THE BLACK SHALE PARADOX: PRESUMED PELAGIC, PSEUDOPLANKTONIC, AND BURROWING AND OTHER BENTHIC ORGANISMS PRESERVED IN THE CLEVELAND SHALE (FAMENNIAN), A "DEEP WATER" BLACK SHALE DEPOSITED IN ANOXIC CONDITIONS

The Cleveland Shale is a Famennian black shale notable for fossil arthrodires such as Dunkleosteus and the unit is considered a major Konservat-Lagerstätten based upon the exceptional preservation of the soft parts of fossil sharks. Very few taxa of invertebrate macrofossils, however, have been noted in most reports on this and other Famennian black shales that have been interpreted as being deposited in relatively deep, anoxic environments: Inarticulate brachiopods are among the most commonly cited invertebrate fossils. Based on Cleveland Museum of Natural History specimens collected over several decades from sites in northeastern Ohio, and a review of previous published and unpublished work, we have identified, or confirmed the identity of, almost 40 species of fossil invertebrates from northeastern Ohio. The relatively diverse, albeit sparse, fauna includes a monograptid graptolite; Paraconularia; crinoids; lingulid and orbiculoid brachiopods; chonetid and other articulate brachiopods; small to large (up to 38 cm long) orthocerids and other nautiloid and ammonoid cephalopods; loxonemid and other gastropods; nuculoid and grammysiid bivalves; various vermiform (tubular and segmented) organisms; and several taxa of crustaceans including Angustidontus. Some material is phosphatic or phosphatized, many specimens are pyritized, some are preserved in carbonate concretions, and some are preserved within fossil fish guts. A few specimens of arthropods are preserved on siltstone beds within the unit. The occurrence of many of these organisms in a "deep water" anoxic environment of deposition can be explained by possible nektonic or planktonic (cephalopod, graptolite, conulariid) life styles or pseudoplanktonic (orbiculoid brachiopod, crinoid) lifestyles, supported in some cases by association with plant fossils, but the occurrence of presumed burrowers (lingulid brachiopods, nuculoid and grammysiid bivalves) and other benthic organisms is difficult to reconcile with current models of black shale deposition. Thus analysis of this invertebrate fauna, large for a Famennian black shale, only accentuates the black shale paradox.