Role of Climate and Active Rifting in Sedimentation on the Shore Lake Edward-George Basin, Albertine Graben, Uganda
Published:December 01, 2015
Wilson M. Tumushabe, Joshua Lukaye, Tonny Sserubiri, Christopher J. Nicholas, 2015. "Role of Climate and Active Rifting in Sedimentation on the Shore Lake Edward-George Basin, Albertine Graben, Uganda", Petroleum Systems in “Rift” Basins, Paul J. Post, James Coleman, Jr., Norman C. Rosen, David E. Brown, Tina Roberts-Ashby, Peter Kahn, Mark Rowan
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The project area is the onshore Ugandan Lake Edward-George basin, Albertine rift that is located in the northernmost part of the western arm of East African Rift System (EARS). Dominion Petroleum Ltd carried out petroleum exploration in the Lake Edward basin; i.e., field geological mapping, seismic data acquisition, and interpretation, etc. This resulted in the drilling of the Ngaji-1 well, the only deep well in the entire area. The major aspects of this research are: (1) to evaluate the sedimentology and stratigraphy of different lithologies in this area using ‘lithofacies’ or ‘lithofacies associations,’ (2) revisit the lithostratigraphic framework of this area, and (3) determine how climate and tectonism have influenced sedimentation style, with the major emphasis on further unravelling the petroleum potential of the area. XRF and clay mineralogy (XRD) studies proved to be of little significance in the paleoclimatic interpretations of sediments within the study area, Lake Edward basin and therefore only ICP-MS/OES data has been used in this project.
From field geology and geochemical data (ICP-MS/OES), it is confirmed that climate and tectonism played a significant role during sedimentation in this basin. It has been found that all scenarios raised in the predictive coupled climatic-tectonic model are present within the Lake Edward-George basin. Results from this research however also show that rift-fill sediments in the south and eastern Lake Edward-George basin (close to the rift shoulders) are strongly dominated by fluvial and alluvial distributary fan complexes, and within these fan complexes, could be recognized and described during detailed stratigraphic logging the different lacustrine packages encountered within the basin-fill sediments close to the present-day Lake Edward.
Sediments within the study area were identified and classified into four members: (1) Kabagwe, (2) Rushaya, (3) Kiruruma, and (4) Kisenyi members. However, as in previous research work within the area, the main challenge was to locate the definitive chronostratigraphic markers for these members. It has been further confirmed that sediments in the Lake Edward-George basin represent a petroleum play for hydrocarbon generation and accumulation, in which the necessary elements of a valid petroleum system were identified; i.e., there was excellent or good potential for reservoirs and top seals as well as circumstantial evidence of regionally source rocks, possible seals, traps and hydrocarbon migration pathways.