MULTIPLE TILLS/MULTIPLE GLACIAL ADVANCES IN NORTHEASTERN KANSAS

In the 1960's, a vertical face excavated in the sideslope of the Missouri River valley south of Wathena exposed a series of 12 thin layers of till separated by equally thin beds of well-sorted sand. The large number of units, plus an absence of soil development, led to an interpretation of deposition during repeated short advances and retreats of a dynamic icefront rather than an unreasonably large number of distinct glaciations. On the other hand, a quarry exposure a few miles farther south near Doniphan clearly displayed four till units separated by well-developed paleosol profiles indicative of the passage of significant intervals of time, but no definitive dating was then possible. A few more miles south, in Atchison, is a well-known creek-bluff exposure of till and outwash that has been described as evidence of both "Kansan" and "Nebraskan" glacial advances, yet here again, a basis for firm dating has not been reognized. The rapid expansion of the urban area west of Topeka in the 1970s and 1980s caused excavation of numerous foundations, sewer trenches, etc., some of which revealed two thin tills separated by a paleosol, but no chronologies could be developed. More recently, field studies betweeen Wamego and McFarland found highly weathered till south of the prominent line of large Sioux Quartzite erratics that had heretofore been considered to comprise the line of absolute farthest advance of glacial ice. The strong weathering is thought to be evidence that this till is much older than the surface deposit that is rich in Sioux Quartzite. Most recently, exposures of intensely weathered till have been found beneath the Sioux boulder till. Inasmuch as the Sioux boulder till has been considered to be a product of the "Kansan" Glaciation and the older "Nebraskan" ice terminated at Atchison in northern Kansas, it then follows that this newly discovered, highly weathered till must be the product of some heretofore unrecognized and unnamed "very old" glaciation.