They sunk.
An oil guy was saying he thought that oil is abiotic & produced deeply in intense heat & pressure areas where friction & pressure break down carbon elements & turn it into gas, and it works it’s way up, cools and congeals and is OIL.
>>How did dinosaurs get at the bottom of the North Sea?
>They sunk.
Present ocean bottom observation does not support your response. The bottom of 90% of the ocean is devoid of any organic debris because it is eaten by other ocean dwelling creatures on the way down and at the bottom, so that by time it settles on the bottom only bones remain. There is NO WAY to form oil from bones.