SUBSURFACE IMAGING OF BILIONIAI HILLFORT, LITHUANIA

Around 4,000 potential hillfort sites exist throughout the Baltic region. Hillfort sites are generally described as larger oval shaped mounds, usually less than a hectare in size at the highest platform. Hillforts usually have terracing up the sides to provide a location to place ramparts. Commonly, the base of a hillfort is an area designated for a settlement. Hillforts often served multiple purposes, including defensive forts to protect against attack, wooden castles, and as settlements. To better understand hillfort sites and guide future excavations, a ground penetrating radar (GPR) study was conducted at a prominent 1^st millennia hillfort in the Šilalė district of western Lithuania. The hillfort is located in the town of Bilioniai and is one of the 34 recognized hillforts within the district. GPR is a noninvasive technology that sends high frequency pulsed energy into the ground. The resulting images could aid in locating subsurface anomalies such as previously existing walls or structures left within a buried hillfort. Subsurface grid data was collected on the highest platform of the Bilioniai hillfort using a pulseEKKO GPR system equipped with 500 MHz antennae. The initial grid size was 40mx20m, with the Y-lines extended to the edge of the hillfort when needed. Grid line spacing was 0.25m with a step size of 0.02m. A handheld Garmin GPSMap 64st was used to collect corner GPS coordinates of the grid while a Topcon RL-H4C laser leveler equipped with a telescoping 5-meter measuring stick was used to collect topography at 1.0 meter increments within the grid. The GPR data was processed using GFP Edit, EKKO_Project, and GPR Slice software packages. The results of the grid data contain: 1) two rectangular shaped structures with one being 5.2mx11.5m in size, while the second is 4.7mx11.3m in size, with each approximately 0.6m-1.4m in depth, 2) linear feature approximately 3.3m long at a depth of 0.75m-1.0m, and 3) two circular shaped objects, one is approximately 2.1m in diameter at 0.15m-0.4m in depth and the second approximately 3.9m in diameter at 1.1m-1.5m in depth. The results will help guide future archaeological excavations and aid in preserving the cultural artifacts within the Bilioniai hillfort as well as to help further explain the history of the Šilalė district hillforts.