Sedimentary record of late Holocene event beds in a mid-ocean atoll lagoon, Maldives, Indian Ocean: Potential for deposition by tsunamis
Sedimentary record of late Holocene event beds in a mid-ocean atoll lagoon, Maldives, Indian Ocean: Potential for deposition by tsunamis
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DOI：
10.1016/j.margeo.2013.11.014
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发表时间：
2014-02
期刊：
影响因子：
2.9
通讯作者：
L. Klostermann;E. Gischler;D. Storz;J. Hudson
中科院分区：
文献类型：
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作者：
L. Klostermann;E. Gischler;D. Storz;J. Hudson
在马尔代夫Rasdhoo环礁泻湖（4°N, 73°W）中发现了6个全新世沉积事件（年龄范围为420-890年、890-1560年、2040-2340年、2420-3380年、3890-4330年和5480-5760年），从而强调了环礁泻湖作为环境变化潜在记录的重要性。全新世海岸沉积物已作为过去海啸和风暴事件的档案进行了研究，但对海洋中部环礁泻湖的可比沉积学研究很少。在过去6.5年的10个以泥岩、尾岩和浮石为背景沉积特征的震核中，我们发现了两种类型的事件沉积：(1)几厘米厚的粗糙岩层，其中有像acroporasp这样的再沉积珊瑚。andSeriatoporasp。(2)由珊瑚红藻、礁有孔虫（如Amphisteginaspp.、Calcarinasp.）和再沉积的珊瑚碎片等珊瑚礁衍生成分组成的薄层（几毫米）的尾岩、浮石和硬石。这两种类型的事件层可能在几个核之间相互关联，我们将其解释为海啸沉积。六个事件中的五个在泰国、苏门答腊岛和印度海岸有时间上的对应。在靠近赤道的马尔代夫，没有记录到1-5级台风，但只有热带低气压和风暴作为沉积事件的潜在触发因素很少发生。印尼西部发生的大地震引发的海啸可能会波及印度洋的大部分地区，这是很常见的。
Six Holocene sedimentary events (ranging in age from 420–890, 890–1560, 2040–2340, 2420–3380, 3890–4330, and 5480–5760 yrs BP) have been identified in the lagoon of Rasdhoo Atoll (Maldives; 4°N, 73°W), thereby underlining the importance of atoll lagoons as potential archives of environmental change. Holocene coastal sediments have been studied as archives for past tsunami and storm events but comparable sedimentological studies of mid-ocean atoll lagoons are rare. In ten vibracores covering the past 6.5 kyrs that are characterized by mudstone, wackestone, and floatstone background sedimentation, we found two types of event deposits: (1) several cm thick rudstone layers with redeposited corals likeAcroporasp. andSeriatoporasp., which derive from the marginal and/or lagoonal reefs and have been transported into the lagoon and (2) thin (several mm) layers of wackestone, floatstone, and rudstone consisting of reef-derived components like coralline red algae, reef foraminifera (e.g.,Amphisteginaspp.,Calcarinasp.), and redeposited coral fragments. Both types of event layers may be correlated among several cores, which we interpret as tsunami deposits. Five of the six events have temporal counterparts identified at the coasts of Thailand, Sumatra, and India. In the Maldives, close to the equator, no category 1–5 typhoons were recorded, but only tropical depressions and storms as potential triggers of event sedimentation have occurred rarely. Major earthquakes off western Indonesia and generated tsunamis, which potentially reach most parts of the Indian Ocean, are common.