Deposition of the 2011-2012 Cordón Caulle tephra (Chile, 40°S) in lake sediments: Implications for tephrochronology and volcanology Tephra deposition in lake sediments
Deposition of the 2011-2012 Cordón Caulle tephra (Chile, 40°S) in lake sediments: Implications for tephrochronology and volcanology Tephra deposition in lake sediments
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2011-2012 年 Cordón Caulle 火山灰（智利，南纬 40°）在湖泊沉积物中的沉积：对火山年代学和火山学的影响 湖泊沉积物中的火山灰沉积
DOI：
10.1002/2014jf003321
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
Bertrand S
中科院分区：
文献类型：
--
作者：
Bertrand S
湖泊沉积物中保存的Tephras通常用于同步气候和环境变化的沉积档案，并将其与陆地环境相关联。它们还提供了重建火山爆发活动的机会，例如，喷发频率和火山扩散。虽然沉积过程可能会影响湖泊中tephras的记录，但湖泊沉积物通常被认为是tephras地层学的最佳档案之一。2011-2012年Cordón Caulle火山（智利，40°S）的喷发为研究影响湖泊中tephra沉积的过程提供了理想的机会。虽然盛行的西风带将喷发的火山碎屑物质从附近的Puyehue湖带走，但在这个相对较大的湖泊内发现了火山碎屑，厚度从1到10厘米不等。这与较小的湖泊形成对比，在较小的湖泊中，火山的厚度与火山灰分布图一致。地貌观测和沉积学分析表明，普耶hue湖沉积的tephra完全由上游流域的再加工物质组成，由河流输送，并根据颗粒大小和密度由湖流分布。我们的研究结果对地表年代学和火山学具有重要意义。他们认为：(1)湖泊不是被动的热圈闭；(2)流域大的湖泊比小湖泊记录的火山喷发次数多，而小湖泊只记录直接的火山灰落下，影响了火山喷发是否会再次发生的结论；(3)系统地利用具有大流域的湖泊进行等层制图会导致对喷发火山体积的高估。排水盆地有限的较小湖泊通常更适合火山学研究。
Tephras preserved in lake sediments are commonly used to synchronize sedimentary archives of climate and environmental change and to correlate them with terrestrial environments. They also provide opportunities to reconstruct volcanic explosive activity, e.g., eruption frequency and tephra dispersal. Although sedimentary processes may affect the record of tephras in lakes, lake sediments are generally considered as one of the best archives of tephra stratigraphy. The 2011–2012 eruption of Cordón Caulle volcano (Chile, 40°S) offered an ideal opportunity to study the processes affecting tephra deposition in lakes. Although the prevailing westerlies transported the erupted pyroclastic material away from nearby Puyehue Lake, the tephra was identified within this relatively large lake with a thickness ranging from 1 to >10 cm. This is in contrast with smaller lakes, where tephra thickness was in agreement with ashfall distribution maps. Geomorphological observations and sedimentological analyses provide evidence that the tephra deposited in Puyehue Lake entirely consists of material reworked from the upper watershed, transported by rivers, and distributed by lake currents according to particle size and density. Our results have important implications for tephrochronology and volcanology. They suggest that (1) lakes do not act as passive tephra traps; (2) lakes with large watersheds record more eruptions than smaller lakes, which only register direct ashfalls, affecting conclusions regarding the recurrence of volcanic eruptions; and (3) using lakes with large watersheds for isopach mapping systematically leads to an overestimation of erupted tephra volumes. Smaller lakes with limited drainage basins are generally better suited for volcanological studies.