Figure 1.
Map of 0- to 50-ft clay interval with color ramp (Olejnik, 2006b). The color ramp emphasizes the end members of the unconsolidated materials with the mostly clay sediments in blue and the less clay-rich, or mostly granular, sediments in red. The middle of the color ramp, in white, shows the areas that contain more equal mixtures of clay and granular sediments. The amounts of clay shown are not continuous amounts of clay but are a total amount of the clay present in the top 50 ft of sediment.

The Allen County interactive map displays two clay thickness map layers. One layer shows the amount (thickness) of clay in the uppermost 25 ft of unconsolidated sediments; the other shows the thickness of clay in the uppermost 50 ft of sediments. These maps show the total amount of clay in each respective interval. The maps were constructed using the CLAY lithology from the "Interpreted" field in the iLITH database and calculating the total thickness of clay in each water well for the 0- to 25-ft and 0- to 50-ft depth intervals (Olejnik, 2006a, b). A grid was created by interpolating between the water-well data using inverse distance weighing. The color ramps used for both maps are similar, except that the number of ranges increases with the 0- to 50-ft interval.

The 0- to 50-ft clay thickness map shows the distribution of the amount of clay in the upper 50 ft of unconsolidated material in Allen County (fig. 1). The color ramp emphasizes the end members of the unconsolidated materials showing the mostly clay sediments in blue and the less clay-rich, or mostly granular, sediments in red. The middle of the color ramp, in white, shows the areas that contain approximately equal mixtures of clay and granular sediments. The amounts of clay represented are not necessarily continuous amounts of clay but show the total amount of the clay present in the top 50 ft of sediment.

Comparison of the landforms as defined by Fleming (1994) (fig. 2) combined with the 0- to 50-ft clay interval is shown in Figure 3. Areas having the greatest amounts of clay are associated with the Wabash and Fort Wayne Moraines. The clay-rich till of the Lagro Formation dominates both morainal areas. The alluvial valleys have lesser amounts of clay. In the Maumee Lacustrine Plain, the amount of clay ranges from 0 to 50 ft.

Figure 2.
Map of glacial terrains. From Fleming (1994).

Figure 3.
Map of glacial terrains combined with the 0- to 50-ft interval.

References:

Fleming, A. H., 1994, The hydrogeology of Allen County, Indiana–a geologic and ground-water atlas: Indiana Geological Survey Special Report 57, 111 p.

Olejnik, J., (digital compiler), 2006a, CLAY_0_25FT_IGS_ALLEN: Cumulative thickness of clay in the 0- to 25-foot interval in Allen County, Indiana, based on iLITH data: Indiana Geological Survey, ESRI grid, 30 m.

Olejnik, J., (digital compiler), 2006b, CLAY_0_50FT_IGS_ALLEN: Cumulative thickness of clay in the 0- to 50-foot interval in Allen County, Indiana, based on iLITH data: Indiana Geological Survey, ESRI grid, 30 m.