Eight samples of unwashed cuttings from 1500-3510 metres (Aptian to late Eocene) were measured to determine thermal history. A major jump in the apatite grain age profile between the Tertiary and Cretaceous is attributed to a major shift in sediment provenance from along a developing continental rift system in the Cretaceous, especially from the east, to the crystalline basement to the north during the Tertiary. A general decrease in apparent fission trackage and mean track length indicates apatite grain annealing since burial and suggests that the deeper Cretaceous rocks, at least, have been heated to the stage where oil might be generated. In the deepest sample (3510 metres) all the apatite fission tracks have been lost, due to active annealing under the present-day thermal regime, implying that temperatures are probably now at their maximum.