Analysis of the Merden Lake Esker, Stearns County, Minnesota: A New Interpretation

• Main Authors: Aaron C. Hirsch, Larry E. Davis
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2004
• Subjects: Stearns; Ice Sheet
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.595.3165; http://www.ajur.uni.edu/v3n2/Davis%26Hirsch.pdf

A gravel pit in south central Stearns County, Minnesota exposes sand and gravel of the Merden Lake esker which is thought to have been deposited by a subglacial stream associated with the Wisconsinan-aged Superior Lobe of the Laurentide ice sheet. An analysis of these sediments was conducted from samples collected through a vertical trench on an east-facing exposure of the gravel pit. A total of 12 distinct stratigraphic horizons were recognized. Each horizon was described in terms of overall color, grain size, and lithology, carbonate content, and sedimentary structures. A total of 436 clasts (>3 cm) were collected for lithology studies. Trench samples were collected across each horizon for grain size sieve analysis. Clasts were dominated by basalt (37.6%), granite (28.2%), gabbro (14.5%), quartzite (6.2%), diorite (3.5%), mica schist (3%), and andesite (1%). Minor components consisted of pisolitic claystone, shale, sandstone, limestone, dolostone, ironstone, bauxite, quartz, agate, and amethyst. The sedimentology provides an overall color of yellowish-orange to brown. Many of the large clasts (>5 cm) contained a rind of calcareous-cemented course sand. Several large (18-35 cm) armored clay balls were collected from the basal horizon. Grain size ranged from boulders (up to 37 cm in