A Preliminary Stratigraphic Study of the Galena Group of Winneshiek County, Iowa

The rocks of the Galena Group have proved to be problematic in correlation. This problem is due to a variable lithofacies development. A preliminary investigation, although based upon exposures studied just within Winneshiek County, provides a method for field identification in Iowa of stratigraphic units currently used by the Illinois State Geological Survey within Illinois. Units under consideration at this time are restricted to the Dunleith, Wise Lake, and Dubuque Formations. Methods of identification and correlation employ in part such physical features as sequences of nodular chart bands, discontinuity surfaces, and sparry calcarenite bands. Investigation has disclosed a close relationship of these three features. A composite graphic column is provided, with key identification factors, for each of the subdivisions together with reference localities where the strata under investigation may be observed in sequence