It depends on what you want the molehill soil to do: If you are on a river then a more claylike soil could be better like a terre de rivierre but a shallow canal could mean looking for a lighter weight, black, almost peatlike.
There are some fields near the Oxford Canal at Claydon that are on a steep incline and they used to have peaty hills at the top and more claylike at the bottom.
I used to go there and bag a load and store it in a chest freezer as it was spot on for each application I wanted… If you don’t freeze it it goes mouldy! What’s all that about then? Never seen a mouldy field! lol