LEGEND CHRONOSTRATIGRAPHIC MAP OF THE REPUBLIC OF … · chronostratigraphic map for South Africa...
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Ermelo Barberton Musina Louis Trichardt Rustenburg Thabazimbi Vryburg Pofadder Port Nolloth Vanrhynsdorp Vredenburg Worcester Laingsburg Oudtshoorn Grahamstown Queenstown Umtata Port Shepstone Richards Bay Vryheid Klerksdorp Vredefort Swellendam Aliwal North Calvinia Prieska Kuruman Welkom Phalaborwa Harrismith Z I M B A B W E M O Z A M B I Q U E B O T S W A N A N A M I B I A L E S O T H O SWAZILAND Carnarvon Colesberg Maseru Durban Mbabane Mafikeng Upington Pretoria Springbok Nelspruit Kimberley Cape Town Mossel Bay Polokwane East London Bloemfontein Johannesburg Graaff-Reinet Beaufort West Port Elizabeth Pietermaritzburg 32° 32° 30° 30° 28° 28° 26° 26° 24° 24° 22° 22° 20° 20° 18° 18° 16° 16° 34° 22° 22° 24° 24° 26° 26° 28° 28° 30° 30° 32° 32° 34° 34° CHRONOSTRATIGRAPHIC MAP OF THE REPUBLIC OF SOUTH AFRICA AND THE KINGDOMS OF LESOTHO AND SWAZILAND NOTES ON THE CHRONOSTRATIGRAPHIC MAP OF THE REPUBLIC OF SOUTH AFRICA AND THE KINGDOMS OF LESOTHO AND SWAZILAND With the completely digital production of the 1:1 000 000-scale geological map, the task of compiling a chronostratigraphic map for South Africa became considerably easier than it would have been in the past. The data used in the production process were captured using a Geographical Information System (GIS) and contain full attributes relating to the stratigraphy and lithology of the various geological units on the map. The data are stored in a GIS database for use in other projects. For this project, an important initial task was deciding on the cut-off points of the age groupings to be shown on the map. Once this had been done, the chronostratigraphic map could be created simply by assigning each of the existing lithostratigraphic units to the correct time interval. Different colours, ranging from purple/red for the oldest to blue for the youngest, were then allocated to each of the relevant time intervals. The original lithostratigraphic boundaries were retained as background lines on the chronostratigraphic map. In order to provide a quick visual impression of the extent of intrusive igneous activity within each time interval, a distinctive ornamentation has been used to highlight the intrusive rocks. In the Archaean and Proterozoic Eons the standard local eras and periods were used as the primary time divisions, since they correlate better with the local geology than the international subdivisions. The Namibian has, however, been combined with the Cambrian in view of the fact that a number of units have ages close to or straddling the boundary (e.g., the Cape Granite Suite). In the Phanerozoic, the Ordovician, Silurian and Devonian Periods form a convenient grouping extending from the base of the Table Mountain Group to the top of the main quartzite unit of the Witteberg Group (i.e., the Witpoort Formation). The boundary between the Carboniferous and Permian Periods falls somewhere within the Dwyka Group, making it necessary to combine them as well. The Permo-Triassic boundary conveniently coincides with the contact between the Adelaide and Tarkastad Subgroups of the Beaufort Group in the main Karoo Basin, but in the small Karoo basins to the north this boundary is unclear and the undifferentiated Permo-Triassic strata in these basins have been arbitrarily assigned to the Permian- Carboniferous interval. The base of the extensive Clarens Formation is a reasonably close approximation of the top of the Triassic. The Jurassic and Cretaceous successions are generally quite distinct except that in the Algoa Basin and its equivalents further west the Kirkwood Formation (Uitenhage Group) may straddle the boundary; all of it has here been assigned to the Cretaceous Period. A list of the main geological and palaeontological events in South Africa’s geological history has been combined with the legend. The ages of these events, relative to the time scale, have been indicated, and it can be seen that there are no major gaps present, with all the eras (in the Precambrian) and periods (in the Phanerozoic) being represented. In other words, South Africa has a fairly continuous geological record covering some 3500 million years. Special emphasis has been placed on South Africa’s mineral wealth, and the restricted time slots in which the country’s extensive gold, iron, manganese, platinum, chromium, coal and diamond deposits formed can be clearly seen. While the terrestrial vertebrate fossils (reptiles, mammal-like reptiles and amphibians) in the Karoo Supergroup and hominid remains in cave deposits such as Sterkfontein and Swartkrans are world famous, there are many other important fossil-bearing units and the most significant of these have also been noted. It is anticipated that this map will prove to be particularly useful to students, overseas visitors and non- geologists wanting a bird’s-eye view of the distribution of rocks of different ages