GEOMORPHIC TECTONIC CONTROL OF SEDIMENT DISCHARGE TO THE OCEAN - THE IMPORTANCE OF SMALL MOUNTAINOUS RIVERS
GEOMORPHIC TECTONIC CONTROL OF SEDIMENT DISCHARGE TO THE OCEAN - THE IMPORTANCE OF SMALL MOUNTAINOUS RIVERS
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DOI：
10.1086/629606
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发表时间：
1992-09-01
影响因子：
1.8
通讯作者：
SYVITSKI, JPM
中科院分区：
文献类型：
--
作者：
MILLIMAN, JD;SYVITSKI, JPM
对280条入海河流数据的分析表明，泥沙负荷/产沙量是流域面积和流域最大高程的对数线性函数。控制沉积物排放的其他因素（例如，气候，径流）似乎具有次要的重要性。一个明显的例外是人类活动、气候和地质对南亚和大洋洲河流的影响。来自小型山区河流的沉积物通量，其中许多河流直接排放到活动边缘（例如，在以前的全球沉积物预算中，对海洋沉积物（包括南美洲和北美洲西部以及大多数高海拔海洋岛屿）的估计被大大低估，可能被低估了三倍。相比之下，从大河（几乎所有的河流都流入被动大陆边或边缘海）流入海洋的沉积物通量被高估，因为一些沉积物负载在下沉的三角洲中被水下隔离。在本世纪后半叶水坝建设激增之前，河流每年可能向海洋排放约200亿吨沉积物。然而，在大规模耕作和森林砍伐之前（2000-2500年前开始），沉积物排放量可能不到目前水平的一半。在海平面高的时候，由于偶发事件的影响更大（即，洪水和地震），以及与活动边缘相关的狭窄大陆架。由此产生的三角洲/扇沉积物可能明显不同于从较大河流排放到被动边缘的沉积物。
Analysis of data from 280 rivers discharging to the ocean indicates that sediment loads/yields are a log-linear function of basin area and maximum elevation of the river basin. Other factors controlling sediment discharge (e.g., climate, runoff) appear to have secondary importance. A notable exception is the influence of human activity, climate, and geology on the rivers draining southern Asia and Oceania. Sediment fluxes from small mountainous rivers, many of which discharge directly onto active margins (e.g., western South and North America and most high-standing oceanic islands), have been greatly underestimated in previous global sediment budgets, perhaps by as much as a factor of three. In contrast, sediment fluxes to the ocean from large rivers (nearly all of which discharge onto passive margins or marginal seas) have been overestimated, as some of the sediment load is subaerially sequestered in subsiding deltas. Before the proliferation of dam construction in the latter half of this century, rivers probably discharged about 20 billion tons of sediment annually to the ocean. Prior to widespread farming and deforestation (beginning 2000-2500 yr ago), however, sediment discharge probably was less than half the present level. Sediments discharged by small mountainous rivers are more likely to escape to the deep sea during high stands of sea level by virtue of a greater impact of episodic events (i.e., flash floods and earthquakes) on small drainage basins and because of the narrow shelves associated with active margins. The resulting delta/fan deposits can be distinctly different than the sedimentary deposits derived from larger rivers that discharge onto passive margins.