HORIZONTAL WATERMILL CHRONOLOGIES BASED ON 14C DATING OF ORGANICS IN MORTARS: A CASE STUDY FROM JARASH, JORDAN

Horizontal watermills in the southern Levant have proved difficult to date. This study investigates the use of radiocarbon (14C) dating of various organic carbon fractions in structural mortars and carbonate deposits to identify terminus post quem (TPQ) construction dates for seven arubah watermills and two chute watermills in northern Jordan. Dating results from the various organic fractions are discussed in the contexts of carbon fraction integrity and mortar type. The arubah watermill construction dates fall into two chronological groups. Four arubah watermills have Middle Islamic (late 12th to early 14th century AD) construction dates based on macrocharcoal and bulk organic fraction ages, whereas the bulk organic fraction ages of two earlier arubah watermills straddle the Byzantine-Early Islamic transition. Their possible fifth to seventh-century construction dates are among the earliest in the southern Levant. Limited 14C data from the chute water mills suggests that the earliest may date to the sixth–seventh century period, concurrent with the older arubah watermills. The study supports the viability of the AMS 14C method to provide estimated TPQ construction dates for watermills, providing caution is exercised. Short-lived macrocharcoals have the highest integrity but are subject to severe sample loss during pretreatment. 14C ages from humic and humin fractions in earthen mortars are influenced by “old carbon” contamination, possibly a soil reservoir effect, and are centuries older than the probable construction date. Attention is drawn to the potential use of arubah carbonate deposits as proxy records of water flow, watermill use, and hydroclimate.