Non soluble organic matter
Kerogen is neither soluble in organic solvents nor in water. Kerogen includes the altered remains of recalcitrant biopolymers as well as macromolecules made resistant to biodegradation by the formation cross links such as sulfide bonds and ether bonds between its constituents.
Not all biopolymers or biomacromolecules are created equal. DNA and RNA, which are shared among every living organisms on Earth, are very easily degraded, most probably because all heterotrophic organisms have the enzymatic tools necessary to breakdown these macromolecules. As a result, the preservation of DNA or RNA in ancient geological material is rare and RNA and DNA are insignificant contributors to kerogen.
Cellulose, a carbohydrate based polymer that can be argued to be the most abundant polymer at the surface of continents is mostly found in ancient sediments when closely associated to lignin (as a lignocellulosic complex). Ligin, a lipid based macromolecules
Biopolymers that are made to be resistant