KANSAS RIVER MEANDER SCROLLS: RECORD OF A MIGRATING CHANNEL AND CHANGING CLIMATE

Receiving drainage from most of northern Kansas, southernmost Nebraska, and northeastern Colorado, the mainstem Kansas River joins the Missouri River at Kansas City. Its valley floor, above deep sandy fill, is 2-3 miles wide for most of its 175-mile length. Throughout the time of coverage by modern, reliable maps the channel has been nearly straight (average sinuosity of about 1.1). However, a complex belt of well-preserved meander scrolls provides evidence of a preceding phase of extensive meandering (sinuosity of 2.0 or greater) through most of the river's length and for almost the full width of its valley floor. These scrolls are present on the Newman Terrace, a prominent surface that makes up most of the valley floor. About 10 feet beneath this surface is a buried paleosol that yields radiocarbon dates approximating 1900 BP. This is the maximum age of the scrolls - minus sufficient time for accumulation of the sub-scroll ca l0-foot layer of sand that apparently extends across the entire valley width, perhaps deposited by a migrating braided stream. Subjective estimation places the time of extensive meandering at 1000 to 800 years ago, during the waning Medieval Warm Period...or perhaps later at the transition into the Little Ice Age. Although widespread in nature, meander scrolls are scarcely mentioned in geomorphology textbooks. They constitute a valuable resource for reconstruction of past environments and surficial processes.