Contrasting Architecture and Dynamics of the Transantarctic Mountains

Bell and Buck：1009615704 Blankenship：1009615832 摘要大陆伸展产生了各种各样的结构，从东非裂谷的线性狭窄裂谷到美国西部盆岭省的扩散延伸。裂谷肩隆起在裂谷侧翼之间变化很大。 初始热流和地壳厚度的变化很好地解释了裂谷宽度变化和地壳减薄的原因。 岩石圈的机械拉伸与裂谷肩隆起有关，但对可变裂谷侧翼隆起的原因仍知之甚少。 横贯南极山脉是裂谷侧面隆起的一个极端例子，横跨南极洲3 500公里，海拔高达4 500米，因此构成地球地壳的一个独特特征。 它形成于中、新生代冈瓦纳大陆裂解的伸展环境。 地质和地球物理工作表明，TAM沿着东南极洲和西南极洲之间的长期岩石圈边界发展，该边界被复杂的伸展和平移微板块运动历史重新激活。 TAM沿走向沿着不均匀。 沿着OWilkes FrontO，裂谷的北方部分从北维多利亚地延伸到伯德冰川。 威尔克斯前缘结构包括：（1）形成罗斯海维多利亚陆盆地的薄而伸展的地壳，（2）TAM裂谷肩，（3）形成威尔克斯盆地的长波向下。 对比鲜明的结构被绘制成沿着彭萨科拉/极地前沿，从尼姆罗德冰川延伸到彭萨科拉山脉的裂谷南段。 沿着沿着这一南段，迄今为止还没有绘制出裂谷盆地的地图，而沿着东南极沿着向下的山脉边缘，即ObacksideO，则不那么明显。 罗斯海的伸展与山脉和威尔克斯盆地的形成之间的挠曲模型被认为是整个山脉隆升的机制。 沿着TAM的基本结构的变化表明，既不是一个单一的事件，也不是一系列相同的事件产生的裂谷侧翼隆起。 可变架构的观察表明复杂的机制，并可能是一个根本的限制，在最大的可持续裂谷侧翼海拔。 研究TAM的动机是试图了解这个极端海拔裂谷侧翼的地球动力学。 该地区的地球动力学是独特的，还是冰川作用和相关侵蚀的历史导致了极端的隆起？ 利用现有的数据集，很难有把握地约束跨TAM的代表性部分的地质结构。 任何改进地球动力学机制的努力都需要对TAM体系结构有基本的了解。 该项目的目标是（1）通过获取三个长波长地球物理断面，结合重力、磁力、冰层穿透雷达和冰面测量，限制裂谷系统的结构以及裂谷侧面周围沉积盆地、冰川侵蚀和镁铁质火成岩的分布和结构，（2）量化各种地球动力学机制的贡献，以了解可能导致极端裂谷侧翼隆起的地质条件，以及（3）利用对结构和地球物理数据的更好理解来测试地球动力学模型，以提高我们对TAM和地球动力学和世界范围内裂谷翼隆升地球动力学的普遍问题。 该项目将允许开发一个通用的框架，以了解裂谷侧翼隆起的发展，以及解决TAM的具体地球动力学演化的问题。

Bell and Buck: OPP 9615704 Blankenship: OPP 9615832 Abstract Continental extension produces a great variety of structures from the linear narrow rifts of the East African Rift to the diffuse extension of the Basin and Range Province of the Western U.S. Rift shoulder uplift varies dramatically between rift flanks. The cause of variable rift width and crustal thinning is fairly well explained by variable initial heat flow and crustal thickness. Mechanical stretching of the lithosphere has been linked to rift shoulder uplift but the cause of variable rift flank uplift remains poorly understood. The Transantarctic Mountains (TAM) are an extreme example of rift flank uplift, extending over 3500 km across Antarctica and reaching elevations up to 4500 m and thus constitute a unique feature of EarthOs crust. The range was formed in the extensional environment associated with the Mesozoic and Cenozoic breakup of Gondwanaland. Geological and geophysical work has shown that the TAM developed along the long-lived lithospheric boundary between East and West Antarctica reactivated by a complex history of extensional and translational microplate motions. The TAM are not uniform along strike. Along the OWilkes FrontO, the northern segment of the rift extends from North Victoria Land to Byrd Glacier. The Wilkes Front architecture consists of (1) thin, extended crust forming the Victoria Land Basin in the Ross Sea, (2) the TAM rift shoulder, and (3) a long-wavelength down- ward forming the Wilkes Basin. Contrasting structures are mapped along the OPensacola/PoleO Front, the southern segment of the rift extending from the Nimrod Glacier to the Pensacola Mountains. Along this southern section no rift basin has been mapped to date and the down-ward along the East Antarctic, or ObacksideO, edge of the mountains is less pronounced. A flexural model linking the extension in the Ross Sea to the formation of both the mountains and the Wilkes Basin has been considered as a me chanism for uplift of the entire mountain range. The variability in fundamental architecture along the TAM indicates that neither a single event nor a sequence of identical events produced the rift flank uplift. The observation of variable architecture suggests complex mechanisms and possibly a fundamental limitation in maximum sustainable rift flank elevation. The motivation for studying the TAM is to try to understand the geodynamics of this extreme elevation rift flank. Are the geodynamics of the area unique, or does the history of glaciation and related erosion contribute to the extreme uplift? With the existing data sets it is difficult to confidently constrain the geological architecture across representative sections of the TAM. Any effort to refine geodynamic mechanisms requires this basic understanding of the TAM architecture. The goal of this project is to (1) constrain the architecture of the rift system as well as the distribution and structure of sedimentary basins, glacial erosion and mafic igneous rocks surrounding the rift flank by acquiring three long wavelength geophysical transects with integrated gravity, magnetics, ice- penetrating radar, and ice surface measurements, (2) quantify the contribution of various geodynamic mechanisms to understand the geological conditions which can lead to extreme rift flank uplift, and (3) use the improved understanding of architecture and geophysical data to test geodynamic models in order to improve our understanding both of the TAM geodynamics and the general problem of the geodynamics of rift flank uplift worldwide. This project will allow development of a generalized framework for understanding the development of rift flank uplift as well as address the question of the specific geodynamic evolution of the TAM.