Rapid, high-resolution ¹⁴C chronology of ooids

Ooids are small, spherical to ellipsoidal grains composed of concentric layers of CaCO₃ that could potentially serve as biogeochemical records of the environments in which they grew. Such records, however, must be placed in the proper temporal context. Therefore, we developed a novel acidification system and employed an accelerator mass spectrometer (AMS) with a gas accepting ion source to obtain radiocarbon (¹⁴C) chronologies extending radially through ooids within one 8-h workday. The method was applied to ooids from Highborne Cay, Bahamas and Shark Bay, Australia, yielding reproducible ¹⁴C chronologies, as well as constraints on the rates and durations of ooid growth and independent estimates of local ¹⁴C reservoir ages.