Chemical Analyses of Caliche Profiles from the High Plains, New Mexico

1970 ◽  
Vol 78 (2) ◽  
pp. 201-212 ◽  
Author(s):  
L. F. Aristarain
Keyword(s):  
New Mexico ◽  
High Plains ◽  
Chemical Analyses

Correlation of a Volcanic Ash bed in Pleistocene Deposits near Mount Blanco, Texas, with the Guaje Pumice Bed of the Jemez Mountains, New Mexico

1972 ◽  
Vol 2 (4) ◽  
pp. 554-578 ◽  
Author(s):  
Glen A. Izett ◽  
Ray E. Wilcox ◽  
Glenn A. Borchardt
Keyword(s):  
New Mexico ◽  
Volcanic Ash ◽  
Fission Track ◽  
Major Elements ◽  
Flow Sheet ◽  
Chemical Analyses ◽  
Sedimentary Deposits ◽  
Jemez Mountains ◽  
Bandelier Tuff ◽  
Minimum Age

A rhyolitic volcanic ash bed about 0.3 m thick is exposed in a roadcut along Texas Highway 193 near Mount Blanco in the upper part of a sequence of Pleistocene sedimentary deposits at the type locality of the Blanco Formation, about 59 km northeast of Lubbock, Texas. This ash, here named informally the Guaje ash bed, has chemical and petrographic characteristics closely resembling those of the rhyolitic air-fall tephra (Guaje Pumice Bed) that directly underlies ash flows of Pleistocene age in the Jemez Mountains of northern New Mexico. The Guaje Pumice Bed and the ash flows belong to the Otowi Member of the Bandelier Tuff. Properties common to the Guaje ash bed and the Guaje Pumice Bed include: refractive index of glass, 1.497–1.498; microphenocrysts of quartz, sanidine (Or42–44), ferrohedenbergite (Fe51Ca42Mg7), chevkinite, allanite, zircon, and magnetite. Chemical composition of the glass of the Guaje ash bed matches that of the Guaje Pumice Bed for all major elements except K and Na and for trace elements determined by standard chemical analyses, atomic absorption, and neutron activation. Paleomagnetic measurements indicate that the ash has reverse depositional remanent magnetization. Glass shards of the ash have a fission-track age of about 1.4 ± 0.2 m. y. Sanidine from the Guaje Pumice Bed and its genetically related ash-flow sheet in the Jemez Mountains was K-Ar dated at about 1.4 m. y. by R. R. Doell and his colleagues in 1968. Correlation of the Guaje ash bed with the radiometrically dated Guaje Pumice Bed establishes a minimum age of about 1.4 m. y. for the Blanco Formation.

Sign in / Sign up

Export Citation Format

Share Document