The Wilkes Land Anomaly revisited

Abstract

International audienceThe Wilkes Land Gravity Anomaly, first reported in 1959–60, is located in northern Victoria Land in the Pacific Ocean sector of East Antarctica, 1400 km west of the Ross Sea and centred at 70°00'S-140°00'E. Initially described on the basis of ground-based seismic and gravity survey, and estimated at the time to have a diameter of 243 km, the original data are now supplemented by data from airborne radiosound survey, airborne gravity survey, airborne magnetic survey and satellite remote sensing. These new data enable us to expand upon the original data, and reveal that the structure has a diameter of some 510 km, is accompanied by ice streams and a chaotically disturbed region of the continental ice sheet, has a subglacial topographical relief of ≥1500 m, and exhibits a negative free air gravity anomaly associated with a larger central positive free air gravity anomaly. The feature has been described as a volcanic structure, an igneous intrusion, an ancient igneous diapir, a subglacial sedimentary basin, a glacially eroded subglacial valley, a tectonic feature and a meteorite impact crater. We re-examine the feature on the basis of these collective data, with emphasis on the free air gravity anomaly signs, magnitudes and patterns, magnetic signature magnitudes and patterns, and the size, shape, dimensions and morphology of the structure. This enhanced view adds substantially to the original description provided at the time of discovery, and suggests several explanations for the origin of the Wilkes Land Anomaly. However, the importance of this feature lies not only in determining its origin but by the fact that this part of the Wilkes Subglacial Basin is one of the most prominent regional negative geoid and associated gravity anomalies of the Antarctic continent

On the detection of the Wilkes Land impact crater

“…By applying recent gravito-topographic models valid for Antarctica (SatGravRET 2014 and Bedmap 2), we support findings by von Frese et al (2006, 2009), Weihaupt et al (2015 and others who claimed that in the Wilkes Land there is a huge impact basin with a mascon centered at ϕ = -70°S and λ = 120°E from an extraterrestrial origin. This would be the greatest impact crater known or the only one impact basin on the Earth preserved (but only partly and under the ice or sea) till the present, with over 500 km in diameter.…”

“…This paper has been written with one of the aims to confirm prior published controversial findings, including von Frese et al (2013) and Weihaupt et al (2015) arguing that the Wilkes Land anomaly beneath the ice in East Antarctica is consistent with the geophysical characteristics of an impact crater/basin. The Wilkes Land anomaly (also known as the Wilkes Land) is centered at ϕ = -70°S and λ = 120°E.…”

“…They used data from the GRACE mission (Gravity recovery and climate experiment, see, e.g., https ://www.nasa.gov/missi on_pages / Grace /index .html) in spherical harmonic expansion to degree and order 90 (half-wavelength resolution on the ground ~ 200 km); they worked with gravity anomalies and the derived first vertical derivative of them to enhance the resolution and the accuracy of the Wilkes Land anomaly. Their findings were further supported by magnetic data in von Frese et al (2013) and by Weihaupt et al (2015). The latter authors wrote: "…recent data from various sources revealed that the structure has a diameter of some 510 km, …, has a subglacial topography relief of ≥ 1500 m, and exhibits a negative free air gravity anomaly associated with a larger central positive free air gravity anomaly…".…”

“…The latter authors wrote: "…recent data from various sources revealed that the structure has a diameter of some 510 km, …, has a subglacial topography relief of ≥ 1500 m, and exhibits a negative free air gravity anomaly associated with a larger central positive free air gravity anomaly…". A more comprehensive review of the Wilkes Land anomaly, and its plausible origin, is described in detail by Weihaupt et al (2015).…”