This SU is a Basin used for production of mortar. It seems to have been constructed on an ad hoc basis, perhaps regularized only at the top edge, in the course of production, as it is built of the sane materials of its fill 8183. However, it may have had an earlier function, as the depresion in the center suggests a design meant to collect liquid. Alternatively, this Depression may have formed when the basalt rocks from SU 8149 were dumped.