| Autor: |
Janikian, Liliane, de Almeida, Renato Paes, Fragoso-Cesar, Antonio Romalino Santos, Martins, Veridiana Teixeira de Souza, Dantas, Elton Luiz, Tohver, Eric, McReath, Ian, D'Agrella-Filho, Manoel Souza |
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| Zdroj: |
Gondwana Research; Mar2012, Vol. 21 Issue 2/3, p466-482, 17p |
| Abstrakt: |
Abstract: During the Ediacaran, southern Brazil was the site of multiple episodes of volcanism and sedimentation, which are best preserved in the 3000km2 Camaquã Basin. The interlayered sedimentary and volcanic rocks record tectonic events and paleoenvironmental changes in a more than 10km-thick succession. In this contribution, we report new U–Pb and Sm–Nd geochronological constraints for the 605 to 580Ma Bom Jardim Group, the 570Ma Acampamento Velho Formation, and a newly-recognized 544Ma volcanism. Depositional patterns of these units reveal the transition from a restricted, fault-bounded basin into a wide, shallow basin. The expansion of the basin and diminished subsidence rates are demonstrated by increasing areal distribution and compressed isopachs and increasing onlap of sediments onto the basement to the west. The Sm–Nd isotopic composition of the volcanic rocks indicates mixed sources, including crustal rocks from the adjacent basement. Both Neoproterozoic and Paleoproterozoic sources are indicated for the western part of the basin, whereas only the older Paleoproterozoic signature can be discerned in the eastern part of the basin. [Copyright &y& Elsevier] |
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