Crustal structure of the East-African Limpopo Margin, a strike-slip rifted corridor along the continental Mozambique Coastal Plain and North-Natal Valley

• Main Authors: Evain, Mikael, Schnurle, Philippe, Lepretre, Angelique, Verrier, Fanny, Watremez, Louise, Thompson, Joseph Offei, De Clarens, Philippe, Aslanian, Daniel, Moulin, Maryline
• Format: Text
• Language: English
• Published: Copernicus GmbH
• Subjects: geo; archeo; Antarc*; Antarctica
• Online Access: https://doi.org/10.5194/se-2020-209; https://archimer.ifremer.fr/doc/00678/79004/81397.pdf; https://archimer.ifremer.fr/doc/00678/79004/88042.pdf; https://archimer.ifremer.fr/doc/00678/79004/88043.pdf; https://archimer.ifremer.fr/doc/00678/79004/88044.pdf; https://archimer.ifremer.fr/doc/00678/79004/

Deep seismic acquisitions and a new kinematic study recently highlighted the presence of continental crust in both the southern Mozambique's Coastal Plain (MCP) and further offshore in the North Natal Valley (NNV). Such findings falsify previous geodynamic scenarios based on the kinematic overlap between Antarctica and Africa plates, thus profoundly impacting our understanding East-Gondwana break-up. Using an updated position of Antarctica with respect to Africa this study reconsider the formation mechanism of East-African margins and most specifically of the Limpopo margin (LM). Coincident wide-angle and multi-channel seismic data acquired within the PAMELA project are processed to image the sedimentary and deep crustal structure along a profile that runs from the northeastern NNV to the Mozambique basin (MB) striking through the LM. This dataset is combined with companion deep seismic profiles and industrial onshore-offshore seismic lines to provide a robust scenario for the formation and evolution of the LM. Our P-wave velocity model consists of an upper sedimentary sequence of weakly compacted sediments including intrusions and lava flows in the NNV while contourites and mass transport deposits dominates the eastern edge of the LM. This sequence covers a thick acoustic basement that terminates as a prominent basement high just west of the contourites and mass transport deposits domain. The acoustic basement has a seismic facies and velocity signature typical of a volcano-sedimentary basin and appears widespread over our study area extending toward the eastern MCP and NNV. Based on industrial well logs that calibrate our tectono-stratigraphic analysis we constrain its age to be pre-Neocomian. We further infer that either strike-slip or trans-tensional deformation occurred at the basement high which sustained uplift up to the Neocomian. At depth, the crystalline basement and uppermost mantle velocity structures show a progressive eastward crustal thinning of continental crust along the edge of the MCP/NNV and ...