Deep crustal architecture of the Parnaíba basin of NE Brazil from receiver function analysis: implications for basin subsidence

Abstract

We investigated the crustal architecture of the Parnaíba basin of NE Brazil by analysing receiver functions along a c. 600 km long transect crossing the central portion of the basin. The transect consisted of nine broadband stations interspaced at c. 70 km distance recording continuously for a period of 15 months, with the goal of improving our understanding of the origin and evolution of this large cratonic basin. Our results show that crustal thickness varies between 39 and 45 km along the transect, gradually thickening towards the depocentre, and that bulk Vp/Vs ratios vary between 1.70 and 1.78. The crust can be divided into a 2.0–3.5 km thick layer of low-velocity sediments, a 15–20 km thick upper crust (3.5 < Vs < 3.6 km s−1) and a 18–22 km thick lower crust (3.7 < Vs < 3.8 km s−1). Near the depocentre, where the crust is thickest, the bottom 10–12 km of the crust are characterized by fast S-velocities (4.0–4.2 km s−1). Our findings confirm that stretching of the lithosphere is minimal and compatible with flexural subsidence. However, loading from a thick, high-density layer of mafic intrusive rocks pervading the lower crust – as recently proposed for the basin – is found to be inconsistent with our bulk Vp/Vs ratios and lower crustal S-velocities. Flexural bending by a deeper load, perhaps related to deep mantle convection, seems more plausible.

An Updated Crustal Thickness Map of Central South America Based on Receiver Function Measurements in the Region of the Chaco, Pantanal, and Paraná Basins, Southwestern Brazil

“…Besides the data analyzed in this study, other published results were included such as (a) the Moho models from active experiments in the Parnaíba Basin, northern Brazil (Daly et al, 2014;Soares et al, 2018), and the continental shelf in southern Brazil (Evain et al, 2015), (b) crustal thicknesses from RF studies in the Parnaíba Basin and Boborema Province (Coelho et al, 2018;Julià et al, 2018;Trindade et al, 2014), and (c) new RF results from the Andes in Bolivia, Peru, and Colombia (Condori et al, 2017;Poveda et al, 2015;Ryan et al, 2016). Stations with good results from Albuquerque et al (2017) in the Amazon region were also included.…”

“…More details can be found in Bianchi et al (2018). The publications used to compile recent results from the literature, since the previous compilation of 2013, are from Argentina (Ammirati et al, 2013;Perarnau et al, 2012), Brazil Assumpção et al, 2015;Berrocal et al, 2004;Coelho et al, 2018;Daly et al, 2014;Evain et al, 2015;Julià et al, 2018;Luz et al, 2015a;Luz et al, 2015b;Moreira, 2013;Soares et al, 2018;Trindade et al, 2014), Colombia (Monsalve et al, 2013;Poveda et al, 2015), Ecuador (Araujo, 2013;Font et al, 2013), Peru (Condori et al, 2017;James & Snoke, 1994;Ryan et al, 2016), and Patagonia (Buffoni et al, 2019;Rodríguez & Russo, 2016) and can be found in the supporting information. The database is available in the Zenodo platform (https://doi.org/10.5281/zenodo.2604359).…”

Cratonic basin formation: a case study of the Parnaíba Basin of Brazil

“…They also record an unexpected bulk conductivity increase in the crust beneath the central part of the Parnaíba Basin. This broadly corresponds to the observations of the sediment-corrected Bouger gravity anomaly high of + 40-60 mGal of Watts et al (2018), and the anomalously high, uppermantle (V p 8.2-8.4 km s −1 ) and lower-crust (V p 6.7-6.8 km s −1 ) P-wave velocities of Soares et al (2018) and lower-crustal S-wave velocities (V s 3.7-3.8 km s −1 ) of Coelho et al (2018). Solon et al (2018) suggest this zone may be related to Brasiliano orogenesis or to the igneous events of the Triassic and Cretaceous.…”

Joint Inversion of Receiver Functions and Surface‐Wave Dispersion in the Pantanal Wetlands: Implications for Basin Formation

“…The origin of the Parnaíba basin is also under debate. Recent research with seismic (Coelho et al, ; Soares et al, ) and gravity (Tozer et al, ) data indicates that the main subsidence mechanism could be flexural, which contrasts with the prevalent view that invoked mechanical stretching of the lithosphere (De Castro et al, , ). Similarly, the Amazon basin is also debated to have formed in relation to a failed rift concealed under the basin's sediments (De Castro et al, ) or to flexural subsidence and lithospheric relaxation due to a dense body in the basin's underlying lower crust (Nunn & Aires, ).…”