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

随着断层的移动和火山活动的持续，盆山伸展省是世界上研究大陆伸展的首要地区。 盆地山脉省的西北部位于内华达州北部，与盆地山脉的其他地方一样，也有以断层为界的山脉和山谷，但根据地质研究，大陆地壳上部因断层作用而发生的伸展程度比其他地方要少得多。 矛盾的是，整个地壳很薄（仅 28 公里），并且看起来与盆地和山脉的其他部分（平均厚度为 30-35 公里）一样拉伸或变薄，或者更加拉伸。 此外，延伸的年龄跨度、其与火山活动的关系，以及从这个明显的低上地壳延伸区域到盆地和山脉南部和东部更高延伸区域的过渡性质尚不清楚。 人们认为岩浆/火山活动会加热并削弱地壳，导致地壳变薄和裂谷。 然而，内华达州北部的大多数岩浆活动和火山活动发生在大约 1600 万年前（与斯内克河-黄石火山趋势相关），但正在进行的研究表明，伸展断层活动发生在近 1000 万年后。这项对内华达州北部伸展断层活动的调查依赖于现有和正在进行的地质现场研究，并将其汇编成数字数据库，以更好地记录该地区断层活动的分布、几何形状和年龄。 结合最先进的岩石和矿物地质年代学和热年代学测定，将准确确定盆地和山脉这一部分发生的年龄或时间以及延伸量。 这个新数据库将有助于回答几个重要问题：什么条件导致大陆变薄及其破裂和裂谷？ 岩浆作用在地壳伸展中起什么作用？ 整个地壳尺度上的拉伸和变薄是如何发生的？下地壳是否可以独立于上地壳而变薄或拉伸？ 这些问题的答案适用于内华达州北部以外的各个地区，特别是有助于解决有关在世界广阔的近海大陆架的薄大陆壳上形成的沉积盆地的起源和演化的基本问题。

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.