Imaging exhumed lower continental crust in the distal Jequitinhonha basin, Brazil

Type Article
Date 2018-07
Language English
Author(s) Loureiro Afonso1, Schnurle Philippe2, Klingelhofer F.2, Afilhado A.1, 3, Pinheiro Joao Marcelo2, Evain MikaelORCID2, Gallais Flora2, Dias N. A.1, 3, Rabineau MarinaORCID4, Baltzer Agnes5, Benabdellouahed Massinissa4, Soares J.6, Fuck R.6, Cupertino J. A.7, Viana A.7, Matias L.1, Moulin MarylineORCID2, Aslanian DanielORCID2, Vinicius Aparecido Gomes De Lima M.8
Affiliation(s) 1 : Univ Lisbon, Inst Dom Luiz, Fac Ciencias, Campo Grande,Ed C1,Piso 1, P-1749016 Lisbon, Portugal.
2 : IFREMER, REM GM, Ctr Brest, F-29280 Plouzane, France.
3 : ISEL, Inst Politecn Lisboa, R Conselheiro Emidio Navarro, P-1959007 Lisbon, Portugal.
4 : Univ Bretagne Occidentale, Lab Geosci Ocean, UMR6538, Pl Nicolas Copern, F-29280 Plouzane, France.
5 : Univ Nantes, Geolittomer, LETG UMR CNRS 6554, Inst Geog & Amenagement Reg, Campus Tertre,BP 81227, F-44312 Nantes 3, France.
6 : Univ Brasilia, Inst Geociencias, Campus Darcy Ribeiro, BR-70910900 Brasilia, DF, Brazil.
7 : Petrobras SA, Cenpes Res Ctr, Rio De Janeiro, Brazil.
8 : Univ Fed Pampa, Dept Geofis, Campus Cacapava Sul, BR-96570000 Cappaya Do Sul, RS, Brazil.
Source Journal Of South American Earth Sciences (0895-9811) (Pergamon-elsevier Science Ltd), 2018-07 , Vol. 84 , P. 351-372
DOI 10.1016/j.jsames.2018.01.009
Keyword(s) NE Brazil, South Atlantic Ocean, Passive margins, Wide-angle refraction seismic, PSDM, Crustal structure, Cretaceous breakup, Lower continental crust
Abstract

Twelve combined wide-angle refraction and coincident multi-channel seismic profiles were acquired in the Jequitinhonha-Camamu-Almada, Jacuípe, and Sergipe-Alagoas basins, NE Brazil, during the SALSA experiment in 2014. Profiles SL11 and SL12 image the Jequitinhonha basin, perpendicularly to the coast, with 15 and 11 four-channel ocean-bottom seismometers, respectively. Profile SL10 runs parallel to the coast, crossing profiles SL11 and SL12, imaging the proximal Jequitinhonha and Almada basins with 17 ocean-bottom seismometers. Forward modelling, combined with pre-stack depth migration to increase the horizontal resolution of the velocity models, indicates that sediment thickness varies between 3.3 km and 6.2 km in the distal basin. Crustal thickness at the western edge of the profiles is of around 20 km, with velocity gradients indicating a continental origin. It decreases to less than 5 km in the distal basin, with high seismic velocities and gradients, not compatible with normal oceanic crust nor exhumed upper mantle. Typical oceanic crust is never imaged along these about 200 km-long profiles and we propose that the transitional crust in the Jequitinhonha basin is a made of exhumed lower continental crust.

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Loureiro Afonso, Schnurle Philippe, Klingelhofer F., Afilhado A., Pinheiro Joao Marcelo, Evain Mikael, Gallais Flora, Dias N. A., Rabineau Marina, Baltzer Agnes, Benabdellouahed Massinissa, Soares J., Fuck R., Cupertino J. A., Viana A., Matias L., Moulin Maryline, Aslanian Daniel, Vinicius Aparecido Gomes De Lima M. (2018). Imaging exhumed lower continental crust in the distal Jequitinhonha basin, Brazil. Journal Of South American Earth Sciences, 84, 351-372. Publisher's official version : https://doi.org/10.1016/j.jsames.2018.01.009 , Open Access version : https://archimer.ifremer.fr/doc/00428/53928/