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的南极地质和地球物理方案提供，支持应用数值模拟来约束横贯北极山脉的隆起和折返历史的研究。横贯北极的山脉()是一个异常高(4500米)和相对宽(达200公里)的裂谷-侧翼隆起，划分了南极东部和西部的边界。东南极冰盖的动力学和气候都受到山脉的影响，了解山脉的隆起历史对于理解这些过程至关重要。该项目将根据热机械模型，忠实于热年代学、地质和地球物理数据，来约束横贯北极山脉的抬升和剥蚀历史。这项研究将由博士后研究员奥德丽·韦尔塔与丹尼斯·哈里(1名本科生和1名研究生)合作进行。内部白垩纪通过新生代快速冷却的热年代学证据表明，明显的抬升和折返时期。然而，如果不了解在隆升前和隆升过程中不断演化的热结构和地形，就很难更详细地解释隆升历史。了解不断演变的区域构造环境可以最好地限制山脉的这些方面。与西南极裂谷系统(WARS)的接近表明，的抬升与WARS内部的伸展之间存在联系。该项目将结合两项技术：岩石圈尺度的地球动力学模拟和地壳尺度的热模拟。的岩石圈尺度变形和热演化将由一个有限元模型模拟，该模型旨在跟踪南极岩石圈对长期伸展环境的热和变形响应。以前的研究人员将的高海拔和宽与深部的颈缩联系在一起，在这种颈缩中，地幔减薄抵消了地壳伸展的位置。在本研究中，将使用一个三维动力学模型来追踪深部缩颈、壳内伸展和地幔伸展相互抵消的背景下的隆升和热演化。应用于模型边缘的速度边界条件将随时间变化，以模拟战争的伸展和横张演变。由于模型是动态的，热结构、强度和应变场随着这些初始条件和边界条件的变化而自然演化。动力学模型特别适合于理解岩石圈的变形和热演化，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，将设计一个二维运动-热模型来模拟的抬升历史以及由此产生的侵蚀、地形和热演化。隆起将被模拟为一组离散断层面上的正断层运动，隆起速率随时间变化。侵蚀将被模拟为一个扩散过程，其中侵蚀速率可以随时间而变化(模拟气候变化)，并在空间上作为坡度和距排水分水岭的距离的线性函数变化。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.