SOAR Airborne Geophysical Data Collected on the Pensacola/Pole Transect, Transantarctic Mountains. Antarctica

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
Earth's 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 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 downward 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 down-ward 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 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.