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

在活跃的造山中，最具挑战性的问题之一是，气候可能如何以大规模再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的增加，并可能像数值模型预测的那样影响构造过程，如隆起和断裂？通过观测和分析数据研究这一问题具有挑战性，因为大多数正在进行造山活动的地区都被新近纪末(23？250万年前)的残存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地带由于其广泛的冰川作用，是解决这一问题的最佳地点。这一活跃山脉最近的侵蚀记录储存在阿拉斯加湾，并在综合大洋钻探计划(IODP)341次远征中被发现。对在大陆架、斜坡和深海测量员Fan钻探获得的深海岩心材料进行综合分析，将提供量化全球和局部气候变化对山脉侵蚀和构造演变的影响的手段。圣埃利亚斯带的年轻，以及构造和侵蚀过程的高速率，以及它靠近阿拉斯加湾，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影响地表过程的速率，如侵蚀，从而通过质量的重新分配影响构造过程，如断层作用，地球科学界存在长期的争论。拟议的研究将检验根据数字和分析数据提出的假设，即冰川侵蚀的增加导致了圣埃利亚斯造山带核心的集中挖掘。已经提出了两个可能的目标区域，在那里可能已经形成了构造-气候反馈：在褶皱冲断带和在雅库塔特板块凹陷的角落。现有丰富的陆上地质和热年代学数据全面描绘了当前掘尸速度的空间格局，但量化随时间变化的速度和模式一直具有挑战性。研究小组？S的方法是调查沉积在阿拉斯加湾的圣埃利亚斯造山作用的近海沉积记录。这一造山作用发生在全球气候显著变化的时期，包括约2.6 Ma的更新世-更新世转换(PPT)和1.2-0.7 Ma的中更新世转换(MPT)的北半球冰川(InHg)加剧，但也是当地气候变化导致的高山冰川，最早可能是中新世晚期/上新世(6.5 Ma)。IODP Expetion 341岩心的高分辨率磁性地层和生物地层年龄控制使沉积岩相和结构、物源、折返和沉积物路线和分布的变化紧密联系在一起，以测试阿拉斯加南部边缘气候-构造相互作用的记录。阿拉斯加湾地震反射数据与来自341个岩心的年龄和物源控制相结合，使得能够从时间的三维角度检查区域近海沉积系统--测量者扇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.