Collaborative Research: High-resolution Basin Analysis of a Large-offset Extensional System, Lake Mead Domain, East-Central Basin and Range Province

该项目旨在通过对同张性盆地的高分辨率分析，确定内华达州拉斯维加斯附近米德湖地区中央盆地和山脉的构造和古地理发育。该区包括低角度滑脱断裂、正断层、张拉断裂体系、三维复杂应变带及张拉收缩构造区和局部体积岩浆活动区。本研究将集中在全球范围内对伸展构造学有重要意义的三个主要问题上：(1)在盆地和山脉等建立在厚地壳上的宽岩浆裂谷中，主要伸展事件的演化是否存在一系列可预测的过程？(2)宽大陆板块边界内部的伸展过程是否受远场力或内力控制？(3)气候变化和地形演化如何影响拉张造山带的沉积？研究小组验证的主要假设是：(1)米德湖域自东向西发育，从滑脱断裂到张拉断裂，再到构造逃逸伴缩短；(2)伸展、滑脱断裂和掘出作用最初受过厚地壳驱动，但时间演化受远场板块边界变化控制；(3)断裂模式和速率的变化对盆地几何形状和地层厚度起着一级控制作用，但气候对地层结构的重要细节起着控制作用，而这些细节迄今为止一直被认为是构造作用的结果。盆地分析技术——包括地层结构特征、相分析、地质年代学、构造制图和稳定同位素地球化学——正在被用来解决这些假设。这项研究将检查米德湖中新世时期的盆地，以确定600万至1000万年前地壳伸展期间断层的详细发展和变化的景观。这一地质事件从根本上形成了该地区的低地地貌，并使盆地和山脉成为与毗邻的科罗拉多高原不同的省份。尽管进行了数十年的研究，但该项目旨在解决的关于盆地和山脉中部变形的机制和演化的基本问题仍未得到解决。该研究具有广泛的应用价值，因为伸展区是全球油气的共同宿主，盆地和山脉被认为是这些过程的一个很好的例子。

This project aims to determine the tectonic and paleogeographic development of the central Basin and Range in the Lake Mead area near Las Vegas, Nevada, through a high-resolution analysis of syn-extensional basins. This region includes low-angle detachment faults, normal faults, transtensional fault systems, areas of complex three-dimensional strain with extensional and contractional structures, and locally voluminous magmatism. This study will focus on three major questions that are important for extensional tectonics globally: (1) Is there a predictable series of processes in the evolution of a major extensional episode in wide, magmatic rifts built on thick crust such as in the Basin and Range? (2) Are extensional processes in the internal part of wide continental plate boundaries controlled by far-field or internal forces? (3) How does climate change and evolving topography affect sedimentation in a major extensional orogen? The main hypotheses the research team is testing are that: (1) the Lake Mead domain developed from east to west in discrete stages from detachment faulting to transtensional faulting, to tectonic escape accompanied by shortening; (2) extension, detachment faulting, and exhumation were initially driven by over thickened crust, but the temporal evolution was controlled by far-field plate boundary changes; (3) changes in patterns and rates of faulting exert a first-order control on basin geometry and stratal thickness, but climate controls significant details of the stratal architecture that have heretofore been attributed to tectonic processes. Basin analysis techniques - including characterization of stratigraphic architecture, facies analysis, geochronology, structural mapping, and stable isotope geochemistry - are being utilized to address these hypotheses.This research will examine Miocene age basins in Lake Mead to determine the detailed development of faulting and the changing landscape between 6 and 10 million years ago during an episode of crustal extension. This is the geologic episode that fundamentally formed the low landscape of the region and made the Basin and Range a distinct province from the adjacent Colorado Plateau. Despite decades of research, there remain fundamental unanswered questions about the mechanism and evolution of deformation in the central Basin and Range that this project aims to address. The research has wide application because extensional regions are common hosts of oil and gas globally and the Basin and Range is considered a well exposed example of these processes.