IDENTIFICATION AND MEASUREMENT OF GLACIAL LAKE TERRACES USING AIRBORNE LIDAR-DERIVED DTM IN WILL AND GRUNDY COUNTIES, ILLINOIS, UNITED-STATES

The main objective of this study is to reconstruct the complex successions of ice marginal and frontal deposits in Will County, Illinois by a geomorphologic approach based on LiDAR DTM. Therefore specific goals are to: (1) identify the nature of landforms and surficial deposits, (2) define their spatial and chronological relationships and (3) describe the paleogeography of Will County. This study presents the main features associated with glacial lakes in the southwestern and southern Chicago metropolitan area. Using GIS tools, glacio-lacustrine terraces were identified in two specific areas: on the Valparaiso Morainic system in the eastern part of Will County and, in the Morris basin in the western part of Will County. The earliest terraces are interpreted as remnants of small ice-dammed lakes. Field work confirmed the presence of fine-grained sediments in those basins. The latest terraces are associated with the lower stages of glacial Lake Wauponsee. ArcGIS 10.3 – 3D Analyst was used to produce cross sections that permitted the identification and measurement of the top of those lacustrine terraces. On the Valparaiso Morainic system, the larger lakes are located near University Park (241 m) and east of Beecher (c.226 m and 219 m). In the Morris basin, three levels of terraces were measured in Will and Grundy Counties. In the Coal City area, a terrace at an elevation ranging between 167 to 172 m, is correlated with the Willow terrace associated with glacial Lake Morris as described by Curry et al. (2014). An intermediate level terrace was identified north of Morris between 166 to 169 m. This terrace is associated with glacial Lake Cryder (Ibid). The lowest terrace level was measured at an elevation ranging from 161 to 162 m. This terrace is located at the actual junction of the Des Plaines and Kankakee rivers. For all terraces, we observed that their highest level is always located toward the east. For the latest terrace by, using ArcGIS - Spatial Analyst, we observed that the top of the terrace is tilted (0.15m/km) towards the NNE (023°). Measurement of the tilt for the Morris and Cryder Lake terraces are forthcoming.