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

在活跃的造山运动中，最具挑战性的问题之一是气候如何以物质再分布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像数值模型预测的那样，导致山地带暴露程度增加，并可能影响隆起和断层等构造过程？通过观测和分析数据来研究这个问题是具有挑战性的，因为大多数正在发生活跃造山活动的地区都被新第三纪末期的残余冰川和冰川景观所覆盖。250万年前)。位于阿拉斯加东南部的圣伊莱亚斯山带，由于其广泛的冰川作用，是解决这个问题的最佳地点。这个活跃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）远征341期间恢复。对大陆架、斜坡和深海测量员Fan号钻探获得的深海岩心材料进行综合分析，将为量化全球和当地气候变化对山脉侵蚀和结构演变的影响提供手段。年轻的圣伊莱亚斯带，伴随着高速率的构造和侵蚀过程，它靠近阿拉斯加湾，为研究气候-构造相互作用提供了理想的自然环境。关于新近纪气候变化是否会影响地表过程（如侵蚀）的速率，从而通过物质的再分配影响构造过程（如断层），地球科学中存在着长期存在的争论。拟议的研究将检验这样一种假设，即冰川侵蚀的增加导致在圣埃利亚斯造山运动的核心集中挖掘，这是由数值和分析数据提出的。提出了构造-气候反馈可能发育的两个目标区域：褶皱冲断带和雅库塔板块缩进角。丰富的陆地地质和热年代学数据提供了当前挖掘率空间格局的全面图景，但对挖掘率和模式随时间变化的量化一直具有挑战性。研究小组？他的方法是研究阿拉斯加湾圣埃利亚斯造山带的近海沉积记录。这一造山运动发生在全球气候显著变化时期，包括上新世-更新世过渡时期（PPT）的北半球冰川（iNHG）强化（~2.6 Ma）和中更新世过渡时期（MPT） （1.2 ~ 0.7 Ma），以及早在晚中新世/上新世时期（6.5 Ma）的局部气候变化导致高山冰川的形成。来自IODP远征341岩心的高分辨率磁地层学和生物地层学时代控制使得沉积岩相和结构、物源、挖掘、沉积物路线和分布的变化紧密联系起来，以测试阿拉斯加南部边缘气候-构造相互作用的记录。将阿拉斯加湾地震反射数据与341个岩心的年龄和物源控制相结合，可以从三维角度随时间检查区域近海沉积系统（Surveyor Fan）中的沉积物质量通量。

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.