Provenance and sedimentology of the Archean Mapepe Formation, southeastern Barberton Greenstone Belt, South Africa
Abstract/Contents
- Abstract
- The 3.5 to 3.2 Ga Barberton Greenstone Belt (BGB), South Africa, offers a view into the surface of the Early Archean Earth. The Fig Tree Group and the Buck Reef Chert of the Onverwacht Group, the subjects of this thesis, are comprised mostly of sedimentary rocks. These rocks still display primary sedimentary structures, and some original geochemical and geochronological signatures are preserved. This study is broken into two parts. The first chapter examines the relationship between three different types of banded cherts seen in the BGB: black and white banded chert (B&W), banded ferruginous chert (BFC), and banded iron formation (BIF). These banded cherts represent a spectrum of related processes and depositional settings. Based on sedimentary structures, petrography, and lithologic associations, we infer that BIF was deposited in deeper water than BFC, and B&W chert was deposited in shallower water than BFC, at depths commonly affected by storms. These relationships suggest that silica was precipitated within the uppermost part of the water column and settled to all depths. Siderite formed mainly in waters of intermediate depth, below the storm agitated surface layer but above the deep basin bottom settings and is a major component of BFC and deeper BIF. A hematite precursor formed in the deepest waters, producing BIF made up of hematite and other components that settled into this setting from shallower sites of precipitation, including silica and siderite. The second chapter is a provenance study of a newly mapped and analyzed structural block, the Mlumati Syncline, and the neighboring blocks in the southeastern part of the BGB. Its proximity and similar stratigraphy to the adjacent Manzimnyama Syncline suggest that these two structural blocks represent parts of the same Archean depositional system. Their similar sandstone petrography, shale geochemistry, and detrital zircon geochronology emphasize the similarity in their source terrains, affirming the hypothesis that they represent parts of a single depositional basin. The sedimentary rocks in these synclines are also compared to those in other structural blocks in the southeastern BGB. The provenance proxies suggest different source terrains, implying the sequences were not part of a single large source, transport, and depositional fairway.
Description
| Type of resource | text |
|---|---|
| Date created | June 2020 |
Creators/Contributors
| Author | Stoll, Emily |
|---|---|
| Primary advisor | Lowe, Donald R. |
| Advisor | Graham, Stephan |
| Degree granting institution | Stanford University, Geological Sciences |
Subjects
| Subject | School of Earth Energy & Environmental Sciences |
|---|---|
| Subject | Geological Sciences |
| Subject | Archean |
| Subject | banded chert |
| Subject | provenance |
| Genre | Thesis |
Bibliographic information
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- User agrees that, where applicable, content will not be used to identify or to otherwise infringe the privacy or confidentiality rights of individuals. Content distributed via the Stanford Digital Repository may be subject to additional license and use restrictions applied by the depositor.
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
Preferred citation
- Preferred Citation
- Stoll, Emily. (2020). Provenance and sedimentology of the Archean Mapepe Formation, southeastern Barberton Greenstone Belt, South Africa. Stanford Digital Repository. Available at: https://purl.stanford.edu/qj766fj7564
Collection
Master's Theses, Doerr School of Sustainability
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- Contact
- emilystoll47@gmail.com
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