The presence of 18α(H)-oleanane in Pennsylvanian and Mississippian rocks in the Anadarko Basin, Oklahoma

•18α(H)-Oleanane is reported in Pennsylvanian and Mississippian rock extracts.•Identity of 18α(H)-oleanane was confirmed by GCMS, GCMSMS and coinjection.•18α(H)-Oleanane present in multiple wells and depth sequence from one well.•Results suggest angiosperms split from gymnosperms earlier than previously proposed.•Alternatively a previously unidentified source(s) is responsible for the oleanane.•1,2,7-Trimethylnaphthalene present in all samples containing 18α(H)-oleanane.