The Surat Basin's Walloon coals (Oxfordian) record peat accumulation under changing base level.
The coals show a positive excursion in δ13C towards the top of the coal measures.
This follows the global δ13C trend as recorded in marine carbonates from the same age interval.
The positive excursion in δ13C corroborates a global climatic shift in the Mid-Oxfordian.