Building Ice-Age Dyngjufjöll: Processes, Products and Environments

对于大体积、多成因、冰封火山的形成过程、产物和古环境，人们知之甚少。冰岛的丁居joll（“Askja”）是地球上最大、最暴露的火山之一，以前是冰封的玄武岩火山，但以前的工作集中在它最近的全新世（即无冰）进化上。该项目将重点研究更新世的历史，目标是一个大型地块（Austurfjoll），该地块保存了数百米的冰川火山岩。最近，人们对火山成因、冰下冰融化和排水作为快速冰盖运动的润滑剂的作用及其对冰盖不稳定的潜在影响产生了相当大的兴趣。此外，大量火山融水洪水（即jokulhlaups）的源区过程和产物对冰岛南部的基础设施（道路、桥梁）和当地经济构成重大危害。这项研究的结果将有助于填补关于火山-冰相互作用过程的地质和环境影响的一些知识空白。像丁巨山这样的火山也是地球上与大型长寿玄武岩盾状火山和火星冰相互作用的约束模型最相关的类似物。这项研究将作为与英国和冰岛科学家国际合作的一部分进行。该项目将提供对融水源区的两个相关方面的见解，即上覆冰厚度的时间变化和排水和池塘的性质，包括可能的jokulhlaup（即释放大量火山融水）事件。目前还没有关于火山大厦源头的jokulhlaups记录的研究。对Austurfjoll的枕皮玻璃的挥发性分析将有助于限制对冰岛中部古冰厚度的估计，以及将冰川消融与该地区火山活动增加率联系起来的模型。丁jufjoll冰川火山块体的年龄目前尚不清楚，但自2.5Ma以来，在冰岛已经发现了多达16次陆地冰川事件，因此这些岩石有可能记录冰川晚期前最大冰厚的证据。建议采用详细的定量玻璃结构和成分分析、地球化学分析、40Ar-39Ar测年、详细的构造和相填图以及测井等综合方法进行地层学研究。这个项目和对比方法特别适用于解释非常多（1000）个裂隙喷发、冰川火山、碎屑岩为主的序列(即。“tindars”)，它代表了冰岛冰川历史的庞大数据库。这个项目的结果将有助于完善冰川火山（特别是碎屑）序列中存在的前冰的识别标准，从而有助于越来越多地使用这些岩石作为过去气候的指标。

The processes, products and paleoenvironments of large volume, polygenetic, ice-confined volcanoes are very poorly known. Dyngjufjoll ("Askja"), in Iceland, is one of the largest and best exposed, formerly ice-confined,basaltic volcanoes on Earth, but previous work has concentrated on its more recent Holocene (i.e. ice-free) evolution. This project will focus on its older Pleistocene history by targeting one large massif (Austurfjoll) that preserves several hundred meters of glaciovolcanic rocks. There has been considerable interest recently in the role of volcanogenic, subglacial ice melting and drainage as a lubricant for rapid ice sheet movement, and its potential for sheet destabilization. Also, source area processes and products of large-volume volcanogenic meltwater floods (i.e.jokulhlaups)are a significant hazard to infrastructure (roads, bridges) and the local economy in south Iceland. The results of this study will help close some gaps in knowledge regarding the geologic and environmental impacts of volcano-ice interaction processes. Volcanoes like Dyngjufjoll are also the most relevant terrestrial analogs to constraining models of the interaction of large long-lived basaltic shield volcanoes and ice on Mars. The study will be conducted as part of an international collaboration with scientists from the UK and Iceland.This project will offer insights into two relevant aspects of the meltwater source region, namely temporal variations in the overlying ice thickness and the nature of water drainage and ponding, including possible jokulhlaup (i.e. release of large-volume volcanogenic meltwater) events. There are no studies of the record of jokulhlaups at a volcanic edifice source. Volatile analysis of pillow rind glass at Austurfjoll will help constrain estimates of paleo-ice thicknesses in central Iceland, and models that link deglaciation with increased rates of volcanism in this area. The age of the Dyngjufjoll glaciovolcanic massifs are currently unknown, but up to 16 terrestrial glacial events have been recognized in Iceland since 2.5Ma, so there is potential for these rocks to record evidence of pre-late glacial maximum ice thicknesses. It is proposed to apply an integrated approach to stratigraphy using detailed quantitative glass texture and component analysis, geochemical analysis, 40Ar-39Ar dating, detailed structural and facies mapping and logging. This project and approach to correlation is particularly relevant to interpreting the very many (1000) fissure-erupted, glaciovolcanic, clastic-dominated sequences (i.e. 'tindars') in Iceland, which represent an enormous database on the glacial history of Iceland. The results of this project will help refine the criteria by which the presence of former ice in glaciovolcanic (particularly clastic) sequences is recognized, and hence contribute to the growing use of such rocks as indicators of past climate.