A geochemical and sedimentary record of high southern latitude Holocene climate evolution from Lago Fagnano, Tierra del Fuego
A geochemical and sedimentary record of high southern latitude Holocene climate evolution from Lago Fagnano, Tierra del Fuego
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火地岛法尼亚诺湖高南纬全新世气候演化的地球化学和沉积记录
DOI：
10.1016/j.epsl.2010.11.011
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发表时间：
2011
影响因子：
5.3
通讯作者：
F. Anselmetti
中科院分区：
文献类型：
--
作者：
C. Moy;R. Dunbar;T. Guilderson;N. Waldmann;D. Mucciarone;C. Recasens;D. Arizteguí;J. Austin;F. Anselmetti
火地岛位于半球西风带的南缘，紧邻南极极地锋带以北，处于监测南高纬度海洋-大气系统耦合变化的有利位置。在这里，我们描述了从 Lago Fagnano（南纬 55°火地岛南部的一个大湖）沉积岩芯中获得的全新世古气候记录，以调查与全球气候系统这两个重要特征相关的过去气候变化。我们使用基于花粉浓缩物的过去 8000 年的 AMS 放射性碳年表，从而避免来自基岩衍生褐煤的污染。我们的年代学与全新世哈德逊火山喷发中期沉积物的年代学年龄一致。将大量有机同位素（δ13C 和 δ15N）和元素（C 和 N）参数与物理沉积物特性相结合，使我们能够更好地了解沉积物来源和迁移机制，并解释过去 8000 年的全新世气候和构造变化。 C/N 比、碳积累率和磁化率的协变性和长期趋势反映了全新世向东部盆地深处输送陆地有机和成岩物质的总体增加。我们将这种变化归因于西风引起的降水。全新世晚期风力增强和降水增加，驱使黄毛榉森林向东移动，增加了径流和对湖泊的陆源输入。叠加在长期趋势上的是 C/N 比的一系列突然的 9 个负偏差，这限制了记录中地震驱动的质量流事件的存在。我们发现，在 7000 至 5000calyr BP 之间，总体 δ13C 有所增加，我们将其归因于夏季气温升高所驱动的水产生产力的提高。 Lago Fagnano δ13C 记录与中纬度智利大陆架的全新世海面温度记录和东南极洲泰勒圆顶冰芯记录的南极气温记录有相似之处。整个南极锋带同时发生了全新世中期变暖，特别是在目前受南极绕极流影响的地区。
Situated at the southern margin of the hemispheric westerly wind belt and immediately north of the Antarctic Polar Frontal zone, Tierra del Fuego is well-positioned to monitor coupled changes in the ocean–atmosphere system of the high southern latitudes. Here we describe a Holocene paleoclimate record from sediment cores obtained from Lago Fagnano, a large lake in southern Tierra del Fuego at 55°S, to investigate past changes in climate related to these two important features of the global climate system. We use an AMS radiocarbon chronology for the last 8000yr based on pollen concentrates, thereby avoiding contamination from bedrock-derived lignite. Our chronology is consistent with a tephrochronologic age date for deposits from the middle Holocene Volcán Hudson eruption. Combining bulk organic isotopic (δ13C and δ15N) and elemental (C and N) parameters with physical sediment properties allows us to better understand sediment provenance and transport mechanisms and to interpret Holocene climate and tectonic change during the last 8000yr. Co-variability and long-term trends in C/N ratio, carbon accumulation rate, and magnetic susceptibility reflect an overall Holocene increase in the delivery of terrestrial organic and lithogenic material to the deep eastern basin. We attribute this variability to westerly wind-derived precipitation. Increased wind strength and precipitation in the late Holocene drives the Nothofagus forest eastward and enhances run-off and terrigenous inputs to the lake. Superimposed on the long-term trend are a series of abrupt 9 negative departures in C/N ratio, which constrain the presence of seismically-driven mass flow events in the record. We identify an increase in bulk δ13C between 7000 and 5000calyr BP that we attribute to enhanced aquatic productivity driven by warmer summer temperatures. The Lago Fagnano δ13C record shows similarities with Holocene records of sea surface temperature from the mid-latitude Chilean continental shelf and Antarctic air temperatures from the Taylor Dome ice core record in East Antarctica. Mid-Holocene warming occurred simultaneously across the Antarctic Frontal Zone, and in particular, in locations currently influenced by the Antarctic Circumpolar Current.