【摘要】 综述海啸沉积特征,认为岸上细粒海啸沉积物具有以下特点:(1)地层层序上向上变细、减薄;(2)水流方向的重复反向(即重复的双向水流);(3)含有撕裂的碎屑;(4)较差的分选性;(5)向陆地延伸更远;但将以上任何单一特征看成是海啸沉积的特征性依据都是不恰当的,需要将以上特征结合起来判断,才能作为海啸沉积的依据。而有关岸上巨砾的海啸或是风暴来源,至今仍争论不清,但较一致认为巨砾堤坝复合体是风暴成因。浅水碎屑海啸岩通常为夹在低能稳定状态的背景沉积粉砂—黏土层内的一套独特砂层,可以根据海啸能量的增加到衰减分为Tna—Tnd四个不同单元;而地震海啸岩通常具有震积岩—海啸岩的沉积序列;碳酸盐海啸岩则显示了与海啸入射流和回流相关的冲刷—充填结构。深海的海啸沉积作用机制仍然不清。尽管海啸传播阶段可以产生地中海A型均质岩,但深海海啸岩可能主要与海啸回流有关,如目前讨论最多的K—T撞击海啸岩。尽管目前的研究促进了对海啸的认识,但存在诸如海啸沉积机制仍然不明确,海啸沉积识别依然困难等许多问题,海啸沉积学的进一步发展将为解决这些问题提供坚实基础。更多还原

【Abstract】 Tsunamis are catastrophic events in a process of evolution of the Earth.Tsunami deposits is benefit for correctly recognizing tsunami behavior and reducing hazard and also is an important subject in the geosciences for understanding the whole truth of natural phenomena and history of the Earth.A tsunami is a water wave train triggered by submarine earthquake,landslide,bolide impact and volcanism with long wavelengths and long periods which differentiate from other waves.The physics of tsunamis generally link four distinct processes: generation,propagation,inundation of onshore areas and backwash.In general,tsunamis seem unlikely that most earthquake-generated tsunamis can induce a deep water sedimentary imprint,but impact-generated tsunamis may do so close to source when tsunamis propagate from source to coast.Tsunamis erode coast and transport sediments to onshore,shallow water bay and lagoon and are deposited during run-up.Backwash flows follow the maximum landward inundation of individual tsunami waves and are traction flows to seaward.Backwash generally induced not only debris flows and turbidity currents,but also suspended clouds of mud resulting in hemipelagic setting.Because tsunami behavior depends strongly on bathymetric and topographic configurations,tsunami deposits show differences in diverse environment.Detailed sedimentary study had been carried out about onshore fine-grain tsunami deposits and storm deposits to differentiate both.Our composited view is that the deposits characterized by(1) fining and thining upward sequences;(2) repeated bi-directional currents;(3) rip-up clasts;(4) less well sorted grains;(5) large inland extent;although each of these five points of evidence could be attributed to storm or other depositional processes individually,no sedimentary process except tsunami can account for all of them simultaneously.The emplacement of onshore boulders is usually attributed to high-energy events tsunamis or storms,but the interpretation remains unsolved.However,the boulders ridge complexes may be the result of storms.Siliciclastic tsunamiites in shallow water generally show intercalation of exceptionally high-energy regimen into underlying and overlying low-energy fine-grain background deposits and can be divided into 4 different Tna-Tnd units.And earthquake-generated tsunamiites have special characteristics that show seismites-tsunamiites sequences while carbonate tsunamiites show scour-fill structure related to incoming and backwash flows.The sedimentary process of deep sea tusnamiiites remains unclear.Propagation of tsunami can induce deep sea Mediterranean A type homogenite,but deep sea tsunamiites may mainly be related to backwash,for example the current hot topic K-T impact-related tsunamiites.Although current research promotes the understanding of tsunamis,many open questions remain such as the sedimentary process of tsunamis and identification of tsunami deposits.We believe that further development of tsunamis sedimentology will supply sufficient foundation for it.更多还原