What is the ultimate source of the carbon contained in fossil fuels?

Question

What is the ultimate source of the carbon contained in fossil fuels?

Answer 1

Dead organic matter (e.g. plants and animals that have died).

Answer 2

The ultimate sources of the carbon contained in fossil fuels are the stars that forged the carbon from lighter elements under intense heat and pressure.  The carbon atoms were dispersed after the stars were at the end of their existences.

Once the carbon was in the gravitational field of the developing earth, it could never leave.  The carbon cycles between living and nonliving phases.  It may be in the air as carbon dioxide, in the water as carbonate and bicarbonate, and as a solid as carbonates and carbides.  In living systems, carbon is part of virtually every molecule of life.  When an organism dies, its carbon can become incorporated into nonliving systems as well as other living systems.

Answer 3

Go with scottsdale. I was going to say atmospheric CO2 from ancient earth, but his answer is better. Why do some people provide long narratives that never answer the question?

Answer 4

According to the biogenic theory, petroleum is formed from the preserved remains of prehistoric zooplankton and algae which have settled to the sea (or lake) bottom in large quantities under anoxic conditions. Over geological time, this organic matter, mixed with mud, is buried under heavy layers of sediment. The resulting high levels of heat and pressure cause the organic matter to chemically change during diagenesis, first into a waxy material known as kerogen which is found in various oil shales around the world, and then with more heat into liquid and gaseous hydrocarbons in a process known as catagenesis.

Terrestrial plants, on the other hand, tend to form coal. Many of the coal fields date to the carboniferous period.