Barren sediments are often as difficult to classify, in respect to their age, as certain igneous and metamorphic rocks. This lack of age determination has long been the status of some of the old sandstones and shales of eastern Minnesota. In the region to the southward, from the Lake Superior district to the Iowa State line, about twenty-five wells, some of recent date, have penetrated or passed through these deposits and have thus continually called for a more definite correlation of the sands and shales in the deeper part of these logs. In order to arrive at more satisfactory conclusions in regard to their age, some time has been devoted to them, during the last two years, with the results as given here-with.
In eastern and southeastern Minnesota there is a great thickness of red sediments lying below the Saint Croix Series and above the . . .