Using Palynofacies as Climate Proxies in Mid-Pliocene Sediments from the Amazon and West Antarctica

• Grant number: 24/21402-4
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: March 01, 2025
• End date: February 28, 2026
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geology
• Principal Investigator: Marcelo Augusto de Lira Mota
• Grantee: Daniel Bernardo Chabu
• Host Institution: Instituto de Geociências (IGC). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 18/23899-2 - Trans-Amazon Drilling Project: origin and evolution of the forests, climate, and hydrology of the South American tropics, AP.PFPMCG.TEM

Abstract

The study of past climate intervals, such as the Mid-Pliocene Warm Period, provides valuable insights into Earth's response to elevated atmospheric CO¿ levels, which were similar to those projected for the near future. This research aims to utilize palynofacies analysis as a proxy to reconstruct paleoenvironmental changes in two key regions: the Amundsen Sea, adjacent to the West Antarctic Ice Sheet (WAIS), and the Marajó Basin, representing the Amazon Rainforest (AMAZ). I will examine 70 palynological slides from sediment cores recovered by International Ocean Discovery Program Expedition 379 (2019; 35 slides) and the Trans-Amazon Drilling Project (2024; 35 slides), applying standard techniques to count palynomorphs, phytoclasts, and amorphous organic matter (AOM). Key parameters, such as the percentage of AOM, phytoclasts, palynomorphs, and various phytoclast ratios, will be assessed to infer dysoxic conditions, proximity to terrestrial sources, and sea-level changes. The results will help reconstruct episodes of glacial advance and retreat of the WAIS, as well as fluctuations in the hydrological cycle and sea levels in the Amazon region. By correlating palynofacies changes between these two regions, this study will test two main hypotheses (H): (H1) Palynofacies differences between warmer and cooler intervals will align with expected sea-level and ice-sheet changes; (H2) Palynofacies variations can be used to infer regional climate changes during the Pliocene. The findings will contribute to our understanding of climate dynamics and the interconnections between the WAIS and AMAZ systems, offering a valuable paleoclimate analogue for predicting current and future climate scenarios.