Identifying of buried archaeological remains with ground penetrating radar, polarized microscope and confocal Raman spectroscopy methods in ancient city of Nysa, Aydin – Turkey

Abstract

The aim of this study was to image buried remains and appoint buried Hellenistic street system, and identify minerals and rock types of the ancient city of Nysa, one of the most important historical sites of Turkey. This study used polarized microscope and confocal Raman spectroscopy (CRS) ground penetrating radar (GPR) method, to identify the buried remains, rock types and minerals.Small rock samples from Nysa remains were analysed under polarized microscope and confocal Raman spectroscopy (CRS) and the results were compared with a nearby area. The polarized microscope findings indicated that the main rocks of the remains comprised white marble with granoblastic texture, composed of mainly pressure-twinned calcite with coarse grain size. The CRS studies revealed that the marble remains of Nysa were mainly built from Jurassic–Cretaceous carbonate rocks of the western Anatolia marble quarry, located within the surrounding region.Two-dimensional (2D) GPR data were measured on parallel GPR profiles using 250 MHz shielded antennas for selected areas of the ancient city. A processed GPR profile data set formed a solid 3D view by aligning the profiles. An interactive interpretation of depth slices, 2D and 3D subsets of the data were performed. The depth slices and the subsets clearly imaged the remains of walls and streets. Slices with different amplitude–colour ranges and cutoff values were compared. The compared slices showed that amplitude–colour range and cutoff value affected the imaging indicating buried remains. Finally, three streets were determined with 3D depth slices and their 3D subsets using the GPR data. Two streets were on the west part of the gerontikon (council building), aligned east–west and north–south. The third street was aligned east–west on the southwest part of the gerontikon. Partial excavations of the northwestern and southwestern parts of the research area encouraged the 3D image results exactly.