Complex sentence: Clay or clay-sand and water were mixed together to make mud mortar, which were usually made from canyon deposits; but some of the clays may have been obtained from rock-clay exposures at the base of the cliffs.
Split into simpler sentences: Clay or clay-sand and water were mixed together to make mud mortar. Mortars were usually made from canyon deposits; but some of the clays may have been obtained from rock-clay exposures at the base of the cliffs.