Alluvial plain dynamics in the southern Amazonian foreland basin
Alluvial plain dynamics in the southern Amazonian foreland basin
复制标题
亚马逊前陆盆地南部冲积平原动态
DOI：
10.5194/esdd-6-2063-2015
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
U. Lombardo
中科院分区：
文献类型：
--
作者：
U. Lombardo
抽象的。冲积平原是由河流存款沉积在相邻的洪水流域，主要是通过决口扇和撕脱。这是一系列过程的结果，其中一些过程将河流推向裂缝阈值，而另一些过程则是触发器。根据南部亚马逊河前陆盆地的大型河流的洪泛平原沉积模式，有人认为，冲积平原沉积物的积累主要是由于拉尼娜现象引起的高于正常水平的降水事件所引发的河流决口扇和席状砂。然而，超过90%的亚马逊河网络是由小河流组成的，目前还不清楚小河流洪泛区沉积是否也受到ENSO循环的影响。利用1984年至2014年的陆地卫星图像，我在这里分析了马莫雷河所有12条支流的行为，这些支流都有一个位于安第斯山脉的集水区。我表明，这些都是非常活跃的河流和裂缝的频率是没有联系到ENSO活动。这些数据表明，马莫雷河支流从安第斯山脉侵蚀而来的大部分沉积物在到达母河之前沉积在冲积平原上。这些河流的全新世中晚期古河道位于距离安第斯山脉比现代裂缝远数十公里的地方。我的结论是，裂缝的频率是由盆地内的过程，每年到十年的时间尺度上的行为，而裂缝的平均位置是由气候或新构造事件，在千年尺度上的行为控制。最后，我讨论了河流动态对农村生计和生物多样性的影响，在Llanos de Moxos，季节性洪水覆盖大部分的亚马逊河流域南部前陆盆地和世界上最大的拉姆萨尔网站稀树草原。
Abstract. Alluvial plains are formed with sediments that rivers deposit on the adjacent flood-basin, mainly through crevasse splays and avulsions. These result from a combination of processes, some of which push the river towards the crevasse threshold, while others act as triggers. Based on the floodplain sedimentation patterns of large rivers in the southern Amazonian foreland basin, it has been suggested that alluvial plain sediment accumulation is primarily the result of river crevasse splays and sheet sands triggered by above-normal precipitation events due to La Nina. However, more than 90 % of the Amazonian river network is made of small rivers and it is unknown whether small river floodplain sedimentation is influenced by the ENSO cycle as well. Using Landsat images from 1984 to 2014, here I analyse the behaviour of all 12 tributaries of the Rio Mamore with a catchment in the Andes. I show that these are very active rivers and that the frequency of crevasses is not linked to ENSO activity. The data suggest that most of the sediments eroded from the Andes by the tributaries of the Mamore are deposited in the alluvial plains, before reaching the parent river. The mid-to-late Holocene paleo-channels of these rivers are located tens of kilometres further away from the Andes than the modern crevasses. I conclude that the frequency of crevasses is controlled by intrabasinal processes that act on a yearly to decadal timescale, while the average location of the crevasses is controlled by climatic or neo-tectonic events that act on a millennial scale. Finally, I discuss the implications of river dynamics on rural livelihoods and biodiversity in the Llanos de Moxos, a seasonally flooded savannah covering most of the southern Amazonian foreland basin and the world's largest RAMSAR site.
影响因子：
12.1
作者：
J. Lewin;P. Ashworth
通讯作者：
J. Lewin;P. Ashworth
影响因子：
18.3
作者：
Constantine, Jose Antonio;Dunne, Thomas;Lazarus, Eli D.
通讯作者：
Lazarus, Eli D.