Boron isotope, stable isotope and trace elemental composition of fossilised Liostrea hisingeri oyster samples and sequentially leached paired bulk rock samples. Samples were taken from Lavernock Point in Wales covering the Triassic-Jurassic boundary interval and used to assess the role ocean acidifcation may have played in the end-Triassic mass extinction. Samples were analysed for trace element composition by inductively-coupled mass spectrometry (ICPMS) on an Agilent 7500 at the University of St Andrews. Boron then purified from the sample matrix by separation using a boron specific ion-exchange resin, Amberlite IRA-743 (Kiss, 1988), following the column chemistry procedure of Foster (2008). Boron isotope composition was then analysed on the Neptune Plus multi-collector ICPMS (MC-ICPMS) at the University of St Andrews following the procedures of Rae (2018), using 0.3M HF in samples, standards and blanks to aid washout (Zeebe and Rae, 2020). Dataset supporting the publication 'Pulses of ocean acidification at the Triassic–Jurassic boundary' (Trudgill et al. (2025).