Collaborative Research: Linking climate-driven changes in erosion to tectonic processes along the southern Alaska Margin

合作研究：将气候驱动的侵蚀变化与阿拉斯加南部边缘的构造过程联系起来

• 批准号: 1435121
• 负责人: Sean Gulick
• 金额: $ 5.22万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1435121&HistoricalAwards=false
• 关键词: Collaborative; Research; Linking; climate; driven

One of the most challenging questions in active mountain building is how climate might drive tectonic processes, in the form of mass redistribution. In other words, do climate-driven changes in erosion lead to increased exposure of mountainous belts, and perhaps influence tectonic processes, like uplift and faulting, as predicted by numerical models? The study of this question, by means of observational and analytical data is challenging because most areas where active mountain building is occurring are covered by remnant glaciers and glaciated landscapes from the end of the Neogene period (23 ? 2.5 million years ago). The St. Elias mountain belt, in southeast Alaska, is a prime location to address this question due to its extensive glaciation. The recent erosional record of this active mountain range is stored in the Gulf of Alaska and was recovered during Integrated Ocean Drilling Program (IODP) Expedition 341. Integrated analysis of deep-sea core material obtained from drilling at the continental shelf, slope, and the deep-sea Surveyor Fan will provide means to quantify the effect of global and local climate changes on the erosional and structural evolution of a mountain range. The youthfulness of the St. Elias belt, along with high rates of tectonic and erosional processes, and its close proximity of the Gulf of Alaska provide an ideal natural setting to study climate-tectonic interactions. Long-standing debates exist in the Earth sciences on whether Neogene climate change affects rates of surface processes, such as erosion, and consequently influences tectonic processes, such as faulting, through redistribution of mass. The proposed study will test the hypothesis that an increase in glacial erosion has led to focused exhumation in the core of the St. Elias orogeny as proposed by numerical and analytical data. Two possible target regions have been suggested where a tectonic-climate feedback may have developed: in the fold-thrust belt and at the indenting Yakutat plate corner. The wealth of existing onshore geo- and thermochronological data provide a comprehensive picture of the current spatial pattern of exhumation rates, but the quantification of changes in rates and patterns through time has been challenging. The research team?s approach is to investigate the offshore sedimentary record of the St. Elias orogeny deposited in the Gulf of Alaska. This orogeny developed during a period of significant global climate change, including the intensification of Northern Hemisphere glaciation (iNHG) at the Plio-Pleistogene transition (PPT), ~2.6 Ma, and the mid-Pleistocene transition (MPT) from 1.2 to 0.7 Ma, but also a change of local climate resulting in alpine glaciers, perhaps as early as the Late Miocene/Pliocene (6.5 Ma). The high-resolution magnetostratigraphic and biostratigraphic age control from the IODP Expedition 341 cores allow close linking of changes in sedimentary lithofacies and textures, provenanace, exhumation, and sediment routing and distribution, to test the record of climate-tectonic interactions along the southern Alaska margin. The integration of Gulf of Alaska seismic reflection data with the age and provenance control from the 341 cores allow examination of sediment mass flux in the regional offshore depositional system, the Surveyor Fan, from a 3-D perspective through time.

积极造山活动中最具挑战性的问题之一是气候如何以大规模重新分配的形式驱动构造过程。换句话说，气候驱动的侵蚀变化是否会导致山区暴露增加，并可能影响构造过程，如数值模型预测的隆起和断层？通过观测和分析数据来研究这个问题具有挑战性，因为大多数正在发生活跃造山活动的地区都被新近纪末期（23 – 250 万年前）的残余冰川和冰川景观所覆盖。阿拉斯加东南部的圣埃利亚斯山脉由于其广泛的冰川作用，是解决这个问题的最佳地点。这座活动山脉的最新侵蚀记录保存在阿拉斯加湾，并在综合海洋钻探计划 (IODP) 第 341 次探险期间恢复。对从大陆架、斜坡和海底钻探获得的深海岩心材料进行综合分析深海测量员范将提供量化全球和当地气候变化对山脉侵蚀和结构演化影响的方法。圣埃利亚斯带年轻，构造和侵蚀过程发生率高，而且靠近阿拉斯加湾，为研究气候与构造相互作用提供了理想的自然环境。地球科学界长期以来一直存在争论，即新近纪气候变化是否会影响地表过程（例如侵蚀）的速率，从而通过质量的重新分配影响构造过程（例如断层）。拟议的研究将检验数值和分析数据提出的假设，即冰川侵蚀的增加导致圣埃利亚斯造山运动核心的集中折返。已经提出了两个可能形成构造气候反馈的可能目标区域：褶皱逆冲带和缩进的雅库塔特板块角部。现有丰富的陆上地质和热年代学数据提供了当前折返率空间模式的全面图景，但对随时间变化的速率和模式的变化进行量化一直具有挑战性。研究小组的方法是调查阿拉斯加湾圣埃利亚斯造山运动的近海沉积记录。这种造山运动是在全球气候发生重大变化的时期发展起来的，包括北半球冰川作用（iNHG）在上皮奥-更新世过渡期（PPT）约2.6 Ma和中更新世过渡期（MPT）从1.2 Ma到0.7 Ma期间的加剧，而且当地气候的变化导致高山冰川的形成，可能早在晚中新世/上新世（6.5 Ma）。 IODP Expedition 341 岩心的高分辨率磁性地层和生物地层年龄控制可以将沉积岩相和结构、物源、折返以及沉积物路线和分布的变化紧密联系起来，以测试沿阿拉斯加南部边缘的气候-构造相互作用的记录。将阿拉斯加湾地震反射数据与 341 个岩心的年龄和来源控制相结合，可以从 3D 角度随时间变化检查区域近海沉积系统（Surveyor Fan）中的沉积物质量通量。