DEVELOPMENT OF THE CYCLOTHEM CONCEPT BY CYCLIC GEOLOGISTS

Cyclothem, a term coined by J. Marvin Weller in 1932, ‘...is a series of beds deposited during a single sedimentary cyclic of the type that prevailed during the Pennsylvanian Period.' The subject of cyclic sedimentation became a hotly discussed one in the 1930s after the early pioneering work of Johan August Udden in Illinois two decades earlier. In 1929 Raymond C. Moore first reported on cyclic sedimentation in the northern Midcontinent at the GSA annual meeting in Washington, D.C. In 1931 a symposium on the subject was held at the Illinois State Geological Survey with most of the major players of the time presenting papers including Moore (1892-1974), Weller (1899-1976), and Harold R. Wanless (1898-1970). Papers were given describing cyclic sediments in Ohio, Pennsylvania, Texas, and West Virginia in addition to those in Illinois and Kansas. Not obvious at the time was some personal and professional competitiveness of the players involved. Shortly after the Illinois symposium, J. Mark Jewett (1896-1970) and Maxim K. Elias (1889-1982) joined the fray with their contributions from the Kansas perspective while the Illinois contingent continued their contributions. As the two schools developed independently, this rivalry kept the subject in the limelight for several decades. The competition continued intermittently until the next symposium on the subject sponsored by the Kansas Geological Survey in 1964 where some of the major players from the earlier symposium presented their last views on the subject. By the mid 1970s these early major players were retired or passed on, but the seeds of genetic stratigraphy had been planted.