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首页> 外文学位 >Understanding Mississippi Delta Subsidence through Stratigraphic and Geotechnical Analysis of a Continuous Holocene Core at a Subsidence Superstation
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Understanding Mississippi Delta Subsidence through Stratigraphic and Geotechnical Analysis of a Continuous Holocene Core at a Subsidence Superstation

机译：通过沉降沉降站连续全新世岩心的地层和岩土分析来了解密西西比三角洲沉降

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摘要

Land-surface subsidence can be a major contributor to the relative sea-level rise that is threatening many coastal communities. Loosely constrained subsidence rate estimates across the Mississippi Delta make it difficult to differentiate between subsidence mechanisms and complicate modeling efforts. New data from a nearly 40 m long, 12 cm diameter core taken during the installation of a subsidence monitoring superstation near the Mississippi River, southeast of New Orleans, provides insight into the stratigraphic and geotechnical properties of the Holocene succession at that site. Stratigraphically, the core can be grouped into four units. The top 12 m is dominated by clastic overbank sediment with interspersed organic-rich layers. The middle section, 12--35 m, consists predominately of mud, and the bottom section, 35--38.7 m, is marked by a transition into a Holocene-aged basal peat (~11.3 ka) which overlies densely packed Pleistocene sediment. Radiocarbon and OSL ages are used to calculate vertical displacement and averages subsidence rates as far back as ~3.5 ka, yielding values as high as 8.0 m of vertical displacement (up to 2.34 mm/yr) as obtained from a transition from mouth bar to overbank deposits. We infer that most of this was due to compaction of the thick, underlying mud package. The top ~80 cm of the core is a peat that represents the modern marsh surface and is inducing minimal surface loading. This is consistent with the negligible shallow subsidence rate as seen at a nearby rod-surface elevation table--marker horizon station. Future compaction scenarios for the superstation can be modeled from the stratigraphic and geotechnical properties of the core, including the loading from the planned Mid-Barataria sediment diversion which is expected to dramatically change the coastal landscape in this region.
机译：地表沉降可能是导致相对海平面上升的主要因素，海平面上升正威胁着许多沿海社区。整个密西西比三角洲的沉降率估算受到限制，使得很难区分沉降机理和使建模工作复杂化。在新奥尔良东南部密西西比河附近的沉降监测超级站的安装过程中，从近40 m长，直径12 cm的岩心中获得了新数据，从而提供了对该位置全新世演替的地层和岩土属性的洞察力。从地层学上讲，岩心可以分为四个单元。顶部的12 m以碎屑性的岸上沉积物为主，上面散布着富含有机物的层。中段12--35 m主要由泥浆组成，而下段35--38.7 m以过渡到全新世时代的基底泥炭（〜11.3 ka）为标志，该泥炭覆盖着密集堆积的更新世沉积物。放射性碳和OSL年龄用于计算垂直位移，平均沉降速率可追溯到〜3.5 ka，从口栏过渡到堤岸的过渡过程中，产生的垂直位移高达8.0 m（最高2.34 mm / yr）。存款。我们推断，这大部分是由于压实了下面厚厚的泥包所致。核心的约80厘米顶部是一个泥炭，代表了现代的沼泽表面，并导致最小的表面负荷。这与在附近的杆面高程表-标记地平线站看到的浅层沉降率可忽略不计。可以根据岩心的地层和岩土工程特性来模拟超级电站未来的压实情况，包括计划中的巴拉塔里亚中部泥沙分流的负荷，这有望显着改变该地区的沿海景观。

著录项

  • 作者

    Bridgeman, Jonathan G.;

  • 作者单位

    Tulane University School of Science and Engineering.;

  • 授予单位 Tulane University School of Science and Engineering.;
  • 学科 Geology.
  • 学位 M.S.
  • 年度 2018
  • 页码 96 p.
  • 总页数 96
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 物理化学（理论化学）、化学物理学;
  • 关键词

  • 入库时间 2022-08-17 11:38:44

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