It is probable that the rounded flint has partly originated from these [Flint] hills. G.C. Broadhead (1880).
High-level (upland) chert [flint] gravels occur in almost all of the counties in the Osage Cuesta country of eastern Kansas. The locations of the high-level chert gravel deposits now are well known as a result of recent remapping of the state on a scale of 1:24:000, but the origin and age of the chert gravels remain as debatable today as they were 125 years ago. The gravels are composed of brownish, smooth, angular to subangular chert pebbles and cobbles ranging up to 6 inches (15 cm) in size.
The chert clasts have been derived from Lower Permian limestones that contain abundant chert [flint] and crop out in the topographically high Flint Hills in east-central Kansas. The chert weathers from the limestones to create lag gravels, which in turn are reworked and transported eastward and southeastward by streams.
In the glaciated region in northeastern Kansas, remnants of high-level chert gravel deposits occur in association with glacial tills, outwash, and erratics. In places the chert gravels occur beneath glacial deposits. South of the glaciated region, however, the remnants of the high-level gravels occur on bedrock surfaces whose elevations range from 20 to 200 feet (6 to 60 m) above the floodplains of major streams.
The chert itself that forms the gravels is known to be Early Permian in age, based on fossils preserved in the pebbles and cobbles. Deposition of the high-level gravels, however, cannot be dated directly, but information bearing on their relative ages is provided by the degree of soil development over them and their elevations with respect to modern floodplains. Deposits at higher elevations may be Pliocene, whereas deposits at lower elevations may be early to middle Pleistocene. Chert gravels that occur on low-lying floodplains and in modern alluvium and are judged to be late Pleistocene to Recent in age.