Archaeol Prospection 14 (2)

The lower reaches of major river valleys usually present archaeologists with considerable problems where thick sequences of stratified alluvium bury archaeology. The authors demonstrate how mixed method approaches, utilizing a range of borehole methods, cone penetration testing and surface and subsurface geophysics coupled with microfossil assessment (Foraminifera/Ostracoda), can be used to model these deposits and predict locations and depths at which important archaeological remains may be located. It is argued that the novelty of this approach is not in the application of individual techniques to the problem but in the combined methodology, which enables a structured and cost effective programme of works to be formulated and provides the best chance to understand the subsurface. Although this approach has been developed to facilitate the location of archaeological sites buried at depth within the route corridor of development projects it is also suitable for locating fossil-bearing sequences and mapping stratigraphical units in Quaternary science. The authors demonstrate the approach using two examples from southern England.

A range of specific processing steps are available to correct the geometrical distortion of the georadar data produced by ground-penetrating radar (GPR). Nevertheless it is not yet possible to correct for pull-up/pull-down effects due to changes of velocity in target features. Unfortunately these effects can easily change the lower boundary of a structure by more than 30% of the preserved height. Hence pull-up/pull-down is one of the most important geometrical distortions in archaeological prospection. It is argued that, after a detailed three-dimensional interpretation of the data cube, the calculation of an individual correction becomes possible and can be applied to each structure separately.