Geophysical models for the tectonic framework of the Lake Vostok region, East Antarctica

Details Geophysical models for the tectonic framework of the Lake Vostok region, East Antarctica Geophysical models for the tectonic framework of the Lake Vostok region, East Antarctica

Dec 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003e%26psl.216..663s&link_type=abstract

Earth and Planetary Science Letters, Volume 216, Issue 4, p. 663-677.

Physics

Geophysics

20

Lake Vostok, East Antarctica, Airborne Geophysics, Gravity, Magnetics, Tectonics

Scientific paper

Aerogeophysical and seismological data from a geophysical survey in the interior of East Antarctica were used to develop a conceptual tectonic model for the Lake Vostok region. The model is constrained using three independent data sets: magnetic, seismic, and gravimetric. A distinct change in the aeromagnetic anomaly character across Lake Vostok defines a crustal boundary. Depth to magnetic basement estimates image a 400-km-wide and more than 10-km-deep sedimentary basin west of the lake. Analysis of teleseismic earthquakes suggests a relatively thin crust beneath Lake Vostok consistent with predictions from kinematic and flexural gravity modelling. Magnetic, gravity, and subglacial topography data reveal a tectonic boundary within East Antarctica. Based on our kinematic and flexural gravity modelling, this tectonic boundary appears to be the result of thrust sheet emplacement onto an earlier passive continental margin. No data presently exist to date directly either the timing of passive margin formation or the subsequent shortening phase. The preserved thrust sheet thickness is related to the thickness of the passive margin crust. Because a significant amount of time is required to erode the thrust sheet topography, we suggest that these tectonic events are Proterozoic in age. Minor normal reactivation of the thrust sheet offers a simple mechanism to explain the formation of the Lake Vostok Basin. A low level of seismicity exists in the vicinity of this tectonic boundary. The existence of a crustal boundary in the Antarctic interior provides new constraints on the Proterozoic architecture of the East Antarctic craton.
Present address: Ocean Research Institute, The University of Tokyo, Tokyo 164-8639, Japan.

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