Sampling will begin well down in what is believed to be the Peoria Loess and continue all the way to the present land surface. We should thereby include the Late Pleistocene-Holocene transition, the interval of post-glacial high temperature (the Altithermal or Climatic Optimum), and the period of temperatures lower than present (the Neoglaciation, including the Little Ice Age). We will routinely collect samples from the lower, middle, and upper portions of each visually detectable geological or pedological unit, and take samples at intermediate levels of thick, apparently massive units. In this way data will be obtained for all variations of material, yet form a basis for statistical manipulation of analyses with depth if that becomes desirable. All samples will be subjected to routine soil characterization procedures such as determination of grain size, organic matter content, pH, carbonate content, bulk density, and cation exchange capacity. Carbon-nitrogen ratio, base saturation, and clay mineralogy may also prove useful for elucidation of variations in climatic parameters. The modern surface soil and all buried paleosols will be described according to standard soil survey criteria. At least one monolith will be prepared and removed from the face in order to preserve the stratigraphy for possible restudy after the exposure has been eroded away. Carbon from the organic- rich horizons in the paleosols will yield a sequence of radiocarbon dates to develop a firm chronologic framework for the proxy climatic data. At least two radiocarbon dates will be obtained for each of the paleosols.
