Geophysical survey to the Petrified Forest of Sigri in Lesvos Island (North Aegean)
Résumé
Remains of fossil plants, which form the famous «Petrified forest of Lesvos», have been found in many localities on the western part of Lesvos Island. The fossilized forest of Lesvos was developed during Late Oligocene to Lower - Middle Miocene, due to the intense volcanic activity in the area (Velitzelos and Zouros, 1997). The products of the volcanic activity had covered the vegetation of the area and the fossilization process took place due to favorable conditions. The fossilized plants in Lesvos are silicified remnants of a sub-tropical forest that existed on the northwest part of the island 20-15 million years ago. In the present study the results of the geophysical survey that has been applied to several locations of the petrified forest are presented. Electrical tomography, magnetic mapping and Ground Penetrating Radar methods of geophysical prospecting have been applied. The surrounding material, which is formed mainly by volcanic ash, contains also volcanic rocks in that size that it could be detected as petrified trunk. So, the effectiveness of the geophysical methods in such an environment has been tested in selected areas where petrified trunks were semi-uncovered. Lied trunks have been successfully detected by the electric tomography in several cases, since the resistivity of the fossilized material is much higher that the resistivity of the volcanic ash. The horizontal mapping of the total magnetic field in the same cases of lied trunks has been also successful since it was combined with the electric tomography and the anomaly were located in the same place and shape. Detection of petrified trunks looks to be uncertain in cases of standing trunks. That, because anomaly of the same pattern could be produced by an intrusion of a rock which the magnetic susceptibility is lower than this of the fossilized material. The same problem has been noticed also to the GPR (Ground Penetrating Radar) data. Several positions to be excavated have been proposed.
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ΒΑΡΓΕΜΕΖΗΣ Γ., ΦΙΚΟΣ Η., ΜΕΡΤΖΑΝΙΔΗΣ Ι., ΖΑΝΑΝΙΡΙ Ε., ΡΟΥΜΕΛΙΩΤΗ Ζ., ΖΟΥΡΟΣ Ν., ΚΟΝΤΗΣ Ε., & ΒΑΛΙΑΚΟΣ Η. (2001). Geophysical survey to the Petrified Forest of Sigri in Lesvos Island (North Aegean). Bulletin of the Geological Society of Greece, 34(4), 1285–1291. https://doi.org/10.12681/bgsg.17215
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- Geophysics
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