 Geochemical evidence suggests these rocks provided most of the basin's oil, and a major pulse of oil generation and migration was in the Cenozoic.The overlying Upper Jurassic-Upper Cretaceous clastic succession, ~ thick, has negligible source potential but contains high-quality reservoirs with largely secondary porosity of ~15% or more.Above, mostly offshore, lie Cenozoic mudstone, sandstone and volcanic deposits, up to ~ thick in some fault-bounded depocenters.