Sand supply to the Lake Albert Basin (Uganda) during the Miocene‐Pliocene: A multiproxy provenance approach

Abstract

A multiproxy provenance approach (heavy mineral analysis, U‐Pb zircon geochronology, and Pb isotopic analysis of K‐feldspar) has constrained sediment supply within the Upper Nile drainage system in the Miocene‐Pliocene. Provenance data from sandstones were obtained from three exploration wells, two situated on the north‐eastern margin and one on the eastern flank of the Lake Albert Basin, NW Uganda. Data suggest that high‐grade to low‐grade metamorphic rocks and granitoids have variably supplied the heavy mineral assemblages around the Lake Albert Basin during the Miocene‐Pliocene, with contributions from the isotopically heterogeneous Archean Cratons (including the local Ugandan Craton, Tanzanian, and Congo Cratons) and the Pan‐African rocks (the Mozambique Belt) with possible contributions from the Neoproterozoic and Paleoproterozoic rocks. These data also highlight clear differences between supply to the eastern basin margin, compared with the northeast, which is reconcilable with current models for Miocene‐Pliocene drainage in the region. Supply to northeastern Lake Albert during the Miocene‐Pliocene appears to have been through a proto‐Albert Nile (draining from NE to SW) and from a proto‐Victoria Nile or similarly oriented palaeo‐river systems draining from the east. In contrast, the eastern flanks of the basin were likely supplied via the palaeo‐Nkusi river, tapping local hinterland sources and more distal basement to the far‐east (Mozambique Belt). This study highlights the importance of utilizing a multiproxy approach in provenance analysis as no one signal is capable of distinguishing the different source lands and constraining the evolving drainage patterns.

Constraining recycled detritus in quartz‐rich sandstones: Insights from a multi‐proxy provenance study of the Mid‐Carboniferous, Clare Basin, western Ireland

“…Using a multi‐proxy provenance approach has been proven effective to recognise first‐cycle versus polycyclic detritus in a sandstone. For example, utilising Pb isotopes in K‐feldspar, a mineral prone to chemical weathering, with zircon U‐Pb geochronology, has helped identify likely first‐cycle detritus (Franklin et al., 2019; Gagnevin et al., 2017; Johnson, Kirkland, Evans, McDonald, & Cutten, 2018; Lancaster et al., 2017; Shulaker et al., 2019; Tyrrell, Haughton, Daly, Kokfelt, & Gagnevin, 2006; Tyrrell et al., 2009). However, this technique cannot be applied in compositionally mature sandstones where there is little or no feldspar (whether it has been removed through chemical weathering during transport and/or burial diagenesis).…”

An exceptional sedimentary record of initial rifting on the East African Plateau in the Miocene: Lessons from depositional cyclicity and palaeoenvironmental proxies

“…Most probably, this drainage system had its headwaters in the mountains of the Pan‐African Orogen to the east (Mozambique Belt). Gagnevin et al (2017) could confirm this through U–Pb zircon chronology, and Pb isotopic analysis of K‐feldspar from well samples in the northern Albertine Rift. Based on this geochronology the distance of sediment transport can be constrained to more than 500 km during the Miocene.…”

“…In the road cut succession, the majority of clay minerals stem from soil erosion and are redeposited with some time delay after their formation because no mature in-situ palaeosols were developed. In addition, provenance data indicate admixed detritus from sources several hundred kilometres to the north-east (Gagnevin et al, 2017;Schneider et al, 2016aSchneider et al, , 2016b. Hence, the climate signal deduced from the clay composition can be assumed to be of regional significance.…”

Depositional Structures, Tectonic and Stratigraphic Units and Their Effect on The Reservoir Rock Units of South Lake Albert Basin, Albertine Rift, Uganda.

“…Furthermore, the contribution of lacustrine environment as the hydrocarbon reservoir has been widely known. Alluvial deposits consist of silt, sand, clay, and gravel, as well as much organic matter, fluvial deposits consist of sand and gravel grain size and mud in floodplain deposits of meandering systems, and they have moderate to poor sorting and deltaic deposits are thick, expanded sections of predominantly clastic sedimentary facies [21]. This study also discovered that sediments in the sections close to the basin boundary fault are mainly composed of fluvial and alluvial deposits, and the sediments close to the lake margins are comprised of deltaic and lacustrine deposits.…”