Synchronous oceanic spreading and continental rifting in West Antarctica

Magnetic anomalies associated with new ocean crust formation in the Adare Basin off north-western Ross Sea (43 – 26 Ma) can be traced directly into the Northern Basin that underlies the adjacent morphological continental shelf, implying a continuity in the emplacement of oceanic crust. Steep gravity gradients along the margins of the Northern Basin, particularly in the east, suggest that little extension and thinning of continental crust occurred before it ruptured and the new oceanic crust formed, unlike most other continental rifts and the Victoria Land Basin further south. A pre-existing weak crust and localisation of strain by strike slip faulting are proposed as the factors allowing the rapid rupture of continental crust

Electrical structure across a major ice-covered fault belt in northern Victoria Land (East Antarctica)

A Geomagnetic Depth Sounding profile was performed across the glaciated Rennick Graben and the adjacent fault-bounded terranes of northern Victoria Land in East Antarctica. Induction arrows analysis and a 2D inversion model provide a unique deep electrical resistivity window beneath these fault zones. The electrical resistivity break across the Lanterman Fault is apparently restricted to the upper crust, suggesting that this strike-slip fault may not represent a deep lithospheric suture. Further east, a westward-dipping conductor is traced to a depth of 40 km beneath the Robertson Bay Terrane. It may image a remnant of the paleo-Pacific oceanic plate, which subducted beneath the Bowers Terrane. Within the Wilson Terrane, the Rennick Graben is an upper-crust resistive block. The Rennick Graben lacks a deep crustal or upper mantle conductor, in contrast to several continental rifts. However, similar resistive lower crust underlies some other major strike-slip fault belts

An anomaly of the upper mantle below the Rhine Graben, studied by the inductive response of natural electromagnetic fields

The methods of Magnetotellurics (MT) and Geomagnetic Deep Sounding (GOS) have been applied to study the electromagnetic response of the rift structure of the Rhine Graben. The measurements at 17 MT and 7 GOS stations were carried out along a profile running perpendicular across the Graben. Fourier analysis and numerical filters were tried for separation of the frequencies and a least squares technique was applied for data reduction. The thus gained transfer functions can be explained well by two-dimensional models under the following assumption: a well conducting layer at the depth between about 80 and 100 km exists at distances 50 km West and 100 km East of the Rhine Graben. Immediately below the Graben, however, a zone of similar good conductivity lies between about 25 and 45 km depth. The lateral extension of this zone is only some tens of km from the Graben's edges.           ARK: https://n2t.net/ark:/88439/y032853 Permalink: https://geophysicsjournal.com/article/276 &nbsp

The Nivlisen, an Antarctic ice shelf in Dronning Maud Land: geodetic-glaciological results from a combined analysis of ice thickness, ice surface height and ice flow observations

Extensive observations on Nivlisen, an ice shelf at Antarctica's Atlantic coast, are analysed and combined to achieve a new-quality description of its complex glaciological regime. We generate models of ice thickness (primarily from ground-penetratingradar), ellipsoidal ice surface height (primarily from ERS-1 satellite altimetry), freeboard height (by utilising precise sea surface information), and ice flow velocity(from ERS-1/2 SAR interferometry and GPS measurements). Accuracy assessmentsare included. Exploiting the hydrostatic equilibrium relation we infer the 'apparent air layer thickness' as a useful measure for a glacier's density deviation from a pure ice body. This parameter exhibits a distinct spatial variation (ranging from 2 m to 16 m) which we attribute to the transition from an ablation areato an accumulation area. We compute mass flux and mass balance parameters on a local and areally integrated scale. The combined effect of bottom mass balance and temporal change averaged over an essential part of Nivlisen is -654±170 kgm2a-1 which suggests bottom melting processes to dominate. We discuss our results in view of temporal ice mass changes (including remarks on historical observations),basal processes, near-surface processes, and ice-flow dynamical features. The questionfor temporal changes remains open from the data at hand, and we recommendfurther observations and analyses for its solution