Thesis Defense
Student: Antonio Carlos de Siqueira Neto
Program: Geofísica
Title: “Underwater archaeological investigations using Ground Penetrating Radar (GPR) and Side Scan Sonar (SVL) in stilt houses sites at Maranhão state.”
Advisor: Prof. Dr. Jorge Luis Porsani - IAG/USP
Judging Committee:
- Prof. Dr. Jorge Luis Porsani - Presidente e Orientador - IAG/USP
- Prof. Dr. Rodrigo Corrêa Rangel - Universidade de Toronto (por videoconferência)
- Prof. Dr. Leonardo Gonçalves de Lima - UFMA (por videoconferência)
- Prof. Dr. Alexandre Guida Navarro - UFMA (por videoconferência)
- Dr. Otávio Coaracy Brasil Gandolfo – IPT
Abstract
Wooden stilts are archaeological remains of ancient stilt houses from pre-colonial indigenous villages in the Amazon region. Normally, wood decomposes quickly in
the soil. However, in the stilt houses of the Maranhão wetlands, these archaeological materials can be well preserved, either submerged under water or
buried in sediments at the bottom of rivers and lakes. Around these stilts, it is possible to find archaeological artifacts, such as ceramic materials, lithic
instruments and amulets, such as the nephrite jade Muiraquitã found at the Boca do Rio site. The main objective of this study is to deepen the understanding of stilt
houses in the Maranhão wetlands, eastern region of the Brazilian Amazon. To this end, the methods of Ground Penetrating Radar (GPR) and Side Scan Sonar (SSS)
were used in five underwater archaeological sites: Jenipapo, Formoso, Armíndio, Boca do Rio and Caboclo. The use of GPR allowed mapping the bed of the Turiaçu
and Paraná rivers, as well as the bed of Lake Formoso, in addition to identifying diffraction hyperbolas in the water column, which are probably associated with the
wooden supports that supported the ancient stilt houses. Results of 2D GPR numerical modeling showed good agreement with the real data, validating this
interpretation. The results obtained with the SSS method provided images with smooth textures, which correspond to the sedimentary cover of the bed of the
Turiaçu and Paraná rivers and Lake Formoso, and images with rough textures were associated with a greater concentration of wooden supports and ceramic materials
found in the bed of the rivers and Lake Formoso. These results allowed the support to be located in a larger area than that initially mapped by archaeologists,
suggesting that the construction area of the stilt houses may be significantly wider.
The combination of GPR and SSS methods guided the collection of new archaeological materials during geophysical surveys and may provide important subsidies for the planning of future archaeological campaigns in the estuaries of the Maranhão lowlands.
Keywords: Underwater archeology; Stilt houses; Wooden pillars; Maranhão wetland; Ground penetrating radar; Side scan sonar.