The Neogene Succession of the Albertine Graben, Uganda — Recent Efforts to Set up a Coherent Stratigraphic Scheme

Lukaye, Joshua M.¹; Worsley, David ²; Kincoco, Lyoidah ¹
(1)Petroleum Exploration and Production, Ministry of Energy and Mineral Development, Uganda, Entebbe, Uganda. (2) PRW Geological consulting, Oslo, Norway.

The Albertine Graben forms the northernmost part of the western arm of the Great East African Rift System (EARS). It stretches over a total distance of over 500km from Rwanda in the South to Sudan in the North along Uganda’s western boundary with the Democratic Republic of Congo. It has been known for many years for its oil seeps along the margins, with no major oil discovery until recently after massive discoveries in Uganda, demonstrating its hydrocarbon potential. The lithostratigraphic schemes that have been existent in this petroliferious Neogene succession have been inconsistent, each depending on its author and for a limited part of the Graben. They are based almost solely on surface exposures using mammalian and molluscan evolutionary trends. Sediment thickness of upto 6 km have been suggested but hydrocarbon discoveries that have been made so far are in perched terraces on the graben’s margins hence, additional discoveries can be expected in the deeper and more central parts of the Graben once exploration progresses to this parts.

In order to facilitate more targeted exploration and to enable a reliable total resource assessment for the entire Graben, a coherent regional stratigraphical framework must be established. Recent work, involving re-examination of all relevant data has however led to significant new insights into the development of this Neogene petroleum province. The interplay of lacustrine and alluvial environments, with varying degrees of subsidence, tectonism and resultant variations in lake levels, have all affected axial and marginal clastic input to the basin. These in turn have led to the development of a complex stratigraphical scenario: although correlation between surface and subsurface intervals is not always immediately evident, our work displays the importance of integrating information from both realms including a systematic sampling and resampling of surface tuffs together with bottom hole and shallow core palynostratigraphic studies among other methods as the tools to resolve problems of intrabasinal correlation.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.