253 Journal of Paleolimnology 22: 253–257, 1999. © 1998 Kluwer Academic Publishers. Printed in the Netherlands. Improved mapping of the Lake Agassiz Herman strandline by integrating geological and soil maps Eric C. Brevik & Thomas E. Fenton Soil Morphology and Genesis, Agronomy Department, Iowa State University, Ames, IA 50011, USA Received 16 July 1998; accepted 27 September 1998 Key words: Lake Agassiz strandlines, mapping, soils and geology Abstract Several discontinuous, segmented strandlines that mark the former shores of Lake Agassiz can be found in eastern North Dakota. These strandlines are difficult to map and correlate because of their segmented nature. Better mapping would benefit researchers working on a number of problems involving Lake Agassiz including dating the strandlines, reconstructing the lake’s history, and calculation of asthenosphere viscosity beneath the Lake Agassiz basin. Elongated soil delineations representing beach-indicative soils with a north-northwest trend and extending from currently mapped areas of the Herman strandline were identified on Grand Forks County soil maps. This information was combined with the geologic map of Grand Forks County in an attempt to better define the location of the Herman strandline in the southern part of the county. This approach worked well, and it is recommended that similar studies be attempted on other Lake Agassiz strandlines in North Dakota and the surrounding area. Brevik & Gosnold 1998b), and ice thickness and rebound calculations in the Lake Agassiz basin (e.g., Brevik & Reid, 1994; Brevik, 1994). Techniques and tools to improve mapping should be aggressively pursued because of the wide range of geological subdisciplines that stand to benefit from improved mapping of the Lake Agassiz strandlines. This study concentrates on the Herman strandline, and compares the geologic map of Grand Forks County (Hansen and Kume, 1970) to soil maps in the Grand Forks County Soil Survey (Doolittle et al., 1981) (Figure 1). The Herman strandline is the oldest of the well-preserved Lake Agassiz strandlines (Bluemle, 1991), and as such is of particular interest to some researchers. The Herman strandline has been mapped in Grand Forks County, but is largely absent from the southern 16 km of the Grand Forks County geologic map (Hansen & Kume, 1970). The Herman strandline is preserved as either beaches or wave-cut scarps in Grand Forks County, depending on location (Bluemle, 1991; Hansen & Kume, 1970). In the parts of Grand Forks County where the Herman strandline is preserved as beaches most of the deposits are sand and gravel, Introduction Several north-northwest trending strandlines were formed along the western shores of glacial Lake Agassiz as the lake receded from eastern North Dakota. In many places these strandlines exhibit very little topographic relief, making it difficult to trace and correlate them. The strandlines tend to occur as dis– continuous segments that are often less than 5 km long (Bluemle, 1991). Numerous large gaps, which are frequently larger than 3 km and may be as large as 10 km or more, occur between mapped strandline segments (Bluemle, 1991; Hansen & Kume, 1970). Better mapping and correlation of the Lake Agassiz strandlines would be helpful to a number of researchers working on a wide range of problems. Examples include work on dating Lake Agassiz stages (e.g., Fenton et al., 1983), determination of the volume, extent and drainage of Lake Agassiz at various times in its history (e.g., Teller & Thorliefson, 1983; Teller, 1990; Fisher & Smith, 1994), calculation of astheno- sphere viscosity beneath the Lake Agassiz basin (e.g., Brevik, 1994; Brevik, 1997; Brevik & Gosnold, 1998a,