INCIPIENT SILICA CEMENTATION IN CENTRAL NEVADA ALLUVIAL SOILS INFLUENCED BY TEPHRA (DURIPAN, TAXONOMY, OPAL-CT, GENESIS).

Persistent Link:
http://hdl.handle.net/10150/187945
Title:
INCIPIENT SILICA CEMENTATION IN CENTRAL NEVADA ALLUVIAL SOILS INFLUENCED BY TEPHRA (DURIPAN, TAXONOMY, OPAL-CT, GENESIS).
Author:
CHADWICK, OLIVER AUSTIN.
Issue Date:
1985
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Silica cemented pedogenic horizons known as duripans occur on relict landforms in climates having limited leaching potential. Under the influence of tephra, incipient silica cementation may also occur in late Quaternary soils. The source of silica for cementation in Holocene soils is rapidly weatherable volcanic glass. In response to wetting and drying cycles volcanic glass weathers to form sand-size composite particles composed of silt, clay and redeposited silica. A portion of the hydrolyzed silica is eluviated as monosilicic acid which accumulates as the wetting front evaporates. Illuvial silica augments existing composite particles eventually forming a continuously cemented duripan. In actively forming late Quaternary soils, the cementation process is a complex interaction between illuvial silica, clay and calcium carbonate and the soil matrix. Surface reactions between monosilicic acid and illuvial clay or soil matrix particles provide nucleation sites for polymerization of silica concentrated by evaporation. The resulting opaline silica bonds adjacent soil grains without necessarily plugging intervening pore spaces. In contrast, calcium carbonate preferentially precipitates in large pores and interped voids. Cementation occurs by the plugging of progressively smaller pores with relatively pure calcite rather than by heterogeneous bonding of mineral grains. In illuvial zones containing both silica and calcium carbonate, cementation may occur rapidly because the former holds small soil particles in place while the latter plugs large pores. The mineralogy of silica cement is determined by identification of varying amounts of crystal order using X-ray diffraction. Opal-A is recently polymerized, noncrystalline, highly hydrated silica gel. The more prevalent, partly crystalline opal-CT forms where surface reaction with clays create crystal orientation, where silica gel dehydrates or when silica precipitates from soil solutions having high concentrations.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Duricrusts.; Soil formation.; Alluvium.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Soil and Water Science; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Hendricks, D. M.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleINCIPIENT SILICA CEMENTATION IN CENTRAL NEVADA ALLUVIAL SOILS INFLUENCED BY TEPHRA (DURIPAN, TAXONOMY, OPAL-CT, GENESIS).en_US
dc.creatorCHADWICK, OLIVER AUSTIN.en_US
dc.contributor.authorCHADWICK, OLIVER AUSTIN.en_US
dc.date.issued1985en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractSilica cemented pedogenic horizons known as duripans occur on relict landforms in climates having limited leaching potential. Under the influence of tephra, incipient silica cementation may also occur in late Quaternary soils. The source of silica for cementation in Holocene soils is rapidly weatherable volcanic glass. In response to wetting and drying cycles volcanic glass weathers to form sand-size composite particles composed of silt, clay and redeposited silica. A portion of the hydrolyzed silica is eluviated as monosilicic acid which accumulates as the wetting front evaporates. Illuvial silica augments existing composite particles eventually forming a continuously cemented duripan. In actively forming late Quaternary soils, the cementation process is a complex interaction between illuvial silica, clay and calcium carbonate and the soil matrix. Surface reactions between monosilicic acid and illuvial clay or soil matrix particles provide nucleation sites for polymerization of silica concentrated by evaporation. The resulting opaline silica bonds adjacent soil grains without necessarily plugging intervening pore spaces. In contrast, calcium carbonate preferentially precipitates in large pores and interped voids. Cementation occurs by the plugging of progressively smaller pores with relatively pure calcite rather than by heterogeneous bonding of mineral grains. In illuvial zones containing both silica and calcium carbonate, cementation may occur rapidly because the former holds small soil particles in place while the latter plugs large pores. The mineralogy of silica cement is determined by identification of varying amounts of crystal order using X-ray diffraction. Opal-A is recently polymerized, noncrystalline, highly hydrated silica gel. The more prevalent, partly crystalline opal-CT forms where surface reaction with clays create crystal orientation, where silica gel dehydrates or when silica precipitates from soil solutions having high concentrations.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDuricrusts.en_US
dc.subjectSoil formation.en_US
dc.subjectAlluvium.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineSoil and Water Scienceen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorHendricks, D. M.en_US
dc.contributor.committeememberBull, W. B.en_US
dc.contributor.committeememberPost, D. F.en_US
dc.contributor.committeememberHutchinson, C. F.en_US
dc.contributor.committeememberBaker, V. R.en_US
dc.identifier.proquest8514904en_US
dc.identifier.oclc693617156en_US
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