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Characterisation of regional strains in the western Saldania Belt and implications for the structural evolution of Pan-African Rocks in the Western Cape, South Africa
Thesis (MSc)--Stellenbosch University, 2024.
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| Format: | Thesis |
| Language: | en_ZA en_ZA |
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Stellenbosch : Stellenbosch University
2024
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| _version_ | 1867613899338022912 |
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| access_status_str | Open Access |
| author | Rheeder, Christie George |
| author2 | Kisters, Alexander |
| author_browse | Kisters, Alexander Rheeder, Christie George |
| author_facet | Kisters, Alexander Rheeder, Christie George |
| author_sort | Rheeder, Christie George |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2024. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/130683 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA en_ZA |
| last_indexed | 2026-06-10T12:43:28.625Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2024 |
| publishDateRange | 2024 |
| publishDateSort | 2024 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/130683 Characterisation of regional strains in the western Saldania Belt and implications for the structural evolution of Pan-African Rocks in the Western Cape, South Africa Rheeder, Christie George Kisters, Alexander Stellenbosch University. Faculty of Science. Dept. of Earth Sciences. Pan-African Rocks -- South Africa -- Western Cape -- Saldania Belt Geology, Structural -- South Africa -- Western Cape Geological mapping Strains and stresses UCTD Thesis (MSc)--Stellenbosch University, 2024. ENGLISH ABSTRACT: The western Saldania Belt records the closure of the Adamastor Ocean and the amalgamation of southwest Gondwana during the late Neoproterozoic and early Phanerozoic. Still, uncertainties regarding its geodynamic setting and tectonic evolution remain. The lack of outcrop and deceptive monotony of the belt added to the uncertainty about the Saldania Belt and has seen the belt linked to the well-understood northern Pan-African belts. Structural mapping included numerous type localities, made up of widespread surface mapping and 3D exposures in quarries throughout the region, together with historical data, which formed an integrated regional geodatabase to reveal the juxtaposition of structural domains characterised by distinct fabric development and kinematics. Two structurally overlying domains, namely an upper and a lower domain, form the main regions within the study area. The rocks in the upper domain exhibit transpressional strain partitioning into (1) broad regions of north to northwesterly-trending folds (F2) indicating horizontal, mainly coaxial, east-northeast to west-southwest-directed shortening at high angles to the continental margin, and (2) margin-parallel, non-coaxial deformation along the sinistral strike-slip Colenso Fault Zone (ca. 555 and 520 Ma). Non-coaxial strain was further promoted by strain localisation into synkinematic plutons of the Cape Granite Suite. Structures within the belt record Pan-African strains and signify sinistral transpression dominated by strike-slip motion during southeast-directed subduction and convergence at shallow angles to the continental margin (< 20°). In contrast, lower domain rocks present a pervasively transposed, mélange-like sequence that documents episodes of vertical, coaxial shortening alternating with non-coaxial top-to-the-west and -northwest thrusting. The coaxial shortening strains are linked to the thickening and gravitational loading of the succession in response to thrusting and tectonic underplating. In contrast, non-coaxial strains signify episodes of seismic slip during underthrusting. The distinct differences in the fabrics observed in the contrasting domains represent a deformed fore- arc region, made-up of a deeper-level accretionary prism (lower domain), overlain by a folded fore- arc basin fil (upper domain). The transfer of lower-domain phyllites, utilising thrusts, into the overlying fore-arc sequence is indicated by regional-scale klippen structures. The proposed fore-arc setting of the Saldania Belt suggests the subduction of the Adamastor Ocean beneath the leading edge of the Kalahari Craton, challenging pre-existing stratigraphic and structural correlations. AFRIKAANSE OPSOMMING: Die westelike Saldania Gordel dokumenteer die sluiting van die Adamastor Oseaan en die samevoeging van suidwes Gondwana gedurende die laat Neoproterosoïese en vroeë Faneroïese tydperke, maar onsekerhede oor sy geodinamiese opstelling en tektoniese evolusie bly voortduur. Die gebrek aan