Some geology words just add confusion to the reader.
Carbonaceous – Relating to the organic or carbon content of the rock. Example: “This siltstone is really carbonaceous!” when referring to an organic-rich siltstone.
Could be confused with:
Carbonate or derivative – Being made up of a carbonate compound (usually calcium carbonate). Example: “The carbonate shale was very thick” when referring to a mix of clay and limestone minerals.
Since “Carbonate” is a word many geologists learn much earlier than “Carbonaceous”, I think the latter should fall out of use. “Organic-rich” is a much more descriptive term.