in South Africa without getting bogged down in the details of lithostratigraphic nomenclature. As mentioned above, the lithostratigraphic contacts as they appear on the 1:1 000 000-scale geological map have been retained and those wishing to know the name of a specific unit within a certain age band can obtain this information by referring to the geological map. I N D I A N O C E A N A T L A N T I C O C E A N Council for Geoscience Compiled by: M.R. Johnson and L.G. Wolmarans COPYRIGHT: COUNCIL FOR GEOSCIENCE 2008 Cartographically prepared by C. Thomas Copies of the Map (also in digital format) are obtainable from the Council for Geoscience, Private Bag X112, Pretoria, 0001, http://www.geoscience.org.za Important hominid fossils (Taung, Sterkfontein, etc.) Abundant mammal fossils (Langebaan, etc.) Initiation of Kalahari Basin Intrusion of most diamond-bearing kimberlite pipes Main offshore oil and gas deposits; invertebrates (ammonites, etc.) common in onshore basins Separation of Africa and South America starts Gondwana break-up begins; West Gondwana (Africa and South America) and East Gondwana (Antarctica, Australia, Madagascar and India) drift apart Widespread basalt and (in the east) rhyolite flows, numerous dolerite intrusions (Karoo Igneous Province) Abundant plant fossils (Dicroidium flora) in Molteno Formation, followed by extensive dinosaur remains in Elliot Formation Folding and thrusting (Cape Fold Belt) in south Terrestrial vertebrates (including mammal-like reptiles) common (Beaufort Group) Glossopteris flora flourishes and major coal deposits formed (Ecca Group) Widespread glaciation (Dwyka Group) Northward subduction of palaeo-Pacific plate initiates foreland Karoo Basin behind magmatic arc Fish fossils near top of Witteberg Group Plant remains (lycopod stems, etc.) in Witteberg Group Invertebrate fossils (trilobites, etc.) in Bokkeveld Group form part of Gondwana's distinctive "Malvinokaffric fauna" Marine invertebrate fossil assemblage in Cedarberg Formation (Table Mountain Group) includes several unique forms Glacial event in Table Mountain Group Initiation of Cape and Natal Basins Granite plutons (Cape Granite Suite) emplaced in Western Cape Late "Pan-African" sedimentation (Nama Group, etc.); distinctive late Precambrian Ediacaran-type fossils in Nama Group Waterberg and Soutpansberg Basins formed Early "Pan-African" sedimentation, volcanism and tectonism: Gariep, Malmesbury, etc. basins formed Intense tectonism, high-grade metamorphism and granite magmatism (Namaqua-Natal Metamorphic Province) accompany accretion along southern margin of Kalahari Craton Intrusion of numerous large alkaline complexes (Pilanesberg, etc.); late-stage sedimentation and volcanism in Namaqua-Natal Belt Formation of Olifantshoek Basin; oldest dated sedimentary/volcanic rocks east of 22° E Meteorite forms world's largest confirmed inpact structure (Vredefort Dome) Emplacement of world's largest layered intrusion (Bushveld Complex) with vast platinum, chromium and vanadium reserves Extensive iron and manganese deposits (Transvaal Supergroup) Proliferation of stromatolite-forming algae (Transvaal Supergroup) Initiation of Transvaal Basin; major orogeny in Limpopo Belt Extensive basaltic and rhyolitic eruptions (Ventersdorp Supergroup) World's largest gold deposits (Witwatersrand Supergroup) Formation of Witwatersrand and Pongola Basins Consolidation of Kaapvaal Craton largely completed Intrusion of many large granite plutons in and north of Swaziland Formation of Barberton Basin, site of the world's best-preserved early Archaean greenstone belt Possible single-celled organisms (among world's oldest) in the Onverwacht Group (Barberton Supergroup) * Comprises Palaeogene (65 - 25 Ma) and Neogene (25 - 1.8 Ma) + Some undifferentiated Permian - Triassic units outside the main Karoo Basin are included in the Permian - Carboniferous interval on this map EON ERA Ma CENOZOIC MESOZOIC 1.8 50 100 150 PHANEROZOIC 200 250 300 350 400 450 500 PALAEOZOIC Time scale expanded 7.5x Ma 545 MOKOLIAN PROTEROZOIC ARCHAEAN 1000 2000 1500 2500 3000 3500 MOKOLIAN 0 500 1000 1500 2000 2500 3000 3500 3700 LEGEND PERIOD Cretaceous Jurassic Triassic + Permian Carboniferous Devonian Silurian Ordovician Cambrian Namaquan Kheisian Quaternary Tertiary * NAMIBIAN VAALIAN RANDIAN SWAZIAN International border Provincial border Lithostratigraphic boundaries Intrusive rocks Faults (including thrusts and shear zones) 2008 Projection: Albers Equal Area Central meridian: 24° E Standard parallels: 20° S ; 30° S 1:2 000 000 Kilometers 50 0 50 100 150 200 250 300 NORTHERN CAPE WESTERN CAPE EASTERN CAPE LIMPOPO NORTH WEST FREE STATE KWAZULU-NATAL MPUMALANGA GAUTENG 32° 32° 30° 30° 28° 28° 26° 26° 24° 24° 22° 22° 20° 20° 18° 18° 16° 16° 34° 22° 22° 24° 24° 26° 26° 28° 28° 30° 30° 32° 32° 34° 34° KEY TO PROVINCES
LEGEND CHRONOSTRATIGRAPHIC MAP OF THE REPUBLIC OF … · chronostratigraphic map for South Africa became considerably easier than it would have been in the past. The data used in
