Prospección magnetométrica en la placa de Scotia occidental.

LIPPAI, H.; TASSONE A.; PERONI J. I,; OSIROFF, S

Mendoza

Congreso; XXIV Reunión Científica de Geofísica y Geodesia; 2009

Asociación Argentina de Geofísicos y Geodestas (AAGG)

The generation of the western Scotia plate (WSP) at about 30 Ma led to the separation of South American and Antarctic plates. This geodynamic process produced an enormous impact in the movement of the oceanic waters as well as in the tectonic evolution of associated continental margins. The Shackleton Fracture Zone (ZFS) represents the western boundary of the WSP and had a major role in controlling the relative diverging movements of South America and Antarctic plates. Several parallel spreading axes were generated during the opening of WSP (since about 30 to 7 Ma) and the associated volcanic blocks acquired magnetism in relation to the instantaneous magnetic pole. A series of transforming faults normal to the ridge accommodated the opening movements and displaced the volcanic blocks. The segments bounded by these transforming faults are known as W1 to W10 opening corridors. The opening blocks display bands of magnetic anomalies that by their intensity and location are associated to reverse and inverse remanent magnetizations allowing assigning age by relating them to the regional geomagnetic time scale. During December-2008 a magnetometric survey was carried out on board of the oceanographic ship CONICET-Puerto Deseado, crossing the WSP from Tierra del Fuego in the north to the zone of Orkney Islands to the South, between W3 and W4 opening corridors. The data acquisition was severely limited by the meteorology; therefore there are some gaps in the magnetic registration as well as in the sea floor sampling profiles. Magnetic data were acquired along 3 profiles with a total length of about 624 km. A marine magnetometer Geometrics G882 SX of Cesium steam (sensitivity of 0,004 nT/Hz) was employed which allowed the acquisition of 10 samples per second with an absolute precision of ± 1 nT. The magnetometer was programmed for a speed of sampling of 1 data every 3 seconds, which resulted in a progression between sampling points of 12.28 m and a total of 56207 data. Data were recorded with the program Mag Log and data conversion was done with the Magmap 2000 software. Two pairs of GPS Trimble & Fugro allowed the continuous DGPS of sampling profiles. The collected data will be correlated with other profiles of our data base and those reported in bibliography to generate a detailed map of the magnetic anomalies related to the opening of the Scotia Sea.