Dissertation Defense
Student: Thalita Borba da Silva
Program: Geophysics
Title: “GPR Investigations in Underwater Archaeological Sites at Lake Cajari, Baixada Maranhense"
Advisor: Prof. Dr. Jorge Luis Porsani - IAG/USP
Judging Committee
- Prof. Dr. Jorge Luis Porsani - IAG/USP
- Prof. Dr. Rodrigo Corrêa Rangel - Universidade de Toronto – on videoconference
- Dr. Otávio Coaracy Brasil Gandolfo - IPT
Resumo
This research presents and analyzes the results of a Ground Penetrating Radar (GPR) survey conducted at the Cacaria and Trizidela underwater archaeological sites, located in Cajari Lake, Maranhão, Brazil. These areas are part of the Maranhão wetland region, where pre-colonial indigenous populations constructed stilt houses over rivers and lakes, dating between AD 100 and 1000. The main objective of this study is to enhance the location of submerged wooden pillars, also known as esteios, in the lake and guide archaeological excavations in search of ceramic artifacts. A total of 24 GPR profiles were acquired using a 270 MHz antenna mounted on a wooden boat, covering both the Cacaria and Trizidela sites. The GPR results revealed distinct reflections from the lakebed and several hyperbolic diffractions in the water column and beneath the sediment, interpreted as submerged wooden pillars. Numerical modeling GPR 2D was employed to replicate the diffraction patterns, and synthetic data showed good agreement with the real data, reinforcing the interpretation of the structures as remnants of stilt houses. These findings not only delineate the submerged archaeological sites but also provide guidance for future underwater excavations. The application of GPR in this study demonstrates its effectiveness in identifying submerged archaeological structures and mapping their distribution along the lakebed. This significantly contributes to the understanding of indigenous settlement patterns in the Amazon region. The results also provide crucial information for the preservation and investigation of Maranhão's underwater archaeological heritage, with potential to expand similar techniques to other wetland areas in Brazil.
Palavras-chave: GPR, Numerical modeling, Underwater archaeology, Cacaria Site, Trizidela Site, Stilt villages, Stilt houses, Maranhão wetland