Part 1

• SU-8: Fluvial Geomorphology of South Africa – Part 1

  
• Physical Geography
• Lecturer: Dr Brigitte Language
• Office: Building E4, Office G35
• 1. Mail: [e-mail]
• Module Outcomes


  After engaging with the module content, you should be able to:
• Learning Outcomes


  At the end of this unit, you should be able to:
• Areas of interest


  • SU6
  • Karoo
  • SU7
  • Pilansberg
  • Drakensberg
  • SU8
  • Eastern Escarpment
  • Augrabies Falls
  • SU9
  • Dunes & Dry Valleys of the Kalahari
  • Western Free State Pans
• Geographic Locations
• South African Geology
• Geomorphic Provinces
• PART 1 (Chapter 3: The Mpumalanga/Limpopo (Eastern Great) Escarpment – Geology and Fluvial Landforms)

  
• Geological Terms


  • Stratigraphy
  • Morphology
  • Lithology
  • Formations
  • Groups
  • Supergroups
  • Unconformity
  • Succession
  • Outcrop
  • Isostatic readjustment
  • Epiorogenic uplift
  • Orogeny
  • Glacio-eustatic
  • Planation
  • Coal measures
  • Greenstone belt
  • Fault
  • Joint
  • Dyke
  • Stromatolites
  • Fluvial systems
  • Talus
  • Potholes
  • Dripstone
  • Calcareous rocks
  • Tufa deposit
  • Plateau
  • Mesa
  • Undulating hills
  • Escarpment
  • Ridge
  • Valley
  • Gorge
  • River valley
  • Furrows
  • Knickpoints
• Isostasy


  Primarily caused by a mantle plume beneath the African continent, led to the uplift and deformation of the continental crust
• Glacioeustatic oscillations


  Changes in sea level, river incision, and land surface planation during the Neogene and Pleistocene
• Dominant processes shaping the Eastern Great Escarpment


  • Backward retreat
  • Incision of drainage lines
  • Lateral spread of newly formed valleys
• Eastern Great Escarpment extent


  • ~300 km from Badplaas to Haenertsberg
  • Altitudes of over 2,000 m.a.s.l.
• Topography of the Eastern Escarpment


  • Distinct and varied topography
  • Lowveld - flat, low-lying terrain
• Prominent fluvial systems


  • Komati River
  • Crocodile River
  • Sabie River
  • Blyde River
  • Olifants River
• Fluvial systems originate


  • In the high mountain land west of the escarpment edge
  • Mpumalanga/Limpopo portion of the Eastern Escarpment exhibits dramatic erosional features
• Geotourism attractions


  • Bourke's Luck potholes
  • Blyde River Canyon
  • Waterfalls
• Geological Setting & Evolution
• Lowveld region


  • Below the escarpment edge
  • Underlain by basement rocks
  • Includes the Barberton Greenstone Belt
• Barberton Greenstone Belt (BGB)


  • Ancient volcanic and sedimentary formation (~3,500 Ma)
  • Granites intruded into the greenstone belt (~3,200 to 3,400 Ma)
  • Subsequently undergoing metamorphism, forming granitic gneisses
• Geological map of the Barberton Greenstone Belt (BGB) of South Africa and Swaziland and its surrounding plutons in the eastern part of the Kaapvaal Craton

  
• Generalized stratigraphy and structure of the Barberton Supergroup north and south of the Inyoka Fault with the indicated stratigraphic position of reported macro- and microscopic traces of Paleoarchean life in the Barberton Greenstone Belt
• Barberton Greenstone Belt (cont.)

  • Less resistant granitic gneisses now make up the low-lying terrain
  • Resistant potassium and silica-rich granites intruded the older basement terrain (~3,100 Ma)
  • Undulating mini-plateau east of the Eastern Escarpment edge
  • Younger sedimentary basins overlay the basement rocks to the west, creating dramatic features of the Eastern Escarpment edge
• Wolkberg Group Basin (~2700 Ma)


  • Developed beneath the main portion of the Transvaal succession
  • Between Sabie and Potgietersrus
  • Underlies the Black Reef Formation
  • ~2630m thick
  • Consists of siliciclastic sedimentary rocks and minor basic volcanics
  • Well developed north of Sabie, forming the scenery of the Blyde River canyon and Marieps Kop on the escarpment edge
• Relationship between the Wolkberg basin and Archaean floor structural features (greenstone belts)
• Black Reef Formation (~2650 Ma)


  • Overlays the Wolkberg Group
  • Predominantly consists of quartzite, including lenses of grit and conglomerate
  • Crops out 25 km southwest of Badplaas and at Makapansgat
• Locality map showing the outcrop of the Chuniespoort and Ghaap Groups of the Transvaal Sequence
• Buffelspruit: Thin quartzite veneer (<1 m) overlays Archaean granite at an unconformity, with pebble-conglomerate-filled channels locally eroding the contact, and the upper boundary being a consistent carbonaceous shale zone observed across eastern Transvaal
• Grootkop: At a location 25 km north of Badplaas, there is a distinct nonconformable contact with Archaean granite
• GEOG211


  2024
• Buffelspruit


  1. Thin quartzite veneer (<1 m) overlays Archaean granite at an unconformity

  2. Pebble-conglomerate-filled channels locally erode the contact

  3. The upper boundary is a consistent carbonaceous shale zone observed across eastern Transvaal
• Grootkop


  1. At a location 25 km north of Badplaas, there is a distinct nonconformable contact with Archaean granite

  2. The contact reveals a sturdy conglomerate, but further along the same direction, conglomerates are found only ~1 m above the contact

  3. These conglomerate units are believed to be channel deposits
• Kaapsehoop


  1. Unconformable contact at Kaapsehoop escarpment

  2. Local deposition of robust conglomerates in channels carved into the surface

  3. Channel widths vary from a few meters to hundreds of meters

  4. Cobbles up to 18 cm present in the channels

  5. Clasts primarily composed of vein quartz, multi-colored chert, quartzite, and occasional shale

  6. Small-pebble conglomerate or trough cross-laminated quartz arenite overlays granite basement in channel-absent areas
• Kaapsehoop


  • Quartzite rock in the fields
• Sudwala Caves


  1. 5 m-thick coarse-grained quartz arenite over certified shale of Godwan Formation

  2. Shallow angular unconformity observed between the two units

  3. Evident erosional contact relationships
• Sabie


  1. Coarse-grained quartz arenite above distinct erosional contact with volcanic unit

  2. Correlation of volcanic unit with Abel Erasmus Basalt Formation of Wolkberg Group

  3. Identification of angular unconformity with overlying Black Reef Formation