Gondwana - Formation

Formation

The assembly of Gondwana was a protracted process. Several orogenies led to its final amalgamation 550–500 Mya at the end of the Ediacaran, and into the Cambrian. These include the Brasiliano Orogeny, the East African Orogeny, the Malagasy Orogeny, and the Kuunga Orogeny. The final stages of Gondwanan assembly overlapped with the opening of the Iapetus Ocean between Laurentia and western Gondwana. During this interval the Cambrian explosion occurred.

Gondwana was formed from the following earlier continents and microcontinents, among others, colliding in the following orogenies:

• Azania: much of central Madagascar, the Horn of Africa and parts of Yemen and Arabia. (Named by Collins and Pisarevsky (2005): "Azania" was a Greek name for the East African coast.)
• The Congo–Tanzania–Bangweulu Block of central Africa.
• Neoproterozoic India: India, the Antongil Block in far eastern Madagascar, the Seychelles, and the Napier and Rayner Complexes in East Antarctica.
• The Australia/Mawson continent: Australia west of Adelaide and a large extension into East Antarctica.
• Other blocks which helped to form Argentina and some surrounding regions, including a piece transferred from Laurentia when the west edge of Gondwana scraped against southeast Laurentia in the Ordovician. This is the Famatinian block (named after Famatina in northwest Argentina) and it formerly continued the line of the Appalachians southwards.

One of the major sites of Gondwanan amalgamation was the East African Orogeny (Stern, 1994), where these two major orogenies are superimposed on each other. The East African Orogeny at ~650–630 Mya affected a large part of Arabia, north-eastern Africa, East Africa and Madagascar. Collins and Windley (2002) propose that in this orogeny Azania collided with the Congo–Tanzania–Bangweulu Block.

The later Malagasy orogeny at ~550–515 Mya affected Madagascar, eastern East Africa and southern India. In it Neoproterozoic India collided with the already combined Azania and Congo–Tanzania–Bangweulu Block, suturing along the Mozambique Belt.

At the same time, in the Kuunga Orogeny Neoproterozoic India collided with the Australia/Mawson continent.