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Title: Relationship of uranium to petrography of caliche paleosols with application to precisely dating the time of sedimentation

Abstract

The authors use petrography combined with fission-track mapping to evaluate qualitatively the phases that concentrate uranium in caliche paleosols from late Paleozoic cyclothems of Texas and New Mexico. They also discuss geochemical analyses of U and Pb concentrations and Pb isotopic compositions. Uranium concentrations in brown caliche calcite range from 1 to 9 ppm. Lead concentrations in the same calcites range from 0.5 to 1 ppm. Lead-isotope compositions range from common (no apparent radiogenic component) to lead with a substantial radiogenic component. Cliches with brown calcite most likely developed near the vadose-phreatic interface--often a redox boundary where organic material (and uranium) is expected to be concentrated. In contrast, uranium concentrations in light-colored caliche nodules from the vadose zone have uranium concentrations that are 1 ppm or less. Fifteen of forty-five samples from this study have a range in U/Pb that would permit precise dating of the rocks, but only the data from three give precise ages. Some of the samples have hematite, which has high concentrations of U and Pb. For one of the precisely dated samples, the two-sigma uncertainty was improved from 10 to 2.6 Ma by avoiding hematite when sampling.

Authors:
; ; ; ;
Publication Date:
Research Org.:
State Univ. of New York, Stony Brook, NY (US)
OSTI Identifier:
20076061
Resource Type:
Journal Article
Journal Name:
Journal of Sedimentary Research, Section A: Sedimentary Petrology and Processes
Additional Journal Information:
Journal Volume: 70; Journal Issue: 3; Other Information: PBD: May 2000; Journal ID: ISSN 1073-130X
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; TEXAS; NEW MEXICO; URANIUM DEPOSITS; CALCITE; ISOTOPE DATING; URANIUM; LEAD; GEOCHEMISTRY; ECOLOGICAL CONCENTRATION; SEDIMENTATION

Citation Formats

Rasbury, E.T., Meyers, W.J., Hanson, G.N., Goldstein, R.H., and Saller, A.H. Relationship of uranium to petrography of caliche paleosols with application to precisely dating the time of sedimentation. United States: N. p., 2000. Web. doi:10.1306/2DC4092B-0E47-11D7-8643000102C1865D.
Rasbury, E.T., Meyers, W.J., Hanson, G.N., Goldstein, R.H., & Saller, A.H. Relationship of uranium to petrography of caliche paleosols with application to precisely dating the time of sedimentation. United States. doi:10.1306/2DC4092B-0E47-11D7-8643000102C1865D.
Rasbury, E.T., Meyers, W.J., Hanson, G.N., Goldstein, R.H., and Saller, A.H. Mon . "Relationship of uranium to petrography of caliche paleosols with application to precisely dating the time of sedimentation". United States. doi:10.1306/2DC4092B-0E47-11D7-8643000102C1865D.
@article{osti_20076061,
title = {Relationship of uranium to petrography of caliche paleosols with application to precisely dating the time of sedimentation},
author = {Rasbury, E.T. and Meyers, W.J. and Hanson, G.N. and Goldstein, R.H. and Saller, A.H.},
abstractNote = {The authors use petrography combined with fission-track mapping to evaluate qualitatively the phases that concentrate uranium in caliche paleosols from late Paleozoic cyclothems of Texas and New Mexico. They also discuss geochemical analyses of U and Pb concentrations and Pb isotopic compositions. Uranium concentrations in brown caliche calcite range from 1 to 9 ppm. Lead concentrations in the same calcites range from 0.5 to 1 ppm. Lead-isotope compositions range from common (no apparent radiogenic component) to lead with a substantial radiogenic component. Cliches with brown calcite most likely developed near the vadose-phreatic interface--often a redox boundary where organic material (and uranium) is expected to be concentrated. In contrast, uranium concentrations in light-colored caliche nodules from the vadose zone have uranium concentrations that are 1 ppm or less. Fifteen of forty-five samples from this study have a range in U/Pb that would permit precise dating of the rocks, but only the data from three give precise ages. Some of the samples have hematite, which has high concentrations of U and Pb. For one of the precisely dated samples, the two-sigma uncertainty was improved from 10 to 2.6 Ma by avoiding hematite when sampling.},
doi = {10.1306/2DC4092B-0E47-11D7-8643000102C1865D},
journal = {Journal of Sedimentary Research, Section A: Sedimentary Petrology and Processes},
issn = {1073-130X},
number = 3,
volume = 70,
place = {United States},
year = {2000},
month = {5}
}