The X-Tepe of Pergamon: Magnetic Investigation of an Intermediate-size Tumulus

The X-Tepe tumulus is located on the alluvial fan of the Bergama Çayı (Selinus) south of the city-hill of Pergamon. It belongs to a funerary landscape characterised by the largest tumuli of the region and may be related to the royal burials of ancient Pergamon. Being 85 m in diameter and 11 m high it is the fourth largest burial mound of the Bergama area. To explore the interior of the X-Tepe we conducted a magnetic survey with an Overhauser gradiometer enabling sounding depths on the order of 10 to 15 m. The resulting magnetic map shows elongated anomalies of up to ± 500 nT with irregular contours. Their comparatively large magnitudes indicate that the magnetic sources are most likely composed of strongly magnetised andesite, a rock typical of the Bergama region. To determine the contours of the magnetic bodies at depth, we performed an inversion computation on the magnetic field data using the concept of magnetised layers. The magnetic inversion computations show that strong local magnetisation anomalies exist at the base level of the X-Tepe, which can be interpreted as evidence of architectural structures. These potential funeral constructions most likely consist of reworked bedrock in large volumes. The magnetic anomalies are concentrated within an area of 25 × 25 m and display a certain rectangular ordering. Their clustering suggests that there may be more than one grave chamber or structures with antechambers that are arranged at right angles to each other.

Keywords:

tumulus, funeral architecture, magnetic prospection, magnetic inversion