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向伸展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。该区域包括低角度滑脱断层、正断层、伸展断层系统、具有伸展和收缩构造的复杂三维应变区，以及局部巨大的岩浆活动。这项研究将集中于对全球伸展构造具有重要意义的三个主要问题：(1)在盆地和山脉等厚地壳上建造的宽阔的岩浆裂谷中，是否存在一系列可预测的主要伸展幕的演化过程？(2)宽阔大陆板块边界内部的伸展过程是由远场还是内力控制的？(3)气候变化和地形演变如何影响主要伸展造山带的沉积？研究小组正在检验的主要假说是：(1)米德湖域从东到西从拆离断裂到扭张断裂，再到构造逃逸伴随缩短的离散阶段；(2)伸展、拆离断裂和折返最初是由过厚的地壳驱动的，但时间演化受远场板块边界变化的控制；(3)断裂模式和速率的变化对盆地几何和地层厚度施加了一级控制，但气候控制了迄今为止被归因于构造过程的地层结构的重要细节。正在利用盆地分析技术--包括地层结构表征、相分析、地质年代学、构造制图和稳定同位素地球化学--来解决这些假说。这项研究将研究米德湖中新世时代的盆地，以确定600万至1000万年前地壳伸展期间断裂作用的详细发展和地貌的变化。这一地质事件从根本上形成了该地区的低地貌，并使该盆地和山脉成为与邻近的科罗拉多高原截然不同的省份。尽管进行了几十年的研究，但关于中央盆地和山脉变形的机制和演化仍存在一些根本问题，这是该项目旨在解决的。这项研究具有广泛的应用，因为伸展区域是全球共同的油气赋存区域，而盆地和山脉被认为是这些过程的一个很好的暴露的例子。

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.