Large scale pantelleritic ash flow eruptions during the Late Miocene in central Kenya and evidence for significant environmental impact

Claessens, L and Veldkamp, A and Schoorl, J M and Wijbrans, J R and van Gorp, W and Macdonald, R (2016) Large scale pantelleritic ash flow eruptions during the Late Miocene in central Kenya and evidence for significant environmental impact. Global and Planetary Change, 145. pp. 30-41. ISSN 09218181

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Abstract

In the area south-east of Mount Kenya, four previously unrecorded peralkaline rhyolitic (pantelleritic) ash flow tuffs have been located. These predominantly greyish welded and non-welded tuffs form up to 12 m thick units, which are sometimes characterized by a basal vitrophyre. The four flow units yielded 40Ar/39Ar ages ranging from 6.36 to 8.13 Ma, indicating a period of ~ 1.8 Ma of pantelleritic volcanic activity during the Late Miocene in central Kenya. Tentative compositional and age correlations with other known tuff deposits suggest that the pantelleritic tuffs originally covered 40,000 km2 in central Kenya, extending much further than earlier recorded Pliocene tuffs. This newly identified magmatic phase occurred between the phonolitic flood eruptions (16–8 Ma) and the Pliocene tuff eruptions (6–4 Ma). The occurrence of multiple ash flow tuff deposits up to 150 km away from the inferred eruptive center(s) in the central sector of the Kenya Rift, indicates multi-cyclic peralkaline supereruptions during the Late Miocene. By analogy with more recent pantelleritic eruptions, the tuffs are thought to have been sulfur-rich; during eruption, they formed stratospheric aerosols, with significant environmental impact. The timing of the eruptions coincides with the shift towards more savannah-dominated environments in East Africa.

Item Type:	Article
Divisions:	Research Program : East & Southern Africa
CRP:	CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS)
Uncontrolled Keywords:	Tuff; Ash flow; Ignimbrite; Vitrophyre; Peralkaline rhyolites; 40Ar/39Ar geochronology
Subjects:	Others
Depositing User:	Mr Ramesh K
Date Deposited:	10 Nov 2016 05:14
Last Modified:	18 Apr 2017 09:26
URI:	http://oar.icrisat.org/id/eprint/9770
Official URL:	http://dx.doi.org/10.1016/j.gloplacha.2016.08.006
Projects:	UNSPECIFIED
Funders:	UNSPECIFIED
Acknowledgement:	Alan Deino is thanked for providing more background information about the Mpesida tuffs in the Tugen Hills. Fieldwork was partly supported by the CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS).We thank HenryWichura for useful suggestions and comments on an earlier version of the manuscript.
Links:	Google Scholar

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