄为13,000 cal BP。血压14,900卡尽管这种年龄差异（14.9与13.0 cal ka）需要解决，但在岩芯MD 982195中N-Ym的发生率表明其比迄今为止证明的更广泛。这两个标志火山灰的广泛分布和关键地层位置表明，它们是精确对比九州南部末次冰消期古环境变化和史前文化事件的关键等时线，并通过海洋氧同位素年代地层学将这些变化和事件与冰芯年代学联系起来。
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 MD982195) in the northern part of the East China Sea and on the central part of Tanegashima Island, and we related their stratigraphic positions to the marine oxygen isotope-based chronology. In MD982195, 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 (7300 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 northwest from the vent. Stratigraphically, Sz-S occurs at around the start of the late-glacial reversal (cooling) in oxygen isotope records of MD982195, 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 on14C assay of charcoal of c. 14,900 cal BP. Although this age discrepancy (14.9 vs 13.0 cal ka) needs resolution, the occurrence in core MD982195 of N-Ym shows that it is more widespread than hitherto demonstrated. The widespread distributions and key stratigraphic positions for the two marker tephras indicate that they are thus critical isochrons for precise correlation of palaeoenvironmental changes and prehistoric cultural events during the last deglaciation in southern Kyushu, and for relating such changes and events to the ice-core chronology via the marine oxygen isotope chronostratigraphy.