3D geological modelling of the South Orkney Microcontinent (southern Scotia Arc, Antarctica) from seismic and potential field data

The South Orkney Microcontinent (SOM) is located in the central sector of the South Scotia Arc, at the Weddell Sea northern edge. The SOM is the largest continental block in the southern Scotia Arc with a surface of more than 70.000 km². Its current location is the result of the continental break-up from the Antarctic Peninsula related to the Powell Basin opening, considered one of the first steps in the formation of the Drake Passage during the Eocene-Oligocene.

In this work we present a 3D geological model of the SOM built with Geomodeller® using free-air gravity anomaly data from Topex and magnetic data from WDMAM. To obtain a reliable result, some constrains have been taken into account: (1) GEBCO data are used to establish the bathymetric level, (2) basement depth and geometry is calculated from multi-channel seismic profiles over the study area obtained from the Seismic Data Library System (SDLS), and (3) the analytic signal of total field magnetic anomalies has been used to limit the extension of the bodies that cause the PMA (Pacific Margin Anomaly).

All these data, together with additional geological and geophysical interpretation, have allowed to build the 3D model. The characterization of the sedimentary basins shape, the deep crust structure and Moho geometry, the volume of the magnetic bodies and the nature and geometry of the SOM margins will provide a better understanding of the complex SOM structure resulting from different tectonic phases since the Mesozoic and related to the Scotia-Drake opening.

The preliminary result shows a good fit between the observed and calculated gravimetric anomaly. We are currently working on the gravimetric inversion to obtain an optimal adjustment.