This is a deposit of an unknown, white-grey substance. Its original limits are also unknown because it may have been truncated by the backhoe, makng it difficult to understand its original shape. The depth is irregular. A sample was sent to Laura Motta for further analysis. We excavated this layer after it had been exposed to the sun for several weeks and at ths point it was quite dry and covered our hands with a white, powdery film when we touched it. Initial theories when it was first exposed and was slightly wetter include: degraded tufo and possibly a natural lime-calcium deposit.

Update: More of the white-grey material from this SU was found in non-discript, blotchy patces several inches down into SU 5581 (below SU 5605). This suggests that SU 5605 may originally have been a non-discript shape and may have only appeared to be linear because of the backhoe excavation.