Shore-zone sedimentation and facies in a closed rift lake: the Holocene beach deposits of Lake Bogoria, Kenya

Small beach bars, spits, and barriers, composed predominantly of coarse sand, granules, and pebbles, are present along much of the modern shoreline of Lake Bogoria, a perennial saline, alkaline lake in the Kenya Rift Valley. Study of their distribution and composition indicates that most of the sediments are derived from peripheral fan-deltas, including material brought down in flood, and that derived by erosion of older exposed fan-delta sediments. Much of the sediment is redistributed by longshore currents, induced by winds funnelled along the axis of the lake. Surrounding the lake, a series of regressive littoral terraces, composed of angular gravels, record shoreline sedimentation associated with former higher lake levels during the Holocene. During terrace formation, many fan-delta platforms were drowned and shoaling effects reduced, thereby increasing wave energy around much of the shoreline. The terraces record a complex history of Holocene lake-level fluctuations. -from Authors