Section 37
Chapter 36,680

The Rwenzori Mountains of western Uganda – Aspects on the evolution of their remarkable morphology within the Albertine Rift

Coimbra, Joao Carlos; Pinto, Iraja Damiani; Wurdig, Norma Luiza; Do Carmo, Dermeval Aparecido

Journal of African Earth Sciences 73-74(none)


ISSN/ISBN: 1464-343X
DOI: 10.1016/j.jafrearsci.2012.07.001
Accession: 036679213

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The Rwenzori Mountains form a narrow mountain range within the western branch of the East African Rift System. They rise to heights of more than 5000m a.s.l. and are composed of Precambrian metamorphic rocks. Lacking a volcanic origin the Rwenzoris are regarded as an extreme example of rift flank uplift and a key area to study rift-related uplift processes within an extensional setting. To determine these processes and underlying rift dynamics, the presented study provides constraints on the temporal and spatial exhumation history of the Rwenzori Mts. Recent and former geomorphology is investigated, addressing geomorphologic proxies as well as the cooling history. Associated erosion rates are derived from thermochronological data, allowing constraining relief changes over time. It could be demonstrated, that inherited tectonic structures play a major role in routing erosion processes. The cooling history of the Rwenzori Mts derived from low-temperature thermochronology reaches back to Jurassic times. Final exhumation was recorded for Neogene times, with differentiated erosion and uplift movements during the last 10Ma and a fast final uplift of the Rwenzoris in the near past, where erosion could not compensate for (Bauer et al., 2010a). This paper integrates geomorphologic and thermochronological constraints, in order to provide a basis for understanding the development of the evolution of the Albertine Rift area, with focus placed on the Mesozoic and Cenozoic history of the central Rwenzori Mts. Rwenzori Mts exhumation reaches far beyond Neogene rifting, mirroring far field effects like S-Atlantic opening. Inherited tectonic structures play a major role in routing erosion processes in the Rwenzori Mts. Dense vegetation impedes erosion, resulting in much lower erosion rates than expected for alike mountainous areas.

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