TEMPORAL-SPATIAL COMPARISON OF GENESIS AND EVOLUTION PROCESSES BETWEEN ALLUVIAL FANS IN BRAZIL (SOUTHERN COAST AND WESTERN REGION OF BAHIA) AND CHILE (MAIPO AND VOLCÁN RIVER BASINS - HIGH ANDEAN MOUNTAINS)

• Grant number: 24/04998-0
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• Start date: August 01, 2024
• End date: January 31, 2025
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Physical Geography
• Principal Investigator: Archimedes Perez Filho
• Grantee: Mateus Moriconi Prebianca
• Supervisor: Maria Victoria Alejandra Soto Bauerle
• Host Institution: Instituto de Geociências (IG). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Institution abroad: Universidad de Chile, Chile
• Associated to the scholarship: 22/11563-5 - TEMPORAL-SPATIAL SCALE OF NATURAL AND ANTHROPIC PROCESSES RELATED TO THE GENESIS AND EVOLUTION OF ALLUVIAL FANS: HOLOCENIC CLIMATE PULSATIONS AND LAND USE, BP.MS

Abstract

The first researches that identified and studied Alluvial Fans stated that these deposits were characteristic only of arid and semi-arid environments. However, with the advancement of scientific research, a consensus was reached that such features can be found in any terrestrial environment and present variations in terms of their form and genesis, as is the case of Dejection Cones (or Debris Cones) at one end and Megafans (or Fluvial Fans) at the other. Just like the shape of alluvial fans, their genetic processes also change depending on a conjunction of local and regional controls, such as the predominant lithology, size and characteristics of the feeding drainage basin, slope of the hillside, vegetation, accommodation space, distal incision by channels in the valley, climatic variations, tectonic history and other factors. Regarding the last two aspects, it is understood that tectonic action is responsible for creating the accommodation space for fan deposition and the altimetric difference between the drainage basin upland and the adjacent valley, while climatic action serves as input for the main natural processes that lead to the deposition of these forms, such as debris flow, sheetfloods, and incision of braided channels. In this sense, a system of coalescent alluvial fans in the basins of the Maipo and Volcán rivers, region of High Andean Mountains near the city of Santiago, has been mapped and identified, where there are still no studies that determine the absolute ages of these deposits, likely of Pleistocene-Holocene. On the other hand, in the project related to the scholarship in the country (Brazil), the scholarship holder works with two distinct alluvial fans in the state of Bahia, of Holocene age, in which natural and anthropic processes mix in their elaboration. Despite the form being the same, the alluvial fans studied in Brazil and those to be studied in Chile through this BEPE project present different spatial and temporal characteristics, as well as different formation processes. Thus, the main objective of this project is to compare the temporal-spatial scale related to the genesis and evolution processes of the alluvial fans in question between the two countries, advancing the literature and discussion about these forms in the Brazilian and South American scenario, in addition to bringing unprecedented OSL dating and grain-size analysis to the study area to be worked on in Chilean territory.