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| Detailed Reference Information |
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Casadevall, T.J. and Dzurisin, D. (1987). Stratigraphy and petrology of the Uwekahuna Bluff section, Kilauea Caldera. In: Volcanism in Hawaii; USGS Professional Papers. Decker, R.W., Wright, T.L. and Stauffer, P.H. (Editors), USGS, Reston, VA. P 1350: 351-375. |
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Samples from 63 lava flows in a 135-m vertical section at Uwekahuna Bluff within Kilauea caldera were analyzed for major oxides, trace elements, and rare-earth elements. Four stratigraphically defined suites of subaerial lava flows are present. (A) units 1-14 (youngest suite), plagioclase-porphyritic flows (6.4-7.3 weight percent MgO); (B) units 15-30, aphyric flows (6.5-8.0 weight percent MgO); (C) units 31-51, olivine rich flows (9.0-19.7 weight percent MgO) with the Uwekahuna Ash Member of the Puna Basalt at base; (D) units 44A-52A (oldest suite), nonvesicular, aphyric flows (7.1-7.8 weight percent MgO). Suite D flows were erupted at about 2.8 ka, probably in an ancient caldera. At about 21 ka, catastrophic eruption of the Uwekahuna Ash Member may have unloaded Kilauea's deep magma-transport system and triggered extrusion of olivine porphyritic lavas of suite C. Suites A and B may be genetically related, possibly from the top of a single reservoir; the plagioclase-porphyritic flows of suite A may represent the later eruptive product of a shallow reservoir that earlier was the source for the aphyric lavas of suite B. We interpret this sequence of aphyric lavas followed by plagioclase-porphyritic lavas as indicating a two-stage drawdown of a post-Uwekahuna ash Member magma reservoir. Comparison of published major- and trace-element data from Kilauea and Mauna Loa with data for the Uwekahuna Bluff flows indicates the latter are all from a Kilauea source; apparently no Mauna Loa flows occur in the west wall of Kilauea caldera, although surface flows from Mauna Loa have been mapped within 1 km of the caldera rim |
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