These diagrams from The Environmental Geology of Allen County, Indiana (Special Report No. 13), published by the Indiana Department of Natural Resources (1978), show the probable stages of Cedar Creek's development at the end of the last ice age.

Summary: Sequential Development of Cedar Creek

Cedar Creek Canyon forms as a sub-ice channel of the Wisconsin Glacier's Saginaw Lobe

The Saginaw Lobe retreats and the canyon is buried by the advancing Erie Lobe

The ancestral Eel River, which includes upper Cedar Creek, forms as an ice-marginal channel to the Erie Lobe

Cedar Creek Canyon, now a sub-ice channel of the Erie Lobe takes drainage from the melting Erie Lobe into the
        ancestral Eel River

The St. Joseph River forms at the edge of the Fort Wayne Moraine and takes drainage from Lake Maumee to the
        Wabash River; Cedar Creek Canyon takes drainage from the St. Joseph to the Eel

Outwash from Cedar Creek Canyon "beheads" the Eel, diverting upper Cedar Creek into the canyon, making it a
        tributary of the St. Joseph

The Maumee River opens as Lake Maumee recedes; the St. Joseph reverses flow, making the Cedar Creek watershed
        part of the Maumee drainage system.

Source: Bleuer and Moore, Environmental Geology of Allen County, Indiana (Special Report No. 13), published 1978 by the Indiana Department of Natural Resources. (Out of print. Special thanks to DeKalb County amateur geologist Ed McDonald for making his copy available.)

Other Reference: Jack A. Sunderman, "The Three Faces of Cedar Creek," ACRES Quarterly, vol. 39, no. 4 (Autumn 2000), pp. 6-7, published by ACRES Land Trust, Inc., 1802 Chapman Road, Huntertown, IN 46748.