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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Role of basin-wide landslides in the formation of extensive alluvial gemstone deposits in Sri Lanka
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Role of basin-wide landslides in the formation of extensive alluvial gemstone deposits in Sri Lanka

机译：斯里兰卡全盆地滑坡在广泛的冲积宝石矿床形成中的作用

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摘要

The tectonically stable central highlands of Sri Lanka and its alluvial valleys are the source areas and sinks, respectively, for one of the most prolific Quaternary gemstone provinces in the world. However, the known Be-10/Al-26 cosmogenic-nuclide-determined low natural (preanthropogenic) denudation rates of 2-11 mm kyr(-1), and resulting sediment fluxes, are grossly inadequate to deliver the vast throughputs of overburden required to concentrate the known gemstone deposits. Basin-wide, unstable, slow-moving channelized landslides and debris flows, aided by biotic factors, are the dominant mechanisms of mass-wasting on hill-slopes and bulk delivery of sediment to the alluvial valleys and fluvial networks. Channelization ensures modulated sediment transfer and run-out during an erosional-depositional continuum. In a selected inventory of landslides, mobilized sediment volumes ranged from less than 1000 cubic metres to a maximum of -800 000 cubic metres per event. Monsoonal rainfall (both cumulative seasonal and total daily thresholds) is the primary external factor, which interacts with colluvium thickness and steep slopes in triggering landslides. There are three to five `threshold' rainfall events per year in the highlands that can be expected to generate landslides. They can occur under conditions of decreasing daily rainfall as the seasonal total rainfall increases. GIS databases show a very significant spatial overlap and direct causal linkage between several hundred landslide occurrences and the innumerable gem pits and mines in the catchments of the best known mining region of Sri Lanka. Landslide-associated mass movements, besides providing significant numbers of gemstones to the alluvial valleys over time, are also a fundamental factor in the geomorphic evolution of the rugged central highland landscape. Rainfall-driven landslide activity may be a natural geological response affecting erosional equilibrium in high-relief tectonically stable terrains. Climatically forced base level changes will, over time, control sediment storage, removal or reworking in the valleys. Copyright (C) 2007 John Wiley & Sons, Ltd.
机译：构造上稳定的斯里兰卡中部高地及其冲积山谷分别是世界上最多产的第四纪宝石省份之一的来源地和汇。然而，已知的Be-10 / Al-26宇宙成因核素确定的2-11 mm kyr（-1）的低自然（人类活动前）剥蚀率以及由此产生的沉积物通量严重不足以提供所需的大量覆盖层集中已知的宝石矿床。在生物因素的帮助下，全盆地范围内不稳定的，缓慢移动的渠道滑坡和泥石流是在山坡上进行大量浪费以及将沉积物大量输送到冲积山谷和河流网络的主要机制。通道化可确保在冲蚀沉积连续过程中调节沉积物的输送和流失。在选定的滑坡清单中，每个事件的动员沉积物量范围从少于1000立方米到最大-800 000立方米。季风降雨（季节性和总日累积阈值）是主要的外部因素，它与崩塌层的厚度和陡坡相互作用。在高地，每年有三到五次“阈值”降雨事件，预计会产生滑坡。随着季节性总降雨量的增加，它们可能在日降雨量减少的条件下发生。 GIS数据库显示，在斯里兰卡最著名的矿区，数百个滑坡事件与无数的宝石坑和矿山之间存在非常显着的空间重叠和直接因果联系。与滑坡有关的群众运动，除了随着时间的推移为冲积山谷提供大量宝石外，也是造成崎central的中央高地景观地貌演变的基本因素。降雨驱动的滑坡活动可能是一种自然地质响应，影响了高浮雕构造稳定地形中的侵蚀平衡。随着时间的推移，气候强迫的基准面变化将控制沉积物在山谷中的存储，清除或重新加工。版权所有（C）2007 John Wiley＆Sons，Ltd.

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