Map of Lee County Sand Distribution Nearing Completion
Xiaodong Miao is working on a map showing the surficial eolian and outwash sand distribution of Lee County. Sand and gravel deposits are found in southwestern Lee County (part of the Green River Lowland) and are also in the northeastern part of the county. The deposits are largely the direct or indirect result of the glacial process. Sand in Lee County has two major origins: windblown eolian sand and water-lain glacial and fluvial outwash sand. Eolian sand, previously classified as Parkland Sand, consists of topographically distinct dune sand and relatively flat sand sheet in interdune areas. Eolian sand is very well sorted and medium to fine grained, containing no gravels. Soil formed in eolian sand is excessively well drained due to its sandy texture. In contrast, thick glacial and fluvial outwash sand and gravel classified as Batavia Member of Henry Formation was deposited by meltwater from the ice front that built the Bloomington Morainic System in Lee County. Therefore, outwash sand can vary in grain size and often coexists with gravel.
The geological significance of this map is the distribution of eolian sand versus outwash sand. The sands are not mutually exclusive at some localities because eolian sand is generally above glacial and fluvial outwash sand in the Green River Lowland. Classifications of eolian versus glacial and fluvial sands are based on data from topography, parent materials of soil reported in U.S. Department of Agriculture Soil Survey, water and related well records, and grain size. Previous differentiation of eolian and outwash sand has been at the statewide scale. The ISGS county map now in preparation gives much more detailed information. It improves the understanding of the distribution and use of this sand and gravel resource and enhances the scientific understanding of the eolian and the glacial and fluvial processes.
With this new map, the sand distribution of the entire Green River Lowland (Bureau, Henry, Lee, Rock Island, and Whiteside Counties) can be finalized. A similar map of Bureau County has been completed, and the surficial geology of Henry, Rock Island, and Whiteside Counties has been mapped by Richard Anderson, Augustana College. Collective information from these mapping projects will provide a clear picture of sand distribution in the Green River Lowland.