Subsidence evolution of the conjugate passive continental margins of southwestern Africa and eastern Argentina
Even though the present-day structure of the South Atlantic passive continental margins has been thoroughly investigated, uncertainties remain, particularly regarding the subsidence evolution during the post-rift phase and its causative processes. This thesis therefore focuses on the subsidence hist...
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| Other Authors: | , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
| Published: |
2016
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| Subjects: | |
| Online Access: | https://publications.rwth-aachen.de/record/660582 https://publications.rwth-aachen.de/search?p=id:%22RWTH-2016-05469%22 |
| Summary: | Even though the present-day structure of the South Atlantic passive continental margins has been thoroughly investigated, uncertainties remain, particularly regarding the subsidence evolution during the post-rift phase and its causative processes. This thesis therefore focuses on the subsidence history of the passive continental margins within the Southern Segment of the South Atlantic Ocean. The subsidence history is inferred from restored paleobathymetries along the passive margins using their present-day structural configuration as well as their thermal field.In a first part of this thesis a 1D backward modelling approach is used to reconstruct the paleobathymetries offshore SW Africa. Therefore, individual subsidence components are separated according to the load induced by the sediments and the thermal cooling of the lithosphere. Starting from the present-day configuration, sedimentary units are successively “backstripped” to quantify the amount of load induced subsidence. The amount of thermal subsidence is calculated assuming uniform stretching of the lithosphere. Considering both subsidence components allows reconstructing paleobathymetries of the SW African margin in order to infer its subsidence history. The results obtained show a general subsidence of the margin with intermittent phases of seafloor uplift, as indicated by elevations above sea level in some parts of the research area. Summing up, the amount of elevations above sea level (i.e., seafloor uplift) during the post-rift phase yields about 1200 m. Although this quantification cannot fully identify the causative processes behind the vertical movements, their timing and magnitude give evidence for a mantle mechanism causing seafloor uplift rather than ridge-push related to spreading of the South Atlantic Ocean.Improving the understanding of the subsidence evolution of the South Atlantic passive margins requires also a subsidence analysis along the conjugate margin offshore SE South America. Hence the Colorado Basin along the Argentine margin ... |
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