Late Quaternary primary tephras in Sacred Lake sediments, northeast Mount Kenya, Kenya |
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| Authors: | DO Olago FA Street-Perrott RA Perrott M Ivanovich DD Harkness |
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| Institution: | 1 Department of Geology, University of Nairobi, PO Box 30197, Nairobi, Kenya;2 Department of Geography, University of Wales Swansea, Swansea SA2 8PP, UK;3 Analytical Sciences Centre, Business Development Office, Harwell Laboratory B7, Oxfordshire OX11 0RA, UK;4 NERC Radiocarbon Laboratory, NEL Technology Park, East Kilbride, Glasgow G75 0QU, UK |
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| Abstract: | In this paper, a sequence of five Late Quaternary tephras occurring as discrete, well-preserved horizons in lake sediments on the northeastern flank of Mount Kenya are characterised and their ages determined by a combination of high-resolution indirect radiocarbon dating and direct 
dating. The grain size characteristics suggest that the tephras are of fairly local origin. These Na---K-rich alkali pyroclasts with a trachytic chemical composition have a highly correlated chemistry and mineralogy, suggesting that they were probably derived from the same genetic series and possibly erupted from a single source vent. Morphological differences are attributed to the peculiar characteristics of each eruption episode. The magma source was probably a small, highly differentiated magma chamber following the olivine basalt-trachyandesite-trachyte-phonolite series, which broadly reflects the Quaternary rock suite of Mount Kenya. |
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