Exploring ground-penetrating radar and sediment magnetic susceptibility analyses in a sandstone rockshelter in northern Australia

Abstract

Ground-penetrating radar (GPR) surveys offer several advantages for non-invasively assessing stratigraphy in archaeological rockshelters, including providing information about subsurface stratigraphy and the location of features such as roof fall and bedrock. Challenges to understanding the record of human impact and site formation processes in Australian rockshelter deposits include where to position archaeological excavations, how best to determine the onset of human occupation within sequences beyond the presence of stone artefacts (which can be limited at depth owing to sampling issues) and how to resolve issues relating to stratigraphic associations. This paper demonstrates how GPR can be used to gain a better understanding of buried deposits in a Pleistocene-aged rockshelter. When compared with results from sediment magnetic susceptibility studies, GPR verified the major stratigraphic units identified at the site, the depth of bedrock and the presence of roof fall, but it also provided information on the sediment volume within the stratigraphic units. This is a unique outcome for exploring rockshelter deposits and geophysical signatures overall, aiding in the interpretation of complex site sediments and offering a useful tool for future site investigations. Abbreviations: GPR: ground-penetrating radar; GS1: Gledswood Shelter 1; SU: stratigraphic unit; LOI: loss on ignition; MHz: mega hertz; ns: nanosecond; GSSI: Geophysical Survey Systems Inc.; Hz: hertz; P: phosphorus; Xfd: frequency dependence; PSA: particle size analysis; Tc: Curie temperature; YR: yellow red