Uplift and Exhumation of the Transantarctic Mountains and Relation to Rifting in West Antarctica

该奖项由极地方案办公室南极地质和地球物理方案提供，支持研究应用数值建模来限制横贯南极山脉的隆起和剥露历史。横贯南极山脉（TAM）是一个高得惊人（4500米）和相对较宽（达200公里）的裂谷侧翼隆起，划分了东南极洲和西南极洲之间的边界。东南极冰盖的动态和气候受到山脉的影响，了解山脉的隆升历史对了解这些过程至关重要。该项目将限制的隆起和剥蚀历史的横贯南极山脉的基础上举行忠实于热年代学，地质和地球物理数据的热机械建模。该研究将是博士后研究员奥黛丽Huerta的主要责任，与丹尼斯哈里，1名本科生，1名研究生合作。热年代学证据的幕式白垩纪通过新生代快速冷却TAM内表明不同时期的隆起和折返。然而，隆起历史的更详细的解释是困难的，而不了解不断变化的热结构和地形的TAM之前和期间隆起。山脉的这些方面可以通过了解不断变化的区域构造环境来最好地加以限制。TAM与西南极裂谷系（WARS）的接近表明TAM的隆升与WARS内的伸展之间存在联系。该项目将综合两种技术：岩石圈尺度地球动力学模拟和地壳尺度热模拟。TAM的岩石圈尺度的变形和热演化将模拟设计跟踪南极岩石圈的热和变形的长期伸展环境的响应的有限元模型。以前的研究者已经将TAM的高海拔和宽宽度与深层次的颈缩联系起来，在颈缩中，地幔变薄与地壳伸展的位置相抵消。在这项研究中，一个三维的动态模型将被用来跟踪TAM的隆起和热演化的设置中，颈缩是在一个深层次的，在地壳内的扩展和地幔内的扩展是抵消。应用于模型边缘的速度边界条件将随着时间的推移而变化，以模拟WARS的拉伸和扭张演化。由于该模型是动态的，因此热结构、强度和应变场响应于这些初始和边界条件而自然地演化。动态模型是唯一适合于理解岩石圈变形和热演化的模型，然而运动学模型最适合于处理地壳隆起的详细热历史和折返历史。 因此，将设计一个二维动力学-热模型来模拟TAM的隆起历史以及由此产生的侵蚀、地形和热演化。Ucrose将被建模为一组离散断层面上的正断层运动，其抬升速率随时间变化。侵蚀将被模拟为一个扩散过程，其中侵蚀率可以随着时间的推移而变化（模拟气候变化），并在空间上作为梯度和距离分水岭的线性函数而变化。将计算合成时间-温度（t-T）历史，以将模型结果与热年代学数据进行比较。

This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports research to apply numerical modeling to constrain the uplift and exhumation history of the Transantarctic Mountains. The Transantarctic Mountains (TAM) are an anomalously high (4500 m) and relatively broad (up to 200 km) rift-flank uplift demarcating the boundary between East and West Antarctica. Dynamics of the East Antarctic ice-sheet and the climate are affected by the mountain range, and an understanding of the uplift history of the mountain range is critical to understanding these processes. This project will constrain the uplift and denudation history of the Transantarctic Mountains based on thermo-mechanical modeling held faithful to thermochronological, geological, and geophysical data. The research will be the primary responsibility of post-doctoral researcher Audrey Huerta, working in collaboration with Dennis Harry, 1 undergraduate student, and 1 graduate student.Thermochronologic evidence of episodic Cretaceous through Cenozoic rapid cooling within the TAM indicates distinct periods of uplift and exhumation. However, a more detailed interpretation of the uplift history is difficult without an understanding of the evolving thermal structure and topography of the TAM prior to and during uplift. These aspects of the mountain range can best be constrained by an understanding of the evolving regional tectonic setting. Proximity of the TAM to the West Antarctic Rift System (WARS) suggests a link between uplift of the TAM and extension within the WARS.The project will integrate two techniques: lithospheric-scale geodynamic modeling and crustal-scale thermal modeling. The lithospheric-scale deformational and thermal evolution of TAM will be modeled by a finite element model designed to track the thermal and deformational response of the Antarctic lithosphere to a protracted extensional environment. Previous investigators have linked the high elevation and broad width of the TAM to a deep level of necking in which mantle thinning is offset from the location of crustal extension. In this study, a three-dimensional dynamic model will be used to track the uplift and thermal evolution of the TAM in a setting in which necking is at a deep level, and in which extension within the crust and extension within the mantle are offset. Velocity boundary conditions applied to the edges of the model will vary through time to simulate the extensional and transtensional evolution of the WARS. Because the model is dynamic, the thermal structure, strength, and strain field, evolve naturally in response to these initial and boundary conditions.Dynamic models are uniquely suited to understanding lithospheric deformational and thermal evolution, however kinematic models are best suited for addressing the detailed thermal and exhumation history of crustal uplifts. Thus, a 2-dimensional kinematic-thermal model will be designed to simulate the uplift history of the TAM and the resulting erosional, topographic, and thermal evolution. Uplift will be modeled as normal-fault movement on a set of discrete fault planes with uplift rate varying through time. Erosion will be modeled as a diffusive process in which erosion rates can be varied through time (simulating climate changes), and vary spatially as a linear function of gradient and distance from the drainage divide. Synthetic time-temperature (t-T) histories will be calculated to compare model results to thermochronologic data.