Amalgamating eastern Gondwana: The evolution of the Circum-Indian Orogens

The Neoproterozoic global reorganisation that saw the demise of Rodinia and the amalgamation of Gondwana took place during an incredibly dynamic period of Earth evolution. To better understand the palaeogeography of these times, and hence help quantify the interrelations between tectonics and other Earth systems, we here integrate Neoproterozoic palaeomagnetic solutions from the various blocks that made up eastern Gondwana, with the large amount of recent geological data available from the orogenic belts that formed as eastern Gondwana amalgamated. From this study, we have: (1) identified large regions of pre-Neoproterozoic crust within late Neoproterozoic/Cambrian orogenic belts that significantly modify the geometry and number of continental blocks present in the Neoproterozoic world; (2) suggested that one of these blocks, Azania, which consists of Archaean and Palaeoproterozoic crust within the East African Orogen of Madagascar, Somalia, Ethiopia and Arabia, collided with the Congo/Tanzania/Bangweulu Block at ∼ 650–630 Ma to form the East African Orogeny; (3) postulated that India did not amalgamate with any of the Gondwana blocks until the latest Neoproterozoic/Cambrian forming the Kuunga Orogeny between it and Australia/Mawson and coeval orogenesis between India and the previously amalgamated Congo/Tanzania/Bangweulu–Azania Block (we suggest the name ‘Malagasy Orogeny’ for this event); and, (4) produced a palaeomagnetically and geologically permissive model for Neoproterozoic palaeogeography between 750 and 530 Ma, from the detritus of Rodinia to an amalgamated Gondwana.