Abstract

We examined the radiocarbon (C-14) reservoir effect in Lake Kutubu using tephrochronology and terrestrial plant material to deliver a precise age-depth profile and sedimentation rates for this lake. Based on the presence of two tephra horizons (Tibito and Olgaboli), we found a reservoir age offset in sediments of between 1490 and 2280 C-14 yr using the sediment ages derived from the lead-210 (Pb-216) dating method. The live submerged biological samples collected exhibited a higher reservoir age offset than the sediment. This is most likely a result of delayed transport of "bomb" C-14 from the atmosphere to aquatic and sedimentary system. The C-14 reservoir effect increased with distance from the lake inlet and also decreased with depth. Dissolution of C-14-depleted carbon from surrounding limestone and direct in-wash of old soil or vegetation remnants from the catchment are the most likely causes of the C-14 reservoir effect. Based on limestone areas mapped in Papua New Guinea, we indicate lakes which may be subject to a significant C-14 reservoir effect. The results of this study demonstrate the magnitude of the C-14 reservoir effect in lakes and provide insights to the correct interpretation of past environmental and archaeological events in PNG.