The SU is a compact deposit possibly associated with leveling for later floor surfaces excavated in this southern area. These floor preparation deposits (and their leveling deposits) run beneath the surrounding walls, suggesting that the walls are part of a later phase. During post-excavation study, this feature was reinterpreted as a leveling fill suggesting activity and likely some type of flooring at the southern limit of the Phase 1B building.

The SU is a colluvial layer.