Combined geophysical surveys using a novel approach to characterize ancient burnt soils: A field experiment at Liangzhu city site in Hangzhou, China

Abstract

Ancient burnt soils are valuable records in environmental and archaeological studies, and thus it is important to prospect such buried historical remains. By far, the study on geophysical exploration of the burnt soil is still rare. To investigate the effectiveness of geophysical methods for investigating such ancient relics, we designed a controlled field experiment at Liangzhu city site in Hangzhou, China, where there are plenty of Neolithic burnt remains in the shallow subsurface. We acquired common-offset ground penetrating radar (GPR) and electrical resistivity tomography (ERT) data, performed archaeological drilling and measured the physical properties of soil cores. The GPR and ERT data were first analyzed individually and compared with the borehole logs. We observe that the major reflected energy in the GPR data come from the vicinity of the burnt soil layer, while the energy below that is generally weak. The conductivity estimated from the ERT data is overall small in the shallow part but has a sudden increase from the lower interface of the burnt soil layer. The slopes estimated from two types of geophysical data show local similarities and complementarity, based on which we propose a novel workflow for geophysical data fusion based on the technique of predictive painting. The scheme can generate easy-to-understand images of soil layers with low computational costs, and its extension to 3D case is conceptually straightforward. It is also feasible to extend our work to large-scale surveys of ancient burnt soils.