This is what i believe is part of the same structure, on the opposite side of the beck, what i think has happened is the tree roots from the large tree above over a long time of slow growth have caused the sandstone structure? to splay to the left and right, as well as pushing some of the sandstone down into the gravel bed it sat on.
The image above shows one of at least two large sandstone pieces that have been undisturbed by the roots and sit on the gravel bed in the same way as the structure? on the opposite bank, a believe it will go a lot deeper into the clay deposits, its going to be very hard to expose further as the roots of the dead tree above are huge.