Bellan-bandi Palassa, Sri Lanka: Formation processes of a Mesolithic open-air site identified through thin section micromorphology

Abstract

The streamside site of Bellan-bandi Pallassa, with the richest skeletal record of terminal Pleistocene-early Holocene hunter-gatherers on the island, is one of the most important prehistoric sites in Sri Lanka. We use thin section micromorphology of two samples from terminal Pleistocene (ca. 11,150-12,250 years BP) levels to infer processes of sediment accumulation and post-depositional change that led to the formation of the archaeological site. Charcoal and bone fragment-bearing gravely silty sand accumulated from a combination of colluvial, with possible contribution of aeolian, and anthropogenic processes, including combustion and associated bone-splintering activities. Some degree of reworking of bone and charcoal by slope wash processes and sediment fauna is evident. Post-depositional processes included incipient bone dissolution and calcrete formation in the vadose zone, probably reflecting wet/dry climatic seasonality in the early Holocene, and pervasive iron / manganese impregnation and rare vivianite authigenesis, reflecting later water-logging as a result of more humid phases in the Holocene and / or construction of a water tank above the site in historical times (probably 4th century CE). Our findings are consistent with the current interpretation of the site as a hunter-gatherer campsite, reflecting successful hunting adaptation to seasonally wet and dry conditions.