Is the lower formation of Wapsipinicon Group (rank raised) in northern IA, Iowa shelf. Unconformably overlies eroded surface of Upper Ordovician rocks and is overlain by Kenwood Member which is reassigned as basal member of Pinicon Ridge Formation (new), upper formation of Wapsipinicon Group. Is 19 m thick at its type locality. Reaches a maximum thickness of 25 to 30 m in northeast IA. The lower 0.5 to 4.2 m of argillaceous to shaly dolomite and shale which is partly sandy, partly conglomeratic with reworked Ordovician chert clasts, has been called "informally" the Lake Meyer Member. The remainder of the formation is medium- to thick-bedded dolomite, partly stylolitic with scattered to abundant fossil molds and vugs, and locally dolomitic limestones. Of early Middle Devonian, Eifelian age. Nomenclature charts. Graphic sections.

Source: GNU records (USGS DDS-6; Denver GNULEX).