GEOPHYSICAL PROSPECTING FOR MYCENAEAN CHAMBER TOMBS IN ANCIENT NEMEA, KORINTHIA, GREECE

Ground-penetrating radar surveys were conducted in 2006 and 2008 at the 1-hectare Ayia Sotira archaeological site. This south-facing hillside in the Nemea Valley (northeastern Pelopponese) has provent to be a Late Bronze age (Mycenaean) cemetery containing at least six chamber tombs. The site's geology comprises interbedded and faulted Tertiary marls and limestone conglomerates locally overlain by Quaternary alluvium. Prior to recent olive cultivation, the lower part of the site had been ripped by tractor to loosen resistant caliche and marl beds. The upper part of the site had not been recently cultivated, and was vegetated by scrub bushes and small trees, whereas the lower field contained rows of olive trees.

In 2006 we conducted ground-penetrating radar surveys using 200 and 100 MHz antennas with a 1000V pulseEkko system. Although GPR penetration was relatively limited (< 3 m), a number of promising subsurface targets were identified. Ambiguity and uncertainty was introduced, however, by air-wave and subsurface returns from olive trees and their roots, as well as by faults and conglomerate beds. Excavations revealed three chamber tombs containing Mycenaean human remains and artifacts; these were the subject of excavations in 2006 and 2007. At the start of the 2008 summer season, we surveyed the upper field with a dual magnetic field gradiometer system as well as 200 MHz GPR. Despite repeated attempts to remove small metal debris from the area, the magnetometer survey was hampered by the presence of abundant shotgun shells, wires, bolts, roof tiles and Byzantine pottery. The GPR was less sensitive to these small objects, and a number of co-located anomalies were identified in both the magnetometer and GPR surveys. Subsequent trenching showed that most of the buried anomalies also were 20th century metal objects, although a single intact chamber tomb was identified and excavated late in the 2008 season. Geophysical surveys in this environment have presented a number of challenges. In hindsight, we would optimize the GPR surveys by conducting initial magnetometer surveys followed by spot soundings to remove shallow “contaminant” objects. If possible, trees also should be removed prior to a gridded GPR survey.