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Mineralogy and Geochemistry of the Main Glauconite Bed in the Middle Eocene of Texas: Paleoenvironmental Implications for the Verdine Facies

The Main Glauconite Bed (MGB) is a pelleted greensand located at Stone City Bluff on the south bank of the Brazos River in Burleson County, Texas. It was deposited during the Middle Eocene regional transgression on the Texas Gulf Coastal Plain. Stratigraphically it lies in the upper Stone City Membe...

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Autores principales: Harding, Sherie C., Nash, Barbara P., Petersen, Erich U., Ekdale, A. A., Bradbury, Christopher D., Dyar, M. Darby
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2014
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3913656/
https://www.ncbi.nlm.nih.gov/pubmed/24503875
http://dx.doi.org/10.1371/journal.pone.0087656
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author Harding, Sherie C.
Nash, Barbara P.
Petersen, Erich U.
Ekdale, A. A.
Bradbury, Christopher D.
Dyar, M. Darby
author_facet Harding, Sherie C.
Nash, Barbara P.
Petersen, Erich U.
Ekdale, A. A.
Bradbury, Christopher D.
Dyar, M. Darby
author_sort Harding, Sherie C.
collection PubMed
description The Main Glauconite Bed (MGB) is a pelleted greensand located at Stone City Bluff on the south bank of the Brazos River in Burleson County, Texas. It was deposited during the Middle Eocene regional transgression on the Texas Gulf Coastal Plain. Stratigraphically it lies in the upper Stone City Member, Crockett Formation, Claiborne Group. Its mineralogy and geochemistry were examined in detail, and verdine facies minerals, predominantly odinite, were identified. Few glauconitic minerals were found in the green pelleted sediments of the MGB. Without detailed mineralogical work, glaucony facies minerals and verdine facies minerals are easily mistaken for one another. Their distinction has value in assessing paleoenvironments. In this study, several analytical techniques were employed to assess the mineralogy. X-ray diffraction of oriented and un-oriented clay samples indicated a clay mixture dominated by 7 and 14Å diffraction peaks. Unit cell calculations from XRD data for MGB pellets match the odinite-1M data base. Electron microprobe analyses (EMPA) from the average of 31 data points from clay pellets accompanied with Mössbauer analyses were used to calculate the structural formula which is that of odinite: Fe(3+) (0.89) Mg(0.45) Al(0.67) Fe(2+) (0.30) Ti(0.01) Mn(0.01))( Σ = 2.33) (Si(1.77) Al(0.23)) O(5.00) (OH)(4.00). QEMSCAN (Quantitative Evaluation of Minerals by Scanning Electron Microscopy) data provided mineral maps of quantitative proportions of the constituent clays. The verdine facies is a clay mineral facies associated with shallow marine shelf and lagoonal environments at tropical latitudes with iron influx from nearby runoff. Its depositional environment is well documented in modern nearshore locations. Recognition of verdine facies clays as the dominant constituent of the MGB clay pellets, rather than glaucony facies clays, allows for a more precise assessment of paleoenvironmental conditions.
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spelling pubmed-39136562014-02-06 Mineralogy and Geochemistry of the Main Glauconite Bed in the Middle Eocene of Texas: Paleoenvironmental Implications for the Verdine Facies Harding, Sherie C. Nash, Barbara P. Petersen, Erich U. Ekdale, A. A. Bradbury, Christopher D. Dyar, M. Darby PLoS One Research Article The Main Glauconite Bed (MGB) is a pelleted greensand located at Stone City Bluff on the south bank of the Brazos River in Burleson County, Texas. It was deposited during the Middle Eocene regional transgression on the Texas Gulf Coastal Plain. Stratigraphically it lies in the upper Stone City Member, Crockett Formation, Claiborne Group. Its mineralogy and geochemistry were examined in detail, and verdine facies minerals, predominantly odinite, were identified. Few glauconitic minerals were found in the green pelleted sediments of the MGB. Without detailed mineralogical work, glaucony facies minerals and verdine facies minerals are easily mistaken for one another. Their distinction has value in assessing paleoenvironments. In this study, several analytical techniques were employed to assess the mineralogy. X-ray diffraction of oriented and un-oriented clay samples indicated a clay mixture dominated by 7 and 14Å diffraction peaks. Unit cell calculations from XRD data for MGB pellets match the odinite-1M data base. Electron microprobe analyses (EMPA) from the average of 31 data points from clay pellets accompanied with Mössbauer analyses were used to calculate the structural formula which is that of odinite: Fe(3+) (0.89) Mg(0.45) Al(0.67) Fe(2+) (0.30) Ti(0.01) Mn(0.01))( Σ = 2.33) (Si(1.77) Al(0.23)) O(5.00) (OH)(4.00). QEMSCAN (Quantitative Evaluation of Minerals by Scanning Electron Microscopy) data provided mineral maps of quantitative proportions of the constituent clays. The verdine facies is a clay mineral facies associated with shallow marine shelf and lagoonal environments at tropical latitudes with iron influx from nearby runoff. Its depositional environment is well documented in modern nearshore locations. Recognition of verdine facies clays as the dominant constituent of the MGB clay pellets, rather than glaucony facies clays, allows for a more precise assessment of paleoenvironmental conditions. Public Library of Science 2014-02-04 /pmc/articles/PMC3913656/ /pubmed/24503875 http://dx.doi.org/10.1371/journal.pone.0087656 Text en © 2014 Harding et al http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
spellingShingle Research Article
Harding, Sherie C.
Nash, Barbara P.
Petersen, Erich U.
Ekdale, A. A.
Bradbury, Christopher D.
Dyar, M. Darby
Mineralogy and Geochemistry of the Main Glauconite Bed in the Middle Eocene of Texas: Paleoenvironmental Implications for the Verdine Facies
title Mineralogy and Geochemistry of the Main Glauconite Bed in the Middle Eocene of Texas: Paleoenvironmental Implications for the Verdine Facies
title_full Mineralogy and Geochemistry of the Main Glauconite Bed in the Middle Eocene of Texas: Paleoenvironmental Implications for the Verdine Facies
title_fullStr Mineralogy and Geochemistry of the Main Glauconite Bed in the Middle Eocene of Texas: Paleoenvironmental Implications for the Verdine Facies
title_full_unstemmed Mineralogy and Geochemistry of the Main Glauconite Bed in the Middle Eocene of Texas: Paleoenvironmental Implications for the Verdine Facies
title_short Mineralogy and Geochemistry of the Main Glauconite Bed in the Middle Eocene of Texas: Paleoenvironmental Implications for the Verdine Facies
title_sort mineralogy and geochemistry of the main glauconite bed in the middle eocene of texas: paleoenvironmental implications for the verdine facies
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3913656/
https://www.ncbi.nlm.nih.gov/pubmed/24503875
http://dx.doi.org/10.1371/journal.pone.0087656
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