Final answer:
Mixed soils in a grave are identified by the presence of both well-preserved, articulated bodies (primary deposits) and disarticulated bones (secondary deposits), indicating variations in the time and conditions of burial.
Step-by-step explanation:
Mixed soils occur in a grave when there is evidence of both primary and secondary deposits within the same burial site. Primary deposits refer to the bodies that have decomposed entirely onsite, showing good anatomical articulation, indicating the body was buried shortly after death and has remained undisturbed. Secondary deposits, on the other hand, include disarticulated bones or bodies that began to decompose before burial, suggesting that they were exposed or stored elsewhere prior to being buried. An example of this is the graves FS 161, FS 162, and FS 164, where the core group of individuals buried displayed good articulation accompanied by secondary bone deposits on one side. Soil profiles and their characteristics also provide insights into the drainage and environmental conditions of the burial site, affecting the preservation of remains.