The better understanding of the initial rifting would complement the knowledge of continental breakup and the oceanic opening process. Traditionally, mechanisms controlling the initial rifting have been divided into two schools of end-member models, magma-rich vs magma-poor rifting and pure-shear vs simple shear rifting. However, the linkage between these two schools has been rarely addressed. In our study, extension magnitude and ratio obtained from the balanced cross-sections were applied in magma-poor and magma-rich segments in South Atlantic margins to establish the possible linkage, as classic pure-shear and simple-shear models predict different extension magnitudes and ratios. Two pairs of structural sections Campos basin‒Kwanza basin from the central segment and Pelotas basin‒Walvis basin from the south segment, the southern segment temporally and spatially related to the (Paraná‒Etendeka Large Igneous Province) were subjected to balanced cross-section analysis to determine the extension magnitudes and ratios at the initial rifting stage predating finally opening of South Atlantic Ocean. Comparing the results in the South Atlantic margins with those obtained in classic shear models may suggest the magma-rich segment would return a larger extension ratio and possibly prefer to pure-shear rifting. Results of this study might build a likely linkage between the magma-rich and pure-shear mechanisms during the initial rifting of the oceanic opening process.

The Bongor basin is a WNW–ESE trending basin located within the West and Central Africa Rift System (WCARS). The trend of this basin is quite similar with the Doba Basin. The tectonic history of the Bongor Basin is dominated by extension and inversion, but evidence of inversion tectonics has not been well documented. This study presents a structural study of the Delo depression area located on the northwest of the Bongor Basin. 3D seismic interpretation allows a better understanding of the structural style of the Delo east, Delo west and Delo depression. The structural analysis indicated that the Delo depression area exhibit a multifaceted structural framework, characterized by various structural styles. The extensional features are shaped by inversion tectonics that occurred during the upper Cretaceous (Santonian), resulting in the formation of anticline structure with varying dip orientations, which have been further modified by subsequent extensional movements leading to the development of tilted fault blocks. The structural inversion plays a critical role in determining the geometry of the reservoir and the distribution of hydrocarbon accumulation with the basin. This inversion process has led to the fragmentation of the upper hydrocarbon-rich units and the subsequent biodegradation of hydrocarbons. As a result of these phenomena, oil and gas trend to concentrate in the lower reservoir group adjacent to the source rocks. Consequently, the lower reservoir situated with the enriched hydrocarbon depression is expected to be a primary target for future exploration in the Basin.