¹⁴C age of recent natural earthworm biospheroids - Implications for paleosol dating

Earthworm biospheroids are a useful alternative to radiocarbon (¹⁴C) soil dating. In this study, we undertook a series of measurements to test the ¹⁴C dating potential/performance of recent earthworm biospheroid granules. A novel sample preparation protocol for ¹⁴C in biospheroids was developed and elaborated at Atomki (Institute for Nuclear Research) and tested on IAEA reference materials. 24 natural biospheroid samples were extracted from five different location/environment-eight topsoils (A-horizon soils). Bomb-peak-based, high-resolution ¹⁴C dating show very uniform ¹⁴C results at 105.6 ± 2.6 pMC (1σ) and none of the biospheroids are older than 30 yr. It also shows that no biospheroid with a ¹⁴C bomb-peak as high as that observed in the 1960s and 1990s were observed. The results confirmed that earthworms do indeed consume almost exclusively recent biogenic carbon, not other organic compounds or inorganic carbonates previously bound in the soil. The calendar age of their biospheroids were extremely close to the real (zero) age of the surface. Thus, no reservoir effect is seen for these macrofossils. We conclude that a biospheroid-based ¹⁴C age determination method may be suitable to measure the burial time as long as earthworm biospheroids can be found in the soil.