Signatures of Changing Eruptive Style, and Bias in the Sedimentary Record of Volcanism, Challis Volcanic Field, Idaho

这个项目是对爱达荷州中部始新世查利斯火山田重新改造的火山碎屑沉积进行的为期三年的研究。该项目侧重于两个主要目标。第一个是确定不同类型的火山喷发导致的沉积方式和模式的变化。第二个目标是分析火山作用沉积记录中的偏差。Challis火山田的沉积物代表了一个很长的火山活动期(5100万至4000万年前)，其特点是最初的时期主要是非爆发性的中期火山作用，随后是形成火山口的火山作用。与火山作用有关的沉积体系包括高曲度和低曲度河流、湖泊(粘土凝灰岩和浊积岩成分)和由拉哈尔沉积的泥石流停机坪。这项研究将确定不同沉积环境组合中不同喷发类型的信号。这项研究还将确定哪些环境对火山喷发的扰动最敏感，因此包含了最好的火山活动记录。这项研究是面向现场的，结合了岩石地层学、特弗拉指纹和岩相地层学，以产生实现项目目标所需的详细对比框架。这些方法需要测量详细的地层剖面、砂岩、透辉岩和砾岩岩石学，并对剖面中的沉降物凝灰岩进行化学分析。

This project is a three-year study of reworked volcaniclastic deposits in the Eocene Challis volcanic field in central Idaho. The project focuses on two major goals. The first is identification of changes in sedimentation style and pattern that result from different types of volcanic eruptions. The second goal is analysis of bias in the sedimentary record of volcanism. Deposits of the Challis volcanic field represent a long period of volcanic activity (51 to 40 million years ago) characterized by an initial period of predominantly non-explosive intermediate volcanism followed by caldera-forming volcanism. The sedimentary system associated with this volcanism comprises high - and low - sinuosity streams, lakes (claystone - tuff and turbidite components), and debris - flow aprons deposited by lahars. The study will identify the signal of different eruption types in a diverse assemblage of depositional environments. The study will also identify which environments are most sensitive to perturbation by eruption and therefore, contain the best record of volcanic activity. The study is field - oriented, combining lithostratigraphy, tephra fingerprinting, and petrofacies stratigraphy to produce the detailed correlation framework needed to achieve the projects goals. These methods require measurement of detailed stratigraphic sections, sandstone, diamictite, and conglomerate petrology, and chemical analyses of fallout tuffs in the sections.