I remember talking to one of the excavators (Mike P-P or Phill H ?) who came up with the cart track theory but the glacial outwash idea seems to be the preferred one. It seems curious that the groves are so "concentrated", one would expect that the water would be much more spread out and the grooves don't follow the present valley landform. One expects glacial outwash to create gross changes to the landscape as is shown by the wet and dry valleys found everywhere on chalk.
What is needed is a wider geo-phiz survey as these shallow features should show up easily. Are there similar anomalies found elsewhere for a comparison?
Jim.