Developing a tephra database to document the evolution of explosive volcanism along the Gulf of Alaska margin for the past six million years

爆炸性火山活动可受到一系列地质和气候过程的影响。在像阿拉斯加湾这样的地区，构造板块的汇聚速度和角度都被认为会影响爆炸性火山活动的速度。人们对冰川的影响以及气候波动导致的冰川涨落是否会通过增加侵蚀率间接影响火山喷发的频率了解较少。更好地了解这些因素是如何影响火山爆发频率的，可以让我们了解阿拉斯加湾等特定构造俯冲带的性质，有助于减轻潜在火山灾害对弱势群体的影响。阿拉斯加湾边缘是世界上火山活动最活跃的地区之一，使它成为一个很好的研究区域。然而，由于过去250万年中广泛的冰川作用和侵蚀作用，该地区过去火山活动的连续记录很少。综合海洋钻探计划（IODP） 341远征队在南阿拉斯加边缘采集的高质量深海岩心为研究该地区在关键构造和气候事件期间的火山活动提供了新的和罕见的材料。拟议的工作旨在建立一个来自这些岩心的火山物质数据库，以量化阿拉斯加湾火山活动在过去600万年中关键构造和气候事件中的发展和演变。技术描述：拟议的工作将确定和开发来自IODP站点U1417和U1418的tephras的地球化学和地质年代学数据库。将收集综合数据以(i)确定该地区的麻风来源？五大火山省；（ii）重建阿拉斯加湾边缘晚中新世至今的火山喷发演化；（iii）设计用于陆地古气候研究的海洋热菌数据库。方法将包括对麻黄的显微镜和磁化率鉴定，对特定颗粒的主要元素和微量元素进行地球化学指纹鉴定，以及对玻璃、角闪石、黑云母和/或苯胺进行40Ar/39Ar放射性测年。结果将与U1417和U1418遗址的古地磁、氧-18同位素和微化石年代地层，以及现有的阿拉斯加和加拿大育空地区的地热数据相结合。本研究的总体结果将在以下方面提供新的约束：(1)不同构造-气候边界力对火山喷发频率的影响；(2)火山喷发速率变化与北半球冰川开始之间的遗传关系；(3)建立一个年代确定的地球化学指纹海洋火山的公共数据库，为重建阿拉斯加和育空地区的古气候历史提供一个改进的框架。

Explosive volcanism can be influenced by a range of geologic and climatic processes. In areas like the Gulf of Alaska, both the rate and angle of convergence of tectonic plates are understood to influence the rate of explosive volcanism. Less well understood is the influence of glaciers and whether climate fluctuations resulting in the ebb and flow of glaciers indirectly impact eruption frequency through increased erosion rates. Gaining a better understanding of how these factors contribute to explosive volcanic frequency can inform us on the nature of particular tectonic subduction zones like the Gulf of Alaska, helping mitigate the impact of potential volcanic hazards on vulnerable populations. The Gulf of Alaska margin is one of the most volcanically active regions in the world, making it a good area for study. However, continuous records of past volcanism in this region are rare due to extensive glaciation and erosion during over the past 2.5 million years. The high-quality deep-sea cores collected during the Integrated Ocean Drilling Program (IODP) Expedition 341 to the southern Alaskan margin provide new and rare material to examine volcanism in this region during key tectonic and climatic events. The proposed work seeks to develop a database of volcanic material from these cores to quantify the development and evolution of Gulf of Alaska volcanism during key tectonic and climate events over the past six million years.Technical Description: The proposed work will identify and develop a geochemical and geochronological database for tephras from IODP sites U1417 & U1418. A combination of data will be collected to (i) determine tephra sources from the region?s three major volcanic provinces; (ii) reconstruct the late Miocene-to-present evolution of eruptive volcanism along the Gulf of Alaska Margin; (iii) design a marine tephra database for use in terrestrial paleoclimatic studies. Methods will include microscope and magnetic susceptibility identification of tephra, grain-specific major and trace element geochemical fingerprinting, and 40Ar/39Ar radiometric dating of glass, hornblende, biotite, and/or sanidine. Results will be integrated with paleomagnetic, oxygen-18 isotope and microfossil chronostratigraphies of Sites U1417 & U1418, as well as with existing terrestrial Alaskan and Canadian Yukon tephra data. The overall results of this research will provide new constraints on (i) the effect of different tectonic-climate boundary forces on eruptive volcanic frequency, (ii) the genetic relationships between variations in eruption rate and the initiation of the Northern Hemisphere glaciations, and (iii) create a public database of well-dated geochemically fingerprinted marine tephras to provide an improved framework for reconstructing the paleoclimatic history of Alaska and the Yukon.