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Assessing the style of advance and retreat of the Des Moines Lobe using LiDAR topographic data.

机译：使用LiDAR地形数据评估得梅因瓣的进退样式。

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摘要

Successive advances of the late-Wisconsinan Des Moines Lobe to form three major end moraines in Iowa---sequentially the Bemis, Altamont, and Algona moraines---are thought to be the result of the lobe surging out of balance with a warming climate. Various styles of hummocky topography, collectively sometimes called stagnation moraine, are interpreted to be the result of widespread stagnation and down-wasting of ice following surges. Alternatively, end moraines could be recessional---a result of incremental back-wasting of the glacier margin and unrelated to surging.;To study the retreat style of the Des Moines Lobe, high resolution LiDAR data were used to re-evaluate the subtle landscape of the lobe's footprint in Iowa. Results indicate that ~90% of the lobe's area, excluding major Holocene stream drainages, consists of stagnation features. Some landforms are more prevalent than mapped previously, including eskers and features interpreted to be subdued ice-walled lake plains. Importantly, subglacially formed minor moraines (a.k.a. washboard moraines), which resulted from sediment filling of transverse crevasses, cover ~60% of the lobe's area with stagnation landforms. Also, ~25 previously unmapped end moraine ridges have been identified.;Transverse crevasse-fill ridges in the forefields of modern glaciers form due to longitudinal ice extension associated with surging and are not found in the forefields of non-surge-type glaciers, so minor moraines are good evidence of Des Moines Lobe surges. Most end moraines have minor moraine sets associated with them, consistent with a surge-like advances, and many areas have multiple sets of minor moraines indicating a surge history more complicated than one advance for each of the three major end moraines. Therefore, asserting stagnation and down-wasting after three surge-like advances provides an incomplete characterization of the Des Moines Lobe's advance and retreat. The surge-type Bering Glacier in Alaska is a good but imperfect modern analog for the lobe.
机译：后来的威斯康星州的得梅因河瓣不断发展，形成了爱荷华州的三个主要端mo-依次为Bemis，Altamont和Algona rain-被认为是由于气候变暖使瓣不平衡而激增的结果。 。各种样式的丘陵地形，有时统称为停滞冰ora，被解释为是冰激增后冰块普遍停滞和倒水的结果。另外，端部动静可能是衰退的-是冰川边缘逐渐消退的结果，与浪涌无关。​​为了研究得梅因河瓣的后退风格，使用高分辨率的LiDAR数据重新评估了细微的变化。衣阿华州的叶足迹的自然景观。结果表明，除了主要的全新世河流外，约90％的裂片区域都具有停滞特征。一些地貌比以前绘制的地图更为普遍，包括埃斯克人和被解释为被冰墙覆盖的湖泊平原所掩盖的特征。重要的是，由于横向裂缝的沉积物充填而造成的冰下形成的次要谷粒（又称搓板谷粒）覆盖了约60％的停滞地形。此外，已经确定了约25个以前未映射的冰m末脊。现代冰川前场中的横向缝隙填充脊由于与涌动有关的纵向冰伸展而形成，在非浪涌型冰川的前场中未发现，因此轻微的mo然是得梅因肺叶激增的良好证据。多数终端mo与它们相关联的是较小的冰ora，这与浪涌状的前进相一致，并且许多地区都有多组次要mo冰，这表明三个主要终端mo中的每一个的浪涌历史要比一个前进更为复杂。因此，在三次类似浪涌的前进之后断言停滞和消沉，这不完全说明了得梅因洛贝的前进和后退。阿拉斯加的浪涌型白令冰川是一种不错的但不完美的现代类似物。

著录项

  • 作者

    Day, Sarah Elizabeth.;

  • 作者单位

    Iowa State University.;

  • 授予单位 Iowa State University.;
  • 学科 Geomorphology.;Geology.
  • 学位 M.S.
  • 年度 2014
  • 页码 84 p.
  • 总页数 84
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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