Banca de QUALIFICAÇÃO: JULIANA APARECIDA GONÇALVES LOPES

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
DISCENTE : JULIANA APARECIDA GONÇALVES LOPES
DATA : 30/11/2016
HORA: 14:00
LOCAL: Sala 1 (Dep. Geologia)
TÍTULO:

Study of tectonic subsidencein the Potiguar basin based on exploratory well data and seismic sections 

PALAVRAS-CHAVES:

TECTONIC SUBSIDENCE, BACKSTRIPPING, POTIGUAR BASIN.

PÁGINAS: 33
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
RESUMO:

The evolution of rift basins can be explained by simple models, which assume that these basins are developed from two steps: extension and thinning of the continental lithosphere, associated with block faulting and initial subsidence; and thermal relaxation, associated with thermal subsidence. Potiguar Basin, formed by distensional efforts during the Early Cretaceous, presents as subsidence mechanisms: a) isostatic responses to the extension and thinning of the crust and lithosphere, during the syn-rift phase, which promoted the formation of asymmetric grabens and internal highs; b) cooling and thickening of the lithosphere, mostly in post-rift phase; and c) sediment loading, which occurred in both phases. Using the backstripping technique, that involves the removal of sedimentary and water loads to obtain the basement depth without these surface charges, it was possible to infer rates of tectonic subsidence of the Apodi, Umbuzeiro and Boa Vista grabens, in the onshore Potiguar Basin. This technique was applied using the BACKSTRIP program, which calculates the total and tectonic subsidence for a given well. This algorithm is based on Airy isostatic model and takes into account parameters related to compression, thickness of the sedimentary layers, paleobathymetry, sea level rise, besides densities for water, sediments and mantle. In this context, synthetic well data were used, constructed from the correlation between exploratory wells and seismic sections, whose positions have been chosen to represent the thickest sedimentary infill in each graben. Tectonic subsidence curves of the onshore Potiguar Basin present an episodic rift phase marked by high rates of subsidence in the initial phase of rifting, followed by a moderate to non subsidence in the final stages in the onshore portion. Periods with high to moderate subsidence rates correspond to the filling of the basin during Rift Phase 1 (Neoberriasian/ Eobarremian). During Rift Phase 2 (Neobarremian/Eo-Aptian), characterized by changes in the rift kinematics, occurred the uplift and erosion of the onshore portion of the basin, resulting in null subsidence rates. In the post-rift phase, the dominant tectonic regime was marked by thermal subsidence, characterized by subsidence rates up to 8 m/My. Also, it can be noted the high similarity of the observed curves with the theoretical curves, showing the great reliability of the lithospheric extension models to explain the tectonic subsidence in distensional basins.

MEMBROS DA BANCA:
Externo ao Programa - 2490483 - ALEX FRANCISCO ANTUNES
Presidente - 1315614 - DAVID LOPES DE CASTRO
Interno - 2042405 - MOAB PRAXEDES GOMES