The Saint Peter sandstone is one of the most prominent Ordovicic formations of the Mississippi valley. Because of its striking characters it has attracted comment from almost every geologist whose work lay within this territory. Most of them have been led to suggest an explanation of its remarkable purity, or its apparent uniformity, or its structural relations. Many have regarded the formation one of the most puzzling of the region, the obscure problem being that of origin.
The following study is primarily one of the physiographic conditions represented in Saint Peter time. It has led to a comparative study of this formation as described from many localities and by many observers. This data has been checked wherever possible by the writer’s own observations,* which, together with his examinations† of material, form the basis of the discussion.
The work has been carried on in the Stratigraphic Laboratory at Columbia . . .