The pavement layers of the Southwest Church of Umm el-Jimal, Jordan: stratigraphy and archaeometric characterization

The article focuses on the stratigraphy of the late Byzantine pavement of the Southwest Church, Umm el-Jimal, Jordan and the production technology of their mortars by applying thin section petrography, x-ray diffractometry (XRD) and scanning electron microscopy with energy dispersive x-ray spectrometry (SEM-EDS). Investigations revealed the similarity between the studied pavement and standard Roman mosaic pavements. The pavement consists of four layers (statumen, rudus, nucleus and bedding), but lacks the tessellatum layer. The statumen was constructed using large stones and then leveled by soil and pebbles, while the other three layers are composed of lime-based mortars formed by two different recipes. The white-beige non-hydraulic mortar of the bedding layer consists of a lime binder and aggregates of scoria and organic fibers, and a Binder:Aggregate (B:A) ratio of 1:2. The grey hydraulic mortars of the rudus and nucleus are mixtures of lime and silica-rich silt/clay, fine sand, volcanic rocks, ceramics, and charcoal; and B:A ratios of 1:4. The rudus and nucleus mortars have high values of hydraulic and cementation indices, reflecting their hydraulic properties, which most probably originated from the reaction between lime, ceramic and volcanic inclusions. In contrast, lack of ceramic and absence of the reactions between lime and scoria of the bedding layer probably produced a mortar with low values of hydraulic and cementation indices, but durable and resistant to weight load.