> As for 50ft topsoil....merely to have written this suggests your connection with farming is extremely tenuous.
Absolutely, that statement baffled me too. I've dug many pits down to over 5 meters and I've never seen topsoil more than 2 meters deep. In those cases it wasn't even proper topsoil, more like loose turf which collects on low lying land due to erosion and percolation. The average is roughly 0.5 meters in my area and it is renowned for the quality of the agricultural land.