Banca de DEFESA: HORTÊNCIA ALMEIDA PIRES

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : HORTÊNCIA ALMEIDA PIRES
DATA : 18/11/2020
HORA: 10:00
LOCAL: Salvador
TÍTULO:

ENVIRONMENTAL EVOLUTION OF THE CONTINENTAL SHELF ADJACENT TO THE DELTA OF THE SÃO FRANCISCO RIVER, USING THE FORAMINIFERA MICROFAUNA

PALAVRAS-CHAVES:

Benthic foraminifers. Subaqueous Delta. São Francisco River. River inputs. Climatic variations

PÁGINAS: 65
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Geociências
SUBÁREA: Geologia
ESPECIALIDADE: Geologia Ambiental
RESUMO:

The delta system of the São Francisco River, on the east coast of Brazil, is subject to strong seasonal variations.This system was affected by alternating dry and wet periods occurred in the basin, and also by a cascade of dams along the river implemented from the 1970s.A core was recovered (ST6) in the subaqueous delta deposit on the continental shelf adjacent to the mouth. Where a study was carried out using the assemblage of benthic foraminifera, granulometry, TOC, TN, CaCO3, in order to understand the expression of recent climatic cycles and anthropogenic interventions. Four flooding periods (Episodes A, B, C and D) were identified, evidenced by the low abundance of benthic foraminifera, low diversity, low richness and low number of species.These episodes were interpreted as periods of increased sediment supply to the platform. Dry periods were evidenced by the high abundance of benthic foraminifera, high diversity, high richness and high number of species. These core intervals were interpreted as periods of decreased sediment supply to the platform. Where new environments were established, with new ecological restrictions, it is possible to identify three biofacies. Biofacies A (Bolivinellina pseudopunctata/ Haynessina orbicularis) represents a slightly brackish environment, influenced by the river plume, more stable hydrodynamic conditions and fine sediments. Biofacies B (Discorbis peruvianus/ Gavelinopsis pregeri/ Nonionella auris/ Quinqueloculina laevigata) represents a more marine environment, with little river influence and a greater supply of phytodetrites. Biofacies C (Cribroelphidium poeyanum/ Elphidium discoidale/ Ammonia tepida) represents a brackish environment, with a greater influence of the river plume and more stable hydrodynamic conditions. The Episodes (A, B, C and D) of fluvial inputs and the Biofacies (A, B and C) show the episodic character of sedimentation in the subaqueous delta region, following the seasonal behavior of precipitation in the basin. However, the plume of the São Francisco River for most of the year is restricted to the areas near the river mouth, but when there is increased flow during the rainy season also increases the extent of the plume area.

MEMBROS DA BANCA:
Presidente - 019.448.195-68 - ALTAIR DE JESUS MACHADO - UFBA
Externo ao Programa - 2529336 - SIMONE SOUZA DE MORAES
Externo à Instituição - MAILI CORREIA CAMPOS - UNIME