SURFICIAL GEOLOGY OF THE NEW HAVEN, IOWA 7.5’ QUADRANGLE

The New Haven Quadrangle is located in Mitchell County in north-central Iowa. The quadrangle is located on the Wisconsin-age Iowan Surface Landform Region. A period of intense cold occurred during the Wisconsin full glacial episode from 21,000 to 16,500 years before present. This cold episode and ensuing upland erosion led to the development of the distinctive landform recognized as the Iowan Surface. A periglacial environment prevailed during this period with intensive freeze-thaw action, solifluction, strong winds, and a host of other periglacial processes.

The data collected to interpret this mapping area was comprised of well cutting samples stored in the repository of the Iowa Geological Survey, field observations, and core samples. This was combined with existing soil surveys, LiDAR, and existing geologic maps. The map area is dominated by unnamed erosion surface sediments of variable thickness overlying Wisconsin-age Sheldon Creek Formation glacial sediments, Pre-Illinoian glacial sediments, or shallow rock. Quaternary deposits in this quadrangle generally vary in thickness from 0 to 14 m (1 to 45 ft), but there are several bedrock valleys with the largest being up to 83 m (275 ft) below the surface on the eastern edge of the quadrangle. Results from this mapping program and others in Worth and Cerro Gordo counties to the west indicate that Sheldon Creek glacial materials extend much farther east than previously thought. Mapping that will be completed in 2016 of the entirety of Mitchell County should help resolve that boundary.