Crustal architecture of the Borborema Province, NE Brazil, from receiver function CCP stacks: Implications for Mesozoic stretching and Cenozoic uplift

• Crustal thickness varies between 30 and 38 km within the Borborema Province.
• Thin crust contains an intra-crustal detachment zone at 9–18 km depth.
• Thin crust is the result of Mesozoic stretching.
• Thick crust (southern Borborema Plateau) is rheologically strong.
• The northern Plateau consists of extended crust that was later uplifted.

We have investigated the crustal architecture of the Borborema Province of NE Brazil by constructing common conversion point (CCP) receiver function stacks from teleseismic P-waveforms recorded at 64 seismic stations in the region. The Borborema Province represents the western portion of a larger Neoproterozoic mobile belt that experienced extension in the Mesozoic, leading to the formation of a number of intra-continental rift basins and, eventually, continental breakup. After continental breakup, episodes of uplift in the Province — perhaps related to coeval episodes of Cenozoic volcanism — helped shape the high topographies of the Borborema Plateau. Our receiver function CCP stacks image clear P-to-S conversions at the crust–mantle boundary and confirm independent evidence for a 36–38 km thick crust under the southern portion of the Plateau and a thinner 30–32 km thick crust in the surrounding regions, including the northern Plateau. The cross-sections also reveal the presence of an intra-crustal discontinuity at 9–18 km depth under the regions of thin crust that fades away under the thick southern Plateau. We argue that the thin crust in the Borborema Province is the result of Mesozoic crustal stretching and that the intra-crustal discontinuity represents a low-angle detachment zone that helped accommodate extension in the crust. The thick crust under the southern Plateau would then represent a rheologically stronger portion of the Borborema Province that resisted deformation by Mesozoic extension, while the thin crust under the northern Plateau would be a portion of formerly depressed thin crust that was uplifted during the Cenozoic.