Contrasting Architecture and Dynamics of the Transantarctic Mountains

大陆伸展产生了各种各样的构造，从东非裂谷的线性狭窄裂谷到美国西部盆地和山脉省的扩散伸展。裂谷肩的隆升在裂谷两侧之间变化很大。初始热流和地壳厚度的变化可以很好地解释裂谷宽度变宽和地壳变薄的原因。岩石圈的机械拉伸与裂谷肩隆升有关，但裂谷翼隆升的原因尚不清楚。横贯南极山脉（TAM）是裂谷侧翼隆起的一个极端例子，在南极洲延伸超过3500公里，海拔高达4500米，因此构成了地球地壳的独特特征。该范围形成于中新生代冈瓦纳陆断裂的拉张环境。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长期存在的岩石圈边界发育，由微板块伸展和平动的复杂历史重新激活。TAM在罢工时并不统一。沿着奥威尔克斯FrontO，裂谷的北段从北维多利亚地延伸到伯德冰川。威尔克斯前缘构造包括：(1)薄而伸展的地壳形成罗斯海维多利亚陆盆地，(2)TAM裂谷肩，(3)长波长向下形成威尔克斯盆地。相反的构造沿着OPensacola/PoleO锋被绘制出来，这是裂谷的南段，从Nimrod冰川延伸到Pensacola山脉。到目前为止，沿着这一南部地区还没有绘制出裂谷盆地的地图，沿着南极东部向下的山脉边缘也不太明显。将罗斯海的伸展与山脉和威尔克斯盆地的形成联系起来的弯曲模式被认为是整个山脉隆起的主要机制。TAM沿线基本构造的变化表明，裂谷侧隆升既不是单一事件造成的，也不是一系列相同事件造成的。对可变结构的观察表明，机制复杂，可能存在最大持续裂谷侧抬高的根本限制。研究TAM的动机是试图了解这一极端高程裂谷侧面的地球动力学。该地区的地球动力学是独特的，还是冰川和相关侵蚀的历史导致了极端的隆起？利用现有的数据集，很难自信地约束跨TAM代表性剖面的地质结构。任何改进地球动力学机制的工作都需要对TAM体系结构的基本理解。本项目的目标是：(1)通过综合重力、磁力、探冰雷达和冰面测量，获取三个长波地球物理样带，确定裂谷系统的结构以及裂谷侧翼周围的沉积盆地、冰川侵蚀和基性火成岩的分布和结构；(2)量化各种地球动力机制的贡献，以了解可能导致极端裂谷翼隆升的地质条件；(3)利用对建筑和地球物理数据的改进理解来测试地球动力学模型，以提高我们对TAM地球动力学和全球裂谷翼隆升地球动力学的一般问题的理解。该项目将为理解裂谷翼隆升的发展提供一个通用框架，并解决TAM的具体地球动力学演化问题。

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.