DOI: 10.1016/j.gloplacha.2015.11.004
论文题名: Streamlined islands and the English Channel megaflood hypothesis
作者: Collier J.S. ; Oggioni F. ; Gupta S. ; García-Moreno D. ; Trentesaux A. ; De Batist M.
刊名: Global and Planetary Change
ISSN: 0921-8181
出版年: 2015
卷: 135 起始页码: 190
结束页码: 206
语种: 英语
英文关键词: Catastrophic flooding
; North-west European glaciations
; Streamlined islands
Scopus关键词: Erosion
; Floods
; Flow of water
; Glacial geology
; Limestone
; Surficial sediments
; Catastrophic floods
; Internal structure
; Length-to-width ratio
; North-west European glaciations
; Sediment movement
; Short-term effects
; Southern North Sea
; Streamlined islands
; Landforms
英文摘要: Recognising ice-age catastrophic megafloods is important because they had significant impact on large-scale drainage evolution and patterns of water and sediment movement to the oceans, and likely induced very rapid, short-term effects on climate. It has been previously proposed that a drainage system on the floor of the English Channel was initiated by catastrophic flooding in the Pleistocene but this suggestion has remained controversial. Here we examine this hypothesis through an analysis of key landform features. We use a new compilation of multi- and single-beam bathymetry together with sub-bottom profiler data to establish the internal structure, planform geometry and hence origin of a set of 36 mid-channel islands. Whilst there is evidence of modern-day surficial sediment processes, the majority of the islands can be clearly demonstrated to be formed of bedrock, and are hence erosional remnants rather than depositional features. The islands display classic lemniscate or tear-drop outlines, with elongated tips pointing downstream, typical of streamlined islands formed during high-magnitude water flow. The length-to-width ratio for the entire island population is 3.4 ± 1.3 and the degree-of-elongation or k-value is 3.7 ± 1.4. These values are comparable to streamlined islands in other proven Pleistocene catastrophic flood terrains and are distinctly different to values found in modern-day rivers. The island geometries show a correlation with bedrock type: with those carved from Upper Cretaceous chalk having larger length-to-width ratios (3.2 ± 1.3) than those carved into more mixed Paleogene terrigenous sandstones, siltstones and mudstones (3.0 ± 1.5). We attribute these differences to the former rock unit having a lower skin friction which allowed longer island growth to achieve minimum drag. The Paleogene islands, although less numerous than the Chalk islands, also assume more perfect lemniscate shapes. These lithologies therefore reached island equilibrium shape more quickly but were also susceptible to total erosion. Our observations support the hypothesis that the islands were initially carved by high-water volume flows via a unique catastrophic drainage of a pro-glacial lake in the southern North Sea at the Dover Strait rather than by fluvial erosion throughout the Pleistocene. © 2015 Elsevier B.V. URL: https://www.scopus.com/inward/record.uri?eid=2-s2.0-84954169340&doi=10.1016%2fj.gloplacha.2015.11.004&partnerID=40&md5=8de5ba337f2d9a3f877fab203bfef5ec
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/11454
Appears in Collections: 全球变化的国际研究计划 气候变化与战略
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作者单位: Dept. Earth Science and Engineering, Imperial College London, Prince Consort Road, United Kingdom
Recommended Citation:
Collier J.S.,Oggioni F.,Gupta S.,et al. Streamlined islands and the English Channel megaflood hypothesis[J]. Global and Planetary Change,2015-01-01,135.