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Transantarctic Mountain Evolution
The Transantarctic Mountains trend for 4000 km across
Antarctica, reach elevations of over 4 km, and form one of the world's
major rift flank mountain chains. The mountains lie along the western
border the West Antarctic Rift System, which is thought to have
formed during extensional rifting events related to continental
breakup. Rifting of lithosphere is a fundamental process in the
development of continents and their margins.
Our research at GNS concentrates on improving understanding
of the evolution, deformation and structure of the Transantarctic
Mountains, the structure of the lithosphere at the rift margin,
together with the associated driving forces of rift initiation,
rift continuation and rift architecture. Several integrated projects,
described below, are closely linked to other investigations of the
rift margin by overseas collaborators. Our current work builds on
previous GNS research involving geological studies in South Victoria
Land, offshore basin structure and evolution, lithospheric studies
using broadband seismological data, and tectonic studies with the
Cape Roberts Project.
Geological investigations
This ongoing study aims to constrain models of mountain range
and rift basin development through onland geological investigations,
focusing on the amount and timing of vertical and horizontal offset
in the Transantarctic Mountains. We are targeting key markers of
deformation in the TAM, and working on obtaining age constraints
for the deformation. Results in South Victoria Land to date indicate
that most rock uplift (exhumation) actually took place 400-450 million
years ago, with only a smaller amount, from 20-50 million years
ago, creating the present day mountain topography. If 20-50 million
year old faults do exist, they are probably offshore in the Ross
Sea, not exposed onland near the ranger front. Proposed new work,
amongst other things, involves examining structural marker horizons
in the Mackay and Ferrar Glacier regions, to constrain slip vectors
and timing on these major cross-range lineaments.
Crustal studies using seismic techniques
Our seismological research primarily targets the structure of
the transition between the Victoria Land Basin/Terror rift and the
Transantarctic mountain range, using both (active-seismic) offshore-onshore
and (earthquake source) broadband seismic techniques. Our current
work involves receiver function inversion of broadband data collected
during a joint GNS/ANU array deployment in the central Transantarctic
Mountains. Preliminary results from the inversion analysis highlight
an extreme velocity gradient beneath Ross Island and a relatively
gentle velocity gradient in the crust beneath the mountain range.
Station locations of the GNS/ANU 1999-2000 broadband seismometer
array
A seismometer station being deployed near the Transantarctic Mountain
Front, as part of the 1999-2000 array
 Seismotectonic
studies
Present day earthquake activity between Ross Island
and the Italian base at Terra Nova Bay, in the David Glacier region,
was recorded by our 1999-2000 broadband array. In future work we
plan further broadband array deployments, together with Italian
colleagues, to investigate the seismotectonics in this area, targeting
the contemporary deformation of the rift margin and structures within
the Transantarctic Mountains.
Contact
us here
Stephen Bannister
Nick Mortimer
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