• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Michigan Academician >Geomorphic Expression of Late Holocene Lake Levels and Paleowinds in the Upper Great Lakes
【24h】

Geomorphic Expression of Late Holocene Lake Levels and Paleowinds in the Upper Great Lakes

机译：大湖上游全新世晚期湖水位和古风的地貌表达

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Late Holocene lake level changes and predominant wind directions can be recognized in the geomorphic distribution of coastal features and deposits throughout the upper Great Lakes, and these geomorphic signatures can be used as valuable reconnaissance tools. Lake level was more than 4 m higher during the Nipissing Ⅰ and Ⅱ phases of ancestral Lakes Michigan, Huron, and Superior than today. Deposits associated with the Nipissing phases commonly occur on platforms and consist of large dunes, beach ridges, barriers, and spits. In many areas, Nipissing Ⅱ phase coastal features separate smaller inland lakes from larger primary lake basins. After the Nipissing Ⅱ phase, lake level fell 4 m in just over 500 years. Depending on available sediment supply to the shoreline and relative rate of lake level fall, the result of the 4 m fall is often expressed as a variable number of beach ridges to a bluff or scarp. Regardless of the coastal features and deposits present, there is a 4 m or more topographic change between features and deposits on the Nipissing platform and those that formed after the fall. During the past 3,500 years, the upper Great Lakes experienced three relatively long-lived highs: the Algoma phase (2,300 to 3,300 cal. yr. B.P.), and two unnamed high phases (1, 100 to 2,000 and 0 to 800 cal. yr. B.P.). Superimposed on these long-term trends are quasi-periodic fluctuations having periodicities of about 160 and 32 years in duration. The ～30-year fluctuation is instrumental in producing individual beach ridges, whereas the 160-year fluctuation produces groups of beach ridges consisting of 4 to 6 ridges in a group. The high from 1,100 to 2,000 cal. yr. B.P. contains very well defined groups that often can be recognized in aerial photographs. In the Lake Superior basin and along the southern shore of the lake, the separation of Lake Superior from Lakes Michigan/Huron about 1,000 to 2,000 years ago can also be recognized in strandplains. The separation point occurs at a topographic change in the ridges from a decline to a rise. Widespread wetland or lagoon development can occur at the topographic low, and drainage development and switches in drainage directions may also be present. Small parabolic dunes commonly occur along beach ridges in sites along the southern and eastern margins of the upper Great Lakes. At the Toleston Beach in southern Lake Michigan, these small dunes show a systematic change in predominant wind direction from westerlies to northerlies throughout the late Hohcene.
机译：在整个大湖区的沿海特征和沉积物的地貌分布中，可以识别出全新世晚期的湖水位变化和主要的风向，这些地貌特征可以用作有价值的侦察工具。在原始密歇根湖，休伦湖和苏必利尔湖的NipissingⅠ和Ⅱ期，湖面水位比今天高出4 m以上。与Nipissing阶段相关的沉积物通常发生在平台上，并且由大型沙丘，海滩山脊，障碍物和垃圾组成。在许多地区，尼皮辛Ⅱ期沿海特征将较小的内陆湖泊与较大的初级湖泊盆地区分开。在NipissingⅡ期之后，湖水位在短短500多年中下降了4 m。根据向海岸线可用的沉积物供应量和相对的湖平面下降速度，4 m下降的结果通常表示为到悬崖或陡峭的海滩山脊数量不定。无论当前的海岸特征和沉积如何，Nipissing平台上的特征和沉积与秋季之后形成的沉积之间的地形变化都在4 m或更大。在过去的3500年中，五大湖上游经历了三个相对较长的高点：阿尔戈玛阶段（2,300至3,300 cal.yr BP）和两个未命名的高阶段（1、100至2000和0至800 cal.yr） BP）。在这些长期趋势上叠加的准周期性波动的周期约为160年和32年。 〜30年的波动有助于产生单个海滩脊，而160年的波动则产生由4至6个脊组成的一组海滩脊。从1,100到2,000 cal的最高点。年。 B.P.包含定义明确的组，这些组通常可以在航空照片中识别。在苏必利尔湖流域和湖南岸，大约一千至两千年前的苏必利尔湖与密歇根湖/休伦湖的分离也可以在平原地区发现。分离点发生在山脊从下降到上升的地形变化上。湿地或泻湖的发展可能会在地形低点发生，排水的发展和排水方向的转换也可能出现。小的抛物线沙丘通常出现在大湖上游和南部边缘的海滩脊上。在密西根湖南部的Toleston海滩上，这些小沙丘显示了整个晚新世以来主导风向从西风向北风的系统变化。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号