Tectonic history of the South Orkney Microcontinent from seismic structure and stratigraphy

Correlation between multichannel seismic data collected over the South Orkney Microcontinent and the ODP Leg 113 well stratigraphy provide the identification and distribution of three main sequences: a) a synrift sequence of ?Eocene/Oligocene, constituted by terrigenous deposits present the main depocenters up to 2000 m. The basin formation and their filling could be related to the rift activity that produced the separation of the South Orkney Microcontinent from Antarctic Peninsula and consequently the development of the Powell Basin ; b) a mainly biosiliceous sequence of Middle Miocene to Lower Pliocene, present in the basins and on some of the structural highs, deposited after the drifting from Antarctic Peninsula; c) a diatom bearing silty and clayey mud of Upper Pliocene to Quaternary, draping over the microcontinent. A 3d reconstruction of the acoustic basement and tectoni frame, from compilation of seismic data, highlight the presence of two main structural trends: an East-West trend of the Newton Basin and the East-West elongated structural high in the Northern part, and the North-South trend of the main basins along the southern passive margin (Airy, Bouguer and Eötvös Basins). Furthermore a new depocenter on the western part has been recognised.