Geology of Angola

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Erosion created cliffs at Miradouro da Lua. Miradouro da Lua (Angola).jpg
Erosion created cliffs at Miradouro da Lua.

The geology of Angola includes large areas of Precambrian age rocks. The west of the country is characterized by meta-sedimentary rocks of Proterozoic age including tillites assigned to the Bembe System. Overlying these are a thick pile of limestones and other marine sediments laid down during the Mesozoic and Cenozoic eras. Amidst the Proterozoic sequence are areas of crystalline basement dating from the Archaean. More Archaean basement rocks form the Kasai Craton in northeastern Angola. In the north, within the Cassanje Graben are clastic sediments and volcanic rocks of the Karoo Supergroup. Kimberlites and carbonatites resulting from magmatic activity during the Karoo period are found along a northeast-southwest line through the country. Continental sediments of the Kalahari Group are widespread in eastern Angola. [1]

Contents

Fossils

The Mesozoic of Angola is very rich of fossil vertebrates, namely marine reptiles such as turtles ( Angolachelys [2] ), mosasaurs and plesiosaurs, [3] related with the opening of South Atlantic. [4] Only a couple of terrestrial fossils have been collected, including the unique dinosaur Angolatitan adamastor . [5]

Geohazards

Aquifers and ground water have been polluted due mining activities in the country. [6] :40

Economic geology

The larger part of Angola's income derives from oil production and by 2008 the country was Africa's second largest producer of crude petroleum. Angola is also the fourth largest producer of diamonds in Africa. Diamonds are obtained both from alluvial deposits and from the hundreds of kimberlite pipes which are scattered along a northeast – southwest line through Angola. The country is also a gold producer, the most important source being alluvium originating from Archaean greenstones dominantly around Cabinda. Angola also has, as yet largely untapped, copper, gypsum, phosphate, iron ore, manganese and other base metal reserves. [7]

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<i>Angolatitan</i> Extinct genus of titanosauriform dinosaurs

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Globidensini Tribe of lizards

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Geology of Zambia

The geological history of Zambia begins in the Proterozoic eon of the Precambrian. The igneous and metamorphic basement rocks tend to be highly metamorphosed and may have formed earlier in the Archean, but heat and pressure has destroyed evidence of earlier conditions. Major sedimentary and metamorphic groups formed in the mid-Proterozoic, followed by a series of glaciations in the Neoproterozoic and much of the Paleozoic which deposited glacial conglomerate as well as other sediments to form the Katanga Supergroup and rift-related Karoo Supergroup. Basalt eruptions blanketed the Karoo Supergroup in the Mesozoic and Zambia shifted to coal and sandstone formation. Geologically recent windblown sands from the Kalahari Desert and alluvial deposits near rivers play an important role in the modern surficial geology of Zambia. The country has extensive natural resources, particularly copper, but also cobalt, emeralds, other gemstones, uranium and coal.

The Itombe Formation is a geological formation of the Kwanza Basin in Angola dated to the Coniacian stage of the Late Cretaceous. The environment of deposition is shallow marine. Reptile fossils have been recovered from the Tadi beds locality within the formation, including the dinosaur Angolatitan, the mosasaurs Angolasaurus and Mosasaurus iembeensis and the turtle Angolachelys.The Itombe formation was formerly considered Turonian in age, but new data suggests to be Coniacian.

Angolachelonia Extinct clade of turtles

Angolachelonia is a clade of extinct turtles from the Late Jurassic to Paleogene of Eurasia. The group is defined as all taxa derived from the ancestor of the type genus Angolachelys and Solnhofia, a definition that could potentially encompass a clade of entirely marine turtles. Angolachelonia was originally inclusive of only Solnhofia, Angolachelys and Sandownia when originally concevied by Octavio Mateus and colleagues in 2009, but later phylogenetic analyses by Serjocha Evers and Roger Benson in 2018 unites the family Sandownidae, including Angolachelys and Sandownia among other taxa, with the entirely Late Jurassic clade Thalassochelydia, where Solnhofia may be a basal member. While the placement of Solnhofia is weak and the clade that Angolachelonia represents may change with further analysis, the clade of Sandownidae and Thalassochelydia is well-supported, and does not collapse despite the uncertain evolutionary history of the group. Three alternative potential origins of Angolachelonia sensu Evers and Benson are shown below.

References

  1. "Angola Geology, The Extractive Industries Source Book". Extractive Industries. Retrieved October 18, 2016.
  2. Mateus, Octávio; Jacobs, Louis; Polcyn, Michael; Schulp, Anne S.; Vineyard, Diana; Buta Neto, André; Telles Antunes, Miguel (December 2009). "The Oldest African Eucryptodiran Turtle from the Cretaceous of Angola". Acta Palaeontologica Polonica. 54 (4): 581–588. doi: 10.4202/app.2008.0063 .
  3. Schulp, AS; Polcyn, MJ; Mateus, O; Jacobs, LL; Morais, ML. "New mosasaur material from the Maastrichtian of Angola, with notes on the phylogeny, distribution and palaeoecology of the genus Prognathodon". Publicaties van het Natuurhistorisch Genootschap.{{cite journal}}: Cite journal requires |journal= (help)
  4. LL Jacobs, O Mateus, MJ Polcyn, AS Schulp… 2015 Cretaceous paleogeography, paleoclimatology, and amniote biogeography of the low and mid-latitude South Atlantic Ocean - Bulletin de la Société géologique de France, 2009
  5. Angolatitan adamastor, a new sauropod dinosaur and the first record from Angola O Mateus, LL Jacobs, AS Schulp, MJ Polcyn, TS Tavares, A Buta Neto, ... Anais da Academia Brasileira de Ciências 83 (1), 221–23
  6. Schlüter, Thomas (April 19, 2008). Geological Atlas of Africa: With Notes on Stratigraphy, Tectonics, Economic Geology, Geohazards, Geosites and Geoscientific Education of Each Country. Springer Science & Business Media. Retrieved October 18, 2016.
  7. "Angola, Oil and Gas, The Extractive Industries Source Book". Extractive Industries. Archived from the original on April 19, 2015. Retrieved October 18, 2016.