Banca de DEFESA: Ana Valéria Alves Calmon Almeida

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Ana Valéria Alves Calmon Almeida
DATE: 20/10/2023
TIME: 14:00
LOCAL: Sala de videoconferência e Teams
TITLE:

The role of diagenesis in the geochemical and mineralogical composition of shells of Corumbella werneri, Tamengo Formation, Corumbá Group, Mato Grosso do Sul.

KEY WORDS:

Marlstones; Ediacaran; Paraguay Belt; Corumba Group; Isotopes; REE.

PAGES: 71
BIG AREA: Ciências Exatas e da Terra
AREA: Geociências
SUBÁREA: Geologia
SUMMARY:

The Neoproterozoic is notable for its tectonic, climatic, and environmental events of great magnitude. The analysis of carbonate sequences from this period has become increasingly relevant, driven by geochemical discoveries, although some are somewhat controversial. In the Brazilian context, the Tamengo Formation stands out, which is part of the upper layers of the Corumba Group, due to its remarkable geological and paleontological importance. It is in this formation that records of the index fossils Corumbella werneri and Cloudina lucianoi are found. This work's main scope is to understand the contributions of diagenesis to the elementary chemical and isotopic data in the carapaces of Corumbella werneri and the rocks of this unit. For this purpose, petrography, imaging from QEM-Scan, electron microprobe, ICP-MS analyses, and C, O, and Sr isotope analyses were used. Corumbellas occur in levels of impure, marly limestone, and present mineralogy composed mainly of calcites. The rock matrix is composed mostly of clay minerals quartz and other minerals. The analysis of rare earth elements (REE) showed a homogeneous and enriched pattern between the matrix and the carapaces. Furthermore, the average values of 87Sr/86Sr were different for the matrix and the carapace, but δ13C and δ18O values were very close in the two constituents. Detailed analysis of the rock and fossil revealed the influence of a regional hydrothermal process after its formation. This phenomenon occurred at a certain distance, resulting in a remarkable enrichment in both matrix and carapaces in REE. However, despite affecting the elemental composition, this process did not alter the textural and isotopic characteristics of the rock.

COMMITTEE MEMBERS:
Interno - ***.138.381-** - CARLOS JOSE SOUZA DE ALVARENGA - AMU
Externo à Instituição - FABRICIO DE ANDRADE CAXITO - UFMG
Externo ao Programa - 3340609 - MARCIO VINICIUS SANTANA DANTAS - nullPresidente - 2339865 - MARTINO GIORGIONI