Effect of the cold Nazca Slab on the depth of the 660 km discontinuity in South America

Adjoint Waveform Tomography of South America

“…(2003) and Bianchi et al. (2021) who did not observe any depth changes of the 410 and 650‐km discontinuities, based on receiver functions, that could be attributed to a thermal anomaly. Portner et al.…”

“…A vertical "cylindrical" low-velocity anomaly beneath the Paraná Basin, first detected by VanDecar et al (1995), was confirmed and extended down to ∼800 km by Schimmel et al (2003) and Rocha et al (2011). The initial interpretation of the anomaly as due to higher temperatures was challenged by Liu et al (2003) and Bianchi et al (2021) who did not observe any depth changes of the 410 and 650-km discontinuities, based on receiver functions, that could be attributed to a thermal anomaly. Portner et al (2020) and Rodríguez et al (2021) showed a low-velocity anomaly in the 150-1,200 km depth range beneath the Paraná Basin, which appears to connect to the Nazca Slab in the top of the lower mantle and transition zone (Figure 15a).…”