Abstract
Summary Lake Bogoria is a perennial, saline, alkaline closed lake fed by hot springs and ephemeral runoff. Detailed studies of the sedimentology, mineralogy and chemistry of the late Quaternary sediments, both from exposures around the shoreline and from lake bottom cores, have provided abundant evidence for early diagenesis and mineral precipitation. Marginal fan-deltaic clastics exhibit carbonate (calcite, dolomite), iron oxide, opaline silica and zeolite (analcime, natrolite) cements, especially where groundwater is shallow and subject to evaporative concentration. Travertines associated with microbial activity around hydrothermal springs are predominantly calcite; high temperature, inorganically precipitated travertines are aragonitic. Most are relic deposits. In places, spring carbonates have been silicified (opal-A) or altered to fluorite in response to changing groundwater composition. Fan-delta conglomerates have been hydrothermally altered by alkaline spring waters yielding zeolites (analcime, thomsonite, clinoptiloite, mordenite), clay minerals, opaline silica and magadiite. The lacustrine sediments include prodeltaic clastics, organic oozes and sodium carbonate evaporites. Trona and nahcolite predominate in the central sub-basin. The local occurrence of thermonatrite may be associated with sub-lacustrine hydrothermal activity. In the north subbasin, evaporites are exclusively gaylussite. Sodium silicates (magadiite, kanemite) occur in black organic oozes and formed in an anoxic environment rich in sodium carbonate and dissolved SiO 2 . Other authigenic minerals in the lacustrine sediments include pyrite, siderite, fluorite, zeolites (analcime, mordenite, clinoptilolite), opaline silica (formed from a gel precursor around sub-lacustrine springs?) and vivianite.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call