The sand deposit underneath the Ishtar Temple in Assur, Iraq: Origin and implications for the foundation of the goddess’s cult and sanctuary

• First-ever systematic mineralogical investigation of sands from an archaeological context in Iraq. • Sand layer beneath temple's first building phase mirrors a southern Mesopotamian practice for the first time in north. • Sands derive from the Zagros Mountains, located upstream from the Tigris tributary, in the Lesser Zab region. • Implications on Ishtar at Assur, linked to Inana in southern Mesopotamia or the Hurrian deity Shawushka (or Shaushka). • Dating above sand (2896–2702 calBC (95.4 %)) predates conventional Early Dynastic Period III (ca. 2600–2340 BCE) date. This study presents the first-ever systematic mineralogical investigation of sands from an archaeological context in Iraq, establishing a methodological precedent for future geoarchaeological investigations in Mesopotamia and studies of ancient architecture more broadly. The sand derives from a deposit underneath the Ishtar Temple at Assur (Ashur; modern Qal’at Sherqat) on the Tigris River, once the political and religious centre of the Assyrian state. Since the earliest layers of the main Assur Temple are inaccessible, this sanctuary is the oldest temple explored through excavation at the site. Thus, data from its early strata are critical for understanding the city’s earliest history. In 2024, coring within the temple cella by the Assur Excavation Project revealed a thick sand layer beneath its foundations, deliberately placed before construction. As no comparable deposits exist locally, the material was sourced explicitly for this purpose. Sand foundations for monumental buildings are known from southern Mesopotamia but are here attested for the first time in the north. Mineralogical analyses indicate that the Ishtar Temple sands mostly consist of epidote-group minerals associated with glaucophane, zoisite, lawsonite sourced from blueschist-facies metamorphic rocks. Their provenance is plausibly from nearby aeolian sand recycled from the Injana Formation and ultimately traceable to the Zagros Mountains, linked to Assur via the Lesser Zab River. Thus, while southern building traditions were adopted, the sand was not imported from the south but sourced in the region and ultimately derived from the eastern Zagros Mountains. Radiocarbon dating from the floor above the sand yielded a date range of 2896–2702 calBC (95.4 % probability), providing new information for the debate surrounding the temple’s foundation and its role within Mesopotamian cultural history. These results significantly inform debates on the origins of Ishtar’s cult at Assur.