If I understand correctly, fossil fuels are ancient swampy bogs. Trying to imagine a situation where hundreds of vertical feet of carbon rich soils can accumul

If I understand correctly, fossil fuels are ancient swampy bogs. Trying to imagine a situation where hundreds of vertical feet of carbon rich soils can accumulate, I think of a river delta slowly extending to sea, or an ancient lake eutrophying. Perhaps a geologist will come along who can explain better.