South Orkney Islands

Figure A84. South Orkney Island anomaly, interpreted as the South Orkney Island slab, with (horizontal) [vertical] cross sections through (A)[D] the UUP07 p-wave) and (B)[D] the combined SL2013 and S40RTS s-wave models at 1790 km; C) the location of the modern geological record that we interpret to have formed during the subduction of the slab.

Figure A84. South Orkney Island anomaly, interpreted as the South Orkney Island slab, with (horizontal) [vertical] cross sections through (A)[D] the UUP07 p-wave) and (B)[D] the combined SL2013 and S40RTS s-wave models at 1790 km; C) the location of the modern geological record that we interpret to have formed during the subduction of the slab.


The South Orkney Island anomaly (Figure A84) is NW-SE trending and is located in the mid-mantle, from below southeastern Patagonia to below the Weddell Sea. Based on the shallower Scotia slab and the Georgia Islands slab to the east, it most likely represents paleo-Pacific lithosphere that subducted at the proto-Andean or Gondwanide margin. Martin (2007) interpreted break-up of the Gondwanide margin by slab rollback and back-arc basin spreading to occur from the Early-Middle Jurassic (190-175 Myr) to the Middle Cretaceous. Subduction rollback was terminated by the Palmer Land tectonic event in West Antarctica from 113 – 103 Ma and by the inversion of the Rocas Verdes/Magallanes Basin in Patagonia around 94 Ma (Vaughan et al., 2002; Fildani and Hessler, 2005), which we interpret to represent the end of the subduction of the slab.


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