Previous compilation of crustal structure in South America had large unsampled areas including the thin crust in the Sub‐Andean lowlands, largely estimated by gravity data, and the sparsely sampled Amazon Craton. A deployment of 35 seismic stations in Brazil, Bolivia, Paraguay, Argentina, and Uruguay improved the coverage of the Pantanal Basin in Western Brazil, the intracratonic Paraná and the Chaco Basins. Crustal thicknesses and Vp/Vs ratios were estimated with a modified H‐k method by producing three stacked traces to enhance the three Moho conversions (the direct Ps and the two multiples Ppps and Ppss). This modified method gives lower uncertainties than previous studies and shows more regional consistency between nearby stations. The temporary stations and the Brazilian Network (RSBR) have characterized the crustal structure as follows. The Paraná Basin has a thick crust 40–45 km and average Vp/Vs ratio (1.71–1.77), while the Chaco Basin has a slightly thinner crust (35–40 km) and higher Vp/Vs ratio (1.75–1.79). This confirms the lack of widespread magmatic underplating in the Paraná Basin that could be related to the origin of the flood basalts during the South Atlantic opening. A belt of thin crust (30–35 km) with low Vp/Vs (<1.74) is confined to the eastern edge of the Pantanal Basin. Normal crust (38–43 km) is observed along the western edge of the Pantanal, from the southern part of the Amazon craton to the Rio Apa cratonic block. This study, combined with other published data, provides an updated crustal thickness map of South America.

The origin and evolution of the Pantanal basin have been investigated through velocity‐depth profiles developed from the joint inversion of receiver functions and surface‐wave dispersion velocities at 33 broadband stations. The Pantanal basin is a shallow and wide depression in South‐Central Brazil that developed within the Andean foreland in response to loads and flexural bending of the South American plate. Our results reveal the existence of up to four different crustal types that correlate with surface geology: (i) crust of 35 km with VS < 4.0 km/s, under the basin and along the SW projection of the Transbrasiliano lineament (TBL); (ii) crust of 45 km with VS > 4.0 km/s below 40 km depth, flanking the basin to the east and west; (iii) crust of 50–55 km with VS > 4.0 km/s below 40 km depth, flanking the basin to the north and south and along the TBL; and (iv) crust of 42.5–45.0 km with VS < 4.0 km/s in the neighboring Paraná basin. Existing geodynamic models propose that the Pantanal basin formed either in the back‐bulge of the flexural system or at the top of the forebulge, due to extensional bending stresses that reactivated preexisting faults in the shallow upper crust. We argue that the Pantanal basin was formed in a structurally weaker portion of the foreland crust that was affected by delamination and enhanced bending of the South American plate. Our findings do not allow for discrimination among the competing models but suggest that the TBL was critical in marking the location, origin, and evolution of this basin.

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