首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1篇
  免费   2篇
地球物理   1篇
地质学   2篇
  2016年   1篇
  2014年   1篇
  1999年   1篇
排序方式: 共有3条查询结果,搜索用时 15 毫秒
1
1.
Lavaka represent a typical erosional landform in Madagascar. The chronology of their formation remains, however, under discussion. Our research focuses on the Ankarokaroka lavaka, a spectacular landform located in NW Madagascar (Ankarafantsika natural reserve), which is characterized by the presence of sandy units of regional extension at its top. The two main units correspond to white and red sands, and are closely associated with specific vegetations (dry dense forest for the white sands, savannah grasslands for the red sands). We applied a geochronological approach based on Optically Stimulated Luminescence (for the coversands) associated with radiocarbon dating performed on archaeological remains found at the contact between the sands and the lavaka. The combination of this approach with field work and sedimentological analyses makes it possible to show that the sands experienced a complex history, both in terms of sedimentation and post‐sedimentary pedogenesis (podzolization of the white sands, rubefaction of the red sands). The numerical ages furthermore indicate that the Ankarokaroka lavaka formed between 18.5 ± 2.3 ka ago and the 14th century AD. The present study demonstrates that this lavaka has a climatic origin, and highlights the potential of OSL to date sediments associated with Madagascar lavaka. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
2.
3.
Sequences of last-glacial age contain valuable palaeoclimatic information but are often difficult to date because the environment has been unfavourable for deposition of datable organic material. This paper presents age-estimates, determined by optically stimulated luminescence, for sediments from the type site of the so-called ‘coversands’ (periglacial aeolian deposits) in The Netherlands. These improve the chronology of this type site considerably, allowing age limits (22–17 kyr BP) to be set, for the first time, for the important phase of widespread permafrost degradation and aeolian deflation recorded in these deposits. Aeolian deposition occurred intermittently for most of the Last Glacial Maximum and the Late-glacial phases. Based on luminescence dating, sand-sheet deposition was concentrated between ca. 17–14 kyr ago, and dune formation was dominant during the Younger Dryas. The Younger Dryas was sufficiently cold to allow the first stages of ice-wedge-cast development in The Netherlands. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   
1
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号