1. Organic Geochemistry Unit, School of Chemistry, University of Bristol, Cantock’s Close, Bristol, BS8 1TS, U.K.
2. Bristol Radiocarbon Accelerator Mass Spectrometer, University of Bristol, 43 Woodland Road, Bristol, BS8 1UU, U.K.
3. UWA School of Agriculture and Environment, University of Western Australia, Crawley, Western Australia 6009, Australia
4. Environment Centre Wales, Bangor University, Deiniol Road, Bangor, Gwynedd, LL57 2UW, U.K.