Banca de DEFESA: Mariana de Assunção Rodrigues

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : Mariana de Assunção Rodrigues
DATE: 18/12/2023
TIME: 10:00
LOCAL: Teams e Sala de Videoconferência
TITLE:

Sedimentary provenance analysis of Cretaceous Basins in the Andes-Amazon Equatorial Margin System and its relation to paleogeography and tectonics.

KEY WORDS:

Provenance, U-Pb dating on zircons, Sm-Nd isotopy, Amazonia, Equatorial Margin, Cretaceous, Equatorial Atlantic Ocean, Sanozama, Araripe, Acre, Madre de Dios.

PAGES: 447
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUBÁREA: Geologia
SUMMARY:

The Cretaceous is characterized by major paleogeographic, geodynamic, and climatic changes, including the formation of new oceans such as the equatorial Atlantic Ocean, the continued fragmentation of Gondwana, and greenhouse effect periods. All these changes are potentially contained in the sedimentary records of the basins. The Andes-Amazonia-Equatorial Margin system is a vast sedimentary system whose geodynamic and palaeoenvironmental evolution is recorded in the Amazonian retroarc foreland basins, the Brazilian intracratonic basins, and those of the equatorial margin. In the western part (Andean region), recent studies suggest that the onset of the Andean orogeny occurred during the Late Cretaceous. However, the development of drainage systems and the source of sediments deposited during the Cretaceous are still poorly understood. The Lower Cretaceous is recorded in Brazilian intracratonic and equatorial basins and bears witness to crustal rifting phases following Gondwana's break-up. The Araripe Basin is a good example of these basins since it contains a complete and particularly well-studied sedimentary record. However, the origin of the sediments from the various tectonic stages of basin formation and the Cretaceous origin of the marine incursions that affected it remain to be determined. This thesis aims to propose a palaeogeographic reconstruction of the Andes-Amazonia Equatorial Margin system during the Cretaceous and to analyze the geodynamic and tectonic changes that affected it. To do this, we used provenance methods, particularly major and trace element geochemistry, Sm and Nd isotopic composition, and U-Pb ages on zircons. The results obtained have enabled us to identify the source zones of the Araripe Basin during the pre-, syn- and post-rift phases and thus to gain a better understanding of the palaeogeographic configuration of the north-eastern region of Brazil at the beginning of the Cretaceous. The sediments in the Araripe basin come mainly from the Palaeoproterozoic (2.3-1.6 Ga) terrains of the Borborema province and the granitic plutons of the Brasiliano cycle (720-541Ma). The basin has a sedimentary history linked to the South Atlantic and equatorial break-up phases. During the pre-rift phase (~152-135 Ma), the basin was part of the Afro-Brazilian depression and received sediments from the N-NW. During the rift phase (~135-125Ma), there was a change in source due to continental break-up and the formation of the South Atlantic, with an influx of sediments from the eastern part of the Borborema province. During the post-rift phase (121-113 Ma), the basin ceased to be fed by the eastern part and marine incursions dominated the sedimentation environment. Finally, during the post-rift II phase (113-100 Ma) a last change in sources was observed, with sources to the NE reflecting the final moment of the fragmentation of Gondwana. A study of the provenance of sediments from the basins of western Amazonia (Acre and Madre de Dios) indicates that the sources are cratonic, originating mainly from the Ventuari-Tapajos (2.0 - 1.82 Ga) and Rio Negro - Juruena (1.82 - 1.54 Ga) terrains. These results indicate that a vast intracontinental drainage network ('Sanozama') emerged in response to the uplift of the Purus Arch and the cratonic regions of Brazil and the Guianas during the opening of the equatorial Atlantic Ocean. The integration of the results obtained compiled with data from the literature has made it possible to propose four palaeogeographic maps of the northern part of the South American platform. They highlight how geodynamic mechanisms linked to the opening of the South Atlantic and equatorial oceans controlled and shaped the paleogeography of this region.

COMMITTEE MEMBERS:
Externo à Instituição - JÉRÔME VIERS - UPS
Interno - ***.138.381-** - CARLOS JOSE SOUZA DE ALVARENGA - AMU
Externo à Instituição - JEAN MICHEL LAFON - UFPA
Interna - 1897668 - NATALIA HAUSER
Presidente - 418662 - ROBERTO VENTURA SANTOS