|
The Antarctic
continent plays a very important role in the plate tectonics context
and its most recent revisions. The study of the lithosphere and the
identification of relevant lateral discontinuities in Antarctica and
surrounding areas are essential to the understanding of the geodynamic
evolution of the continent.
Studies of the
Antarctic continent rely extensively on magnetic anomaly data, because
of the extensive ice cover. Numerous magnetic surveys have been carried
out by the international community. The objective for compiling the
Antarctic digital magnetic database is to enhance the geological and
tectonic utility of these magnetic data. This compilation will provide
an improvement in understanding the regional geology of the Antarctic,
provide a regional framework for the interpretation of smaller scale
areas and enable a more effective selection of areas for further
investigation.
The
multinational Antarctic Digital Magnetic Anomaly Project (ADMAP) has
been launched to compile near-surface and satellite magnetic anomaly
data into a digital map and database for the Antarctic continent and
surrounding oceans. The unified data set will be a powerful tool for
determining the structure, processes and tectonic evolution of the
continent, together with providing information valuable in the
reconstruction of the Gondwanaland and Rodinia supercontinents. The
resulting merged potential field anomaly maps connect geological
mapping studies of the various programmes in terms of parameters such
as:
- major structure
and composition of the continent. The magnetic (and gravity) data
provide 2-dimensional regional maps of structural grain in basement;
suture zones between basement terranes; the basement terranes
themselves; the nature of intra continental rifts and the extent of
major faults;
- geological timing
and kinematics associated with the evolution of the continent. Relative
ages and displacements can be derived from the detailed geophysical
mapping of rock units. The distinctive magnetic signatures of some
plutons, serpentinites, amphibolites, migmatites, young sedimentary
basins and volcanic rocks provide important markers for extracting both
the orientation of regional faulting and relative timing;
- information on the
isostatic state of the lithosphere contained in long wavelength
magnetic anomalies, because the lower crust is a zone of strongly
enhanced magnetisation with respect to the upper crust and mantle.
Magnetic data, especially in combination with correlative gravity
observations, can provide significant insight into the thermal
structure of the Antarctic lithosphere;
- paleoenvironment
and global change; from the reconstruction of Gondwana, it might be
possible to identify the locations of old oceans and therefore infer
circulation paths that would have affected past climates;
- essential information on the
crustal contribution to the Earth's magnetic field from a remote and
poorly understood region. This effort will permit improved global
geomagnetic field modelling and assist with verification and
calibration of magnetometer observations obtained from polar orbiting
satellite missions (e.g. POGO, Magsat, Orsted). The integration of
satellite and near-surface magnetic anomalies will result in a
compilation that accurately portrays the fullest possible spectrum of
magnetic anomalies for the Antarctic lithosphere.
|