Sedimentology, stratigraphy and palaeoenvironments of the Holocene Galana Boi Formation, NE Lake Turkana, Kenya

Abstract

Lake Turkana lies in a closed drainage basin at the northern end of the Kenya Rift Valley. During the early and middle Holocene the lake was fresh, much expanded and subject to many fluctuations in surface level, Periodically it formed one linkage in a greater Nile drainage network. Late Holocene, climatically-induced regression left a ring of sediments stranded up to 80 m above the modern lake. To the NE, these deposits are known as the Galana Boi Beds and here we propose raising them to formation status. They consist of diatomaceous silts, silty diatomites, quartz-arenites, arkoses, litharenites, coquinas and at least one air-fall tuff. Depositional environments ranged fiom low-energy offshore, through littoral, lagoonal and deltaic to alluvial and aeolian. A rich, diverse microfossil assemblage of diatoms, pollen and ostracods has been recorded and used in palaeoenvironmental analysis. Macrofossils include molluscs, fish debris and other vertebrates. With their excellent outcrop and diverse environments represented, the Galana Boi Formation can serve as a model for sedimentation of the margins of a large rift lake, and aid in the interpretation of similar, but poorly exposed graben sequences in the geological record.

Water level history for Lake Turkana, Kenya in the past 15,000years and a variable transition from the African Humid Period to Holocene aridity

“…Owen and Renaut, 1986;Garcin et al, 2012;Forman et al, 2014). The two most common species are Melanoides tuberculata and Corbicula fluminalis africana, which live in maximum water depths of 2 and 5 m, respectively (Cohen, 1986;Leng et al, 1999;Genner and Michel, 2003;De Kock and Wolmarans, 2007).…”

“…The sequence of Late Pleistocene to Holocene lacustrine sediments is part of the Galana Boi Formation, which has variable preservation and stratigraphic continuity around Lake Turkana (Owen et al, 1982;Owen and Renaut, 1986). The sedimentology of beach ridges for the Kalokol strand plain is well exposed in a series excavations and natural stratigraphic sections (Fig.…”

Diatomaceous sediments and environmental change in the Pleistocene Olorgesailie Formation, southern Kenya Rift Valley

“…These studies have largely been based on data from cores recovered from late Pleistocene to Holocene sediments in modern lakes (Richardson and Richardson, 1972;Barker, 1992;Johnson, 1996;Stager et al, 1997;Telford et al, 1999;Chalié and Gasse, 2002;Johnson et al, 2002;Legesse et al, 2002;Russell et al, 2003;Cohen et al, 2007), and to a lesser extent within wetland areas Driese et al, 2004;. Miocene to Pleistocene stratigraphic records have also been developed from lacustrine rocks exposed in outcrops as a result of faulting and/or erosion, although the latter studies tend to reconstruct environmental conditions at discrete intervals rather than attempt to develop detailed stratigraphies through temporally long sequences (Gasse, 1974;Owen, 1981;Owen and Renaut, 1986;Renaut et al, 2000;Trauth et al, 2003).…”

Stratigraphic context of fossil hominids from the Omo group deposits: Northern Turkana Basin, Kenya and Ethiopia

“…These include the Mursi, Usno, and Shungura Formations, the Koobi Fora Formation, and the Nachukui Formation. A third group of deposits in the basin, the Turkana Group (de Heinzelin, 1983), consists of the Kibish Formation, Galana Boi Formation (Owen and Renaut, 1986), and other undifferentiated late Pleistocene and Holocene sediments. cussed by Brown and Feibel (1986).…”