One Million Years tephra record at IODP Sites U1436 and U1437: Insights into explosive volcanism from the Japan and Izu arcs

• Published in: The island arc Vol. 27; no. 3
• Main Authors: Schindlbeck, Julie Christin, Kutterolf, Steffen, Straub, Susanne M., Andrews, Graham D. M., Wang, Kuo‐Lung, Mleneck‐Vautravers, Maryline J.
• Format: Journal Article
• Language: English
• Published: Melbourne John Wiley & Sons Australia, Ltd 01-05-2018; Wiley Subscription Services, Inc
• Subjects: Composition; Correlation; Drilling; Eruptions; IBM; IODP Expedition 350; Provenance; Tephra; tephra provenance; tephra volume; tephrostratigraphy; Trace elements; Volcanic activity; Volcanism; Japan
• ISSN: 1038-4871; 1440-1738
• DOI: 10.1111/iar.12244

The 1 Myr tephra records of IODP (International Ocean Discovery Program) Holes U1436A and U1437B in the Izu‐Bonin fore‐ and reararc were investigated in order to assess provenance and eruptive volumes, respectively. In total, 304 tephra samples were examined and 260 primary tephra layers were identified. Tephra provenance was determined by means of major and trace element compositions of glass shards and distinguished between Japan and Izu‐Bonin arc origin of the tephra layers. A total of 33 marine tephra compositions were correlated to the Japan arc and 227 to the Izu arc. Twenty marine tephra layers were correlated between the two drilling sites. Additionally, we defined eleven correlations of marine tephra deposits to major widespread Japanese eruptions; from the 1.05 Ma Shishimuta‐Pink Tephra to the 30 ka Aira‐Tn Tephra, both from Kyushu Island. These eruptions provide independent time markers within the sediment record and six correlations were used to date tephra layers from Japan in Hole U1436A to establish an alternative age model for this hole. Furthermore, the minimum distal tephra volumes of all detected events were calculated, which enabled the comparison of the tephra volumes that derived from the Japan and the Izu‐Bonin arcs. For some of the major Japanese eruptions these are the first volume estimations that also include distal deposits. All of the Japanese tephras derived from events with eruption magnitude Mv ≥ 5.6 and three of the investigated eruptions reach magnitudes Mv ≥ 7. Volcanic events of the Izu‐Bonin arc have mostly eruption magnitudes Mv ≤ 5.
IODP(国際深海科学掘削計画)の掘削孔U1436AとU1437Bはそれぞれ伊豆弧の前弧と背弧に位置する.  掘削孔から得られた最近100万年のテフラ記録を解析し.  それらの起源と噴出量を推定した.  全304テフラサンプルのうち260の初生テフラを同定した.  テフラ中のガラス片の主要・微量元素組成によって.  伊豆小笠原弧起源であるか.  本州弧起源であるかを識別した.  33のテフラは本州弧起源であり.  227は伊豆弧起源である.  二つの掘削孔において同一噴火による20枚の海底テフラが同定された.  加えて.  日本本土からもたらされた11枚の巨大噴火由来のテフラを識別した.  これには九州からもたらされた.  1.05 Maの猪牟田ピンク火山灰や3万年前の姶良Tn火山灰も含まれる.  これらの火山灰は掘削孔堆積物に独自の時間軸を与え.  U1436A孔においては火山灰に基づいた層序(時間)の代替モデルを確立した.  さらに.  すべての噴火イベントにおいて.  最小の遠隔テフラ体積を計算し.  本州弧と伊豆小笠原弧からのテフラ体積を比較した.
The approximately 1 Myr tephra records of IODP (International Ocean Discovery Program) Holes U1436A and U1437B in the Izu‐Bonin fore‐ and reararc was investigated in order to assess provenance and eruptive volumes, respectively. In total, we examined 304 tephra samples and identified 260 primary tephra layers. Tephra provenance was determined by means of major and trace element compositions of glass shards and distinguished between Japan and Izu‐Bonin arc origin of the tephra layers.