高能洪水沉积研究综述

第四纪巨型堰塞湖溃决产生的高能洪水是地球及其他星球上已知规模最大的陆地淡水事件.越来越多的研究证明高能洪水事件具有普遍性,广泛发育于欧亚大陆、北美洲和南美洲等地区.研究者发现不同地区高能洪水事件的沉积特征具有一定的共性,但其典型沉积序列却依然缺失.本文首先回顾了全球已报道高能洪水案例并介绍了高能洪水的定义,总结了高能洪...

The sedimentology of high-energy outburst flood deposits: an overview

Discoveries of cataclysmic glacial lake outburst floods have expanded the scale and frequency of known mass transport events on Earth and other planets. It has been realized that sedimentary deposits related to high-energy freshwater floods are widespread across continents and these deposits share some commonalities when compared carefully. However, the identification and sophisticated reconstruction of these high-energy flood events require well-conditioned stratigraphic models of depositional successions, yet such models are still lacking. Thus, the primary purpose of this paper is to examine and condense the published stratigraphic and sedimentological evidence to identify the key signatures of megaflood successions. The deposits are often the only record of a flood; therefore, the secondary purpose is to interpret the sedimentary sequences in order to reconstruct the behavior and dynamics of a single and multiple flood events. The deposits of high-energy floods are usually massive and extensive, exhibiting sedimentary structures such as amalgamation, rhythmicity, outsized clasts, intraclasts, and obstacle marks. Typical sedimentary successions of high-energy floods include basal coarse parallel-bedded units, large-scale clinoforms, horizontally bedded thin laminated units, ripple and dune cross-beds, silt beds, and debris flow deposits. Such a succession is usually dominated by high concentration suspension rain-outs, representing a single cycle of waxing and waning flood flow. Clay and silt are generally sparse or absent and are transported further down the system. At the scale of the hydrograph, the successions indicate that flows initially accelerate and then decelerate, with significantly shorter periods of flow pulses also evident in the sedimentary signatures.