The situation as I know it:
The house is about 30 years old, and the land it sits on was an old New England farm. Old stone walls mark some of the property boundaries. The house sits on the highest point on the plot, where the oven is desired to be I will bet is 5' below that grade. We're in an area where there are numerous springs that run year 'round.
We got down 40" with no problem using a 12" auger, at that point the water rushed in from about 15" down from top level. Looks like 4"-5" of topsoil (nice looking topsoil too, makes me jealous), then 4"-6" of a sandy clay mixture, then it appears to be clay. Nothing too big in the way of boulders (yet).
Head over to
here (Started digging, stopped digging. Water problems.), there are a few pics.