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Timing of volcanism and evolution of the northern Kenya Rift

McDougall, Ian; Brown, F H

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The northern Kenya Rift is bounded on the west by uplands of Turkana which comprise horst-like blocks that include metamorphic basement rocks, locally overlain unconformably by the Cretaceous Lubur Sandstone, in turn overlain by predominantly volcanic sequences in which relatively thin sedimentary packages occur. Amphibolite facies crystalline rocks of the basement yield Early Palaeozoic K-Ar cooling ages reflecting the Pan-African Orogeny. Volcanism in Turkana was initiated through voluminous...[Show more]

dc.contributor.authorMcDougall, Ian
dc.contributor.authorBrown, F H
dc.date.accessioned2015-12-10T22:12:35Z
dc.identifier.issn0016-7568
dc.identifier.urihttp://hdl.handle.net/1885/49735
dc.description.abstractThe northern Kenya Rift is bounded on the west by uplands of Turkana which comprise horst-like blocks that include metamorphic basement rocks, locally overlain unconformably by the Cretaceous Lubur Sandstone, in turn overlain by predominantly volcanic sequences in which relatively thin sedimentary packages occur. Amphibolite facies crystalline rocks of the basement yield Early Palaeozoic K-Ar cooling ages reflecting the Pan-African Orogeny. Volcanism in Turkana was initiated through voluminous eruptions of transitional tholeiitic basalts commencing about 36 Ma ago in the Late Eocene, with some evidence for concomitant rhyolitic volcanism. Volcanism became dominantly rhyolitic in the interval from about 27 to 23 Ma ago, but remained bimodal as basaltic lavas are also known from this period. From about 19 to 15 Ma or younger, basaltic volcanism again dominated, often alkaline in nature, with thin but significant sedimentary sequences interleaved that have yielded important vertebrate faunal assemblages. Parallels exist between the volcanic history recorded in Turkana and that found in the Nabwal Hills east of Lake Turkana. In the southern Turkana region, oil exploration by seismic methods and deep drill holes has shown the existence of northerly-trending half-graben with up to 7 km of fill, and that these developed from at least Oligocene and possibly Late Eocene times. This suggests that the widespread basaltic volcanism at about 36 Ma ago (Late Eocene) heralds an earlier initiation of the Kenya Rift in northern Kenya than most workers have previously suggested.
dc.publisherCambridge University Press
dc.sourceGeological Magazine
dc.subjectKeywords: amphibolite facies; basement rock; crystalline rock; Eocene; metamorphic rock; Oligocene; Pan African orogeny; potassium-argon dating; tholeiitic basalt; unconformity; upland region; volcanism; Africa; East Africa; East African Lakes; East African Rift; K Cenozoic volcanism; K-Ar dating; Kenya Rift; Turkana
dc.titleTiming of volcanism and evolution of the northern Kenya Rift
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume146
dc.date.issued2009
local.identifier.absfor040303 - Geochronology
local.identifier.absfor040313 - Tectonics
local.identifier.absfor040314 - Volcanology
local.identifier.ariespublicationu4047674xPUB191
local.type.statusPublished Version
local.contributor.affiliationMcDougall, Ian, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationBrown, F H, University of Utah
local.description.embargo2037-12-31
local.bibliographicCitation.issue1
local.bibliographicCitation.startpage34
local.bibliographicCitation.lastpage47
local.identifier.doi10.1017/S0016756808005347
dc.date.updated2016-02-24T10:31:47Z
local.identifier.scopusID2-s2.0-65749109312
local.identifier.thomsonID000262606100003
CollectionsANU Research Publications

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