A06_P08

Dating the Wilson’s Arch complex, Jerusalem: methodological insights

Regev J¹,  Uziel J², Mintz E¹, Regev L¹, Boaretto E¹

¹Weizmann Institute of Science, Rehovot, Israel, ²Israel Antiquities Authority, Jerusalem, Israel

Radiocarbon dating is rarely applied in Classical and Post-Classical periods in the Eastern Mediterranean, as it is not considered precise enough to solve specific chronological questions, often causing the attribution of historical monuments to be based on circumstantial evidence. This research, applied in Jerusalem, presents a novel approach to solve this problem. Integrating fieldwork, stratigraphy, and microarchaeology analyses with intense radiocarbon dating of charred remains in building materials beneath Wilson's Arch, we absolutely dated monumental structures to very narrow windows of time – even to specific rulers.

Most of the dated samples were organic remains extracted from the mortar between the building stones. As the site was filled and covered over the years, microarchaeological methods were used first to verify the identification of the original mortars. Furthermore, hard work was invested to find and identify sufficiently large single fragments of short-lived samples, confirming that each date represents a single point on the calibration curve.

Various construction technologies were used along the 1300 years time span over which the buildings were constructed. As we searched for, identified, extracted, and dated the organic aggregates within the plasters and mortars, very different stages of preservation were identified: in some cases even fresh straw was extracted, while in other materials, the organic remains were extremely fragile. Another aspect to consider is that different building material functions require different technology. The resulting chemical properties of the context affect the preservation state of the material for dating and allows secure dating by chemically definable original material.