Reply to comment from E. Głowniak and H. Wierzbowski on “The mid-Oxfordian (Late Jurassic) positive carbon-isotope excursion recognised from fossil wood in the British Isles; C.R. Pearce, S.P. Hesselbo and A.L. Coe, Palaeogeography, Palaeoclimatology, Palaeoecology, 221, 343–357”