Affiliation: | 1 Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, PA 19104-6316, USA 2 Department of Archaeology, University of Durham, Durham DH1 3LE, UK 3 Department of Geography, University of Durham, Durham DH1 3LE, UK 4 Posford Haskoning Ltd, Rightwell House, Bretton, Peterborough PE3 8D W, UK |