There is clay all over the place. During this summer I was making (or trying) to make some holes for some posts, and it was impossible, even with a rented auger (not tractor), the clay was so dry that it "cooked" before you were even able to dig in an inch. We had to fill with water, comeback next morning and get 6" out if.. repeat until you get 3feet deep. It took for ever to make 10 holes... The rest I had to use Tpost... So there is definitely plenty of clay to go around...
