Chert Gravel, Drainage Development, and Sinkholes in the Walnut Basin, South-Central Kansas

Abstract

High-terrace and hill-top chert gravel deposits are abundant in the Walnut drainage basin. These gravel deposits are designated here as the Leon Gravel, a formation that is equivalent to the Olpe-Norge soil. The Leon Gravel can be separated in some places into upper (hill-top) and lower (high-terrace) members on the basis of topographic position and soil development. Age of the Leon Gravel is not known with certainty; hill-top gravels are likely late Miocene or Pliocene; whereas, the high-terrace gravels are probably Pliocene or early Pleistocene. The Leon Gravel contains quartzite pebbles that presumably were reworked from Ogallala-type deposits. The quartzite pebbles were likely carried eastward by the ancestral Arkansas River, which may have flowed across the Flint Hills into southeastern Kansas. Bedrock features of the region have exerted a strong influence on the modern drainage pattern and sinkhole development; long-term southward crustal tilting has caused streams to shift to the south during valley entrenchment. High-terrace and hill-top chert gravel deposits are abundant in Butler and northern Cowley Counties within the Walnut drainage basin of south-central Kansas (Fig. 1). The Walnut drainage system is located on the western side of the Flint Hills. Its eastern tributaries flow down the dip slope of the Flint Hills toward the west and southwest. Chert gravel deposits in uplands of the Walnut basin have received little previous study. Bass (1929) and Frye (1955) mentioned these gravels and concluded they had a source to the north or northeast, derived from the western flank of the Flint Hills. Similar chert gravel deposits are widespread in eastern Kansas, east of the Flint Hills, in the Cottonwood, Verdigris, Neosho, and Marais des Cygnes drainage basins (Frye and Leonard, 1952; Frye, 1955; Bayne and Fent, 1963; Seevers and Jungmann, 1963; Aber, 1985, 1988; Aber and Johnston, 1990). These gravels are recognized as remnants of former stream-channel deposits (Frye, 1955; Aber, 1985). Chert was derived from lower Permian cherty limestones that crop out in the Flint Hills upland (Fig. 2). This content downloaded from 207.46.13.133 on Sat, 17 Dec 2016 05:25:00 UTC All use subject to http://about.jstor.org/terms 110 TRANSACTIONS OF THE KANSAS ACADEMY OF SCIENCE vcr* !oa I IPHILIPS M(T.r REUBLI T . . jKAK4 K prdN MAS IcM -Nr POT TrWAT !j t) For ) \ITCHELL CA RIE