Depending on sample size, stable oxygen and carbon isotope measurements were performed using a VG Isogas SIRA mass spectrometer with Multicarb preparation system (>80 μg) and a Thermo MAT253 isotope ratio mass spectrometer with Kiel IV carbonate preparation device (<80 μg) at the Godwin Laboratory, University of Cambridge. δ18O and δ13C is reported relative to the Vienna Peedee belemnite (VPDB) standard, and for both instruments analytical precision is estimated to be better than ±0.07 ‰ and ±0.04 ‰ respectively.