Abstract The Beagle Channel crosses the southernmost tip of South America (Tierra del Fuego), connecting the South Atlantic with the Southeastern Pacific. Raised beaches occur up to 10 m above mean sea level (m a.m.s.l.), especially along the northern (Argentinian) shore, and have been dated using marine shells. The southern (Chilean) shore is well-known for its abundance of shell middens at different levels above the present shore, particularly along the island of Isla Navarino, but the relative sea level history in this glacially impacted landscape has not previously been investigated. In this study we present postglacial relative sea level changes on Isla Navarino, based on sediment cores from six lagoons, bogs or lakes, and stratigraphic investigations of three open sections, of which one is of MIS 5e age. In addition, one core from a lagoon in the south-western Beagle Channel has been analysed and a system of terraces was mapped in the north-western Beagle Channel. The analyses of the core sites have resulted in two tentative relative sea level curves, displaying a rapid sea level rise at 8500−6500 cal yr BP, amounting to ∼10 and 14 m in eastern and western Isla Navarino, respectively, and reaching levels of ∼8 and > 10 m, respectively, followed by a slow relative sea level fall. Our sea level observations have been compared with a range of modelling results of glacial-isostatic adjustments (GIA) for estimating timing of deglaciation and ice sheet thicknesses. Based mainly on the GIA modelling of the altitude of the MIS 5e beach sediments, situated at 13 m, we can conclude that no other uplift than GIA is needed to explain their altitude. Regarding the modelling of postglacial sea levels we can conclude that no model has been found that satisfies all of the observational evidence, but that deglaciation most likely preceded Northern Hemisphere main deglaciation by at least 3 kyr, which agrees with the deglaciation age of Isla Navarino (>16 000 cal yr BP). In addition, our model runs imply that the Patagonian and Tierra del Fuego ice sheet thicknesses were in the order of ∼1500 m.

中文翻译：

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智利火地岛比格尔海峡的相对海平面变化和冰川均衡模型：冰川和构造影响

摘要 比格尔海峡横跨南美洲最南端（火地岛），连接南大西洋和东南太平洋。凸起的海滩最高可达平均海平面 (m amsl) 以上 10 m，尤其是在北部（阿根廷）海岸，并且已使用海洋贝壳进行了测年。南部（智利）海岸以其在当前海岸以上不同高度的丰富贝壳而闻名，特别是在纳瓦里诺岛沿岸，但以前没有研究过这个受冰川影响的景观中的相对海平面历史。在这项研究中，我们基于来自六个泻湖、沼泽或湖泊的沉积物核心以及三个开放部分的地层调查，其中一个属于 MIS 5e 时代，展示了纳瓦里诺岛冰后相对海平面的变化。此外，已经分析了比格尔海峡西南部泻湖的一个核心，并在比格尔海峡西北部绘制了一个阶地系统。对核心站点的分析产生了两条暂定的相对海平面曲线，显示在 8500-6500 cal BP 时海平面迅速上升，分别在纳瓦里诺岛东部和西部上升了约 10 米和 14 米，并达到了分别为~8 和 > 10 m，随后相对海平面缓慢下降。我们已经将我们的海平面观测结果与冰川均衡调整 (GIA) 的一系列建模结果进行了比较，以估计冰川消融时间和冰盖厚度。主要基于 MIS 5e 海滩沉积物高度的 GIA 模型（位于 13 m），我们可以得出结论，除了 GIA 不需要其他隆起来解释它们的高度。关于冰后海平面的建模，我们可以得出结论，没有发现满足所有观测证据的模型，但冰消期很可能比北半球主要冰消期早至少 3 kyr，这与纳瓦里诺岛的冰消期年龄一致（ >16 000 cal yr BP）。此外，我们的模型运行意味着巴塔哥尼亚和火地岛冰盖的厚度约为 1500 m。