Banca de DEFESA: STHEFANY PESSOA DE SOUZA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : STHEFANY PESSOA DE SOUZA
DATE: 26/06/2026
TIME: 14:00
LOCAL: PPGMEG (via canal do Youtube)
TITLE:

Physical and Chemical Volcanology of the Paranapanema Formation in Pitanga (PR) in the Paraná Basin.

KEY WORDS:

Physical volcanology; Paranapanema Formation; Paraná Magmatic Province.

PAGES: 92
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUBÁREA: Geologia
SUMMARY:

This study presents a detailed investigation of the high-Ti basalts of the Paranapanema Formation, located in the Pitanga city (PR). This formation represents the final stage of volcanism in the Paraná Magmatic Province (PMP) during the Lower Cretaceous. This work presents an integrated characterization of the lithostratigraphy, petrography, and lithogeochemistry of ten lava flows of simple and rubbly pahoehoe morphologies. The main objective of the dissertation is to understand the mechanisms of emplacement and the lateral extension of these lavas, as well as to interpret the paleoenvironmental conditions during deposition and the local paleotopography. The results show that both morphologies have similar SiO₂ contents, indicating that silica polymerization was not the primary factor controlling the internal stress of the lavas. However, the rubbly flows are more magnesian, calcic, and titaniferous, showing greater depletion in incompatible trace elements compared to simple pahoehoe lavas. Such chemical discrepancies in samples with similar MgO contents indicate that the two morphologies are not cogenetic in a closed-system differentiation process. It is suggested that the magmas originate from the same chamber with periodic recharging of basaltic magma, a hypothesis supported by the cyclic enrichment of MgO in the stratigraphy and by open-system textures, such as compositional zoning and sieve textures in plagioclase macrocrystals. Petrographically, both morphologies exhibit undercooling textures, including hyalopilitic matrix and swallowtail crystals. Lithogeochemistry proved to be an effective tool for regional correlation, allow establish the minimum lateral extent of two rubbly flows at 14 and 20 kilometers, respectively. This conclusion is based on the observation that the chemical variation between the cores of the flows in different regions is less than the margin of error of the lithogeochemistry analytical techniques. This approach allow to infer a paleotopography with a gentle slope of less than 0.34º. Additionally, the presence of silt and clay and the poorly sorted grains in sedimentary matrix of brecciated top of rubbly lavas, as well as the presence of peperites, indicate a paleoclimatic transition from arid conditions, at the base of the Serra Geral Group, to an environment with greater water availability at the uppermost part of this Group. This work contributes to understanding the emplacement mechanisms of continental flood basalts, and provides information for the paleoenvironmental reconstruction, consolidating a lithostratigraphy of the Paranapanema Formation in the study area.

COMMITTEE MEMBERS:
Interno - 1560386 - ALAN WANDERLEY ALBUQUERQUE MIRANDA
Externa à Instituição - BÁRBARA SANTOS QUEIROZ - UFRJ
Presidente - ***.345.068-** - JULIO CESAR LOPES DA SILVA - UFRJ
Interno - 387109 - SERGIO DE CASTRO VALENTE