THE UPPER PALEOZOIC GENUS LOPHOPHYLLIDIUM IN MID-CONTINENT U.S.A

Moore and Jeffords published the first modern report on Pennsylvanian corals from the midcontinent and southwest United States in 1942. This seminal paper (and subsequent ones) presented serial sections of all species, and was definitive in that respect. However, all coral cross-sections were shown as black and white drawings, with coral skeleton generally presented as solid black and interskeletal spaces as solid white. This talk focuses on the black and white.

Coral skeletal carbonate is not at all uniform, being formed incrementally, with first-formed and later parts having different structure and composition. Skeletal structure now is seen to have primary importance in the interpretation of systematic position, skeletogenesis and diagenetic history. Additonally, geochemical sampling is dependent on understanding coral skeletal microstructure, as minor and trace elements vary from early to later-formed skeleton. Cements (the “white” portion) provide clues to diagenetic history and minor element chemistry of the skeleton. Study of encapsulated corals from shales and asphalt beds provides significant insight into the geochemistry of involved genera and species, but “within capsule” cements must be evaluated along with skeletal carbonate.

Lophophyllidium belongs to the “Cyathaxonia fauna” characteristic of the Carboniferous and Permian. These lack dissepiments and in general inhabited argillaceous and/or deeper water environments. It is probable that these were non-zooxanthellate corals, approximate equivalents to modern non-reef-forming (ahermatypic) corals. Excellent preservation of Lophophyllidium in Pennsylvanian shales and asphalt have led to geochemical study of them, and resulted in the erroneous conclusion that their observed chemistry is “typical” for Paleozoic corals. In actuality, there are major differences between the Lophophyllidium faunas of Upper Paleozoic shales and other Paleozoic Rugosa, in life habit, habitat and resulting skeletal chemistry. Not all is black and white.