The evolution of western Arctic landscape during the past 5 million years

在过去的500万年里，除了冰川侵蚀之外，没有什么比加拿大北极群岛西部波弗特组沉积楔的沉积和切割更剧烈的北极景观变化了。沉积物从东部被侵蚀，沉积在西部岛屿上，进入加拿大盆地和波弗特海。其结果是形成了一个巨大的楔形河流沉积物，从育空地区延伸到美根岛1200多公里。近海的沉积物厚度超过3公里，分隔岛屿的河道在同期的高海平面以上被填满。因为这发生在相对温暖的全球气候中，当水不再通过CAA循环以冷却岛屿时，沉积物与森林床互层，并支持各种动植物，包括铁杉和骆驼。收集和分析这些北极古环境变化记录的重大努力已经证明，例如，北极气候是多么敏感（由于各种海冰和其他反馈，全球变暖2°C转化为埃尔斯米尔岛的15°C变暖）。但全球变暖是引发如此大规模景观反应的唯一必要条件吗？构造过程、海平面变化和西缘沉降是否起主要作用？提出的研究旨在显著改善波弗特组的年代学和类似年龄的沉积物围绕西部CAA。这将有助于将许多孤立的古环境记录纳入一个时间框架，并将古气候记录中的差异与时间差异或空间变化联系起来。此外，精确的年代学将提供一种手段：1)检验关于碎屑楔块沉积和切割控制的假设；2)将沿海沉积物与内陆高阶地和淹没的加拿大盆地陆架沉积物联系起来；3)评估什么样的反馈（海冰、古海洋门户的打开）对于如此重大的景观和环境变化是必要的。除了对我们对这些事件的理解产生重大影响外，对沉积物通量和过程速率的了解将为用于评估碳氢化合物潜力的北冰洋沉积模型提供信息。

Besides glacial erosion, there is no other more dramatic change in Arctic landscape in the past 5 million years than the deposition and incision of the Beaufort Formation sedimentary wedge in the western Canadian Arctic Archipelago (CAA). Sediments were eroded from the east and deposited onto western islands and into the Canada Basin and Beaufort Sea. The result was a voluminous wedge of stream sediments that extended over 1200 km from the Yukon to Meighen Island. Sediment thicknesses reach more than 3 km offshore, and the channels that separate the islands were filled above the contemporaneous high sea level. Because this occurred during a relatively warm global climate when water no longer circulated through the CAA to cool the island, the sediments were interbedded with forest beds and supported a wide variety of flora and fauna, including hemlock and camels. The significant effort to collect and analyse these records of Arctic paleoenvironmental change has demonstrated, for instance, how sensitive the Arctic climate is (2°C of global warming translates to 15°C warming on Ellesmere Island, due to various sea ice and other feedbacks). But was global warming the only condition necessary to trigger such a wide-scale landscape response? Did tectonic processes, sea level change, and subsidence of the western margin play primary roles? The proposed research aims to significantly improve the chronology of the Beaufort Formation and similarly-aged sediments around the western CAA. This will help place the many isolated paleoenvironmental records into a chronological framework and link disparities in the paleoclimate records to temporal differences or spatial variation. Further, a precise chronology will provide a means to i) test hypotheses regarding the controls on deposition and incision of the clastic wedge, ii) relate the coastal sediments to high terraces inland and submerged Canada Basin shelf sediments, and iii) evaluate what feedbacks (sea ice, opening of paleoceanographic gateways) were necessary for such a significant landscape and environmental change. Besides a significant impact on our understanding of these events, the insights into sediment flux and rates of the processes will inform models of Arctic Ocean sedimentation used for evaluating hydrocarbon potential.