The Royal Cemetery was a challenge to excavate. Burials were cut into a trash dump, consisting of sloping layers of soft soil. Woolley dubbed the layers “Seal Impression Strata” (SIS) because they contained hundreds of clay lumps with cylinder seal impressions. The large number of cross-cutting burials made accurate recording difficult.
- Leonard Woolley
By careful observation, Woolley was able to distinguish earlier and later groups separated by debris varying in thickness and composition. The earlier burials, including the royal tombs, were cut into lower SIS layers (SIS 8-5) that contained cuneiform tablets, sealings, and pottery typical of the first part of the Early Dynastic period (ca. 2900–2600 BCE). These earlier burials, then, had to be later than 2600 BCE. Upper SIS layers (SIS 2-1) sealed the earlier burials from the later ones. Artifacts in these upper layers had the names of an historically attested king and his queen, providing a terminus ante quem or date after which the earlier burials would have been dug. As a result, we know that the earlier burials belong to the first half of the later Early Dynastic period (ca. 2500 BCE).
[stextbox id="grey"]Woolley used groups of superimposed burials to put the individual burials he uncovered in a relative sequence.[/stextbox]
Dating the cemetery’s later burials was easier because two of the graves contained inscribed cylinder seals that name officials of Enheduanna, the daughter of Sargon, who founded the Dynasty of Agade (2334–2154 BCE).