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Deep structure of the Pará-Maranhão/Barreirinhas passive margin in the equatorial Atlantic (NE Brazil)

2021-10Journal article Restricted access
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dc.contributor.authorAslanian, Daniel
dc.contributor.authorGallais, Flora
dc.contributor.authorAfilhado, Alexandra
dc.contributor.authorSchnurle, Philippe
dc.contributor.authorMoulin, Maryline
dc.contributor.authorEvain, Mikael
dc.contributor.authorDias, Nuno
dc.contributor.authorSoares, José
dc.contributor.authorFuck, Reinhart
dc.contributor.authorNeto, Otaviano da Cruz Pessoa
dc.contributor.authorViana, Adriano
dc.date.accessioned2021-05-27T15:18:15Z
dc.date.available2021-05-27T15:18:15Z
dc.date.issued2021-10
dc.description.abstractThe Pará-Maranhão/Barreirinhas margin, North Brazil, is a pull-apart passive margin, with two strike-slip borders, formed during the opening of the Equatorial Atlantic Ocean during Cretaceous time. Its geometry and evolution are speculative due to the lack of information on the crustal structure and the crustal nature. We present here the E-W profiles of the MAGIC (Margins of brAzil, Ghana and Ivory Coast) deep seismic experiment, a joint project between French and Brazilian universities, research institutes and the industry. Fifty-six Ocean Bottom Seismometers (OBS) and a 4.5 seismic streamer were deployed at sea along 2 of the 5 MAGIC profiles. One profile was extended onshore by installing 8 land stations. We perform forward modelling through combined interpretation of the multichannel seismic and of the main reflected and refracted of these phases recorded by the OBSs. The final P-wave velocity models reveal distinct structural domains from onshore Brazil towards the Atlantic Ocean characterized by variations of the crustal thicknesses and velocities: (1) an unthinned continental crust below the São Luís Craton, where the crust is 33 km thick, (2) a 60 km wide necking domain below the Ilha de Santana Platform; (3) offshore, east of the continental slope, a 10 km-thick deep sedimentary basin underlain by a 5 km thick crust with velocity of 6.2–6.9 km/s that we interpret as an exhumed lower continental crust, on the top of an Anomalous Velocity Layer (AVL) probably made of intrusions of mantle-derived melts into the lower continental crust, or a mixture of them; (4) eastwards, the limit of the previous domain is marked by NW-SE aligned volcanoes and the disappearance of the AVL. The sedimentary succession becomes thinner (6 km) overlaying a proto-oceanic crust characterized by seismic velocities higher than “normal” oceanic crust in its upper part, but in continuity with the velocity described in the previous domain; (5) followed by a more characteristic but thin oceanic crust. The middle/lower continental crust seems not only to have a crucial role in the genesis of the passive margin but also to be involved in the genesis of the first oceanic crust. The passage to a typical oceanic crust seems to have occurred progressively by steps: first in the deeper layer by the setup of more and more intrusions of mantle-derived melts at the base of the crust or mixture of exhumed lower crust and mantle, producing a domain of proto-oceanic crust, then by the emplacement of an upper 1-2 km-thick layer with typical oceanic characteristics.pt_PT
dc.description.versioninfo:eu-repo/semantics/publishedVersionpt_PT
dc.identifier.citationASLANIAN, Daniel; [et al] – Deep structure of the Pará-Maranhão/Barreirinhas passive margin in the equatorial Atlantic (NE Brazil). Journal of South American Earth Sciences. ISSN 0895-9811. Vol. 110 (2021), pp. 1-23pt_PT
dc.identifier.doi10.1016/j.jsames.2021.103322pt_PT
dc.identifier.issn0895-9811
dc.identifier.urihttp://hdl.handle.net/10400.21/13389
dc.language.isoengpt_PT
dc.peerreviewedyespt_PT
dc.publisherElsevierpt_PT
dc.relation.publisherversionhttps://reader.elsevier.com/reader/sd/pii/S0895981121001693?token=E8906B555885EFE74E7360F52889ACF54B28F69EBAAC3A6F52FF94A225F8F315A1F3A3D82CD24E097B858F22720DB61B&originRegion=eu-west-1&originCreation=20210527141859pt_PT
dc.subjectEquatorial atlantic oceanpt_PT
dc.subjectPará-maranhão/barreirinhas marginpt_PT
dc.subjectNortheast Brazilpt_PT
dc.subjectPassive marginpt_PT
dc.subjectCrustal structurept_PT
dc.subjectLower continental crustpt_PT
dc.subjectProto-oceanicpt_PT
dc.subjectWide-angle seismicpt_PT
dc.titleDeep structure of the Pará-Maranhão/Barreirinhas passive margin in the equatorial Atlantic (NE Brazil)pt_PT
dc.typejournal article
dspace.entity.typePublication
oaire.citation.endPage23pt_PT
oaire.citation.startPage1pt_PT
oaire.citation.titleJournal of South American Earth Sciencespt_PT
oaire.citation.volume110pt_PT
person.familyNameAslanian
person.familyNameAfilhado
person.familyNameSchnurle
person.familyNameMoulin
person.familyNameEvain
person.familyNameDias
person.familyNameFuck
person.givenNameDaniel
person.givenNameAlexandra
person.givenNamePhilippe
person.givenNameMaryline
person.givenNameMikael
person.givenNameNuno
person.givenNameReinhardt
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