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首页> 外文学位 >Late stage lowering and drainage of glacial Lake Hitchcock in the Upper Valley Region of Vermont and New Hampshire.
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Late stage lowering and drainage of glacial Lake Hitchcock in the Upper Valley Region of Vermont and New Hampshire.

机译：佛蒙特州和新罕布什尔州上谷地区的冰川希区柯克湖后期降落和排水。

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摘要

At the end of the last ice age, the Connecticut River Valley was filled by glacial Lake Hitchcock (GLH) which was dammed at its southern end near Rocky Hill, Connecticut. After this dam breached at ~16,100 cal yr BP, GLH in the Upper Connecticut River Valley of Vermont and New Hampshire (hereinafter referred to as the Upper Valley) still held water due to isostatic depression. Although it is estimated that GLH did not exist in the Upper Valley subsequent to ~12,500 cal yr BP, little is known about the timing and style of its lowering and final drainage. In order to improve the understanding of the history of GLH, we examined the transition from varved to organic-rich sediments in cores from four modern lake basins. This transition represents the removal of each basin from GLH and the onset of deposition derived from the local catchment area. Prior to post-glacial isostatic uplift, the four lakes were distributed over a range of elevations in the GLH basin and therefore would have been isolated at different times by GLH lowering. To determine an age of the transition from varved to organic-rich sediment, we correlated the varved sediment with the North American Varve Chronology (NAVC) and assigned an age to the uppermost varved sediments. We also applied radiocarbon dating to determine ages of organic macrofossils within and stratigraphically above the uppermost varved sediments. The ages of the transitions in four basins indicate that, in the Upper Valley, GLH lowered by ~60 m between ~13,280 and 12,290 cal yr BP. We also examined varved sediments for patterns of sudden increases in varve thickness which may register lake-level lowering or other events, such as climate changes. We confirmed one sudden increase in varve thickness at ~13,165 cal yr BP as the result of a rapid drainage of GLH. Our results provide a better understanding of environmental conditions during the last deglaciation as registered by lacustrine sediments. The proximity of this study to the Laurentide Ice Sheet (LIS) also provides an analog and point of comparison for modern receding ice sheets, such as the Greenland Ice Sheet.
机译：在最后一个冰河时代的末期，康涅狄格河谷被冰川希区柯克湖（GLH）充满，该湖被修建在康涅狄格州洛基山附近的南端。该水坝在BP约16100 cal年破裂后，佛蒙特州上康涅狄格河谷和新罕布什尔州（以下称为上谷）的GLH由于等静压低而仍然蓄水。尽管据估计，在大约1200 cal yr BP之后的上谷地区不存在GLH，但对其下降和最终排水的时间和方式知之甚少。为了增进对GLH历史的理解，我们研究了四个现代湖盆地的岩心中从脉动型沉积物到富含有机物的沉积物的过渡过程。这种过渡代表了从GLH中去除了每个盆地，以及从当地集水区衍生出沉积。在冰川后等静压上升之前，这四个湖泊分布在GLH盆地的一定范围的高程上，因此通过GLH降落将在不同的时间被隔离。为了确定从脉状沉积物到富含有机物的沉积物过渡的年龄，我们将脉状沉积物与北美Varve年表（NAVC）相关联，并为最脉状沉积物指定了年龄。我们还应用了放射性碳测年法来确定最上层沉积沉积物内部和地层之上的有机大化石的年龄。四个盆地的过渡年龄表明，在上游谷地，GLH在BP的约13,280和12,290 cal之间降低了约60 m。我们还检查了脉管沉积物的脉管厚度突然增加的模式，这可能表明湖泊水位降低或其他事件，例如气候变化。我们证实，由于GLH快速引流，在BP〜13,165 cal yr处，瓣膜厚度突然增加。我们的结果可以更好地了解湖相沉积物记录的最后一次冰消期间的环境条件。这项研究与Laurentide冰盖（LIS）的距离也为现代后退冰盖（例如格陵兰冰盖）提供了模拟和比较点。

著录项

  • 作者

    Bigl, Matthew F.;

  • 作者单位

    Dartmouth College.;

  • 授予单位 Dartmouth College.;
  • 学科 Geology.;Paleoclimate Science.
  • 学位 M.S.
  • 年度 2013
  • 页码 74 p.
  • 总页数 74
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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