Chronological Analysis of Occupation on Providence Island, Liberia, by Luminescence Dating

In 1822, the American Colonization Society established a settlement on Providence Island, at the mouth of the Mesurado River in present-day Liberia. This settlement, which later became part of Monrovia, marked the beginning of Liberia as a colony for free Black Americans, some of whom were formerly enslaved. Oral histories and limited archival sources suggest that, prior to 1822, Indigenous peoples inhabited the area long before the arrival of these settlers. Since the inception of the Back-to-Africa Heritage and Archaeology (BAHA) project in 2018, excavations have recovered deposits of imported and locally-made pottery, providing invaluable insights into pre-and-post 1822 activities at this significant heritage site. These findings offer a rare opportunity to refine the island’s cultural chronology and better understand the depth, continuity, and complexity of Indigenous activity in the centuries leading up to Liberia’s founding. Here, we evaluate the performance of quartz and feldspar luminescence signals for dating young coastal sediments and associated artifacts from Providence Island. Using Optically Stimulated Luminescence (OSL) on samples collected during the 2022 field season, we determined that deposits containing only local ceramics date to 600–400 years ago (15th-16th century), while a single sherd of local origin dated to 852 ± 140 CE (8th through 10th centuries CE ) . The upper layers, containing both local and imported ceramics date to 360 years ago (17th century). Overall, these results reveal that Providence Island may have a far deeper and more complex occupational history than the well-documented 19th-century settlement, potentially linked to earlier Indigenous activity during the Atlantic trade era (1500–1900 CE). While a comprehensive, island-wide study is needed to clarify the sequence of occupations and fully reconstruct its cultural history, this research highlights the applicability of OSL in African archaeology, where integrating scientific chronologies with oral traditions and ethnography is crucial for illuminating pasts often absent from the written record.