Trachyandesite of Kennedy Table
Trachyandesite of Kennedy Table
middle Miocene
Trachyandesite lava erupted from a vent ~7 km southwest of Mammoth Mountain, in the eastern Sierra, with flow remnants distributed across the range to the west-southwest along the modern San Joaquin River drainage (Hildreth and Fierstein, 2016; Hildreth and others, 2021). Hildreth and others (2021) reported Ar-Ar ages of ~9.3 Ma. Vent site exposes lateral gradations from intrusion to lava flow; unit is generated from one continuous eruption (Hildreth and others, 2021). Chemical composition is remarkably uniform; flow is phenocryst-rich with plagioclase and minor clinopyroxene and olivine (Hildreth and Fierstein, 2016; Hildreth and others, 2021).