FOR 703: Rift Dynamics, Uplift and Climate Change in Equatorial Africa: Interdisciplinary Research Linking Asthenospere, Lithosphere, Biosphere and Atmosphere
Final Report Abstract
The interdisciplinary research unit Riftlink is concerned with the relationship between rift dynamics, uplift and climate change in equatorial Africa. It works on three general scales: (1) on the scale of the Rwenzori Mountains and the adjacent Albertine Rift, (2) on the scale of equatorial East Africa and, (3) on a global scale. The “local scale” Albertine Rift projects focus on the causes of extreme uplift and its effects at or near the Earth surface. The impact that extreme rift-related uplift might have had on African climate and biogeographical zonation patterns is being addressed on a wider regional scale. Because the climate modeling also deals with global climate models a global scale is implied. Understanding the causes of the extreme Rwenzori uplift is one of the most intriguing problems in the geodynamics of rifting. To constrain the dynamic processes, which caused rift-related crustal uplift and to address causal relationships between mantle/lower-crustal and atmospheric/biogeographical processes is our major goal. The specific objectives of this research unit may be summarized as follows: To study tectonic and geological structures and processes in the Earth’s crust and mantle beneath the Rwenzori range. - To analyse near-surface structures and processes in relationship to rifting and rift-flank uplift. - To investigate the causes and evolution of extreme uplift within a rift. - To understand the relationships between climate change and bio-geographical zonation in East Africa. - To finally develop coupled geodynamic-atmospheric models for (extreme) rifting-related uplift. During the previous years we have gained a number of new and important insights relevant to addressing our goals. Magmatic processes of rifting have become a major focus of our research. Geodynamic models were developed that incorporate the new findings from seismological and petrological studies. This has led to the proposal of a new geodynamic mechanism, namely rift-induced delamination, to explain the extreme and rapid uplift of the Rwenzori Mountains. In addition, it has been shown that processes of melt propagation and related alterations of the lithospheric structure play an important role in the generation of mantle earthquakes and rift initiation. We developed a kinematic model of structural evolution, both in time and space, and quantified the long-term to short-term exhumation history of the Rwenzori block and the rift shoulders along the Albertine Rift. We delivered information about the sedimentary environments in the graben segments since the Middle Miocene and considered the glacial history of the Rwenzori Mountains from the numerical modeling perspective. Finally, the timing of rift-related uplift has been related to climate changes in equatorial Africa and also to climate-controlled pulses in biological evolution. However, open questions remain, specifically regarding the development of models to couple geodynamic and atmospheric processes. Such modeling and the testing of the model predictions by comparison with data collected in the field will remain the topic of future research initiatives.
Publications
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(2011): Electrical mantle anisotropy and crustal conductor: a 3-D conductivity model of the Rwenzori Region in western Uganda. Geophysical Journal International, 185, 1235-1242
Häuserer, M., Junge, A.
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(2012): Chemical composition of modern and fossil hippopotamid teeth and implications for paleoenvironmental reconstructions and enamel formation: Part 1: Major and minor element variation. Biogeosciences, 9, 119-139
Brügmann, G., Krause, J., Brachert, T., Kullmer, O., Schrenk, F., Ssemmanda, I., Mertz, D.F.
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(2012): Patterns and origin of igneous activity around the Tanzanian craton. Journal of African Earth Sciences, 62, 1-18
Foley, S.F., Link, K., Tiberindwa, J.V., Barifaijo, E.
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(2014): Environmental heterogeneity predicts species richness of freshwater mollusks in sub-Saharan Africa. International Journal of Earth Sciences
Hauffe, T., R. Schultheiß, B. Van Bocxlaer, K. Prömmel, C. Albrecht
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(2015). Long-term cooling history of the Albertine Rift: new evidence from the western rift shoulder, D.R. Congo. International Journal of Earth Science
Bauer, F.U., Glasmacher, U.A., Ring, U., Grobe, R.W., Mambo, V.S., Starz, M.
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(2015). Shaping the Rwenzoris: Balancing Uplift, Erosion, and Glaciation. Int. J. Earth Sci., 1437, 1-18
Kaufmann, G., Hinderer, M., Romanov, D.
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(2015): Shaping the Rwenzoris: Balancing Uplift, Erosion, and Glaciation. Int. J. Earth Sci.
Kaufmann, G., Hinderer, M. & Romanov, D.
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(2015): The Rwenzori Mountains, a Paleoproterzoic crustal shear belt crossing the Albertine rift system. International Journal of Earth Sciences
Koehn, D., Link, K., Sachau, T., Passchier, C.W., Aanyu, K., Spikings, A., and Harbinson, R.
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(2016): Molecular phylogeny and DNA barcoding confirms cryptic species in the African freshwater oyster, Etheria elliptica Lamarck, 1807 (Bivalvia: Etheriidae). Biological Journal of the Linnean Society. B I J 12734
Elderkin, C.L.; Clewing, C.; Wilke, T. & Albrecht, C.
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(2016): Numerical Models of Mantle Lithosphere Weakening, Erosion and Delamination Induced by Melt Extraction and Emplacement. — International Journal of Earth Science
Wallner, H.; Schmeling, H.
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(2016): Small‐scale thermal upwellings under the northern East African Rift from S travel time tomography, J. Geophys. Res.: SE, 121 (10), 7395-7408
Civiero, C., Goes, S., Hammond, J.O.S., Fishwick, S., Ahmed, A., Ayele, A., Doubre, C., Goitom, B., Keir, D., Kendall, J.M., Leroy, S., Ogubazghi, G., Rümpker, G., Stuart, G.W.
