Evidence for coseismic subsidence events in a southern California coastal saltmarsh.
Evidence for coseismic subsidence events in a southern California coastal saltmarsh.
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DOI：
10.1038/srep44615
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发表时间：
2017-03-20
影响因子：
4.6
通讯作者：
Aranda A
中科院分区：
文献类型：
--
作者：
Leeper R;Rhodes B;Kirby M;Scharer K;Carlin J;Hemphill-Haley E;Avnaim-Katav S;MacDonald G;Starratt S;Aranda A
来自南加州海岸盐沼的古环境记录揭示了全新世晚期同震沉降事件的重复证据。对沉积物泥芯的实地分析建立了横跨湿地的离散岩石地层单位。详细的沉积物分析揭示了岩性、总有机物百分比、粒度和磁化率的突然变化。微体化石分析表明，主要是淡水沉积物掩埋遗迹潮间带沉积在三个不同的深度。放射性碳年代测定表明，这三次埋葬事件发生在过去的2000年里。这三个事件中有两个与沿纽波特-英格尔伍德/罗斯峡谷断层系统的大规模古地震沿着。从这些数据中，我们推断，在大规模地震的一步，沿沿着断裂带的垂直位移约5平方公里的区域，这是一致的足迹的河口在开发前的地图。这些研究结果提供了深入了解盐沼，同震变形和地震复发在南部加州的广大地区的演变，和敏感的栖息地已经受到海平面上升的威胁。
Paleoenvironmental records from a southern California coastal saltmarsh reveal evidence for repeated late Holocene coseismic subsidence events. Field analysis of sediment gouge cores established discrete lithostratigraphic units extend across the wetland. Detailed sediment analyses reveal abrupt changes in lithology, percent total organic matter, grain size, and magnetic susceptibility. Microfossil analyses indicate that predominantly freshwater deposits bury relic intertidal deposits at three distinct depths. Radiocarbon dating indicates that the three burial events occurred in the last 2000 calendar years. Two of the three events are contemporaneous with large-magnitude paleoearthquakes along the Newport-Inglewood/Rose Canyon fault system. From these data, we infer that during large magnitude earthquakes a step-over along the fault zone results in the vertical displacement of an approximately 5-km2 area that is consistent with the footprint of an estuary identified in pre-development maps. These findings provide insight on the evolution of the saltmarsh, coseismic deformation and earthquake recurrence in a wide area of southern California, and sensitive habitat already threatened by eustatic sea level rise.