• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Alpine and subalpine landscape response to post-glacial climate change in the San Juan mountains: A comparison of new landscape and climate records.
【24h】

Alpine and subalpine landscape response to post-glacial climate change in the San Juan mountains: A comparison of new landscape and climate records.

机译：圣胡安山脉的冰川和冰川变化后气候变化的高山和亚高山景观：新景观和气候记录的比较。

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

Post-glacial interactions between climate, landscapes, and soils remain poorly understood, especially in alpine and sub-alpine areas. Here, I aim to increase understanding of the dynamic interactions between climate, landscape evolution, and soil development by compiling detailed records of all three. First, pollen assemblages, diatom assemblages, and sedimentology from Cumbres Bog in the southern San Juan Mountains of Colorado provide a record of climate change since the end of the Last Glacial Maximum (LGM, 16-22 ka regionally). Next, geomorphic mapping in the upper Conejos River Valley of the San Juan Mountains provides evidence of incision and aggradation that has occurred since the end of the LGM. Lastly, nineteen soils, examined for particle size, Fe extractions, and organic carbon, provide a chronosequence across multiple parent materials.;The Cumbres Bog record provides strong evidence of: cooling during the Younger Dryas (∼12.8-11.5 ka), generally warm, stable climate until 6 ka, and cooler, more variable climate after 6 ka. Additionally, pollen ratios and fossil diatoms indicate that cold periods generally match with previously identified periods of rapid climate change and occurred at 10.6, 8.7-7.9, 7.0-6.9, 5.4--5.2, 3.3--3.0, 2.3, 2.0 and 1.5 ka. This record also adds resolution to previous regional records and indicates that the periodicity of climate change changed from 2,000-3,000 years during the interval from 11.5-6 ka to 700-1,100 years for the interval from 6-3.5 ka, then to 500 years after 3.5 ka. These changes correspond with increased El Nino-Southern Oscillation (ENSO) activity after the mid-Holocene (∼6 ka).;The upper Conejos River Valley appears to have undergone three distinct periods of aggradation. The first occurred during the Pleistocene-Holocene transition (∼12.5 -- 9.5 ka) and is interpreted as paraglacial landscape response to deglaciation after the LGM. Evidence of the second period of aggradation is limited but indicates a small pulse of sedimentation at ∼ 6 ka. A third, more broadly identifiable period of sedimentation occurred in the Late Holocene (∼2.2 -- 1 ka). The latest two periods of aggradation are concurrent with the ENSO related increases to the frequency of climate change. This suggests that Holocene alpine and sub-alpine landscapes respond more to rapid ENSO-driven changes in climate than to large singular climatic swings. More specifically, it is likely that landscapes respond to the strengthened ENSO indicated by increased frequency of climate change. Soil development and radiocarbon dating indicate that hillslopes were stable during the Holocene even while aggradation was occurring in valley bottoms. Thus, we can conclude that erosion does not occur equally throughout the landscape but is focused above headwater streams, along tributary channels, or on ridgetops.;Lastly, the soil chronosequences indicate that ratios of oxalate/dithionite Fe extractions exhibit a robust trend with age for all soils. The relationship between extractable iron and time is in contrast with other soil properties, such as reddening, profile thickness, and clay content, which are not good indicators of age. Variation in eolian deposition and parent material sedimentology likely led to the observed variability in soils of similar age.
机译：冰川后气候，景观和土壤之间的相互作用仍然知之甚少，特别是在高山和亚高山地区。在这里，我的目的是通过汇编所有这三个方面的详细记录来增进对气候，景观演变和土壤发育之间动态相互作用的理解。首先，科罗拉多州圣胡安山脉南部Cumbres沼泽的花粉组合，硅藻组合和沉积学提供了自上次冰河末期以来最大的气候变化记录（LGM，区域为16-22 ka）。接下来，圣胡安山脉上游Conejos河流域的地貌图提供了自LGM结束以来发生的切割和积聚的证据。最后，对19种土壤进行了粒度，铁提取和有机碳检测，提供了多种母体物质的时间序列。Cumbres沼泽记录提供了有力的证据：幼树树（约12.8-11.5 ka）降温，总体温暖，直到6 ka之前气候稳定，而6 KA之后温度更低，气候变化更多。此外，花粉比率和化石硅藻表明寒冷时期通常与先前确定的快速气候变化时期相匹配，发生在10.6、8.7-7.9、7.0-6.9、5.4--5.2、3.3--3.0、2.3、2.0和1.5 ka 。该记录还为以前的区域记录增加了分辨率，并指出气候变化的周期从11.5-6 ka间隔的2,000-3,000年变化为6-3.5ka间隔的700-1,100年，然后变为<500年在3.5 ka之后。这些变化与全新世中期（〜6 ka）后厄尔尼诺-南方涛动（ENSO）活动的增加相对应。康尼荷斯河上游地区似乎经历了三个不同的凝结时期。第一次发生在更新世-全新世过渡（〜12.5-9.5 ka）期间，被解释为LGM后冰期对冰消作用的景观响应。第二个凝结期的证据有限，但表明在约6 ka处有一个小的沉降脉冲。在全新世晚期（〜2.2-1 ka），发生了第三个更广泛可识别的沉积期。最近两个阶段的凝结与ENSO相关的气候变化频率增加同时发生。这表明全新世的高山和亚高山景观对ENSO驱动的快速气候变化的反应要比对大型奇异气候波动的反应更大。更具体地说，景观可能对气候变化频率增加所表明的ENSO增强做出了反应。土壤发育和放射性碳定年表明，即使在谷底发生凝集的情况下，全新世期间的山坡也是稳定的。因此，我们可以得出结论，侵蚀在整个景观中并非均等地发生，而是集中在上游水流，支流通道或山脊顶上;最后，土壤的时间序列表明草酸盐/连二亚铁Fe提取物的比例随年龄呈现出强劲的趋势。适用于所有土壤。可提取铁与时间之间的关系与其他土壤性质（例如变红，剖面厚度和粘土含量）形成对比，而后者并不是年龄的良好指标。风积沉积和母体物质沉积学的变化可能导致在类似年龄的土壤中观察到变化。

著录项

  • 作者

    Johnson, Bradley Gordon.;

  • 作者单位

    The University of North Carolina at Charlotte.;

  • 授予单位 The University of North Carolina at Charlotte.;
  • 学科 Climate Change.;Geomorphology.;Paleoclimate Science.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 202 p.
  • 总页数 202
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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