Event Name : Trident Northeast-Ridge Dacite
|Start: 142000 (± 15000 Years) || Years BP K-Ar || |
|Lava flow: ||
|Eruption Product: || dacite ||
From Hildreth and others (2003): "The northeast-ridge dacite, which is stratigraphically high in the pile and extends nearly to the summit (peak 6010), yields a K-Ar age of 142+/-15 ka."
"For East Trident, a near-basal andesitic lava flow resting on oxidized breccia at glacier level on the nose of the north-west prong (which separates Glaciers 1 and 2, fig. 3 [in original text]) yields a weighted mean age of 143+/-8 ka, analytically indistinguishable from an age of 142+/-15 ka on a 100-m-thick dacitic lava flow that caps part of the northeast ridge of the edifice. These samples appear to bracket most of the dozens of lava flows that make up the edifice, suggesting that eruptive activity at the small East Trident cone was short lived. The ages indicate not only that East Trident is the oldest member of the Trident group but also that it predates the oldest recognized eruptive products of neighboring Katmai and Mageik Volcanoes (Hildreth and Fierstein, 2000; Hildreth and others, 2000)."