Kansas River - Geology

Geology

The Kansas River flows through what is known as the Stable Interior region. Since this region is near the center of the North American Plate, it has not experienced any extensive geologic faulting, folding, or mountain building in recent geologic time. In fact, the river flows through limestone and shale strata that, except for diagenesis, remain largely undisturbed since deposition beneath the Western Interior Seaway. The age of the rock exposed by the river becomes progressively older as the river moves downstream for two main reasons. First, downstream areas experience more erosion from increased flow, and second because the slight uplift of the Ozark dome to the southeast caused the strata in Kansas to dip very slightly to the west.

All of the rocks in the area are sedimentary, ranging from Late Pennsylvanian (300 million years ago) to recent, with three minor exceptions. The first is sand and gravel brought down from the Rocky Mountains which have settled in the western extents of the Kansas River basin. Second, the retreat of the Kansan glaciation left behind a combination of ice- and meltwater-deposited sediments known as drifta, a poorly sorted mixture of clay, sand, gravel, and even large boulders that cover parts of the extreme eastern portion of the Kansas River basin. The third is loess, a fine silt that may have originally been deposited by the melting water of the receding glaciers, then redeposited by the wind. The thickest loess deposits can be found in the northwest and north-central part of the Kansas River basin from southern Nebraska into northwest Kansas, as well as near the river's mouth.