Neotectonic evolution of the Brazilian northeastern continental margin based on sedimentary facies and ichnology,

Abstract

Quaternary post-Barreiras sediments are widespread along Brazil's passive margin. These deposits are well exposed in the onshore Paraíba Basin, which is one of the rift basins formed during the Pangean continental breakup. In this area, the post-Barreiras sediments consist of sandstones with abundant soft-sediment deformation structures related to seismicity contemporaneous with deposition. The trace fossilsThalassinoidesandPsilonichnusare found up to 38 m above modern sea level in sandstones dated between 60.0 (± 1.4) and 15.1 (± 1.8) ka. The integration of ichnological and sedimentary facies suggests nearshore paleoenvironments. Such deposits could not be related to eustatic sea-level rise, as this time coincides with the last glaciation. Hence, an uplift of 0.63 mm/yr, or 1.97 mm/yr if sea level was 80 m lower in the last glaciation, would have been required to ascend the post-Barreiras sediments several meters above the present-day sea level during the last 60 ka. This would suggest that the post-rift stage of the South American eastern passive margin may have experienced tectonic reactivation more intense than generally recognized. Although more complete data are still needed, the information presented herein may play an important role in studies aiming to decipher the Quaternary evolution of this passive margin.

Association of Post-Barreiras and Barreiras Formation strata and influence on soil genesis, Southern Bahia – Brazil

“…The geochronology confirmed that sandy deposits are not associated with deposits of the underlying Barreiras Formation, whose age is Miocene to Pliocene times (Rossetti et al, 2013). Therefore, they are Post-Barreiras sediments of late Pleistocene age (Table 1), and these results are in line with other studies along the Brazilian coast (Tatumi et al, 2008;Rossetti et al, 2011;Gandini et al, 2014), including the same characteristic, which when collected in greater depth tend to be older.…”

“…The origin of these features varies between pedological processes forming sandy depressions (Moreau et al, 2006a;Oliveira et al, 2010;Schiavo et al, 2020). Also, by sedimentary deposition, forming the Post-Barreiras sediments (Tatumi et al, 2008;Rossetti et al, 2011;Gandini et al, 2014). In the literature, there are several pedological studies on sediments from the Barreiras Formation (Demattê et al, 1996;Moreau et al, 2006b;Cunha et al, 2019).…”

“…However, the origin of the mussunungas involves the action process of acidolysis on Ultisols clay (Moreau et al, 2006a;Oliveira et al, 2010;Schiavo et al, 2020). On the other hand, the origin of Post-Barreiras is due to sedimentary deposition (Rossetti et al, 2011;Gandini et al, 2014;Souza et al, 2016a), and this aspect can influence pedogenesis.…”

Influência Neotectônica No Estabelecimento Dos Vales Dos Rios Paraíba E Mamanguape, Norte Da Bacia Paraíba (Pb)

“…A unidade PB1 é pleistocênica tardia e inclui arenitos intercalados com argilitos e conglomerados, comumente associados a concreções de laterita. Esses depósitos registram processos fl uviais, de fl uxos gravitacionais subaéreos e, localmente, marinhos GANDINI et al, 2014). A unidade PB2 é principalmente holocênica, sendo constituída por sedimentos arenosos, em geral maciços.…”

Análise Morfoestrutural E Neotectônica Na Porção Norte Da Bacia Paraíba (Pb)

“…Geologicamente, a unidade PB1 inclui arenitos intercalados com argilitos e conglomerados, comumente contendo fragmentos de concreções ferruginosas derivadas de paleossolos lateríticos que tipifi cam a discordância basal. Essa unidade é atribuída a ambientes fl uvial, fl uxos de detritos em leques aluviais e, localmente, marinho raso (ROSSETTI et al, 2012;GANDINI et al, 2014). A unidade PB2 sobrejacente é constituída por sedimentos arenosos, em geral maciços e pelo, menos em grande parte, gerada por processos eólicos (ROSSETTI et al, 2012).…”