Hydrological and Biogeochemical Research in the Shingobee River Headwaters Area, North-Central Minnesota

The Shingobee River Headwaters Area lies within a physiographic region known as the Itasca/St. Croix moraine interlobate area (Norton, 1983) (fig. 1). The glacial history of this area is particularly complex, and the geomorphology and sedimentology provide a record of glacier dynamics, processes of ice stagnation, and the development of an extensive glacial karst system (Mooers and others, 1990; Wright, 1993). The Itasca moraine is 160 km long, 20 to 30 km wide (fig. 1) and composed of as much as 250 m of unconsolidated sediment overlying bedrock. This large end moraine marks a lengthy stillstand of the Itasca phase of the Wadena lobe of the Laurentide ice sheet during Late Wisconsin time (Wright and Ruhe, 1965). The St. Croix moraine of the Rainy lobe extends from its interlobate junction with the Itasca moraine southward to central Minnesota (Wright, 1972; Wright and Ruhe, 1965). Although a prominent geomorphic feature of Minnesota's landscape, the St. Croix moraine is much narrower and has considerably less relief than the Itasca moraine (fig. 1). The glacial geology of the interlobate junction of the two moraines was the focus of an investigation by Norton (1983). The area is characterized by a myriad of glaciofluvial sediments and landforms including ice-contact sands and gravel, collapsed outwash plains, coalescing outwash fans, outwash terraces, and subglacially carved tunnel valleys (Norton, 1983). Other than the investigation of Norton (1983), few detailed studies of the glacial geology of this area have been undertaken. The general sequence of glaciation of the region is discussed by Wright (1972), Wright and Ruhe (1965), and Matsch and Schneider (1986). Seaberg (1985) conducted an investigation of the hydrogeological characteristics of the glacial sediments in the area immediately surrounding Williams Lake. Several regional studies were completed for portions of northwestern and central Minnesota. Several lithostratigraphic studies describe and correlate sedimentary units and regional Late Wisconsin glacial events (Anderson, 1976; Harris, 1975; Martin and others, 1989, 1991; Perkins, 1977; Sackreiter, 1975). The area south of the Itasca moraine was the focus of two regional investigations of stratigraphy, sedimentology, and glacial history (Goldstein, 1985; Mooers, 1988). Recent regional (Dobbs and Mooers, 1990; Mooers and others, 1990) and more detailed local investigations (St. George, 1994) have led to significant revisions of the general glacial history of this area. The discussion below focuses on a general description of the Itasca/St. Croix moraine interlobate area and summarizes the results of recent investigations.