Charcoal can form during "Diagenesis" wherein some layers of organic material , like wood from a beach pile f flotsam and driftwood, or flood deposits , or snags in a riverbed, are compressed by the overlying sediments and they slowly "stew' in anoxic conditions. However, there are also another bunch of reasons that this can appear and these are managese dioxide deposits called "wad' and ultra fine black sediments of melanocratic (dark colored) minerals like diopside, titanium, spinel, magnetite and uraninite.
usually the latter are slightly more coarser grained.
I need to see the context to provide an opinion as to whether its any one of the above (or something else entirely)
P Dale, Im a rocknocker, not a rockhound. My title takes 3 degrees and years of work in the mines. A rockhound isa hobbyist who usually quits thinking about his rock hunting trip after he has his
first beer. A rocknocker thinks about how he can invoice somebody on it