blootgestelde rotsformaties en misleidende monotomie van die gordel het bygedra tot die onsekerheid oor die Saldania Gordel en het gesien dat die gordel gekoppel is aan die goed verstaande noordelike Pan-Afrika-gordels. Strukturele kartering het talle standaard blootstellings ingesluit, wat opgemaak is uit wydverspreide oppervlakkartering en 3D-blootstellings in steengroewe regdeur die streek, tesame met historiese data vorm dit 'n geïntegreerde geodatabasis om die teenstelling van strukturele domeine te openbaar wat gekenmerk word deur duidelike interne struktuurontwikkeling en kinematika. Twee domeine oorlê mekaar struktureel, naamlik 'n boonste en 'n onderste domein, en vorm die hoofgebiede binne die studiegebied. Die gesteentes in die boonste domein vertoon transpressionele spanning wat verdeel word in (1) breë gebiede van noord- tot noordweswaarts- trekkende voue (F2) wat horisontale, hoofsaaklik koaksiale, oos-noordoos tot wes-suidweste gerigte verkorting teen hoë hoeke tot die kontinentale marge aandui, en in (2) marge-parallelle, nie-koaksiale deformasie in die linkslaterale Colenso skuifskeursone (ongeveer 555 tot 520 Ma). Nie-koaksiale spanning is verder bevorder deur spanninglokalisering in sin-kinematiese plutone van die Kaapse Granietreeks. Strukture binne die gordel registreer Pan-Afrikaanse spanning en dui op linkslaterale transpressie wat oorheers word deur skuif-gedrewe beweging tydens suidoos-gerigte subduksie en konvergensie teen lae hoeke tot die kontinentale marge (< 20°). In teenstelling bied gesteentes in die onderste domein 'n deurdringende getransponeerde, mélange-agtige reeks wat episodes van vertikale, koaksiale verkorting afwissel met nie-koaksiale top-tot-die-wes en -noordwes- stootskeuring. Die koaksiale verkortingstrekke is gekoppel aan die verdikking en gravitasielading as reaksie op indrukking en tektoniese onderplating. Daarenteen dui nie-koaksiale spanninge op episodes van seismiese skuif tydens onderindrukking. Die duidelike verskille in die interne strukture wat waargeneem word in die teenstrydige domeine, verteenwoordig 'n herformde voorboog-gebied, wat strek van die dieperliggende akkresionêre prisma (onderste domein) tot die oorliggende, gevoude voorboog-bak-oopvolging (boonste domein). Regionale skaal klipstrukture dui op die oordrag van onderste-domein filiete, deur die gebruik van stootskeurings, na die oorliggende voorboog-reeks. Die voorgestelde voorboog-opstelling van die Saldania Gordel dui op die subduksie van die Adamastor Oseaan onder die voorste marge van die Kalahari Kraton, wat die bestaande stratigrafiese en strukturele korrelasies bevraagteken. Masters 2024-02-13T16:09:25Z 2024-04-27T02:32:10Z 2024-02-13T16:09:25Z 2024-04-27T02:32:10Z 2024-03 Thesis https://scholar.sun.ac.za/handle/10019.1/130683 en_ZA en_ZA Stellenbosch University application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Pan-African Rocks -- South Africa -- Western Cape -- Saldania Belt Geology, Structural -- South Africa -- Western Cape Geological mapping Strains and stresses UCTD Rheeder, Christie George Characterisation of regional strains in the western Saldania Belt and implications for the structural evolution of Pan-African Rocks in the Western Cape, South Africa |
| title | Characterisation of regional strains in the western Saldania Belt and implications for the structural evolution of Pan-African Rocks in the Western Cape, South Africa |
| title_full | Characterisation of regional strains in the western Saldania Belt and implications for the structural evolution of Pan-African Rocks in the Western Cape, South Africa |
| title_fullStr | Characterisation of regional strains in the western Saldania Belt and implications for the structural evolution of Pan-African Rocks in the Western Cape, South Africa |
| title_full_unstemmed | Characterisation of regional strains in the western Saldania Belt and implications for the structural evolution of Pan-African Rocks in the Western Cape, South Africa |
| title_short | Characterisation of regional strains in the western Saldania Belt and implications for the structural evolution of Pan-African Rocks in the Western Cape, South Africa |
| title_sort | characterisation of regional strains in the western saldania belt and implications for the structural evolution of pan african rocks in the western cape south africa |
| topic | Pan-African Rocks -- South Africa -- Western Cape -- Saldania Belt Geology, Structural -- South Africa -- Western Cape Geological mapping Strains and stresses UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/130683 |
| work_keys_str_mv | AT rheederchristiegeorge characterisationofregionalstrainsinthewesternsaldaniabeltandimplicationsforthestructuralevolutionofpanafricanrocksinthewesterncapesouthafrica |