sapropelicadj.

1901 Jrnl. Royal Microsc. Soc. 144 ‘Sapropelic’ Fauna... Dr. R. Lauterborn uses the term ‘sapropelische’ to denote the organisms found in the muddy debris covering the bottom of stagnant fresh-water pools.

1918 M. C. Stopes & R. V. Wheeler Monogr. Constit. Coal 19/2 Potonié's separation of coals into two main groups, sapropelic and humic, is now widely adopted... But the use of the phrase ‘humic coals’ is much in want of elucidation, as it, too, is given different meanings by different authors. As used by Potonié and most palæontologists, it means that the coal was formed from ‘humic débris’, or the various largely undecayed accumulations of mixed organs of plants... When the word ‘humic’ is applied to coals by chemists..it may convey the implication that ‘humic acid’ exists in the substance of the coal.

1963 D. W. Humphries & E. E. Humphries tr. H. Termier & G. Termier Erosion & Sedimentation xi. 239 The presence of a sapropelic bottom inhibits aerobic life over the whole of the lower part of the basin.

1966 B. Simpson Rocks & Minerals xx. 234 The first group is the Humic Coals in which woody tissue is of paramount importance in the composition... The second group, the Sapropelic Coals, have little woody tissue in their composition.

1971 Nature 31 Dec. 508/1 They [sc. labyrinthodonts] are never found in humic coals, but usually in sapropelic coals, laid down in the deep anaerobic mud which formed in stagnant conditions.