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Geochemical composition of sediment linked to the climate and basin evolution of the Albertine Rift in Uganda since the Miocene

In this study the factors that control the geochemical composition of terrestrial clastic sediment were defined for the first time for provenance analysis in a rift basin under humid-tropical climate conditions. We present an almost continuous geochemical profile through the Miocene to Pleistocene terrestrial clastic sedimentary fill of the Albertine Rift in East Africa in order to evaluate changes in sediment provenance and climate conditions and link it to rift evolution. The 500 km long Albertine Rift is part of the East African Rift System, forming the northern end of its western branch. Sediment samples from two areas on the Ugandan side (Kisegi–Nyabusosi and Nkondo-Kaiso area) were analysed using major and trace element geochemistry. Petrographic and mineralogic data including heavy mineral spectra and clay mineralogy were largely available from published data. To best possibly eliminate a grain size effect, the samples were separated into two grain fractions: clay/silt (> 63μm) and sand (63-2000 μm). On the basis of statistical analysis data were compared with published and defined provenance groups and the climate development as inferred from published data on sediment facies, clay mineralogy and pollen analysis. First results indicate for instance that trace element indicators Th/Sc and La/Sc increase upsection, which is in line with increased local tectonic activity due to uplift of the Rwenzori mountains and resulting rift inversion during the Pleistocene. Climate indicators CIA and CIX show maximum values for the clay fractions during the Pliocene likely due to highest humidity at this period.

Details

Author
Ines Bartholomae1, Matthias Hinderer1, Carita Augustsson2, Jens Hornung1
Institutionen
1Institute of Applied Geosciences, TU Darmstadt, Germany; 2Department of Energy Resources, University of Stavanger, Norway
Veranstaltung
GeoSaxonia 2024
Datum
2024
DOI
10.48380/xtej-gp19