A cross-section of one of the siliceous the trace fossil infills, often nodular in appearance, that are characteristic indicators of the weathered upper ledge of the Cottonwood Limestone unit. Generally not considered to be a flint, the color and fracture of this example of the Cottonwood Limestone nodules approaches that of the the bluish flint found in the Threemile Limestone higher in the slopes of the Flint Hills.