Processes of hardpart breakdown and models of stratigraphic disorder in shallow marine environments.

Persistent Link:
http://hdl.handle.net/10150/185678
Title:
Processes of hardpart breakdown and models of stratigraphic disorder in shallow marine environments.
Author:
Cutler, Alan Hughes.
Issue Date:
1991
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:
Taphonomy is the study of the fate of information in the fossil record. Information can be lost through the partial or complete destruction of fossils, or through the disruption of their original spatial relationships. Information can be "gained" if the alteration of fossils allows environmental information to be retrieved. In Bahia la Choya, northern Gulf of California, bioerosion, dissolution/maceration, and abrasion produce distinctive textures on the surfaces of shells in intertidal and shallow subtidal environments. Shells from different environments possess different surface textures, suggesting that textures on fossil shells could serve as paleoenvironmental indicators. Algal bioerosion is the chief mode of shell alteration and destruction in Bahia la Choya, though dissolution/maceration and abrasion are locally important. Algal bioerosion of shell surfaces is accelerated by the grazing activity of snails, and is most intense where snails are abundant. Microstratigraphic resolution is limited by vertical mixing of fossils and by the reworking of older fossils into younger deposits. Stratigraphic disorder is the departure from perfect chronological order of fossils in a stratigraphic sequence. I simulated mixing and reworking of fossils by simple computer models, and measured stratigraphic disorder using rank correlation statistics. As modeled, mixing produces disorder slowly, and its effects can be minimized by increasing sample size at each horizon and by increasing the vertical spacing between sampled horizons (though this reduces vertical resolution). Reworking generates disorder more efficiently, and its effects are not reduced by increasing sample size or spacing. The generation of stratigraphic disorder in fossiliferous sediments can also be modeled using M (depth of vertical mixing), I (thickness of sedimentary increments), and L (taphonomic loss rate) as parameters. Increasing M increases the disorder generated, and increasing I and L decreases disorder. For a worst case--high M and low I and L--the vertical spacing between samples must at least 3 times M to ensure a 5% temporal overlap between adjacent samples. A 1% temporal overlap requires a vertical spacing of 4.6 times M.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Taphonomy -- Mexico -- Bahia la Choya; Mollusks, Fossil -- Mexico -- Bahia la Choya.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Geosciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Flessa, Karl W.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleProcesses of hardpart breakdown and models of stratigraphic disorder in shallow marine environments.en_US
dc.creatorCutler, Alan Hughes.en_US
dc.contributor.authorCutler, Alan Hughes.en_US
dc.date.issued1991en_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.abstractTaphonomy is the study of the fate of information in the fossil record. Information can be lost through the partial or complete destruction of fossils, or through the disruption of their original spatial relationships. Information can be "gained" if the alteration of fossils allows environmental information to be retrieved. In Bahia la Choya, northern Gulf of California, bioerosion, dissolution/maceration, and abrasion produce distinctive textures on the surfaces of shells in intertidal and shallow subtidal environments. Shells from different environments possess different surface textures, suggesting that textures on fossil shells could serve as paleoenvironmental indicators. Algal bioerosion is the chief mode of shell alteration and destruction in Bahia la Choya, though dissolution/maceration and abrasion are locally important. Algal bioerosion of shell surfaces is accelerated by the grazing activity of snails, and is most intense where snails are abundant. Microstratigraphic resolution is limited by vertical mixing of fossils and by the reworking of older fossils into younger deposits. Stratigraphic disorder is the departure from perfect chronological order of fossils in a stratigraphic sequence. I simulated mixing and reworking of fossils by simple computer models, and measured stratigraphic disorder using rank correlation statistics. As modeled, mixing produces disorder slowly, and its effects can be minimized by increasing sample size at each horizon and by increasing the vertical spacing between sampled horizons (though this reduces vertical resolution). Reworking generates disorder more efficiently, and its effects are not reduced by increasing sample size or spacing. The generation of stratigraphic disorder in fossiliferous sediments can also be modeled using M (depth of vertical mixing), I (thickness of sedimentary increments), and L (taphonomic loss rate) as parameters. Increasing M increases the disorder generated, and increasing I and L decreases disorder. For a worst case--high M and low I and L--the vertical spacing between samples must at least 3 times M to ensure a 5% temporal overlap between adjacent samples. A 1% temporal overlap requires a vertical spacing of 4.6 times M.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectTaphonomy -- Mexico -- Bahia la Choyaen_US
dc.subjectMollusks, Fossil -- Mexico -- Bahia la Choya.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorFlessa, Karl W.en_US
dc.contributor.committeememberCohen, Andrew S.en_US
dc.contributor.committeememberParrish, Judith T.en_US
dc.contributor.committeememberStrauss, Richard E.en_US
dc.contributor.committeememberThomson, Donald A.en_US
dc.identifier.proquest9210286en_US
dc.identifier.oclc704284995en_US
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