Mortar under the clay sarcophagus deposited intentionally, as shaped (at least in southern end) to match the clay sarcophagus (1360) and was still bound to it upon removal of the sarcophagus (contributing to the fragmentation of the mortar). The surface below the mortar is darker, with more clay and pottery etc. poking out. This suggests the mortar was used to smooth the underlying surface for the deposition of the clay sarcophagus.