Dr. Verónica Torres Acosta

Morphotectonic evolution of the Kenya rift and erosion processes on different time scales using cosmogenic nuclides and (U-Th)/He dating

The East African Rift system is the archetypal young continental rift, and one the most widely studied on Earth. The rift constitutes a unique region in which to investigate the interplay between active rifting, erosion and sedimentation. Despite this, controversy remains as to the mechanisms and timing of rifting in the region. Most authors agree that active rifting has dominated the East African Rift system (EARs), and argue for the presence of one or more plumes in order to explain the amount of extension, timing and volume of volcanic rocks within the rift and adjacent regions. In addition to the tectonic driving forces of rift basin evolution, the EARs has become the focus of studies investigating the interaction between tectonic activity and climate on uplift. Significant feedbacks between the development of topography in the EARs beginning in the Miocene (?), East African climate, hominid evolution and the rate of rift shoulder exhumation have recently been proposed (Sepulchre et al., 2006; Spiegel et al., 2007; Wichura et al., 2010). On such long time scales it is unclear whether these feedbacks are related to regional uplift or localised rift flank evolution, as studies quantifying the Cenozoic rift evolution are limited. On shorter time scales, involving centennial, millennial time scales, however, it can be expected that tectonic forcing has played a more subdued role in generating and routing sediment in this environment when compared to the dramatic shifts in regional moisture availability. Several studies have shown that such shifts are associated with the dynamics of the dynamics of the African-Indian Summer Monsoon System (e.g., Trauth et al., 2005; 2009) and caused pronounced oscillations of lake levels (e.g., Garcin et al., 2009). Presumably, erosional efficiency, and changes in the transport capacity of fluvial systems also increased during that time. These variations may be recorded in the lake sediments themselves and in terrace and delta deposits associated with changing lake levels. It is at this juncture of the long-term and short-term erosion and sedimentation processes that this study is focused on.

• Bernet, M., Torres Acosta, V., Bermudez M. A., Chapter 17: Dating mountain building: exhumation. Mountains, Climate and Biodiversity. Carina Hoorn, Allison Perrigo and Alexandre Antonelli (editors). 2018

• Garcin, Y., Schildgen, T.F., Torres Acosta, V., Melnick, D., Guillemoteau, J., Willenbring, J., Strecker, M.R. Corrigendum to; Short-lived increase in erosion during the African Humid Period: Evidence from the northern Kenya Rift. Earth and Planetary Science Letters. 457, 2017.

• Garcin, Y., Schildgen, T.F., Torres Acosta, V., Melnick, D., Guillemoteau, J., Willenbring, J., Strecker, M.R. Short-lived increase in erosion during the African Humid Period: Evidence from the northern Kenya Rift. Earth and Planetary Science Letters. 457, 2017.

• Torres Acosta, V., Bande, A., Sobel, E.R., Parra, M., Schildgen, T.F., Stuart, F., Strecker, M.R. Cenozoic extension in the Kenya Rift from low-temperature thermochronology: Links to diachronous spatiotemporal evolution of rifting inEast Africa. doi:10.1002/2015TC003949. Tectonics, v.34; 2015.

• Torres Acosta, V., Schildgen, T.F., Clarke, B.A., Scherler, D., Bookhagen, B., Wittmann, H., von Blanckenburg, F., StreckerM.R. The effect of vegetation cover on millennial-scale landscape denudation rates in East Africa. doi:10.1130/L402.1.Lithosphere,v.7; no. 4, 2015.

• Torres Acosta, V. Denudation processes in a tectonically active rift on different time scales. PhD thesis. publishup.uni-potsdam.de/opus4-ubp/frontdoor/index/index/docId/8453; 2015

• Bande, A., Sobel, E.R., Mikolaichuk, A., Torres Acosta, V. Talas-Fergana Fault Cenozoic timing of deformation and its relation to Pamir indentation. doi:10.1144/SP427.1. The Geological Society, London, Special publications, 427, 2015.

Conference contributions

• Torres Acosta, V., Strecker, M.R., Schildgen, T.F., Clarke, B.A., Scherler, D., Bookhagen, B., Wittmann, H., von Blanckenburg, F., Bande, A., Sobel, E.R., Parra, M., Stuart, F.  Denudation processes in the East African Rift System on different time scales, ISTerre Seminar, University Joseph Fourier- Grenoble I, France, 2015. Oral presentation.

• Torres Acosta, V. Strecker, M.R., Schildgen, T.F., Clarke, B.A., Scherler, D., Bookhagen, B., Wittmann, H., von Blanckenburg, F., Bande, A., Sobel, E.R., Parra, M., Stuart, F. Crossing spatio-temporal scales in The Kenya Rift: Understanding the morphotectonic evolution using themochronology and cosmogenic nuclides. Structural Geology Seminar, Freie Universität Berlin, Germany, 2015. Oral presentation.

• Torres Acosta, V., Schildgen, T.F., Clarke, B.A., Scherler, D., Bookhagen, B., Wittmann, H., von Blanckenburg, F., Strecker, M.R. Effects of vegetation cover on landscape denudation rates. EGU meeting 2014, Vienna, Austria. Oral presentation.

• Torres Acosta, V., Schildgen, T.F., Clarke, B.A., Scherler, D., Bookhagen, B., Wittmann, H., von Blanckenburg, F., Strecker, M.R. Effects of vegetation cover on landscape denudation rates. Scottish Universities Environmental Research Center, SUERC Seminar 2014, East Killbride, Scotland, UK. Oral presentation.

• Torres Acosta, V., Schildgen, T.F., Clarke, B.A., Scherler, D., Bookhagen, B., Wittmann, H., von Blanckenburg, F., Strecker, M.R. The effect of vegetation cover on landscape denudation in The East African Rift. DMG-GV-Sediment 2013 Conference, Tübingen, Deutschland. Oral presentation.

• Torres Acosta, V., Schildgen, T.F., Clarke, B.A., Scherler, D., Bookhagen, B., Wittmann, H., von Blanckenburg, F., Strecker, M.R.  Impacts of vegetation on landscape denudation. Congreso Colombiano de Geologia 2013, Bogota, Colombia. Oral presentation and Session Convener.

• Torres-Acosta, V., Strecker, M.R., Schildgen, Wittmann, H, Scherler, D., Bookhagen, B. Erosion rates along fault scarps and rift shoulder environments in Central and Northern Kenya: Insights from new 10Be-derived basin-wide erosion rates. AGU Fall meeting 2011, San Francisco, USA. Poster presentation.

• Torres Acosta, V., Strecker, M.R., Deino, A., Schildgen, T.F., von Blanckenburg, F. Morphotectonic evolution of the Kenya Rift on different time scales, using cosmogenic nuclides 10Be and thermochronology (U-Th)/He and AFT.  Implementation Workshop Rift Initiation- and Evolution, GeoPrisms 2010, NSF, New Mexico, USA. Poster presentation.

• Torres Acosta, V., Strecker, M.R., Schildgen, T.F., Stuart, F. Miocene onset of rift-related tectonic exhumation of basement rocks in the northern Kenya Rift: New (U-Th)/He thermochronology data from the Elgeyo escarpment. Thermochron meeting 2010, Glasgow, Scotland. Poster presentation.