Defense
Student: Igor Nogueira Fittipaldi
Program: Geophysics
Title: "GPR Investigations at the Coqueiro Underwater Archaeological Site in the Baixada Maranhense, Eastern Amazon"
Advisor: Prof. Dr. Jorge Luis Porsani
Judging Committee:
- Prof. Dr. Jorge Luís Porsani - Presidente e Orientador - IAG/USP
- Prof. Dr. Antonio Carlos de Siqueira Neto - UFOPA (por videoconferência)
- Prof. Dr. Alexandre Guida Navarro - UFMA (por videoconferência)
Other Members:
- Prof. Dr. Vagner Roberto Elis – IAG/USP
- Prof. Dr. Andrea Teixeira Ustra - IAG/USP
- Dr. Otávio Coaracy Brasil Gandolfo - IPT
- Prof. Dr. Rodrigo Corrêa Rangel - UofT, Canadá
- Prof. Dr. Sérgio Fachin - UFMT
Abstract:
This work presents the results of a Ground Penetrating Radar (GPR) survey carried out at the Lago do Coqueiro underwater archaeological site, Baixada Maranhense, Eastern Amazon, Brazil. The region is part of a wetland system where pre-colonial Indigenous populations built stilt-house settlements between approximately AD 100 and 1000. The aim of this research was to locate and map wooden pillars preserved above and below the lakebed, indicating priority areas for future archaeological investigations in search of ceramic materials. A total of 58 GPR profiles were acquired using a 270 MHz antenna installed in a wooden boat, including 53 profiles in the NE-SW direction, referred to as transverse profiles, and 5 profiles in the SE-NW direction, referred to as longitudinal profiles. The GPR results revealed a strong reflector, interpreted as the bottom of Lago do Coqueiro. As a complementary product, a bathymetric map was produced from the GPR lines through time-depth conversion and interpolation using Regularized Spline with Tension (RST) in a GIS environment, aiming to characterize the lakebed morphology. Diffraction hyperbolas were identified in the GPR profiles, both suspended in the water column and buried within the sediments, and were interpreted as wooden pillars used in the construction of pre-colonial stilt houses. These findings guided dives near the pillars, which resulted in the collection of ceramic fragments from the lakebed. The interpretation was supported by 2D GPR numerical modeling, which reproduced the diffraction hyperbola signatures associated with the tops of the pillars, simulated as saturated wood embedded in the lakebed. The results contribute to delimiting areas of greater archaeological interest, guiding future interventions, and reinforcing the applicability of the GPR method in Amazonian lacustrine environments. This work is structured in article format, prioritizing the presentation and discussion of real and numerical GPR results applied to the study of underwater archaeological sites in the Baixada Maranhense, contributing to archaeological research in the Eastern Amazon.
Keywords: GPR, Numerical modeling, Underwater archaeology, Stilt villages, Lago do Coqueiro, Eastern Amazon.