Using Geophysics to locate burials and other cultural features, Isle of the Dead, Port Arthur, Tasmania

Abstract

Multi-technique geophysical investigations have been conducted on the convict-period cemetery on the Isle of the Dead, Port Arthur, Tasmania. With the exception of historic photographs and some limited historical research, very little is known about the layout of burials or physical characteristics of the subsurface. Approximately 1100 burials took place on the island and less than 10% of these were formally marked. Apparent conductivity and magnetic surveys were conducted across the accessible portion of the island to locate subsurface artefact that may be associated with individual burials. The results show gradual variations in soil conditions over the site, some surface cultural features such as pathways, and numerous near-surface unidentified ferrous objects. Although some of these features showed apparent linear patterning, this did not correlate with individual areas of disturbance visible in the ground penetrating radar (GPR) profiles. 500 MHz and 250 MHz GPR surveys provided detailed subsurface information and was used to define the lateral extent of individual anomalous responses and areas containing complex multiple reflectors. The former were classified into various types, according to amplitude, shape and continuity of the reflectors. They were interpreted as possible or probable graves and located on a cultural sensitivity plan as zones of high archaeological potential. Of the techniques used so far, GPR appears to be the most effective method for detecting disturbances associated with graves on the Isle of the Dead.