Salt-driven fluid venting chimneys at the base of the Sigsbee Escarpment, northwestern Gulf of Mexico
Salt-driven fluid venting chimneys at the base of the Sigsbee Escarpment, northwestern Gulf of Mexico
复制标题
DOI：
10.1016/j.marpetgeo.2021.105396
复制
发表时间：
2021-11
影响因子：
4.2
通讯作者：
N. Slowey;Debora Berti;I. MacDonald
中科院分区：
文献类型：
--
作者：
N. Slowey;Debora Berti;I. MacDonald
我们在墨西哥湾西北部Sigsbee陡崖底部的Farnella峡谷（水深约2775 m）侧翼的海底沿着发现了一大片圆柱形沉积物烟囱。烟囱直径约10厘米，轴向空腔宽1厘米;它们高出海底约0.5-1米，并继续向下进入海底。其组成和织物的特点是使用X射线衍射，碳酸盐含量，稳定的氧和碳同位素，扫描电子显微镜和微量分析。对该地点的地震剖面和测深数据进行了分析，以寻找烟囱与海底地质结构之间的联系。结果表明，排出的液体是含盐水的温暖海水，没有碳氢化合物的迹象。这些烟囱是半远洋沉积物在海底形成的残留沉积物填充的流体逸出管道，这些沉积物在邻近管道中通过海底向上移动的流体压力的作用下局部固结，并被氧化铁和无定形二氧化硅沉淀物以及自生白云岩结合在一起。当海底洋流侵蚀周围的海床时，烟囱随后暴露在海底。烟囱横截面上明显的同心和横切带表明排气是偶然发生的（排气目前不活跃）。烟囱区位于侏罗纪盐丘的底部，盐丘延伸到大陆坡的大部分区域之下。盐的移动在海床内产生了压力梯度，引导孔隙水流向烟囱所在的斜坡底部;因此，泄放很可能发生在盐移动期间和之后不久。
We discovered a large field of cylindrically-shaped sediment chimneys at the seafloor along the flank of Farnella Canyon (water depth ∼2775 m) at the base of the Sigsbee Escarpment in the northwestern Gulf of Mexico. The chimneys are about 10 cm in diameter with 1 cm wide axial cavities; they rise about 0.5–1 m above the seafloor and continue down into the seabed. Their composition and fabric were characterized using X-ray diffraction, carbonate content, stable oxygen and carbon isotopes, and scanning electron microscopy and microanalysis. Seismic profiles and bathymetric data from the location were analyzed to seek links between the chimneys and seabed geological structures. Results indicate that the vented liquids were warm seawater with brine and there is no evidence of hydrocarbons. These chimneys are residual sediment-filled fluid-escape conduits formed in the seabed from hemipelagic sediments that were locally consolidated by the pressure of fluid moving upward through the seabed in adjacent conduits and bound together by iron oxide and amorphous silica precipitates, as well as authigenic dolomite. The chimneys were subsequently exposed at the seafloor when bottom currents eroded the surrounding seabed. Concentric and crosscut bands evident in chimney cross sections indicate venting occurred episodically (venting is not currently active). The chimney field is situated at the toe of the Jurassic salt massif that extends beneath much of the continental slope. Salt movement created a pressure gradient within the seabed, directing porewater flow toward the base of the slope where the chimneys occur; thus, venting most likely occurred during times of salt mobility and shortly thereafter.