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首页> 外文学位 >Mud mounds on the continental slope, northwestern Gulf of Mexico and their relation to hydrates and seafloor instability.
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Mud mounds on the continental slope, northwestern Gulf of Mexico and their relation to hydrates and seafloor instability.

机译：墨西哥湾西北部大陆坡上的泥丘及其与水合物和海底不稳定的关系。

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摘要

High resolution seismic data delineate acoustically amorphous mounded structures on the continental slope of the Northwest Gulf of Mexico. The thermogenic gas hydrates reported from Green Canyon Block 184 are associated with one of these mounds. This particular mound occurs in a highly faulted area and overlies an extensive chaotic seismic facies. The chaotic facies indicated underconsolidated, overpressured sediments. Gas and fluids are migrating up the fault plane to the sea floor. The relief of the mound is partially the result of the throw of the associated faults, but also to a combination of other factors such as the upwelling of gaseous muds, in-place expansion of the hydrates and the generation of diagenic carbonates.;The acoustic signature of the known hydrate accumulation of Green Canyon Block 184 was applied to high resolution data in Mississippi Canyon Block 798 and 799 in an attempt to predict the occurrence of hydrates. Piston cores within an acoustically amorphous mound in Block 798 encountered extremely gassy sediments with sizeable chunks of white, presumably biogenic hydrates. The geologic setting in Block 798 was similar to Green Canyon 184 with complex faulting and subsurface sequences of thick chaotic facies.;Numerous other examples of acoustically amorphous mounds occur in areas of Mississippi Canyon, Green Canyon, Ewing Bank, Garden Banks and East Breaks. The acoustic signature of mounds along the upper slope in water depths too shallow for hydrate formation show no appreciable difference from the deep water varieties. The venting of gas and fluids from overpressured zones appears to be the common factor for all mounds thereby making them mud diapir/mud volcano type structures. However, the possibility of pingo-type formation cannot be entirely ruled out.;No evidence of seafloor instability was directly related to the presence or possible presence of gas hydrates. However, if it can be established that massive hydrate formation exist on the continental slope, then a substantial lowering of sea level such as occurred in the late Pleistocene, would result in decomposition of the hydrates and trigger mass wasting. Such a mechanism could explain abundance of buried erosional scars along the continental slope.
机译：高分辨率地震数据描绘了墨西哥西北海湾大陆坡上的声学无定形堆积结构。从格林峡谷184号区块报告的产热天然气水合物与这些土丘之一有关。这种特殊的土丘发生在高度断层的地区，并覆盖了广泛的混沌地震相。混沌相表明沉积物固结不足，压力过大。气体和流体沿断层平面向上迁移到海床。丘的起伏部分是由于相关断层的抛出所致，也归因于其他因素的组合，例如气态泥浆的上升，水合物的就地膨胀和成岩碳酸盐的产生。为了预测水合物的发生，将绿色峡谷184号已知水合物堆积的标志应用于密西西比峡谷798号和799号高分辨率数据。 798区块中一个声学无定形土墩中的活塞芯遇到了极具气态的沉积物，上面带有可观的生物水合物白色块。 798区块的地质环境与格林峡谷184相似，具有复杂的断层和厚厚的混沌相的地下序列;无声冢的其他例子还出现在密西西比峡谷，格林峡谷，尤因河岸，花园河岸和东区。水深过浅而无法形成水合物的高坡上丘丘的声学特征与深水品种没有明显的区别。从过压区排出气体和流体似乎是所有土墩的共同因素，因此使它们成为泥底辟/泥火山型结构。但是，不能完全排除形成针刺型的可能性。没有证据表明海底不稳定与气体水合物的存在或可能的存在直接相关。但是，如果可以确定大陆斜坡上存在大量的水合物形成，那么海平面的大幅下降（如在更新世晚期发生）将导致水合物分解并引发物质浪费。这种机制可以解释大陆斜坡上大量的埋藏侵蚀性疤痕。

著录项

  • 作者

    Neurauter, Thomas William.;

  • 作者单位

    Texas A&M University.;

  • 授予单位 Texas A&M University.;
  • 学科 Physical Oceanography.
  • 学位 Ph.D.
  • 年度 1988
  • 页码 254 p.
  • 总页数 254
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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