A.G. FISCHER’S “CYCLOMANIA”: PHANEROZOIC LONG-PERIOD CYCLES
One of Al Fischer’s more speculative and controversial ideas was a proposed 32-m.y. periodicity in Phanerozoic marine biotic diversity, climate, and ocean chemical/environmental changes. This idea was first outlined in a paper (with me as coauthor) in 1977, and was later explored in several published papers from 1981 through 1986. His thesis was that the 32-m.y. marine diversity cycles (also termed “greenhouse-icehouse" cycles in Al’s parlance) were superimposed over the two long Phanerozoic “super-cycles” and that all were forced by global climatic variations--perhaps the result of episodic volcanism. In this thinking, he was certainly influenced by his earlier reading of treatises by Umbgrove (1949) and Grabau (1940). However, the proposed 32 m.y. periodicity has so far not been supported by later work although other periodicities from 26 m.y. to 36 m.y., and even 62 m.y. have been proposed more recently.