EDMAP - SURFICIAL GEOLOGY OF THE READLYN 7.5' QUADRANGLE BREMER COUNTY, IOWA

This USGS EDMAP project has characterized the surficial geology of the Readlyn (1:24,000) Quadrangle in northeast Iowa. Five surficial units were identified, sampled, and mapped that document Pleistocene and Holocene geologic processes on the Iowan Erosion Surface. The delineated Readlyn units included alluvium (Qal), low terrace alluvium (Qal_lt), sandy eolian sediment (Qe), sand and gravel (Qnw2, Noah Creek Formation), and loamy and sandy sediment to glacial till (Qwa2, unnamed reworked Pre-Illinoian till). The Readlyn landscape represents an interesting example of the Iowan Erosion Surface. The majority of this quadrangle is represented by unnamed and reworked Pre-Illinoian till during the Wisconsin glacial surface. This eroded surface was mantled by loamy sediments and subsequent soil development. An interesting and poorly understood Quaternary feature was identified within the Readlyn area, sand stringers. These sandy depositional features generally occur as elongated northwest to southeast trending stringers a top glacial till. They may also contain solifluction features, stone lines, ventifacts, and silt bands. On-going work seeks to delineate the physical and chemical characteristics of the Iowan Erosions Surface to better understand its depositional setting, chronology, and interrelationships with current land use practices.