Abstract

A study of the lower Mississippian rocks of western Missouri between the Missouri River and the Missouri-Arkansas boundary has resulted in two major revisions of stratigraphic nomenclature:

(1) The Chouteau is re-defined as a group which comprises from bottom to top the Compton, Sedalia, and Northview formations. The usage of the name Compton is extended laterally to replace the "Chouteau (restricted)" of previous literature. The top of the Kinderhookian series is drawn at the top of the Northview formation and therefore at the top of the Chouteau group. In the northern part of the report area, dolomitic beds above the Northview which have been considered as upper Sedalia by many previous workers are assigned to the lower Osagean and are considered to be a northern extension of the Pierson.

(2) The St. Joe is raised to the rank of a group comprising from bottom to top the Compton, Northview, and Pierson formations. The Pierson is considered to be Osagean, the underlying formation as Kinderhookian; therefore the Kinderhookian-Osagean series boundary is placed within the St. Joe group, although previous workers have considered all of the St. Joe to be Osagean.