Details

• Dra. Marta Pérez-Gussinyé, Department of Earth Sciences, Royal Holloway, University of London, Regne Unit
• Date: March, 26, 2015 12:00 am
• Place: Sala d’Actes ICTJA-CSIC
• Location: C/ Solé i Sabarís s/n, Barcelona
• Contact: Manel Fernández

Abstract

Along the margins of the South Atlantic from the Camamu/Gabao to the North Santos/South Kwanza conjugate margin, rift architecture changes considerably. On the Brazilian side, from North to South, the margin width increases, syn-rift subsidence decreases and the degree of conjugate margin asymmetry varies. Here we suggest that these changes in architectonical styles can be explained with a combination of extensional modes: core-complex, wide and narrow rift modes with fourth extensional mode: sequential faulting. This last mode arises at the last stages of extension and accounts for conjugate margin asymmetry. The prevalence of any of these modes during extension determines margin architecture and depends on the strength of the lower crust at the start of rifting and during extension. The onset and distribution of melting and serpentinisation are also strongly linked with lower crustal rheology. Weaker rheologies lead to less coupling between lithospheric layers and a slower mantle uplift, hence relatively less melting and serpentinisation. Here we show how likely changes in crustal strength and lithospheric configuration on the onshore terranes in which rifting developed, from the northern San Francisco craton to the southern Ribeira belt, may have led to the rich variety in extensional and oceanization styles observed in this margin sector.