The Amazonian craton evolution overview: Insights for supercontinent reconstructions
|Location||International Geological Congress,oslo 2008|
|Author||Geraldes, Mauro Cesar|
|Holding Date||07 October 2008|
Supercontinent assemblages developed at several times in the Earth history and major collisional events of the Amazonian craton may be correlated to these continental amalgamations. Based on geologic, structural and paleomagnetic evidence paleocontinental reconstructions have been proposed for Archaean to younger times taking into account paleomagnetic data, orogenic belts match and crustal provinces match. The oldest highly speculative continent (Ur) had joined five Achaean cratonic areas (Kaapvaal, Western Dhawar, Bhandara, Singhhum and Pilbara cratons) where 3.0-2.8 Ga shallow-water supracrustals assemblages are observed. Coeval sediments of Agua Clara formation intercalated with 1.97-1.92 Ga volcanic rocks do not suggest the participation of the Achaean rocks of the Carajلs region in the Ur landmass.
Supercontinental 2.45 Ga Kenorland amalgamation is indicated by paleomagnetic data including Laurentia (Superior and Wyoming cratons), Baltica (Karelia craton), Australia (Yilgarn craton), and Kalahari and Kaapvaal cratons as recorded by glaciogenic and paleoweathering layers. The lack of such sedimentary rocks suggests that Amazonian craton was not part of the Kenorland supercontinent. From 1.83 Ga to 1.25 Ga two supercontinents including Amazonian craton were proposed: Columbia and Hudsonland. They take into account paleomagnetic and tectonic data indicating that NE portion of the Amazonian craton (Maroni/Itacaiunas province) had connection with West Africa and Kalahari cratons at that time. Reconstructions of the Rodinia supercontinent (AUSWUS, SWEAT and AUSMEX hyphothesis) show Amazonia joined to Laurentia-Baltica as result of 1.1-1.0 Ga fusion based on the Sunsas-Aguapei belts, Greenville and Sveconorueguian belts, respectively. The large Late Mesoproterozoic landmass included also Siberia, East Antartica, West Nile, Kalahari, Congo/Sمo Francisco and Greenland.
The 750-520 Ma Gondwana assembly included most of the continental fragments rifted apart during the break-up of Rodinia. Successive collision and plate indentation processes occurred during this global event. The configuration of the South America platform was defined during the Gondwana amalgamation where the Amazonian craton was bordered by the Neoproterozoic belts to the east (Araguaia belt), south (Paraguay belt) and southwest (Tucavaca belt).
The supercontinent Pangea comprises Gondwana and Laurentia at about 230-180 Ma ago. The Amazonian craton margins were not involved in the collisional processes during Pangea because it was probably embebed within Neoproterozoic mobile belt rocks. As consequence, Amazonian craton borders have no record of the orogenic processes responsible for the Pangea amalgamation.