Tephra layers of blind Spring Valley and related upper Pliocene and Pleistocene tephra layers, California, Nevada, and Utah: Isotopic ages, correlation, and magnetostratigraphy

Abstract

Introduction ……………………………………………………………………………… 3 Tephra layers of Blind Spring Valley at the Cowan Pumice Mine …………………… 4 Tephra layers from other source areas in the western United States ……………… 6 Acknowledgments ………………………………………………………………………… 6 Previous work ……………………………………………………………………………… 7 Analytical methods ………………………………………………………………………… 8 Field methods ………………………………………………………………………… 8 Laboratory preparation of samples for analysis ……………………………………… 8 Laser-fusion 40 Ar/ 39 Ar and conventional K-Ar analyses ……………………………… 8 Chemical analysis of volcanic glass shards ………………………………………… 9 Electron-microprobe (EM) analysis …………………………………………… 9 Energy-dispersive X-ray fluorescence (EDXRF) analysis ……………………… 9 Instrumental neutron activation (INA) analysis ………………………………… 9 Methods of data evaluation ………………………………………………………… 12 Stratigraphic section at Cowan Pumice Mine-results of age analysis ………………… 12 Stratigraphic section in and below Pit 6 ……………………………………………… 12 Basal basalt flows ……………………………………………………………… 12 Basal arkosic mudflows and the tuff of Benton Hot Springs …………………… 12 Tuffs of Blind Spring Valley ……………………………………………………… 15 Lower tuffs of Glass Mountain ………………………………………………… 16 Tephra layers exposed in Pits 1 through 5 …………………………………………… 17 The Bishop ash ………………………………………………………………… 17 Tuffs of Blind Spring Valley ……………………………………………………… 17 Isotopic ages of the upper Glass Mountain tephra layers at Chalk Cliffs, at the south end of the Volcanic Tableland …………………………………………………………… 19 Interpretation of the isotopic ages at the Cowan Pumice Mine …………………………… 21 Correlation of the tuffs of Blind Spring Valley to sites in the region ……………………… 28 Northeastern Fish Lake Valley ……………………………………………………… 28 Willow Wash section ………………………………………………………………… 30

Pliocene–Pleistocene hydrology and pluvial lake during Marine Isotope Stages 5a and 4, Deep Springs Valley, western Great Basin, Inyo County, California

“…Collection and preparation of tephrochronology samples followed Sarna-Wojcicki et al (2005). Major (Si, Al, Fe, Ca, Na, K) and minor (Mg, Mn, Ti) -element concentrations were determined by electron microprobe analysis at the New Mexico Bureau of Geology and Mineral Resources (Table 2).…”

Structural Evolution of the East Sierra Valley System (Owens Valley and Vicinity), California: A Geologic and Geophysical Synthesis

“…About 6 km southeast of Bishop, near the deepest part of the basin, the base of the Bishop Tuff lies at a depth of only about 200 m (Plate 7 in [54]), so much of the thick basin fill in this area must be significantly older. Dissected fanglomerate of late Pliocene to early Pleistocene age is exposed along the western front of the White Mountains [98], and farther south the early Pleistocene (2.0-2.2 Ma) Waucoba Lake Beds [99,100] crop out together with overlying fanglomerate in the Waucoba Embayment ( Figure 2). …”

Comparative Rhyolite Systems: Inferences From Vent Patterns and Eruptive Episodicities: Eastern California and Laguna del Maule

“…Apparent ages of 30 rhyolites (0.79–1.20 Ma) are plotted in Figure 13. 16 are K‐Ar ages from Metz and Bailey (1993); 10 are undated lavas bracketed stratigraphically by contiguous dated lavas; and four are downwind plinian fall deposits (Izett et al., 1988; Sarna‐Wojcicki et al., 2005). Similar to the apparent pattern of the Older Glass Mountain sequence, there are a few early ages (1.2–1.05 Ma), followed by ∼19 ages tightly clustered at 1.0 to 0.88 Ma, and finally five ages around 0.8 Ma.…”