Investigação geofísica forense e antropológica com o método GPR no cemitério do Tapanã e no cemitério perdido de Mosqueiro (Belém, Pará)

Abstract

This work was accomplished with ground penetrating radar (GPR), a geophysical method used to investigate the shallow subsurface with high resolution in a non-destructive and noninvasive way. The survey was conducted in two locations in the metropolitan region of Belém, Pará State (Brazil), with 200 and 400 MHz antennas, both in the Tapanã cemetery: the first located in the test site for Controlled Testing of Forensic Geophysics, Environmental and Rescue (FORAMB) and the second one, in a burial zone with concrete cover. Surveys were also conducted in the northwest portion of Mosqueiro Island, across Marajó Bay, with a 400 MHz antenna, where reports of traces of a non-registered cemetery that would have been abandoned for about 80 years and could have been the final destination of cabanos, slaves and indians.These reports led researchers from the Federal University of Pará (UFPA) to visit the site in 1986 to test the veracity of the reports. At FORAMB the monitoring of the three targets that were buried there in 2007 was continued: a human body in a shallow grave 0.8 m deep, a tunnel simulated by a hollow wooden box placed 1 m deep and a box with metal, simulating weapons, deposited at 0.8 m depth. In the burial zone with concrete cover, the survey efforts focused on the effect of the concrete cover.The results obtained in the Tapanã cemetery show the usefulness of GPR in viewing targets under shallow soil cover and saturated clay, typical of the Amazon region, even when it is covered by a layer of concrete. These results reinforce the importance of pooling 2D and 3D data for interpretation of results; the GPR profiles over the concrete covering the bodies in various ages of burial, moreover, show significant variations of the responses, partly observed in other studies. The Mosqueiro results showed that ancient targets in climatic and geological conditions of the Amazon region, do not allow easy detection. It is possible that the remains of the decomposed bodies are not amenable to detection, but the discontinuity of the strata above the burial due to excavation, and the resulting concavity of the collapsed grave infill material may be diagnostic.