Chemical analyses, correlations, and ages of upper Pliocene and Pleistocene ash layers of east-central and Southern California

摘要: Eight widespread Pleistocene ash layers of east-central and southern California are characterized correlated on the basis chemical composition volcanic glass (determined by neutron activation, electron probe, energy-dispersive X-ray fluorescence analysis), stratigraphic criteria, petrographic characteristics. Irt order increasing age, these Lava Creek B bed (formerly referred to as Pearlette type 0 bed; about 0.6 m.y.), Bishop (0.73 Glass Mountain-D (estimated be 0.8-0.9 Mountain-G 1.0-1.1 Bailey (1.2 middle white Manix basin 1.9 Huckleberry Ridge lowermost gray South Mountain area (Huckleberry Ridge? estimated m.y.). Three types recognized assigned an informal ash-bed group. The Friant Pumice Member (of Turlock Lake Formation) San Joaquin Valley is one members this apparent 0.1-m.y. difference in K-Ar ages (0.6 m.y.) Tuff (about 0.7 may due factors other than differences true tephra units; alternatively, there two that have very similar chemistry here belonging Member, but differ age much 0.1 m.y. with same Meade County, Kansas, over a distance 1,500 km. Results analyses permit correlation sedimentary strata deposited diverse environments: marine, fluvial, lacustrine. Chemical characteristics also identification source areas from which was erupted; main eruptive centers were Long Valley-Glass California, Coso field southeastern Yellowstone northwestern Wyoming eastern Idaho. Systematic depletion trends time provide possible independent method estimating family.