I have a hard time believing dinosaurs lived thousands of feet below the surface under thousands of feet of ocean. They also lived underground beneath the polar icecap.
What the earth does have deep underground is carbon, hydrogen, heat and pressure.
EC
When mountains are formed, the crust of the earth is pushed up from several colliding directions. This would bury a lot in the process.
Back to oil. Its the lubricant excreted from the bowls of the earth. The process never stops. Heat from the core....