Most famous and productive source rocks for hydrocarbons are Paleozoic or Mesozoic, but there are also examples from the Neogene. Time is needed for the rock to reach the right depth and temperature for hydrocarbon generation. Younger formations are typically in an active tectonic setting; old source rock risks becoming over-matured.
What are the youngest and oldest source rocks that are generating hydrocarbons in economic quantities today?
According "The youngest natural oil on earth" Doklady Chemistry vol. 438, pages 144-147:
Prior to this paper, it was known that oil of the Guaymas basin is from young sediments and is 5000 years old.
However, their work shows that oil in the Kamchatka volcanic area is "less than 50 years old". Oil is shown through carbon dating to have formed between 1962 and 1973.
At the opposite extreme, this 1986 New York times article reports:
A team of geologists working for the Australian Government's Bureau of Mineral Resources reports in the journal Nature that it has discovered oil formed from the decayed remains of organisms that lived 1.4 billion years ago, when the earth was young. After the group drilled a 1,100-foot-deep test hole beneath the McArthur Basin in northern Australia, the oldest oil of its kind ever found bubbled to the surface.
Tiny amounts of oil as old as 3.2 billion years have been found more recently.
