Opaline cherts associated with sublacustrine hydrothermal springs at Lake Bogoria, Kenya Rift valley

An unusual group of cherts found at saline, alkaline Lake Bogoria in the Kenya Rift differs from the Magadi-type cherts commonly associated with saline, alkaline lakes. The cherts are opaline, rich in diatoms, and formed from a siliceous, probably gelatinous, precursor that precipitated around subme...

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Bibliographic Details
Published in:Geology (Boulder) 1988-08, Vol.16 (8), p.699-702
Main Authors: Renaut, Robin W, Owen, R. Bernhart
Format: Article
Language:English
Subjects:
Africa
alkalic composition
Bacillariophyceae
cementation
chemical sedimentation
chemically precipitated rocks
chert
diagenesis
East Africa
framework silicates
geochemistry
hot springs
hydrochemistry
hydrogeology
hydrology
hydrothermal conditions
Kenya
Kenya Rift valley
lacustrine environment
Lake Bogoria
opal
precipitation
processes
rift zones
rifting
saline composition
sed rocks, sediments
Sedimentary petrology
sedimentary rocks
sedimentation
silica minerals
silicates
springs
sublacustrine environment
surveys
thermal waters
water
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Summary:An unusual group of cherts found at saline, alkaline Lake Bogoria in the Kenya Rift differs from the Magadi-type cherts commonly associated with saline, alkaline lakes. The cherts are opaline, rich in diatoms, and formed from a siliceous, probably gelatinous, precursor that precipitated around submerged alkaline hot springs during a Holocene phase of high lake level. Silica precipitation resulted from rapid drop in the temperature of the spring waters and, possibly, pH. Lithification began before subaerial exposure. Ancient analogous cherts are likely to be localized deposits along fault lines.
ISSN:0091-7613
1943-2682
DOI:10.1130/0091-7613(1988)016<0699:OCAWSH>2.3.CO;2