MICROSTROMATOLITES FROM THE 2.3 G.A. TRANSVAAL SEQUENCE, SOUTH AFRICA (STROMATOLITES, MICROFOSSIL, CHERT).

Persistent Link:
http://hdl.handle.net/10150/187726
Title:
MICROSTROMATOLITES FROM THE 2.3 G.A. TRANSVAAL SEQUENCE, SOUTH AFRICA (STROMATOLITES, MICROFOSSIL, CHERT).
Author:
LANIER, WILLIAM PAUL.
Issue Date:
1984
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:
A unique assemblage of in situ microstromatolites, articulated intraclastic microstromatolites, and disarticulated stromatolites has been identified from drill cores of the 2.3 G.a. Transvaal Sequence, South Africa. These structures occur in organic-rich lenticular and nodular replacement black cherts which are associated with early diagenetic dolomite. Petrographic evidence indicates that the chert has formed via a primary carbonate and organic matrix--partial dolomitization--silicification paragenetic sequence; and that dolomitization and silicification were closely contemporaneous diagenetic events. Microstructures which resemble three dimensionally preserved microfossils are found in the majority of the silicified Transvaal cores. These fossil-like microstructures can be grouped broadly into three morphological types: (1) filaments, (2) ovoid or spheroidal forms, and (3) bacteria-like microstructures. Certain of the filamentous forms which are associated with pyrite mineral grains are clearly of abiological origin, and their formation can be explained in the context of sedimentary diagenesis and mineral paragenesis. The three dimensional association of the ovoid and bacteria-like microstructures to the microstromatolites is such as would be predicted from studies of modern cyanobacterial/microbial mat ecosystems. Hence, these microstructures are considered to be potential microfossils. The Transvaal microstromatolitic materials represent some of the smallest stromatolites yet described from either Proterozoic or Phanerozoic sedimentary rocks. Nearly all of the basic stromatolite growth forms (i.e. columnar, bulbous, nodular, and stratiform) are represented in the Transvaal assemblage. Thus, stromatolite diversity at the "basic growth form" level apparently did not evolve through geologic time. Physical and chemical environmental parameters probably controlled stromatolite morphogenesis only to the extent that they influenced the steady state balance of microstromatolite microbial communities. Indirect evidence suggests that the Transvaal microstromatolites grew via the precipitation of primary carbonate at some level within the structures and that a correlation exists between the degradation of primary producer organic carbon and the precipitation of a structurally supportive carbonate mineral matrix.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Micropaleontology -- South Africa -- Transvaal Region.; Stromatolites.; Transvaal (South Africa)
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Geosciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Nagy, Bartholomew

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleMICROSTROMATOLITES FROM THE 2.3 G.A. TRANSVAAL SEQUENCE, SOUTH AFRICA (STROMATOLITES, MICROFOSSIL, CHERT).en_US
dc.creatorLANIER, WILLIAM PAUL.en_US
dc.contributor.authorLANIER, WILLIAM PAUL.en_US
dc.date.issued1984en_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.abstractA unique assemblage of in situ microstromatolites, articulated intraclastic microstromatolites, and disarticulated stromatolites has been identified from drill cores of the 2.3 G.a. Transvaal Sequence, South Africa. These structures occur in organic-rich lenticular and nodular replacement black cherts which are associated with early diagenetic dolomite. Petrographic evidence indicates that the chert has formed via a primary carbonate and organic matrix--partial dolomitization--silicification paragenetic sequence; and that dolomitization and silicification were closely contemporaneous diagenetic events. Microstructures which resemble three dimensionally preserved microfossils are found in the majority of the silicified Transvaal cores. These fossil-like microstructures can be grouped broadly into three morphological types: (1) filaments, (2) ovoid or spheroidal forms, and (3) bacteria-like microstructures. Certain of the filamentous forms which are associated with pyrite mineral grains are clearly of abiological origin, and their formation can be explained in the context of sedimentary diagenesis and mineral paragenesis. The three dimensional association of the ovoid and bacteria-like microstructures to the microstromatolites is such as would be predicted from studies of modern cyanobacterial/microbial mat ecosystems. Hence, these microstructures are considered to be potential microfossils. The Transvaal microstromatolitic materials represent some of the smallest stromatolites yet described from either Proterozoic or Phanerozoic sedimentary rocks. Nearly all of the basic stromatolite growth forms (i.e. columnar, bulbous, nodular, and stratiform) are represented in the Transvaal assemblage. Thus, stromatolite diversity at the "basic growth form" level apparently did not evolve through geologic time. Physical and chemical environmental parameters probably controlled stromatolite morphogenesis only to the extent that they influenced the steady state balance of microstromatolite microbial communities. Indirect evidence suggests that the Transvaal microstromatolites grew via the precipitation of primary carbonate at some level within the structures and that a correlation exists between the degradation of primary producer organic carbon and the precipitation of a structurally supportive carbonate mineral matrix.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectMicropaleontology -- South Africa -- Transvaal Region.en_US
dc.subjectStromatolites.en_US
dc.subjectTransvaal (South Africa)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.advisorNagy, Bartholomewen_US
dc.contributor.committeememberBaker, Victor R.en_US
dc.contributor.committeememberKidwell, Susanen_US
dc.contributor.committeememberSinclair, Norval A.en_US
dc.contributor.committeememberSchrieber, Joseph F.en_US
dc.identifier.proquest8421973en_US
dc.identifier.oclc691322989en_US
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