Coring disturbances in IODP piston cores with implications for offshore record of volcanic events and the Missoula megafloods
Coring disturbances in IODP piston cores with implications for offshore record of volcanic events and the Missoula megafloods
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DOI：
10.1002/2014gc005447
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发表时间：
2014-09-01
影响因子：
3.5
通讯作者：
Ishizuka, Osamu
中科院分区：
文献类型：
--
作者：
Jutzeler, Martin;White, James D. L.;Ishizuka, Osamu
从IODP钻井平台(及其前身)收集的活塞芯提供了全球海洋沉积物的最佳长期地质和气候记录。从取心初期就认识到了影响原始沉积物结构的取心扰动，包括沉积物对岩心桶的剪切变形、部分冲刷引起的底部流入、地层损失、坠落、通过取心捕集器的沉积物损失以及取心回收和甲板运输过程中形成的结构。最严重的扰动发生在非粘性(砂质)相中，这在火山成因环境和海底扇中特别常见。尽管所有这些类型的取心干扰以前都已被识别，但我们的贡献是新颖的，因为它提供了一个易于获取的识别方法的总结。这篇文章提供了两个具体的例子来说明这些取心扰动的重要性。我们展示了在取芯过程中如何人为地吸入沉积物，在蒙特塞拉特和马提尼克岛(小安的列斯群岛)近海岩心中创造了非常厚的火山碎屑砂层。然后，我们分析了来自埃斯卡纳巴海槽的非常厚的、无结构的沙层，推测这是米苏拉大洪水的记录。这些砂层倾向于与岩心剖面的底部重合，其相表明岩心受到底部流入的干扰，破坏了岩层的原始结构和结构。最后，我们概述并支持IODP牵头的倡议，以进一步减少和识别取心干扰，并承认它们最近在具有挑战性的富砂环境中取得的成功，例如在IODP Expeation 340期间。
Piston cores collected from IODP drilling platforms (and its predecessors) provide the best long-term geological and climatic record of marine sediments worldwide. Coring disturbances affecting the original sediment texture have been recognized since the early days of coring and include deformation resulting from shear of sediment against the core barrel, basal flow-in due to partial stroke, loss of stratigraphy, fall-in, sediment loss through core catchers, and structures formed during core recovery and on-deck transport. The most severe disturbances occur in noncohesive (sandy) facies, which are particularly common in volcanogenic environments and submarine fans. Although all of these types of coring disturbances have been recognized previously, our contribution is novel because it provides an easily accessible summary of methods for their identification. This contribution gives two specific examples on the importance of these coring disturbances. We show how suck-in of sediments during coring artificially created very thick volcaniclastic sand layers in cores offshore Montserrat and Martinique (Lesser Antilles). We then analyze very thick, structureless sand layers from the Escanaba Trough inferred to be a record of the Missoula megafloods. These sand layers tend to coincide with the base of core sections, and their facies suggest coring disturbance by basal flow-in, destroying the original structure and texture of the beds. We conclude by outlining and supporting IODP-led initiatives to further reduce and identify coring disturbances and acknowledge their recent successes in drilling challenging sand-rich settings, such as during IODP Expedition 340.