Sedimentary Flux to Passive Margins From Inversion of Drainage Patterns: Examples from Africa
Abstract
We show that inversion of an inventory of 14801 rivers provides information about Cenozoic uplift and sedimentary flux to northwest Africa's passive margin. First, we measured solid sedimentary flux using 53000 km2 of 2D seismic reflection data and eight wells. Check-shot data were used to convert time to depth and to determine best-fitting compaction parameters. Detailed biostratigraphic records provide excellent age constraint. Six horizons were mapped (seabed, 5.6 Ma, 23.8 Ma, 58.40 Ma, 89.4 Ma and basement). Isopachs were constructed to determine solid sedimentary fluxes: 2x103 km3 /Ma at 58.4-23.8 Ma, 4x103 km3 /Ma at 23.8-5.6 Ma, and 28x103 km3 /Ma at 5.6-0 Ma. Compaction parameter errors were propagated into our history of sedimentary flux. Secondly, we inverted our drainage inventory to explore the relationship between uplift and erosion onshore and our measured flux. The stream power erosional model was calibrated using independent observations of marine terrace elevations and ages. We integrate incision rates along best-fitting theoretical river profiles to predict sedimentary flux at mouths of the rivers draining northwest Africa (e.g. Senegal). Calculated Neogene uplift and erosion is staged. Our predicted history of sedimentary flux increases in three stages towards the present-day, which agrees with our offshore measurements. Finally, using our inverse approach we systematically tested different erosional scenarios. We find that sedimentary flux to Africa's passive margins is controlled up the history of uplift and erosional processes play a moderating role. Predicted fluxes are indistinguishable if precipitation rate varies with a period less than 1 Ma or drainage area varies by less than 50%. We tentatively suggest the history of Cenozoic epeirogeny determined the rate of sediment delivery to northwest Africa's passive margin.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMEP53B0933L
- Keywords:
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- 1824 Geomorphology: general;
- HYDROLOGYDE: 1862 Sediment transport;
- HYDROLOGYDE: 8020 Mechanics;
- theory;
- and modeling;
- STRUCTURAL GEOLOGYDE: 8175 Tectonics and landscape evolution;
- TECTONOPHYSICS