Project Description:

Collaborative Research: Contrasting Architecture and Dynamics of the Transantarctic Mountains

    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 United States. Rift shoulder uplift varies dramatically between rift flanks (Chery et al, 1992). The cause of variable rift width and crustal thinning is fairly well explained by variable initial heat flow and crustal thickness. Mechanical stratching 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 od rift flank uplift, extending over 3500 km across Antarctica and reaching elevations up to 4500 m. 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 Eaast and West Antarctica reactivated by a complex history of extensional and translational microplate motions.

    The TAM are not uniform along strike. Along the "Wilkes Front", 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 downwarp forming the Wilkes Basin. Contrasting structures are mapped along the "Pensacola-Pole" 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 downwarp along the East Antarctic, or 'backside', edge of the mountains is less pronounced. A flexural model linking the extension in the Ross Sea to the formation of both mountains and the Wilkes basin has been considered as a mechanism for uplift of the entire mountain range. The variability in fundamental architecture along the 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 geodynamice 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 robustly constrain the architecture across representative sections of the the TAM. Any effort to redefine the geodynamic mechanism 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 ans mafics 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 maechanisms to paramterize the conditions which can lead to extreme rift flank uplift, and (3) use the improved undertanding of architecture and geophysical data to test geodynamic models in order to improve our understanding both of the TAM geodynamics and the geodynamics of rift flank uplift in general. This project will allow us to develop 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