The Role of Lithospheric Flexure in the Landscape Evolution of the Wilkes Subglacial Basin and Transantarctic Mountains, East Antarctica

Guy J G Paxman,Stewart S R Jamieson,Fausto Ferraccioli,Anthony B Watts,Michael J Bentley,German Leitchenkov,Neil Ross,Egidio Armadillo,Duncan A Young

doi:10.1029/2018jf004705

Abstract

AbstractReconstructions of the bedrock topography of Antarctica since the Eocene‐Oligocene Boundary (approximately 34 Ma) provide important constraints for modeling Antarctic ice sheet evolution. This is particularly important in regions where the bedrock lies below sea level, since in these sectors the overlying ice sheet is thought to be most susceptible to past and future change. Here we use 3‐D flexural modeling to reconstruct the evolution of the topography of the Wilkes Subglacial Basin (WSB) and Transantarctic Mountains (TAM) in East Antarctica. We estimate the spatial distribution of glacial erosion beneath the East Antarctic Ice Sheet, and restore this material to the topography, which is also adjusted for associated flexural isostatic responses. We independently constrain our post‐34 Ma erosion estimates using offshore sediment stratigraphy interpretations. Our reconstructions provide a better‐defined topographic boundary condition for modeling early East Antarctic Ice Sheet history. We show that the majority of glacial erosion and landscape evolution occurred prior to 14 Ma, which we interpret to reflect more dynamic and erosive early ice sheet behavior. In addition, we use closely spaced 2‐D flexural models to test previously proposed hypotheses for a flexural origin of the TAM and WSB. The pre‐34 Ma topography shows lateral variations along the length of the TAM and WSB that cannot be explained by uniform flexure along the front of the TAM. We show that some of these variations may be explained by additional flexural uplift along the south‐western flank of the WSB and the Rennick Graben in northern Victoria Land.

Highlights

The Transantarctic Mountains (TAM) are a >3,000 km‐long mountain range that separates East Antarctica and the West Antarctic Rift System (Figure 1)
The bedrock digital elevation model (DEM) shows that the northern Wilkes Subglacial Basin (WSB) contains deep sub‐basins that extend over 300 km inland from the grounding line (Ferraccioli, Armadillo, Jordan, et al, 2009; Jordan, Ferraccioli, Vaughan, et al, 2010; Figure 2)
These deep basins are superimposed on preexisting tectonic features (Ferraccioli, Armadillo, Jordan, et al, 2009; Jordan et al, 2013) and are separated by elevated, flat‐lying, dissected plateau surfaces that are interpreted as remnants of a widespread low‐lying erosion surface (Paxman et al, 2018)

Summary

Introduction

The Transantarctic Mountains (TAM) are a >3,000 km‐long mountain range that separates East Antarctica and the West Antarctic Rift System (Figure 1). Airborne radio‐echo sounding (RES) surveys reveal that this sector of the EAIS is largely marine‐based (grounded on bedrock that lies below sea level) These surveys show the WSB to be an ~1,400 km‐long and 200 to 600 km‐wide, south‐to‐north trending, subglacial depression, with bedrock elevations on average 500 m below sea level (Ferraccioli, Armadillo, Jordan, et al, 2009; Fretwell et al, 2013). A number of authors have interpreted the TAM as the uplifted flank of the West Antarctic Rift System, which is situated beneath the Ross Sea (Figure 1; Brenn et al, 2017; Hansen et al, 2016; Stern & ten Brink, 1989; ten Brink et al, 1997). Derived crustal thickness estimates lend support to a flexural origin for the TAM and WSB, indicating that the crust is of constant thickness and warps upward at the TAM and downward at the WSB (Hansen et al, 2016)

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