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The East Antarctic Ice Sheet (EAIS) is underlain by a series of low‐lying subglacial sedimentary basins. The extent, geology, and basal topography of these sedimentary basins are important boundary conditions governing the dynamics of the overlying ice sheet. This is particularly pertinent for basins close to the grounding line wherein the EAIS is grounded below sea level and therefore potentially vulnerable to rapid retreat. Here we analyze newly acquired airborne geophysical data over the Pensacola‐Pole Basin (PPB), a previously unexplored sector of the EAIS. Using a combination of gravity and magnetic and ice‐penetrating radar data, we present the first detailed subglacial sedimentary basin model for the PPB. Radar data reveal that the PPB is defined by a topographic depression situated ~500 m below sea level. Gravity and magnetic depth‐to‐source modeling indicate that the southern part of the basin is underlain by a sedimentary succession 2–3 km thick. This is interpreted as an equivalent of the Beacon Supergroup and associated Ferrar dolerites that are exposed along the margin of East Antarctica. However, we find that similar rocks appear to be largely absent from the northern part of the basin, close to the present‐day grounding line. In addition, the eastern margin of the basin is characterized by a major geological boundary and a system of overdeepened subglacial troughs. We suggest that these characteristics of the basin may reflect the behavior of past ice sheets and/or exert an influence on the present‐day dynamics of the overlying EAIS. Key Points: We present new compilations of ice thickness, bedrock topography, and gravity anomalies for the Pensacola‐Pole BasinA significant sedimentary succession, 2–3 km in thickness, is preserved beneath the southern part of the basinBasin topography and geology may have influenced the dynamics of past and present‐day ice sheets [ABSTRACT FROM AUTHOR]

The Gamburtsev Subglacial Mountains are the least understood tectonic feature on Earth, because they are completely hidden beneath the East Antarctic Ice Sheet. Their high elevation and youthful Alpine topography, combined with their location on the East Antarctic craton, creates a paradox that has puzzled researchers since the mountains were discovered in 1958. The preservation of Alpine topography in the Gamburtsevs may reflect extremely low long-term erosion rates beneath the ice sheet, but the mountains' origin remains problematic. Here we present the first comprehensive view of the crustal architecture and uplift mechanisms for the Gamburtsevs, derived from radar, gravity and magnetic data. The geophysical data define a 2,500-km-long rift system in East Antarctica surrounding the Gamburtsevs, and a thick crustal root beneath the range. We propose that the root formed during the Proterozoic assembly of interior East Antarctica (possibly about 1?Gyr ago), was preserved as in some old orogens and was rejuvenated during much later Permian (roughly 250?Myr ago) and Cretaceous (roughly 100?Myr ago) rifting. Much like East Africa, the interior of East Antarctica is a mosaic of Precambrian provinces affected by rifting processes. Our models show that the combination of rift-flank uplift, root buoyancy and the isostatic response to fluvial and glacial erosion explains the high elevation and relief of the Gamburtsevs. The evolution of the Gamburtsevs demonstrates that rifting and preserved orogenic roots can produce broad regions of high topography in continental interiors without significantly modifying the underlying Precambrian lithosphere. [ABSTRACT FROM AUTHOR]

Abstract: The Wilkes Subglacial Basin represents an approximately 1400 km-long and up to 600 km wide subglacial depression, buried beneath the over 3 km-thick East Antarctic Ice Sheet. Contrasting models, including rift models and flexural models, have been previously put forward to explain the tectonic origin of this enigmatic basin, which is located in the largely unexplored hinterland of the Transantarctic Mountains. A major aerogeophysical survey was flown during the 2005–06 austral summer to explore the Wilkes Subglacial Basin. Our new airborne radar dataset reveals that the Wilkes Subglacial Basin contains several subglacial basins, which are considerably deeper than previously mapped. Major aeromagnetic lineaments are detected from total field, pseudo-gravity, tilt derivative and Euler Deconvolution maps. These aeromagnetic lineaments reveal that the Wilkes Subglacial Basin and its sub-basins are structurally controlled. Comparison between aeromagnetic signatures over the Wilkes Subglacial Basin region and the Cordillera in North America, suggests that the basin contains a former broad backarc basin and fold-and-thrust belts, forming the transition between a Precambrian craton and the Ross Orogen. The eastern margin of the Wilkes Subglacial Basin is imposed upon the Prince Albert Fault System and the Priestley Fault. These faults may have been reactivated in the Cenozoic, as major strike–slip faults. The western margin of the Wilkes Subglacial Basin is located along the southern extension of the Precambrian-age Mertz Shear Zone and marks the edge of the Terre Adélie Craton. High-frequency aeromagnetic anomalies in the Wilkes Subglacial Basin image large volumes of Jurassic tholeiites, which were intruded into and extruded over Beacon sediments in a possible rift setting. Depth-estimates of magnetic anomaly sources and forward modelling indicate that major Cretaceous and Cenozoic rift basins with thick sedimentary infill, comparable to the deep Ross Sea Rift basins, are however unlikely beneath this part of the Wilkes Subglacial Basin. More localised graben-like features, with up to 1.5 km of sedimentary infill are identified in the Central Basins. These grabens may be transtensional features related to regional Cenozoic intraplate strike–slip deformation, which has been extensively mapped over the adjacent Transantarctic Mountains, and/or older Cretaceous grabens. Over 3 km deep sedimentary basins are also imaged beneath the Western Basins and are inferred to contain older sedimentary infill of Ross-age, based on recent dating of glacial erratics between Mertz and Ninnis Glacier. [Copyright &y& Elsevier]

Abstract: The Gamburtsev Subglacial Mountains are regarded as a key nucleation site for the Antarctic Ice Sheet and they retain a unique long-term record of pre-glacial and early glacial landscape evolution. Here, we use a range of morphometric analyses to constrain the nature of early glaciation and subsequent ice sheet evolution in the interior of East Antarctica, using a new digital elevation model of the Gamburtsev Subglacial Mountains, derived from an extensive airborne radar survey. We find that an inherited fluvial landscape confirms the existence of the Gamburtsev Subglacial Mountains prior to the onset of glaciation at the Eocene–Oligocene climate boundary (ca. 34Ma). Features characteristic of glaciation, at a range of scales, are evident across the mountains. High elevation alpine valley heads, akin to cirques, identified throughout the mountains, are interpreted as evidence for early phases of glaciation in East Antarctica. The equilibrium line altitudes associated with these features, combined with information from fossil plant assemblages, suggest that they formed at, or prior to, 34Ma. It cannot be ruled out that they may have been eroded by ephemeral ice between the Late Cretaceous and the Eocene (100–34Ma). Hanging valleys, overdeepenings, truncated spurs and steep-sided, linear valley networks are indicative of a more widespread alpine glaciation in this region. These features represent ice growth at, or before, 33.7Ma and provide a minimum estimate for the scale of the East Antarctic Ice Sheet between ca. 34 and 14Ma, when dynamic fluctuations in ice extent are recorded at the coast of Antarctica. The implications are that the early East Antarctic Ice Sheet grew rapidly and developed a cold-based core that preserved the alpine landscape. The patterns of landscape evolution identified provide the earliest evidence for the development of the East Antarctic Ice Sheet and can be used to test coupled ice–climate evolution models. [Copyright &y& Elsevier]