Rio Negro

Figure A72. Rio Negro anomaly, interpreted as the Rio Negro 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 330 km; C) the location of the modern geological record that we interpret to have formed during the subduction of the slab.

Figure A72. Rio Negro anomaly, interpreted as the Rio Negro 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 330 km; C) the location of the modern geological record that we interpret to have formed during the subduction of the slab.


The Rio Negro anomaly (Figure A72) is located in the upper mantle below western Patagonia, southern South America. It is N-S trending and partly flat-lying. It has previously been interpreted to represent still-subducting Nazca lithosphere below the Andean margin (Aragón et al., 2011). We interpret a break in magmatism in the overriding plate between ~30-15 Ma to correspond with the gap between this slab and the deeper San Matias slab. Aragón et al. (2011) estimated that subduction was re-established by ~23 Ma ago. Arc magmatism was re-established at around 15 Ma (Munizaga et al., 2002). We adopt the 23-15 Ma age range date the base of the slab.


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