Space-Time Progression of Faulting in the Northernmost Basin and Range: Implications for Crustal-Scale Processes During Extension

最北盆地和山脉断层的时空演化：对伸展过程中地壳尺度过程的影响

• 批准号: 0229854
• 负责人: Elizabeth Miller
• 金额: $ 16.28万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-01-01 至 2005-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0229854&HistoricalAwards=false
• 关键词: Space; Time; Progression; Faulting; Northernmost

The Basin and Range extensional province is the world's premier region for the study of continental stretching as faults are moving and volcanic activity is ongoing today. The northwestern part of the Basin and Range Province, in northern Nevada, has fault-bounded mountains and valleys like elsewhere in the Basin and Range, but, based on geologic studies, the upper part of the continental crust has undergone much less extension by faulting than elsewhere. Paradoxically, the crust as a whole is thin (only 28 km) and appears to be just as stretched or thinned, or more stretched than the rest of the Basin and Range, which is on average 30-35 km thick). In addition, the age span of extension, its relationship to volcanic activity, and the nature of the transition from this region of apparent low upper crustal extension to the more highly extended areas to the south and east in the Basin and Range are not clearly known. Magmatic/volcanic activity is thought to heat and weaken the crust, leading to thinning and rifting. However, most magmatism and volcanic activity in northern Nevada occurred at about 16 million years ago (associated with the Snake River-Yellowstone volcanic trend), but ongoing studies show that extensional faulting happened almost 10 million years later.This investigation of northern Nevada extensional faulting relies on existing and ongoing geologic field studies and their compilation into a digital data base to better document the distribution, geometry and the age of faulting in the region. Combined with state-of-the-art geochronologic and thermochronologic dating of rocks and minerals, the age or time and the amount of extension that took place in this part of the Basin and Range will be determined accurately. This new data base will help answer several important questions: What conditions lead to the thinning of continents and their rupture and rifting apart? What role does magmatism play in crustal extension? How does stretching and thinning happen on the scale of the entire crust, and can the lower crust thin or stretching independently of the upper crust? Answers to these questions are applicable to a variety of regions beyond northern Nevada, and in particular, will help address fundamental questions about the origin and evolution of sedimentary basins developed on thinned continental crust of the world's vast offshore continental shelves.

盆地和山脉伸展区是世界上研究大陆伸展的主要地区，因为断层正在移动，火山活动正在进行。 盆地和山脉省的西北部，位于内华达州的北方，与盆地和山脉的其他地方一样，有断层限制的山脉和山谷，但是，根据地质研究，大陆地壳的上部比其他地方经历了更少的断层延伸。 奇怪的是，地壳作为一个整体是薄的（只有28公里），似乎只是拉伸或薄，或比盆地和山脉的其余部分，平均30-35公里厚）更拉伸。 此外，还不清楚伸展的年龄跨度、它与火山活动的关系，以及从这一表面上地壳伸展较低的地区向盆地和山脉南部和东部伸展程度较高的地区过渡的性质。 岩浆/火山活动被认为会加热和削弱地壳，导致变薄和裂谷。 然而，北方内华达州的大多数岩浆活动和火山活动发生在大约1600万年前（与蛇河-黄石火山趋势有关），但正在进行的研究表明，伸展断层发生在近1000万年后。对北方内华达州伸展断层的调查依赖于现有和正在进行的地质实地研究及其汇编成数字数据库，以更好地记录分布，几何形状和断层的年龄。 结合最先进的岩石和矿物地质年代学和热年代学测年，将准确确定盆地和山脉这一部分发生的伸展的年龄或时间和数量。 这个新的数据库将有助于回答几个重要的问题：是什么条件导致大陆变薄以及它们的断裂和裂谷分离？ 岩浆活动在地壳伸展中起什么作用？ 在整个地壳的尺度上，拉伸和减薄是如何发生的？下地壳的变薄或拉伸是否独立于上地壳？ 对这些问题的回答适用于北方内华达州以外的各种地区，特别是将有助于解决有关沉积盆地的起源和演变的基本问题，这些盆地是在世界上广阔的近海大陆架的薄大陆地壳上形成的。