(Of course, the oxygen in the carbon dioxide ends up in new water molecules in a later step of photosynthesis, and that water either immediately or eventually finds itself in another photosynthesis reaction, so that carbon dioxide oxygen finds itself released into air sooner or later, but still.)
The geologic carbon and kerogen cycle looks to be be:
plankton + plants -> sedimentary rocks -> kerogen -> "liquid and gaseous hydrocarbons [via] catagenesis"
https://en.wikipedia.org/wiki/Fossil_fuelHowever, relatively recently there has also been the discoveries of extraterrestrial sources of kerogen, including in meteorites, Martian samples and planetary nebulae:
https://en.wikipedia.org/wiki/Kerogen#Extra-terrestrial
It's not clear to me how much to attribute to how much terrestrial kerogen could be present during our planetary formation vs that which is continuously replenished during the carbon cycle.
Anyone know of studies of the relative contributions?