Use of Lightweight Lime Mortar in the Construction of the West Church of Umm el-Jimal, Jordan: Radiocarbon Dating and Characterization

Lightweight concrete was widely used and mainly spread during the Roman period. This technology was used in the West Church, Umm el-Jimal, Jordan. The date of construction of the West Church is debated and different dates have been suggested based on its architectural styles and comparisons with other churches. This research aims to radiocarbon date the construction of the dome (church), archaeometrically characterize the mortar, and determine the source of the scoria. Three charcoals and two broken pieces comprising scoria from the mortar of the fallen dome and six large scoria samples from Quais cone were collected. The research used different analytical methods including accelerator mass spectrometry 14C, X-ray diffraction, petrographic microscopy, inductively coupled plasma mass spectrometry, and scanning electron microscopy-energy dispersive X-ray spectroscopy. 14C determinations dated the dome (church) to the Late Roman–Early Byzantine periods, which contradicted the archaeological data. Analytical results showed that the mortar is lime-based and hydraulic. The similarities in the mineralogical composition, macroscopic and microscopic features, and chemical composition (compared statistically) of the scoria samples and the short distance between Umm el-Jimal and the Quais volcanic cone very likely indicate that the Quais volcanic cone is the source of the scoria used in the fallen dome.