Submarine palaeoenvironments during Emeishan flood basalt volcanism, SW China: Implications for plume-lithosphere interaction during the Capitanian, Middle Permian ('end Guadalupian') extinction event
Submarine palaeoenvironments during Emeishan flood basalt volcanism, SW China: Implications for plume-lithosphere interaction during the Capitanian, Middle Permian ('end Guadalupian') extinction event
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DOI：
10.1016/j.palaeo.2015.06.009
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发表时间：
2016-01-01
影响因子：
3
通讯作者：
Torsvik, Trond H.
中科院分区：
文献类型：
--
作者：
Jerram, Dougal A.;Widdowson, Mike;Torsvik, Trond H.
地幔柱引起的岩石圈抬升和侵蚀被广泛认为是大火成岩省（LIP）侵位的关键特征，因为LIP喷发与大灭绝和海洋缺氧事件（OAE）的巧合。峨眉山LIP在Capitanian（以前称为“结束Guadalupian”）灭绝事件期间爆发，提供了在上升地幔“柱”上方轴对称隆起的最广泛讨论的例子;支持者认为，超过500米的隆起发生在>30000 km（2）的范围内，导致广泛的放射状分布的侵蚀和冲积扇形成。然而，海底水岩浆和蒸汽岩浆式火山作用，以及同火山的海洋沉积物互层的喷发序列的识别，现在需要进一步检查这个简单的羽状隆起model. There我们提供的数据，从中央的推定隆起区（洱海周围，云南西南部），提供了一个更完整的峨眉山火山作用的历史。这些表明，台地碳酸盐沉积终止于快速沉降，随后迅速开始火山作用。重要的是，这些喷发也与梭形有孔虫和石灰藻类的广泛损失相吻合。至少在4-5公里厚的熔岩堆的下三分之二，在海平面或海平面以下继续喷发，这可以从峨眉山内带大量的镁铁质火山碎屑沉积物、枕状熔岩和同火山礁灰岩的发育中得到证明。只有在火山爆发的后期，陆地熔岩流才得到广泛发展。在海底环境中的火山活动以及随后的猛烈的蒸汽岩浆式喷发对海洋动物群产生了深远的影响，并加剧了Capitanian期间火山引起的气候影响。晚二叠世峨眉山时期的中国西南地区是一个具有陆表海的变薄岩石圈的扩展区域，这种陆表海似乎一直持续到LIP侵位开始。因此，虽然峨眉山火山作用的地幔柱起源仍然有大量的地球化学支持，LIP侵位不能普遍与区域喷发前隆起，特别是在复杂的岩石圈结构存在于地幔柱上方。(C)2015 Elsevier B. V.版权所有。
Plume-induced lithospheric uplift and erosion are widely regarded as key features of large igneous province (LIP) emplacement, as is the coincidence of LIP eruption with major extinction and oceanic anoxic events (OAE). The Emeishan LIP, which erupted during the Capitanian (previously termed 'end Guadalupian') extinction event, has provided the most widely discussed example of axisymmetric doming above a rising mantle 'plume'; advocates have argued that in excess of 500 m of uplift occurred over >30000 km(2) causing extensive radially distributed erosion and alluvial fan formation. However, the recognition of submarine hydromagmatic and phreatomagmatic-style volcanism, as well as syn-volcanic marine sediments interbedded in the eruptive succession, now requires further examination to this simple plume-uplift model.Here we present data from newly discovered sections from the center of the putative uplifted area (around Lake Er Hai, SW Yunnan Province,) that provide a more complete history of the Emeishan volcanism. These reveal that platform carbonate deposition was terminated by rapid subsidence, followed quickly by the onset of volcanism. Importantly, these eruptions also coincide with widespread losses amongst fusulinacean foraminifera and calcareous algae. For at least the lower two thirds of the 4-5 km thick lava pile, eruptions continued at or below sea level, as testified by the presence of voluminous mafic volcaniclastic deposits, pillow lavas, and development of syn-volcanic reefal limestones in the Emeishan inner zone. Only in the later stages of eruption did terrestrial lava flows become widely developed. This onset of volcanism in a submarine setting and the consequent violent, phreatomagmatic-style eruptions would have had a profound effect on marine fauna and exacerbated any volcanically induced climate effects during the Capitanian. The late Permian of SW China at the time of the Emeishan was an extended area of thinned lithosphere with epeiric seas, which appear to have been sustained through the onset of LIP emplacement. Therefore, while there remains substantial geochemical support of a plume origin for Emeishan volcanism, LIP emplacement cannot be ubiquitously associated with regional pre-eruption uplift, particularly where complex lithospheric structure exists above a plume. (C) 2015 Elsevier B.V. All rights reserved.