Evidence for a mid-Holocene tsunami deposit along the Andaman coast of Thailand preserved in a mangrove environment
Evidence for a mid-Holocene tsunami deposit along the Andaman coast of Thailand preserved in a mangrove environment
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泰国安达曼海岸红树林环境中保存的全新世中期海啸沉积物的证据
DOI：
10.1016/j.margeo.2011.03.003
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发表时间：
2011
期刊：
影响因子：
2.9
通讯作者：
Choowong, Montri
中科院分区：
文献类型：
--
作者：
Rhodes, Brady P.;Kirby, Matthew E.;Jankaew, Kruawun;Choowong, Montri
Klong Thap拉穆是泰国北方安达曼海岸沿着的一个大型红树林潮汐通道，它为检验古海啸记录可以保存在红树林沉积物中的假设提供了理想的地点。2004年的印度洋海啸摧毁了当地大片的红树林，这些红树林的宽度变化很大-高达300米。海啸过后留下的是一层薄薄的覆盖层，由横向不连续的沙子、浸软的贝壳和局部的珊瑚碎石组成，这些碎石正迅速混入下面的红树林泥炭中。经过海啸改造的海峡海岸的横断面显示，在未受干扰的红树林边界处，沙层突然变薄，这表明波浪的能量在进入森林时迅速消散。2004年海啸存款（单元tI）的分布和沉积学表明，任何古海啸存款在这个红树林环境中应空间限制和彻底的生物扰动。从2004年海啸区内收集的沉积物芯穿透了内陆逐渐变细的埋藏珊瑚壳泥炭单元（单元tIII）。单元tIII与单元tI惊人地相似，除了单元tIII的扩散沉积学，我们将其归因于广泛的生物扰动。单元tIII还横切了一个确定的相边界，该边界可在2004年海啸带的整个宽度范围内追踪。而不是一个相边界与区域早至晚全新世海平面回归，地层对比表明，单位tIII代表一个事件视界（即海啸）。AMS 14 C从单元tIII内的材料结合上括号年龄的日期表明，海啸事件发生在2720年和4290年之间的某个时候。如果正确的话，这次海啸早于在Koh Phra Thong北部确认的3-4次海啸事件。然而，单元tIII是一个潜在的远场相当于最近承认的古海啸存款在西南印度海岸约。距今3,710年（Nair et al.，2010年）。
Klong Thap Lamu, a large mangrove-fringed tidal channel along the northern Andaman Coast of Thailand, provides an ideal location to test the hypothesis that a paleotsunami record can be preserved in the sediments of a mangrove forest. The 2004 Indian Ocean tsunami destroyed local swaths of mangrove forest with highly variable widths — up to 300 m. Left in the wake of the tsunami is a thin mantling of laterally discontinuous sand, macerated shells, and localized coral rubble that is being mixed rapidly into the underlying mangrove peat. Transects across the channel's tsunami-modified shore show that the sand layer thins abruptly at the border of the undisturbed mangroves, suggesting that the energy of the wave dissipated quickly as it entered the forest. The distribution and sedimentology of the 2004 tsunami deposit (Unit tI) suggest that any paleotsunami deposit within this mangrove environment should be spatially restricted and thoroughly bioturbated. Sediment cores collected from within the 2004 tsunami zone penetrate a buried coral-shell peat unit (Unit tIII) that tapers inland. Unit tIII is strikingly similar to Unit tI, except for Unit tIII's diffuse sedimentology, which we attribute to extensive bioturbation. Unit tIII also cross-cuts an identified facies boundary that is traceable across the width of the 2004 tsunami zone. Rather than a facies boundary associated with the regional early-to-late Holocene sea level regression, stratigraphic correlations suggest that Unit tIII represents an event horizon (i.e. tsunami). AMS14C dates on material from within Unit tIII combined with an upper bracketing age suggest that the tsunami event occurred sometime between 2720 and 4290 cy BP. If correct, this tsunami predates the 3–4 tsunami events recognized to the north at Koh Phra Thong. Unit tIII is, however, a potential far-field equivalent of a recently recognized paleotsunami deposit on the southwestern Indian coast ca. 3,710 years before present (Nair et al., 2010).