Topography, structural and exhumation history of the Admiralty Mountains
region, northern Victoria Land, Antarctica
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Abstract
The Admiralty Mountains region forms the northern termination of the northern Victoria Land, Antarctica. Few
quantitative data are available to reconstruct the Cenozoic morpho-tectonic evolution of this sector of the Antarctic
plate, where the Admiralty Mountains region forms the northern termination of the western shoulder of the
Mesozoic–Cenozoic West Antarctica Rift System. In this study we combine new low-temperature thermochronological
data (apatite fission-track and (U-Th-Sm)/He analyses) with structural and topography analysis. The
regional pattern of the fission-track ages shows a general tendency to older ages (80–60 Ma) associated with
shortened mean track-lengths in the interior, and younger fission-track ages clustering at 38–26 Ma with long
mean track-lengths in the coastal region. Differently from other regions of Victoria Land, the younger ages are
found as far as 50–70 km inland. Single grain apatite (U-Th-Sm)/He ages cluster at 50–30 Ma with younger ages
in the coastal domain. Topography analysis reveals that the Admiralty Mountains has high local relief, with an
area close to the coast, 180 km long and 70 km large, having the highest local relief of >2500 m. This coincides
with the location of the youngest fission-track ages. The shape of the area with highest local relief matches the
shape of a recently detected low velocity zone beneath the northern TAM, indicating that high topography of the
Admiralty Mountains region is likely sustained by a mantle thermal anomaly. We used the obtained constraints on
the amount of removed crustal section to reconstruct back-eroded profiles and calculate the erosional load in
order to test flexural uplift models. We found that our back-eroded profiles are better reproduced by a constant
elastic thickness of intermediate values (Te ¼ 20–30 km). This suggests that, beneath the Admiralty Mountains,
the elastic properties of the lithosphere are different with respect to other TAM sectors, likely due to a stationary
Cenozoic upper mantle thermal anomaly in the region.
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