The Submarine Record of a Large‐Scale Explosive Eruption in the Vanuatu Arc: ∼1 Ma Efaté Pumice Formation
The Submarine Record of a Large‐Scale Explosive Eruption in the Vanuatu Arc: ∼1 Ma Efaté Pumice Formation
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瓦努阿图弧内大规模爆炸性喷发的海底记录：∼1 Ma Efaté 浮石层
DOI：
10.1029/140gm18
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
J. McPhie
中科院分区：
文献类型：
--
作者：
Alison M. Raos;J. McPhie
埃法特浮石层 (EPF) 记录了西南太平洋瓦努阿图岛弧约 1 Ma 发生的一次重大爆炸性喷发。公积金是
埃法特岛群最古老的地层单元，由一系列非焊接的粗面英安质浮石角砾岩和富含碎片的沙子和淤泥层组成
最小厚度约为 500 m，最小体积约为 85 km3。 EPF 的下部（Efate 浮石角砾岩）由非常厚的床层组成，几乎全部由玻璃状粗面英岩浮石碎片组成，末端参差不齐。相比之下，上部（Rentabau 凝灰岩）由长达 70 m 的层理良好且分选良好的富含碎片的沙子和淤泥组成。的
该上部的碎屑种群包含 >95% 的玻璃质或以前的玻璃质碎片，但有孔虫化石是普遍存在且重要的非火山成分。
一些玻璃碎片具有块状、等长的形状和弓形断裂表面，这些特征通常与破碎过程中外部水的影响有关，但大多数玻璃碎片是尖头和板状气泡壁碎片。火山碎屑形态表明，埃法特浮石角砾岩主要是由岩浆挥发物驱动（干燥）、爆炸破碎过程和岩相生成的
特征表明，沉积物位于风暴波基部以下的环境中，来自喷发源、水支持的浸水浮石密度流。伦塔鲍凝灰岩被解释为代表水岩浆活动的变化，以响应逐渐减弱的流量，从而允许水（大概是海水）进入喷口。
The Efate Pumice Formation (EPF) is the record of a major explosive eruption that occurred in the Vanuatu arc, southwestern Pacific, at about 1 Ma. The EPF is
the oldest stratigraphic unit of the Efate Island Group and consists of a succession of non-welded, trachydacitic pumice breccia and shard-rich sand and silt beds
with a minimum thickness of ~500 m and a minimum bulk volume of approximately 85 km3. The lower part (Efate Pumice Breccias) of the EPF comprises very thick beds composed almost exclusively of glassy, trachydacitic, pumice fragments with ragged terminations. In contrast, the upper part (Rentabau Tuffs) consists of up to 70 m of well-bedded and well-sorted shard-rich sand and silt. The
clast population of this upper part comprises >95 % glassy or formerly glassy shards, but fossil foraminifera are a ubiquitous and important non-volcanic component.
Some glass shards have blocky, equant shapes and arcuate fracture surfaces, features typically associated with the influence of external water during fragmentation, but most are cuspate and platy bubble-wall shards. Pyroclast morphologies indicate that the Efate Pumice Breccias were largely generated by magmatic-volatile-driven (dry), explosive fragmentation processes, and lithofacies
characteristics indicate deposition in below-storm-wave-base environments, from eruption-sourced, water-supported density currents of waterlogged pumice. The Rentabau Tuffs are interpreted to represent a change to hydromagmatic activity in response to waning discharge that allowed ingress of water (presumably seawater) to the vent(s).