气候变化领域集成服务门户(CCPortal): Focused erosion at the core of the Greater Caucasus: Sediment generation and dispersal from Mt. Elbrus to the Caspian Sea

CCPortal

DOI	10.1016/j.earscirev.2019.102987
	Focused erosion at the core of the Greater Caucasus: Sediment generation and dispersal from Mt. Elbrus to the Caspian Sea
	Vezzoli G.; Garzanti E.; Limonta M.; Radeff G.
发表日期	2020
ISSN	00128252
卷号	200
英文摘要	The highest peaks in Europe are found in the central Greater Caucasus, an orogenic belt characterized by extremely active tectonic and sedimentary processes. In this rugged mountain region, we have investigated sand generation and erosion patterns by using high-resolution petrographic and heavy-mineral data on river sands complemented by detailed morphometric analysis of 9 major mountain branches of the Terek River. Also presented is an extensive review of sediment-transport data available in the Russian literature on glacial-lake outburst floods and rainfall-triggered debris flows, which owing to global warming and glacier retreat have afflicted the Greater Caucasus with increasing frequency in the last 50 years. The accurate definition of mineralogical signatures characterizing detritus derived from six end-member volcanic, metamorphic basement, and sedimentary/metasedimentary rock units allowed us to calculate the relative contribution of each to the sand load, with particular precision for the Baksan River draining Mt. Elbrus. Results clearly indicate that volcanic and basement rocks supply a disproportionate amount of sand relatively to their outcrop area, testifying to strongly focused erosion in the high-relief axial part of the range. River channels here display extreme steepness (ksn up to 200–300) and low concavity indices (θ 0.15 - 0.35) typical of thalwegs shaped by debris flows. Average erosion rates reach as high as 2–4 mm/a, which is explained by the frequency of catastrophic mass-transport events able to mobilize in one single episode between 106 and 107 tons of detritus, corresponding to 10–50 mm of erosion distributed across the catchment upstream. On 20 September 2002, the Kolka “glacier disaster” mobilized 2 × 108 tons of debris, corresponding to ≥ 400 mm of erosion in the upper Genaldon valley. To quantify the intrinsic capacity of different bedrock types to generate sand isolated from such a strong focused-erosion effect, we used the normalized steepness index ksn as a proxy of erosion rate and thus redefined the sand generation index as SGI*= [Formula presented] [Formula presented] [Formula presented]. More realistic values are thus obtained, although far more comprehensive data on sediment load than those presently available are required to discriminate robustly between the effect of focused-erosion versus lithological control on sand generation. © 2019 Elsevier B.V.
关键词	Baksan and Terek rivers Channel steepness and erosion rates Debris flows and glacial-lake outburst floods Elbrus and Kazbek volcanoes Provenance and sediment budgets Sand generation index SGI*Sedimentary petrography and heavy minerals
英文关键词	debris flow; erosion rate; glacial lake; heavy mineral; outburst; petrography; provenance; sand; sediment budget; Baksan River; Caspian Sea; Kabardino-Balkaria; Mount Elbrus; Russian Federation; Terek River
语种	英语
来源期刊	Earth Science Reviews
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/203915
作者单位	Laboratory for Provenance Studies, Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milano, 20126, Italy
推荐引用方式 GB/T 7714	Vezzoli G.,Garzanti E.,Limonta M.,et al. Focused erosion at the core of the Greater Caucasus: Sediment generation and dispersal from Mt. Elbrus to the Caspian Sea[J],2020,200.
APA	Vezzoli G.,Garzanti E.,Limonta M.,&Radeff G..(2020).Focused erosion at the core of the Greater Caucasus: Sediment generation and dispersal from Mt. Elbrus to the Caspian Sea.Earth Science Reviews,200.
MLA	Vezzoli G.,et al."Focused erosion at the core of the Greater Caucasus: Sediment generation and dispersal from Mt. Elbrus to the Caspian Sea".Earth Science Reviews 200(2020).