The Role of Diagenesis in Exfoliation of Submarine Canyons
The Role of Diagenesis in Exfoliation of Submarine Canyons
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成岩作用在海底峡谷剥落中的作用
DOI：
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发表时间：
1993
期刊：
影响因子：
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通讯作者：
B. Schreiber
中科院分区：
文献类型：
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作者：
C. McHugh;W. Ryan;B. Schreiber
在美国大陆边缘新泽西州近海较低的斜坡上，海底峡谷切割碳酸盐沉积，峡谷形态的特点是陡峭的、近乎垂直的墙壁、线形和平坦的峡谷底部、阶梯状的梯田、“U”形的横断面，以及缺乏发育良好的支流沟壑。峡谷形态与上、中坡峡谷形成鲜明对比，上、中坡峡谷被切割成硅质碎屑沉积，具有“V”字形剖面、狭窄的曲折喷口和树枝状支流沟谷。开展了一项研究计划，以研究成岩作用和基岩的物理性质在碳酸盐环境下海底峡谷的形成和生长中所起的作用。阿尔文潜水是在新泽西州较低的斜坡上进行的，峡谷在那里切割出硅质白垩岩或白垩岩和硅质白垩岩。观察和采样了峡谷形态成分，如陡峭的墙壁、平坦的地面和梯田、线性滑道和节理表面。随着富硅白垩岩的逐渐埋藏，蛋白石-A到蛋白石-CT成岩转化导致的流体排出导致体积减少，这对基岩的破裂有很大的贡献。各尺度裂隙在硅质岩中与层理近平行和垂直，在白垩岩中垂直。由于大量浪费，覆盖层和峡谷挖掘的去顶板会导致剥落和成岩产生的裂缝扩大。一旦峡谷开始形成，它就通过正反馈继续发展，因为有持续的应力释放破裂：失去支撑导致破坏，侵蚀继续通过从广泛破碎的岩石中剥落和滑动。这项研究的结果为深海富含二氧化硅的白垩岩提供了裂缝形成的时间。通过目视观察和取样，可以了解裂缝的方向、规模和网络通信。对峡谷/斜坡碳酸盐环境中现代沉积过程的观察有助于了解古代环境。
On the lower slope of the U.S. continental margin offshore New Jersey, submarine canyons incise carbonate sediments, and the canyon morphology is characterized by steep, nearly vertical walls, linear and flat canyon floors, stepped terraces, "U"-shaped cross-sectional profiles, and the lack of well-developed tributary gullies. Canyon morphology contrasts sharply with that of canyons in the upper and middle slope that are cut into siliciclastic sediments and have "V"-shaped profiles, narrow sinuous thalwegs, and dendritic tributary gullies. A research program was undertaken to study the role that diagenesis and the physical properties of bedrock have in formation and growth of submarine canyons in a carbonate setting. Alvin dives were conducted on the New Jersey lower slope where canyons incise siliceous chalks or chalk rocks and siliceous porcellanitic chalks. Morphological canyon components such as steep walls, flat floors and terraces, linear chutes, and joint surfaces were observed and sampled. Volume reduction resulting from fluid expulsion due to the opal-A to opal-CT diagenetic transformation, which occurs with progressive burial of the silica-rich chalks, contributes greatly to fracturing of the bedrock. Fracturing at all scales is oriented subparallel and vertical to bedding in the porcellanites, and vertical in the chalk rocks. Unroofing of overburden and canyon excavation by mass-wasting causes exfoliation and diagenetically generated fractures to expand. Once canyon formation begins, it continues development by positive feedback since there is a continued stress-release fracturing: loss of support leads to failure, and erosion continues by spalling and sliding of blocks from the extensively fractured rocks. Results obtained in this study provide a timing for fracture formation in deep-sea, silica-rich chalks. Visual observations and sampling provide an understanding of fracture orientation, scale, and network communication. Observations of modern sedimentary processes in a canyon/slope carbonate setting help to understand ancient environments.