Mesozoic rocks are dominantly carbonates with shales.
Oligocene to Recent sandstones and shales can exceed 9 km in thickness. Graben source rocks would likely be more oil prone than source rocks from the platforms and platform margins. Mesozoic thermal gradients during rifting were probably higher than Cenozoic thermal gradients during continental collision. Much of the Triassic oil potentially generated from deepest grabens as early as Early to Middle Jurassic time either was not trapped or was subsequently lost from extensional fault-block traps during the later Alpine and Apennine orogenies. A later major episode of hydrocarbon expulsion under cooler thermal conditions occurred from Miocene and shallow-burial Triassic source rocks during the Alpine and Apennine orogenies.