Much of the geo-archaeological survey, which took place in September, was devoted to studying processes of landscape change on the plateaus, both natural and those related to human activity. Continuing from 2005, additional progress was made in the location and measurement of traces of stone quarrying. In addition, the geoarchaeological study of the excavated archaeological site was completed.
Erosion on the surfaces of the upper and lower plateaus, and especially at the plateau edges is a prominent feature of the form of the plateaus.
The rate and style of erosion is strongly influenced by the surface geology, types of vegetation and by 19th-20th century urbanization and agriculture. A feature noted in 2004 -that the contours of the 1:5000 topographic maps of the Greek Army, made some decades earlier, differ significantly from the current appearance of the landscape in places- was investigated in detail. The edge of the upper plateau and parts of the lower plateau were walked systematically and the location of the edge measured with GPS (accuracy of GPS location 4-5 metres). Detailed observations were made on the geology, state of the bedrock, soil types and land usage, together with information on modern constructions such as terraces, roads and retaining walls. Efforts concentrated on the upper plateau, as since antiquity this part of the study area is the least altered part of the survey area, with little construction or landscaping for agriculture having occurred. This part of the study area therefore provides the best opportunities for understanding the effects of natural landscape processes post-antiquity. In contrast, the eastern and parts of the southern edges of the lower plateau have been significantly affected by the evolution of the village of Vasiliko, roads and nearby agricultural land. This has lead to great reductions in the rates of natural erosional processes through the protection of bedrock by retaining walls, artificial drainage and asphalted roads, and/or to the redistribution of erosional agents, especially water runoff and the effects of tree roots.
The map shows some of the preliminary results from the upper plateau. Erosion is influenced by the distribution of relatively hard Pleistocene sediments overlying softer Pliocene marls. (For an image of the marl and thin Pleistocene "cap", see the Introduction to the Geoarchaeological survey.) The undercutting of the Pleistocene sediments proceeds at rates controlled by their condition and thickness and partly by the distribution of fractures that form a network across the plateau. The results suggest markedly different rates of erosion along different sections of the upper plateau edge since the topographical map of the Greek Army was made in the mid 1960s. If the map was accurate at the time of publication, the southern and western edges of the plateau have in certain sections suffered significant erosion due to geological factors and the human activity. It is clear from the preliminary data that the southern edge of the plateau has suffered from a higher rate of erosion than the northern edge, and this accounts for the scarcity of fortifications along this side. Any significant loss of land surface from erosion needs to be taken into account when interpreting the distribution of settlements and communication networks.
Detailed measurement of the surviving stone quarries continued this year and a few additional small quarries were identified.
The measurements made on the stone cuttings provide exact information on quarrying methods and the impact that the rock had on these. They also indicate the ranges of block sizes and shapes that were extracted and give important information on stone working and construction. Minor outcrops of oolitic limestone were added to the small existing number identified during 2004-2005. These appear to confirm the previous conclusion from the study that significant quantities of this important lithology do not occur on the plateau, and that this stone was transported from elsewhere in the Sikyonian territory, or beyond. Finally, measurements were made on blocks in constructions on the excavated site for comparison to the measurements made in the quarries. Interpretation of these data will occur during 2007.
Primary observations of the excavated site were completed this year, while the additional cleaning of the site during 2006 allowed some new observations, in particular on the Stoa and the Bouleterion. With completion of investigations into the Stadium, it is possible to answer questions about its location and form. The Stadium was constructed by the artificial excavation of the elongate space occupied by the seating and track. The pre-construction, natural topography did not provide a space of sufficient length for the track. The location of the Stadium represents a compromise between the need for excessive stone removal at the southwestern end of the structure and the need to construct an excessively large artificial platform for the starting line at the northeastern end. The lack of axial symmetry of the retaining walls built for the one end of the stadium reflects the trend of the terrace scarp in relation to the orientation of the axis of the Stadium.