The balk is the unexcavated area between excavation units. It’s also the side of the excavation unit itself. Usually supervisors will exhort workers again and again to “keep the balk straight” – the sides of the excavation area has to be kept straight and even. For in the balk we can see what we excavated through. In this balk, for example, a very clear line is apparent (yellow arrow). It probably is the base of a pit that was built in ancient times. This pit was not as apparent when we excavated. Those subtle color and texture changes are sometimes not that apparent when excavating. But when we see the changes in the profile of the balk, they are much more noticeable. That’s one of the main reasons to keep the balks straight. It lets us see changes in the soil texture. In this balk you can also see a mudbrick wall (pink arrow). We carved through the mudbrick and now the mudbrick are visible through the subtle color changes in the balk. They are roughly square shapes of uniform color with a thin mortar line (also mud) of a slightly different color running between them.
Above the pit line and the mudbrick wall are the foundation stones of a later wall. Of course we saw that wall clearly when we excavated, but the balk gives us another indication how the levels relate to each other. For example the stone in the middle sits right above the pit line. It is therefore likely that the stone foundations were laid after the pit went out of use. It is also likely that the pit was dug after the mudbrick wall was out of use. Therefore a likely stratigraphy for this balk would be: level one – stone foundations; level two – pit; level three – mudbrick wall. Or in other words, first the mudbrick wall was built, then after it fell into ruin and was covered a pit was dug above it; and finally once the pit was (at least partially) filled in, a wall with stone foundations was built partly above the pit (normally levels are enumerated from the upper, later levels first). Not all levels (strata) are seen in the balk, but it can often get us a good record.