Effect of Soil Grain Size on the Geophysical Response of Graves: Clay Vs Silt Vs Sand

Non-invasive geophysical imaging of Maori ancestral burial sites (urupa) have allowed us to test when and where geophysical surveys are most likely to succeed. Results from five sites, with both marked and unmarked graves, in three coastal settings along the east coast of the South Island of New Zealand show that burials in clay and silt (loess) can be readily identified using geophysical techniques, but burials in sand frequently have no anomalous responses. The differences in responses are likely due to the depositional setting. Clay and loess are usually deposited as layers or massive beds so any disturbance due to burial is relatively clear. In contrast, nearshore, fluvial and dune sands contain sedimentary structures that can be difficult to distinguish from burials, and can mask the geophysical responses of the graves