Dormant state of rifting below the Byrd Subglacial Basin, West Antarctica, implied by magnetotelluric (MT) profiling

Abstract

During the 1994–1995 austral summer field season, we collected twelve, high‐quality MT soundings over the Byrd Subglacial Basin of central West Antarctica (82°36′S lat., 118°14′W long, approx.) in the period range 0.01 s to 400 s. Ten equispaced sites in a 54 km profile cross regional aeromagnetic trends and complement seismic reflection and refraction results collected by others. Our purposes were to prove such measurements were feasible over the 2 km thick interior ice sheet, and to show from deep electrical resistivity whether the Byrd Basin comprises an active rift environment. The difficult acquisition of electric field data on ice was overcome using a custom electrometer system, with preamplifiers located at the electrode sites to buffer the high contact impedances of the ice as close to the source as possible. Two‐dimensional modeling of the profile shows that resistivity of the deep crust and upper mantle is about 2000–3000 ohm‐m to 100 km depth or more. This is much higher than observed in active extensional regimes, suggesting that the current state of rifting, at least in this part of central West Antarctica, is dormant.

Electrical structure beneath Schirmacher Oasis, East Antarctica: a magnetotelluric study

“…Wagner & Lindner (1991) suggested magnetization all the way to the Moho, implying a cool regime. Thus, the lower resistivity of the lower crustal layer observed in our MT traverse is consistent with a cratonic nature and solid-phase conductors (Wannamaker et al 1996).…”

“…They further processed soundings by specifically removing outliers in the tipper, which also showed basic response stability, although that is not carried out here. The high-quality broad-band MT sounding over the thick interior ice sheet of Antarctica was also obtained over the Whitmore MountainsÁRoss Embayment transitional crust (Wannamaker et al 1996).…”

“…MT surveys have been used to tap information on primary structures such as the distribution of sedimentary units and lithologic contacts, secondary structures such as major fault offsets, geochemical fluxes including hydrothermal alteration, remobilized graphite-sulphide mineralization, thermal regimes such as prograde or melt-exsolved fluids, crustal or upper mantle melts, and mineral semi-conduction, among other aspects (Gough 1986;Constable & Duba 1990;Jones 1992Jones , 1999. Although MT studies offer a high potential to evaluate the crustal structure of Antarctica, only a few investigations have been carried out so far in this region (Wannamaker et al 1996;Wannamaker et al 2004;Pedrera et al 2012). The Antarctic continent has been broadly divided into the eastern and western segments, separated by the Transantarctic Mountains (Gregory 1901).…”

Upper mantle shear wave velocity structure beneath northern Victoria Land, Antarctica: Volcanism and uplift in the northern Transantarctic Mountains

“…Alternatively, it has been suggested that volcanism in the EVP and the slow seismic velocities beneath Ross Island result from localized, rift-related decompression melting associated with the Terror Rift (Wannamaker and Stodt, 1996;Rocchi et al, 2005;Karner et al, 2005;Bialas et al, 2007;Huerta and Harry, 2007). Mantle flow may have been directed toward the East Antarctic craton, thereby warming the cratonic lithosphere, and Cenozoic reactivation of Paleozoic tectonic discontinuities may have resulted in localized decompression melting (Rocchi et al, 2003(Rocchi et al, , 2005Storti et al, 2007;Nardini et al, 2009).…”

Intersections, ideals, and inversion

“…This electromagnetic technique is sensitive to conductivity variations of the order of kilometers to tens of kilometers and complements earlier seismic studies of the region. The current experiment was a follow-up to the University of Utah's first successful broadband magnetotelluric survey in Western Antarctica during 19941995 (Wannamaker et al 1996). Using a differential Efield measurement technique this group overcame the difficulty caused by the very high contact impedance of the polar ice.…”