The 26.5 ka Oruanui eruption, New Zealand: A review of the roles of volcanism and climate in the post‐eruptive sedimentary response
The 26.5 ka Oruanui eruption, New Zealand: A review of the roles of volcanism and climate in the post‐eruptive sedimentary response
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26.5 ka Oruanui 喷发，新西兰：火山活动和气候在喷发后沉积响应中的作用综述
DOI：
10.1080/00288306.2004.9515074
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发表时间：
2004
影响因子：
2.2
通讯作者：
C. Wilson
中科院分区：
文献类型：
--
作者：
V. Manville;C. Wilson
摘要火山碎屑岩大爆发的景观响应是沉积学和地貌学中最引人注目的过程之一。喷发后的侵蚀和再沉积过程因大量喷发体积、丰富的未固结灰粒物质、植被覆盖的破坏（特别是被熔结凝灰岩掩埋）和植被再生的抑制（例如，恶劣的气候条件）。新西兰北岛中部陶波火山26.5 ka的Oruanui喷发为大规模沉积反应创造了最佳条件，该反应受到末次盛冰期气候最低点的影响和延长。约530 km3的流纹岩岩浆喷发为420 km3的瀑布沉积物，320 km3的火山碎屑密度流沉积物（主要是非焊接熔结凝灰岩），和430 km3的原生火山口内填充物。奥鲁阿努伊火山的爆发和形成，摧毁了一个主要的湖泊，但创造了现代陶波湖的前身。这个湖最初稳定地向西北溢出，然后在沿现代怀卡托河的东北方向沿着建立出口时爆发灾难性的洪水。抑制植被的同期恶劣的冰缘气候导致强烈的侵蚀和重新活动的Oruanui火山碎屑岩单位，引发大规模的下游河流加积在受影响的集水区。特别是，加积导致怀卡托河下游180公里的河流从其长期建立的路线通过豪拉基平原进入汉密尔顿盆地，随后被困。风成作用形成了局部的沙丘，而火山灰黄土则在北岛中部形成了沉积物。火山爆发对河流沉积系统的初始扰动一般都受到气候条件的影响，直到公元前200年。17 ka.气候的改善最终通过森林植被的重建稳定了原生沉积物的来源，但储存在火山冲积扇中的冲积物的切割和再循环一直持续到公元前。14 ka.总的来说，后Oruanui沉积反应的规模主要由火山爆发的特征驱动，而其持续时间则由末次冰期最大气候控制。
Abstract The landscape response to large explosive pyroclastic volcanic eruptions is one of the most dramatic processes in sedimentology and geomorphology. Processes of post‐eruptive erosion and resedimentation are maximised by large erupted volumes, abundant unconsolidated ash‐sized material, destruction of the vegetation cover (particularly by burial by ignimbrite), and inhibition of vegetation regrowth (e.g., by harsh climatic conditions). The 26.5 ka Oruanui eruption from Taupo volcano in the central North Island of New Zealand created optimal conditions for a large‐scale sedimentary response that was influenced and prolonged by the succeeding climatic nadir of the Last Glacial Maximum. About 530 km3 of rhyolitic magma was erupted as 420 km3 of fall deposits, 320 km3 of pyroclastic density current deposits (mostly non‐welded ignimbrite), and 430 km3 of primary intracaldera fill. The eruption, and formation of the Oruanui caldera, destroyed one major lake but created the forerunner to modern Lake Taupo. This lake initially stably overflowed to the northwest before breaking out in a catastrophic flood during establishment of a northeasterly outlet along the line of the modern Waikato River. Suppression of revegetation by the contemporaneous harsh periglacial climate contributed to intense erosion and remobilisation of Oruanui pyroclastic units, triggering massive downstream fluvial aggradation in impacted catchments. In particular, aggradation caused the lower 180 km of the Waikato River to avulse from its long‐established route via the Hauraki Plains into the Hamilton Basin where it was subsequently trapped. Aeolian reworking created localised dune fields, while generation of tephric loess formed deposits over much of the central North Island. The initial perturbation to fluvial sedimentary systems created by the eruption was generally sustained by climatic conditions until c. 17 ka. Climatic amelioration eventually stabilised primary sediment sources through the re‐establishment of forest vegetation, but incision and recycling of alluvial material stored in volcaniclastic fans continued until as late as c. 14 ka. Overall, the scale of the post‐Oruanui sedimentary response was primarily driven by characteristics of the eruption, whereas its duration was controlled by the Last Glacial Maximum climate.