Banca de DEFESA: Rodrigo Tokuta Castro

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : Rodrigo Tokuta Castro
DATE: 10/05/2023
TIME: 14:00
LOCAL: Sala de Videoconferência do IGD
TITLE:

The brazilian midwest lateritic domains: regolith features and dynamic.

KEY WORDS:

Regolith; Ferruginous lateritic duricrust; Lateritic episodes; Palaeoweathering surface; Apatite Fission Tracks.

PAGES: 84
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUMMARY:

In Midwest Brazil, the Tocantins Province is a large Neoproterozoic orogen that resulted from the collision of the Amazonian, São Francisco and Paranapanema paleocontinents during the Brasiliano/Pan African cycle, as part of the West Gondwana amalgamation. Intracontinental deformations cause the uplift of erosive surfaces and are a consequence of destabilization processes of the lithosphere in cratonic domains. The opening of the Atlantic Ocean influenced processes 2.000 km from the coast with reflections on the regolith. The regolith of the Brazilian Midwest is characterized by a stepwise landscape of highlands, mountains, plateaus, inselbergs, canyons, and alluvial plains that form four morphostratigraphic surfaces. Surface 1 is supported by quartzite saws and surfaces 2 and 3 by ferruginous lateritic crusts. The crusts of surface 2 are quartz-hematitic, hardened, columnar, reddish-pink to yellowish-red, have protonodular, breccia and pisolitic textures and reach up to 3 m in thickness, while the ferruginous lateritic crusts of surface 3 are more friable, quartz - goethitic, columnar, yellowish-red to orange-yellow, they have a vermiform texture with a microaggregated and bioturbated clay-ferruginous matrix, reaching up to 2 m in thickness. Surface 4 includes the lower floodplains. The objective of this study was to understand the formation of these regolith surfaces, their relationships, the impact of lateritic dynamics and continental influences as forming/controlling agents of the landscape. The area was studied using SRTM images, scan profiles and Roughness Concentration Index, as well as field control, textures, mineralogy, geochemical analysis and fission traces in apatite. These techniques allowed contributing to the thermal modeling of the Tocantins Province and investigating cooling/heating episodes and the possible influence of these processes on the evolution of regolith in the Brazilian Midwest. Surface 1 marks the regional erosion event, while surfaces 2 and 3 mark two ferruginization episodes related to lateritization and seasonal dry to wet climate change. Surface 4 carves the plains. The characteristics of these sequential surfaces were produced from the end of the Paleogene in a complex landscape process modelled by an extensive erosion regime resulting from tectonic movements during the evolution of the Atlantic Ocean and tropical climate. The TFA identified two cooling models for the region that indicate erosion rates of 60-80 m Myr-1 compatible with the formation of lateritic UnB|IG|PPG Geologia vi duricrusts only in the last 20 Ma when the erosion rate decreased in consequence of final cooling.

BANKING MEMBERS:
Externo à Instituição - TIAGO AMÂNCIO NOVO - UFMG
Externa à Instituição - MARIA LÍDIA MEDEIROS VIGNOL - UFRGS
Presidente - 1210338 - ADRIANA MARIA COIMBRA HORBE
Interno - 1303786 - ELTON LUIZ DANTAS
Interno - 1852544 - JEREMIE GARNIER