The Chert Gravels of Lyon County, Kansas

Abstract

The chert of these gravels is impure silica. This silica is evidently derived from an alkaline solution of the mineral occurring abundantly in the water of rivers, lakes and the ocean. Billions of diatoms, each with a skeleton of silica, are found, for example, in the water of the Cottonwood river, Kansas. Diatoms are also very abundant in the ocean, together with animals that use silica in their skeletons, such as the sponges and rhizopods. For some unexplained reason the waters contain and deposit, periodically, great quantities of silica in the limestones and sandstones. In this paper we will consider the deposits in certain limestones. There is an abundance of silicified honeycomb coral and chert in the Niagara limestone of the Wisconsin Silurian; the Onondaga limestone of the New York Devonian contains chert and silicified fossils in very great abundance; the Osage limestone of the Mississippian of Kansas and Missouri possesses quantities of chert packed in the zinc sulfid and lead sulfid togethed with silicified fossils; while the Wreford and Florence limestones of the Permian of eastern Kansas contain the chert and silicified fossils that are the subject of this paper. The chert gravel of Lyon county, Kansas, has been studied in three situations: I. These limestones have an average dip of twenty or twenty-five feet to the mile to the westward and are very resistant to erosive agencies, owing to the presence in them of great quantities of chert or impure flint. The Flint Hills, or Permian Mountains, as the early geologists named them, are being eroded more rapidly on their eastern face because the westerly dip exposes the underlying softer formations on this face to more rapid weathering. The chert debris is therefore distributed somewhat evenly for about fifty miles to the eastward of the present position of the Flint Hills. II. At the present time west and east of Emporia we find more than a dozen hills and mounds of chert gravel resting on the Pennsylvanian shales and limestones, at an elevation of about 100 feet above the beds of the Cottonwood and Upper Neosho rivers and mostly between these streams. A brief description of the Cottonwood valley to the sources of the streams which now drain it will help to understand the origin of these stratified deposits of water-worn chert so high above the present level of the rivers. Beginning at Delavan, west of Council Grove and near the Flint Hills, we follow a semicircular ridge with an altitude of about 1,500 feet, past Lost Springs, Canton east of McPherson, Walton west of Peabody, to near Matfield Green into the Flint Hills again, and have the sources of five or six small streams that unite at Florence, altitude 1,270 feet, to form the Cottonwood river. At Strong City the bed of the river has an altitude of about 1,150 feet, the Wreford limestone, 1,340 feet, and the bed of the Cottonwood river about 1,100 feet at Emporia. At McFarland, Kan., the core of a diamond drill prospect hole was interpreted by the Universtiy Geological Survey as to the formations penetrated belonging to the Pennsylvanian except the first 610 feet. This upper part of