There was a song that played during a successful installation of Windows XP. A catchy tune that was embedded in the code. I finally found it as a stand alone MP3. Love sharing it with geeks who remember the tune but do not quite know why.
Just saw an Eons video that pointed out the lack of “wee little beasties” during the Carboniferous age. Trees that fell down were not decomposed and eventually turned into coal.
Given the final chamber that is slanted upwards, mere silting would not have generated a complete fossilization. My guess (and only a guess) is that abandoned burrows were filled with water that leached minerals along the way. Over time, the water evaporated, more hard water flowed in until the former spaces were filled with mineral deposits.