Characterization of Soils and Parent Material of the Arnott Moraine in Portage County, Wisconsin

• Main Author: Nelson, John F.
• Format: Thesis
• Language: English
• Published: University of Wisconsin-Stevens Point, College of Natural Resources 2019
• Subjects: Green Bay; Stevens Point; Ice; Ice Sheet; permafrost; wedge*
• Online Access: http://digital.library.wisc.edu/1793/79507

The Arnott moraine is a landscape unit located four miles east of Stevens Point in Portage County, Wisconsin. It is a low ridge with 50 to 80 feet relief, is 1/2. mile wide, and extends 18 miles in a north-south direction. The purpose of this investigation is to study the soils and geology of this landscape feature in order to evaluate two theories regarding its origin. The two possible origins are as follows; (1) it is an end moraine of early- or pre-Wisconsinan glacial advance and is composed of glacial drift (hence its name), or (2) it has weathered from granite bedrock, is underlain by weathered residuum and has a granite core. Significant differences are apparent when topography, drainage pattern, land use, and soil drainage characteristics of the Arnott moraine are compared to those characteristics of the Outer moraine, a Woodfordian end moraine located 2 miles east of the Arnott moraine. The Outer moraine has steep, irregular slopes, many undrained depressions, and the deranged or internal drainage pattern of a youthful glacial landform. Many of the depressions are well drained indicating the moraine is composed of permeable sandy glacial drift. The Arnott moraine has gentle, smooth slopes with a well integrated drainage pattern characteristic of an older landscape feature. The underlying materials are dense and slowly permeable as indicated by the presence of standing water in road ditches, a few shallow undrained depressions, and a significant area of somewhat poorly drained soils on the features gently sloping uplands. Field investigations of soils and observations in 2 soil pits on the Arnott moraine revealed the presence of 2 or 3 different layers of materials in each soil profile. The C horizon or parent material at each site was sandy loam to loamy sand in texture and contained numerous rounded erratics of gabbro and basalt which often had pronounced weathering rinds. Well drillers provided samples and logs for wells drilled in the Arnott moraine. Materials penetrated by these wells consisted of' 50 to 80 feet of dense loam underlain by coarse sand and gravel considered to be glacial outwash. Ice-wedge casts have been observed on the Arnott moraine and are not found on the Outer or other Woodfordian moraines to the east. This suggests the Arnott moraine was ice-free and subjected to permafrost conditions before or during the time when the Outer moraine was being deposited. Based on the field observations and data from 1aboratory analyses, the Arnott moraine is considered to be a remnant of a moraine formed during an early-Wisconsinan (Altonian) or pre-Wisconsinan (Illinoian) ice advance. This landform was largely buried by the more recent advance of-the Woodfordian age Green Hay lobe of the Wisconsinan ice sheet. The small portion of this older moraine not covered by deposits of the Green Bay lobe is the landscape unit currently designated as the Arnott moraine.