Main Divisions of Pennsylvanian Period and System

ABSTRACT Divisions of the Pennsylvanian System called Pottsville, Allegheny(an), Conemaugh(an), Monongahela(n), Lee, Kanawha(n), Pittsburgh, Springer(an), Morrow(an), Atoka(n), Lampasas (Lampasan), Derry(an), Des Moines (Desmoinesian), Missouri(an), Virgil(ian), Bend(ian), Strawn, Canyon, Cisco, and possibly others, have been designated as series. An analysis of physical characters and paleontological features of the Pennsylvanian rocks in North America leads to the conclusion that stratigraphic cleavage at two positions within the system has paramount significance. Breaks at these horizons provide grounds for recognizing three series: Lower Pennsylvanian deposits are named the Ardian Series, from outcrops in the Ardmore basin, of southern Oklahoma; Middle Pennsylvanian deposits are designated the Oklan Series, from the section of eastern Oklahoma; Upper Pennsylvanian rocks are termed the Kawvian Series, from the splendidly displayed sequence of these deposits in the Kaw (Kansas) River Valley and vicinity, in eastern Kansas. The chosen names for the defined series conform to convention in being derived from place names and in having specified type areas, but the names Ardian and Oklan go a step beyond precedent in using only part of a single geographic name (rather than one part of a binomial or trinomial geographic name, as illustrated by many stratigraphic terms in common use). Among reasons for choosing the new series names is lack of available other names. The Ardian Series includes Springeran and Morrowan rocks, which are classed as stages. The Oklan Series is made up of the Atokan (or Derryan) and Desmoinesian Stages. The Kawvian Series contains the Missourian and Virgilian Stages.