THE GEOMORPHOLOGY OF THE FAIR OAKS DUNE FIELD, INDIANA, USA

The occurrence, distribution, geomorphology, and age of inland dune systems provide valuable insight to the sediment supply, wind speed and direction, and climate of a region. The Fair Oaks Dune Field contains stabilized parabolic and compound parabolic dunes covering approximately 1100 sq. miles of northern Indiana and north-eastern Illinois. Glacial outwash from the Lake Michigan, Lake Huron-Erie, and the Saginaw lobe of the Laurentide Ice Sheet supplied sediment to the region that was reworked to form this extensive dune field.

We identify four major sections within the dune field based on differences in dune size, spacing and orientation. In the northern section an almost continuous series of compound parabolic dunes extends ~40 miles SW to NE along the southern margin of the Kankakee River valley. The occurrence and distribution of this dune cluster appears to have been influenced by the paleochannel bank of the Kankakee River Valley as indicated by surface topography and changes in subsurface geology. The orientation and morphology of the northern dunes indicate a west to southwest primary wind direction. The western section comprises series of parabolic dunes assembled in compound parabolic dune chains indicating southwesterly winds. The smallest dunes are in southern section and mostly simple parabolic dunes created by westerly winds. The tallest dunes are in the eastern section and made of simple and compound parabolic shapes with steep eastern slopes indicating prevalent westerly winds. Most of these dunes are scattered over older outwash or lake plain but some of them are lined against or climb atop of glacial landforms. Optically stimulated luminescence dating of dune sand from the eastern section yields ages of ~13 to 16 ky. Future work will focus on providing OSL ages across the dune field. These ages will potentially provide insight to the timing of the last major meltwater pulse through the Kankakee River Valley.