Evidence of high-energy events in the geological record: Mid-holocene evolution of the southwestern Doñana National Park (SW Spain)
Evidence of high-energy events in the geological record: Mid-holocene evolution of the southwestern Doñana National Park (SW Spain)
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地质记录中高能事件的证据：西南多尼亚纳国家公园（西班牙西南部）的全新世中期演化
DOI：
10.1016/j.palaeo.2005.06.023
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
M. Pozo
中科院分区：
文献类型：
--
作者：
F. Ruiz;A. Rodríguez;L. Cáceres;J. R. Vidal;M. Carretero;M. Abad;M. Olías;M. Pozo
四个阶段区分在中全新世的演变西南部多尼亚纳国家公园（西南西班牙），基于多学科研究的沉积物在钻孔岩心。在最古老的阶段（> 5500 - 5400 cal. years BP），一个沿海的咸水泻湖占据了研究区域的中部，部分被Doñana Spit封闭，并受到河流堤坝的限制。在同一阶段，靠近Doñana沙嘴内侧的地区的特点是从潮下带到潮间带的演变。下一阶段（距今5400 - 5200 cal. years BP）的特征是高能量事件（海啸？），这导致了多尼亚纳沙嘴的突破，并在内部地区形成了新的沿岸的分支。在第三阶段的第一阶段（距今5200 - 4200 cal.years），河口充填可能是主要的过程，在泻湖床的层状硅酸盐丰富的粘土的积累。随后是一个新的不稳定阶段（距今约4200 - 4100 cal.年），这表明存在精细的风暴沉积物和较厚的，可能是海啸引起的贝壳沉积物。最后一个阶段（距今4100 - 3700 cal. years）包括：a）一个充填期，海洋影响减弱;和B）两个新的高能事件，导致Doñana沙嘴的侵蚀和新贝壳堤的形成。在过去的7000年中，这些结果与地质和历史记录的修订进行比较，揭示了在葡萄牙和西班牙南部发生的20次海啸（至少）。这些高能事件的证据是冲刷扇、盐沼沉积物中的生物碎屑粗粒层或巨大巨石和卵石的存在。由于数据非常稀少，很难确定重现周期，尽管我们的数据和其他作者没有放弃两个事件相隔300 - 400年的周期可能为2000年。
Four phases are distinguished in the Mid-Holocene evolution of the southwestern Doñana National Park (SW Spain), based on the multidisciplinary study of sediments in drill cores. In the oldest phase (>5500–5400 cal. years BP), a coastal, brackish lagoon occupied the central part of the study area, partly enclosed by the Doñana spit and limited by fluvial levees. An evolution from subtidal to intertidal conditions characterized the areas located close to the inner side of the Doñana spit during the same phase. The following phase (∼5400–5200 cal. years BP) is characterized by a high-energy event (tsunami?), which caused the breakthrough of the Doñana spit and the creation of new littoral strands in the inner areas. In the first period of the third phase (∼5200–4200 cal. years BP), estuarine infilling was probably the dominant process, with the accumulation of phyllosilicate-rich clays in the lagoon bed. This was followed by a renewed phase of instability (∼4200–4100 cal. years BP) indicated by the presence of fine storm-lain deposits and thicker, probably tsunami-induced shelly deposits. The last phase (∼4100–3700 cal. years BP) comprises: a) an infilling period, with a diminution of the marine influence; and b) two new high-energy events, which caused the erosion of the Doñana spit and the creation of new cheniers. In the last 7000 years, the comparison of these results with a revision of both geological and historical records has revealed the occurrence of twenty tsunamis (at least) during this period in Portugal and southern Spain. Evidences of these high-energy events are washover fans, bioclastic coarse-sized layers within salt marsh deposits or the presence of giant boulders and pebbles. The determination of the recurrence period is very difficult owing to the very scarce data, although our data and other authors do not discard a possible periodicity of 2000 years for a cycle of two events separated by 300–400 years.