The general consensus is that the large basalt boulders separating loci 2/4 and 3/5 are rockfall. These boulders appear to be floating, with no boulders below them to suggest their use in architecture. I removed the boulders and other smaller floating stones after drawing and photographing the trench. The next work day, I plan to combine the matrix under loci 4 and 5 into one locus, after the trench floor is cleaned.