Assessment of environmental variations through the elemental composition of mudbelts sediments from the southern continental shelf of Brazil

Author(s)

Caroline Aparecida Pereira Dias

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto Oceanográfico (IO/DIDC)
• Defense date: 2023-05-03

Examining board members

Rubens Cesar Lopes Figueira; María Alejandra Gómez Pivel

• Advisor: Rubens Cesar Lopes Figueira; Bianca Sung Mi Kim

Abstract

Mud depocenters can be found on continent shelves and are able to adsorb and incorporate organic and inorganic substances to the surface of their grains, being an important archive of environmental changes and anthropic influence in a region. Mudbelts are elongated and confined mud depocenters located on clastic continental shelves. The objective of this work is to evaluate the environmental, natural and anthropogenic variations that occurred in the southern continental shelf of Brazil and adjacent continent, based on the elementary characterization of three long cores from mudbelts. During the Holocene, variations in element ratios and in the scores of the terrigenous component in the principal component analysis suggested increases in chemical weathering and continental input in periods of greater influence of the Rio de La Plata in the region, from 5000 and 3000 years BP. Approximately 5000 years BP there was a decrease in sea level, the establishment of the modern variability of ENSO and the intensification of SAMS, causing an increasing in precipitation on the continent and in the basin of the Rio de La Plata and promoting the transport of the plume from this river to north. From 3000 years BP there was a new intensification of ENSO and cold fronts in southern Brazil, stimulating south-southeast winds and promoting the dominant influence of the Rio de La Plata on the southern shelf of Brazil. Throughout the Anthropocene (last 200 years) there was also an increase in terrigenous input and chemical weathering, which could be associated with the warming of South America due to the anthropic increase in greenhouse gases. In the same period, As, Cr, Cu, Pb, Ni and Zn did not present levels of contamination and potential risk to the biota. However, trends of enrichment of these elements could be associated with different events known for an increase in anthropic activity in Brazil and South America, such as the beginning of the Industrial Revolution in Brazil and the use of organic lead compounds in gasoline from the 1930s. Thus, the sediments of the mudbelts of the southern shelf of Brazil can be considered potential sinks of metals and capable of recording natural and anthropogenic changes that occurred in the region and in the adjacent continent during the Holocene and Anthropocene. (AU)

• FAPESP's process: 21/00940-0 - Evaluation of environmental variations using elemental composition from mudbelts of Brazilian southern shelf
• Grantee: Caroline Aparecida Pereira Dias
• Support Opportunities: Scholarships in Brazil - Master